Overheating Issue Paper
GBE > Encyclopaedia > Code > Issue Paper > Overheating > G#145
GBE > Encyclopaedia > Code > Issue Paper > Overheating > G#145
Overheating before and after energy saving retrofit or future-facing adaptations
Many specialists in the UK have explored overheating in summer but none appear to have found the primary problem and not found the whole solution. Most of the proposals just fine tune the problem but do not solve it. Zero Carbon Hub and NHBC publications are missing the point too. DECC got close with the problem, but not the solution.
Just like the severe and continuous drip feed of storms on the West-country coast 2013-2014 leading to the battering of the coastal towns, closing of a railway line, flooding of the Somerset Levels, Severn estuary and eventually the Thames valley; the nub of the problem was not the congested rivers and drainage dykes, it was the 2 months of prolonged, heavy and incessant rainfall.
Summer overheating is down to the incessant sun heating of the buildings through the transparent surfaces, but more importantly through the opaque surfaces, roof and walls of lightweight construction.
This is exacerbated by the use of the familiar, cheap, but unfit-for-purpose, wrong thermal insulation materials that permits radiant heat to get in and then prevents conducted heat getting out. (Another greenhouse effect)
We used to teach about this issue in University in the 1970’s but the appropriate and competent materials were not available in the UK market place, so we could not engage with it;
In mainland Europe well away from the mild Atlantic weather, in more intensely urbanised settlements, more prevalence for summer overheating will have prompted action, the problem has been understood and they have developed the products to address it for over 30 years.
Today those right materials are in the UK market. The Greens have been bringing these products into the UK for 15-20 years and promoting their use.
However the UK market obsessed with fiduciary rules and making a profit; mainstream construction is not interested in investment, or in climate change, unless regulated or customer driven.
Customers do not understand overheating either, so the problem remains unresolved and the solution remains a green fringe benefit.
Stop the heat getting in and the other proposed solutions by ZCH and NHBC can work more successfully.
There are many other problems and solutions to be addressed.
Overheating in winter is often communal and district heating flow and return pipes inadequately insulated, under-floor heating in confined communal spaces; added to by cavity party walls acting as chimneys moving heat to other parts of buildings.
Passivhaus or EnerPHit designed housing and better specification, commissioning and optimisation of any residual insulated communal services could fix these.
Green Building Encyclopaedia (GBE) has a GBE Issue Paper on Overheating that goes into great detail on all the contributing factors. Its is currently 81 pages, on its 11 update, 235 topics, including:
Start here to see all the pages so far related to Overheating.
https://greenbuildingencyclopaedia.uk/?p=2613
Straight to the Overheating Paper
https://greenbuildingencyclopaedia.uk/?p=145
I have just skimmed through all the ZCH publications about overheating and have not found any evidence that they know the big problem let alone the big answer.
They have lots of clues about the obvious and smaller problems, but not the big one.
If their ambitions for Energy Experts are carried out with conventional know-how we will race faster into oblivion.
Quoting from: Overheating in Homes Drivers for Change
“In recent decades there has been a strong drive towards reducing heat loss in homes and winter heating costs by incorporating energy efficiency measures.
As a result, new-build dwellings are highly insulated and airtight and lose much less energy through the building fabric.
Millions of existing buildings have also been retrofitted with insulation and other energy efficiency measures.
Such measures are extremely beneficial in winter – helping to keep homes warm and to save energy – but could have unforeseen and unintended consequences in summer if not managed.
For example, insulation keeps homes warm in winter and helps keep them cooler in summer, but effects such as solar gain can cause an increase in internal temperatures which are potentially difficult to dissipate”.
GBE Comment:
“Unforeseen and unintended consequences”:
Solar heating through opaque fabric has been understood since the 1970s and taught at university and long forgotten by many, but not understood by Building Regulations and compliance design tools.
Unintended or not the Regulations focussed on conductivity and ignoring solar radiation resistance are causing overheating.
“If not managed”:
You cannot manage solar heat gains through opaque fabric very easily they are of such magnitude; opening windows, ventilation or shading at windows will not manage it.
“insulation…helps keep them cooler in summer”:
Wrong, the vast majority of insulation used in UK pitched or flat roofs will not help keep buildings cooler in summer.
They are the wrong materials with the wrong properties.
They will let the solar radiant heat in and prevent that heat getting out by conduction.
They are more likely to keep them hotter in summer.
“effects such as solar gains”:
Assuming they are referring to solar gains through glazed parts.
“Potentially difficult to dissipate”:
Ventilation will help remove ‘glazed part solar heat gains’ relatively easily, but added to ‘opaque part solar heat gains’ there is a lot less hope of success with ventilation until after the sun has set.
World FM reported on SOM Architect’s Post Occupancy Evaluation (POE) survey report, May 2015, including a recent survey of building occupants in many building use types.
The striking issue was that whilst almost all issues scored fairly well:
See Also:
SOM Post Occupancy Evaluation (POE) survey report, May 2015
You probably think you know what follows and you could leap frog it.
But beware there are quite a few bits you probably don’t know or haven’t joined up before.
They are essential to understand the later bits.
Before we talk about the after effects of energy saving retrofit measure let’s look at buildings in their raw state.
Overheating in summer:
Passive ventilated offices connecting onto atrium that should help cool them but fail
Overheat in winter:
Overheating all year round (including sunny days in winter)
So it’s worth understanding what that is all about before we start thinking about the after effects of adding insulation.
Sun light, Sun-lit building, Sunspaces, Sun-lit surroundings, People/Pets, Services for Living, Consequences
Northern hemisphere
Daytime:
Daylight:
North light:
Overcast sky:
Sunlight:
Moonlight:
Night-time:
Moonlight:
Cloudy or overcast sky:
Clear sky:
Sun’s Solar Heat: drives the wind, its direction, heating or cooling effect of land and ocean masses and weather
Moon: drives the tides and the potential for cooling effect of ocean breezes
Sun and moon: dictate the normal and peak tides
There are at least three aspects to orientation:
‘All buildings face the sun’.
At some point during the day most buildings face the sun.
This is true of detached buildings but this is not always true of:
In some of these cases some properties will not see the sun ever and others will not escape it.
Exposed opaque (solid) parts either permit or prevent solar light/heat gains depending upon their materials and methods of construction.
See Also:
GBE Checklist
GBE Jargon Buster
GBE CPD: Sustaining Towers
GBE CPD: Integer Tower Refurbishment
GBE CPD: Survey Test Analysis
GBE CPD: Refurbishment: Survey Test Analysis
GBE CPD: Zero Carbon Buildings
GBE Case Study: Architectural Competition: Isle of Dogs Mudchute site, Competition Brief Failure
We are encouraged to:
Exposed transparent (glazed) parts permit daylight and solar light/heat gains when they face in the right direction(s).
See Also:
GBE Checklist
GBE Jargon Buster
GBE CPD: L10 Windows
GBE Products: L10 Windows, Rooflights, Roof windows, L20 Glazed Doors
GBE Robust Specification
By others:
Passivhaus Webinar: Passive House Windows for Mediterranean Climates https://youtu.be/YHg4Pt1M5Tw via @YouTube via twitter @JMenendez
Depending upon the geometry of roofs, orientation of predominant ridges and larger slopes is important.
Roof plains include dormers, roof lights, roof windows and can also include solar panels.
Their orientation will determine the quality and amount of light entering the upper floor or attic through glazed parts.
Exposed opaque pitched roofs either permit or prevent solar light/heat gains depending upon their materials and methods.
Exposed transparent parts permit daylight, sunlight and solar light/heat gains depending upon the direction they face.
See Also:
GBE Checklist
GBE Jargon Buster
GBE CPD: Pitched Roofs
Pitched roofs are normally and most often mid to dark tone absorbing the sun and its heat, contributing to overheating of the attic space, room in roof, bedrooms or top floor flat below.
Pitched roofs tile and slates are:
Thatch roof will start lighter yellow and end up mid tone grey and offers some solar radiation resistant thermal insulation.
Exceptionally roof tiles were glazed reflecting some of the sun’s heat and re-radiate the rest inwards.
Malleable metal claddings include:
Exceptionally: (highly reflective; potential glare, migraine or accidents)
Coated profiled metal cladding can be any colour you like from the manufacturers swatch:
Coated flat metal cladding can be any colour you like from the manufacturer’s swatch
Choosing white, lighter colours, lighter tone and low saturation colours potentially:
See Also:
GBE Lectures: Elements: (27.2) Pitched Roofs
Case Study: Self cooling roof: http://www.fastcoexist.com/3047090/with-this-self-cooling-roof-you-might-not-need-a-c?utmcontent=buffer8bbb4&utmmedium=social&utmsource=twitter.com&utmcampaign=buffer
GBE Checklist
GBE Jargon Buster
GBE Products:
GBE Robust Specification
Twitter had a tweet about glass roof tiles available from Sweden asking “What would you do with all that free heat?”
You need expensive kit to exploit it, capture it, store it, move it, use it.
A few years back at a TGR event a ST panel inventor presented a glass slate replacement
And what about the embodied energy and carbon of making glass tiles or slate replacements?
Historically a glass or transparent roof tile would replace a tile or two
So what would you do with all that glass roof tiling and no underlays?
So it’s just another stupid idea then.
I realise that the manufacturer has gone to great lengths to produce the tiles and want to sell a few
What do they say any news coverage, good or bad, is good marketing.
Most pitched and mansard roofs will be made of:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products:
GBE Robust Specification
It is commonplace (seen most times on Grand Design) for timber framed pitched roofs with sloping ceilings to be insulated with foamed plastic insulation for its thinness and high thermal conductivity insulation performance.
Foamed plastics:
Mineral wool:
Cellular glass:
Plant based fibre or flake:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products:
GBE Robust Specification
At the eaves edges of pitched roofs the roof timber framing tapers to a triangle with say 100 mm vertical end at the supporting wall outer edge.
With UK Building Regulations requiring 200-300 mm of insulation it means the ceiling level conductivity thermal insulation will taper and reduce in thickness at the eaves edges of roofs.
Roof usually also need a 50 mm ventilation gap between eaves and attic, this may be achieved with an airtight wood based panel maintaining the air gap, so the insulation will be reduced further.
The result is a risk of greater heat loss through the ceiling, along the eaves at the most vulnerable position.
With bathrooms and bedrooms often at the external wall, this runs the risk of condensation and mould.
The solution is for new build pitched roof trusses to be designed with a ‘heel’ or vertical at the eaves, the height of the heel should correspond to the thickness of the conductivity thermal insulation on the ceiling.
If the roof is only insulated with conductivity thermal insulation then the upper floor rooms will overheat.
So the heel height should correspond to the thickness of solar radiation resistant and conductivity thermal insulation.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products:
GBE Robust Specification
Far fewer pitched roofs are constructed with heavyweight construction
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products:
GBE Robust Specification
Developers regularly want to maximise profits on developments and so refurbishments of commercial or industrial buildings to residential or commercial will usually require extra floors added to the roof of the building.
T&C Planners will want the extra floors set back so as not to change the character and appearance of the existing buildings.
Setting it back will complicate the structural support and encourage the designers to introduce lightweight framing, lightweight insulation and lightweight claddings.
The top floors are often sold as the penthouse and sold for the highest prices, but will suffer the greatest overheating and probably get air conditioning fitted.
The Architects made the decision that they wanted a heavyweight brick plinth with heavy solar shading and a set back lightweight glazed and metal roof on aesthetic grounds.
The result is relatively sombre dark lower floors and bright and airy top floor.
The top floor also overheats.
Just like ‘Build Tight, Ventilate Right’ a slogan that engages with building air-tight and purposeful ventilation.
The issues of overheating of lightweight construction could do with a slogan too.
Explanation: If you BUILD it LIGHT weight you must INSULATE it RIGHT to keep it SOLAR-TIGHT
Initially: BUILD LIGHT, INSULATE RIGHT, SOLAR TIGHT
Ultimately: BUILD LIGHT, SOLAR TIGHT
BrianSpecMan aka Brian Murphy 11th August 2015
See also:
GBE Jargon Buster: Build Light, Solar Tight
Shallow roofs are normally and most often mid to dark tone absorbing the sun and its heat, contributing to overheating of the attic space, room in roof, bedrooms or top floor flat below.
Malleable metal roofing include:
Coated profiled metal roof cladding can be any colour you like from the manufacturers swatch:
Choosing white, lighter colours, lighter tone and low saturation colours potentially:
See Also:
GBE Lectures: Elements: (27.1) Flat Roofs
GBE CPD: Materials
With flat roofs there is a surface area for solar light/heat gain.
High parapets can offer some shading to the roof area,
In winter the sun will be at an acute (shallow) angle and parapets provide more shading.
In summer the sun will be at an obtuse (steep) angle and parapets provide less shading.
Flat roof plains can include roof lights, plant (mechanical and electrical equipment).
These roof plains can also include solar panels.
Exposed opaque flat roofs either permit or prevent solar light/heat gains depending upon their materials and methods.
Exposed transparent parts of flat roofs permit solar light/heat gains to the interior.
GBE Lectures: Elements: (27.1) Flat roofs
Flat roofs have traditionally been light coloured to reflect the sun and its heat, contributing to the albedo effect.
The light colouring of flat roofs was made with solar reflective white aggregate chippings on built up roofing.
More recently these have been replaced with lower cost or available solutions:
If the covering is thin or uninsulated then the heat will pass through the covering and into the supporting structure.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: Q24 & Q25 Solar reflective paving
GBE Robust Specification
GBE Lectures: Elements: (27.1) Flat roofs
Some of our earliest flat roofs are waterproofed with asphalt
It was often laid with no solar protection,
But old buildings (pre 1960s) with asphalt roofs probably have little or no thermal insulation below.
Asphalt roofs may be laid on concrete roofs or timber framed roofs.
Asphalt can cope with being hot and will absorb a considerable amount to heat, once it reaches saturation point then the heat passes through to the roof below.
If it is concrete the roof will absorb the heat, if it is timber the heat will pass through to the space below.
Rooms below these roofs will be hot during the day but the hot asphalt will take time to cool off and keep the building warn late into the evening.
If the heat has not dissipated by morning then the rooms below will remain hot and get hotter.
See Also:
GBE Checklist
GBE Jargon Buster
GBE: Lectures: Flat roofs
The Victorian occasionally used flooded flat roofs to keep the space below, cool; the water has the ability to absorb the heat of the sun and by evaporation from the top surface, keeping the water cool and the building cool.
The Victorian steam railways used cast iron segmental water tanks on the roof of the water towers to recharge steam engine’s fuel and water tender, they had the benefit of cooling the space below.
The Austrian Architect Walter Segal who championed self-build construction in the UK invented the Waster Segal Method when designing a building for temporarily decanting his family whilst their house was refurbished.
It used a lightweight timber framed construction with flat roof which had 150 mm. high upstands and no overflows.
The roof could be transformed from lightweight to heavyweight by flooding it with water.
This flooded roof offers:
The water reservoir needs to be topped up by garden hose on hot or warm windy evaporative days.
See Also:
GBE Checklist
GBE Jargon Buster
GBE: Lectures: Flat roofs
GBE: Link: Walter Segal Self-build Trust
The New British Library on Euston Road, London has asphalt roofing laid on dense concrete secondary slabs laid to 1:40 falls on sleeper walls with cellular glass solar radiation resistant thermal insulation laid in a hot bitumen flood coat, directly on top of the concrete slab.
If the asphalt were applied directly on the concrete, the heat would be soaked up into the concrete, allowing the asphalt to cool quickly and set to harden.
Cellular glass acts as both solar radiation resistant thermal insulation and conductivity thermal insulation.
When asphalt is applied over cellular glass the heat from the asphalt tries to transfer into the insulation.
The heat only enters the surface of the insulation and does not penetrate further, holding the heat in the asphalt preventing it from cooling and keeping it liquid.
Hot liquid asphalt on a 1:40 fall runs down the slope and has to be pushed back up hill, often until it cools to the air and starts to set to harden.
See Also:
GBE Checklist
GBE Jargon Buster
GBE: Lectures: Flat roofs
Albedo is the earth’s brightness or tone (lightness-darkness) as seen by the sun.
Snow/ice capped polar-regions are light, sea is dark, land is light to dark; the overall effect was an albedo of 0.39.
Snow and ice capping to solar regions fluctuates seasonally at opposite poles and the albedo fluctuates with it.
Glaciers shrink permanently and have an affect on the Earth’s albedo.
See Also:
GBE Checklist
GBE Jargon Buster
GBE: Lectures: Flat roofs
GBE CPD: JQ37 Living Roof Specification
What are important are pitched roofs that accommodate renewable energy solar panels on the right slopes.
The panes may be between dormers and chimneys, ideally without being overshadowed by them.
Solar panels include:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Lectures: Elements: (27.2) Pitched Roofs
GBE Products:
GBE Robust Specifications
Flat roofs do not provide slopes for integrated panels.
However panels can be fixed on frames to set them at optimum angles to see the sun.
Panels on frames will create shading below the panels
Flat roofs with parapets can create shading nearest to the parapets.
Winter sun angles should be used to determine the distance for placing panels away from the parapet.
Even a panel laid flat on a flat roof will produce renewable energy, but less than the optimum.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Lectures: Elements: (27.1) Flat Roofs
GBE Products: Support systems for T15 ST, V10 PV, and T15 & V10 PVT
GBE Robust Specifications
GBE Lectures: Elements: (27.1) Flat roofs
Warm or cold flat roofs place thermal insulation below the waterproof membrane within the roof construction:
Concrete flat roof decks offer decrement delay.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Lectures: Elements: (27.1) Flat roofs
Warm or cold flat roofs place thermal insulation below the waterproof membrane within the roof construction:
Thermal insulation in timber or metal framed flat roofs needs to offer decrement delay.
Flat roofs should therefore use solar radiation resistant thermal insulation.
The combination of the following will suffer from over heating of rooms below:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products:
GBE Robust Specifications
GBE Lectures: Elements: (27.1) Flat roofs
Inverted roofs place the thermal insulation above the waterproof membrane and below ballast (paving slabs or gravel)
Thermal insulation in inverted roofs need to remain dry whilst immersed in rainwater, so needs to be hydrophobic and frost resistant.
Membranes are now available to try to keep the water off the inverted conductivity thermal insulation.
Expanded or extruded polystyrene are often used in inverted roofs because they are hydrophobic.
Expanded or extruded polystyrene are conductivity thermal insulation, which do not offer solar radiation resistant thermal insulation and decrement delay.
Concrete flat roofs offer solar radiation protection and decrement delay and are not likely to cause overheating below.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Lectures: Elements: (27.1) Flat roofs
Why have manufacturers started making water barrier membranes to apply over the inverted roof insulation?
Infrared thermography surveys of flat inverted roofs to check to see how well inverted roofs are performing.
Inverted roofs place the thermal insulation above the waterproof membrane and below ballast (paving slabs or gravel)
Thermal insulation in inverted roofs need to remain dry whilst immersed in rainwater, so needs to be hydrophobic.
Expanded or extruded polystyrene are most often used in inverted roofs.
Expanded or extruded polystyrene are conductivity thermal insulation, which do not offer solar radiation resistant thermal insulation properties not enabling decrement delay.
Timber-framed or metal-framed flat roofs without further thermal insulation do not offer decrement delay themselves.
The combination of timber-framed or metal-framed flat roofs and inverted flat roofing will suffer from overheating of rooms below.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Lectures: Elements: (27.1) Flat roofs
Just like ‘Build Tight, Ventilate Right’ a slogan that engages with building air-tight and purposeful ventilation.
The issues of overheating of lightweight construction could do with a slogan too.
Explanation: If you BUILD it LIGHT weight you must INSULATE it RIGHT to keep it SOLAR-TIGHT
Initially: BUILD LIGHT, INSULATE RIGHT, SOLAR TIGHT
Ultimately: BUILD LIGHT, SOLAR TIGHT
BrianSpecMan aka Brian Murphy 11th August 2015
Living roofs include intensive, green roofs or extensive, brown roofs.
Living roofs are usually flat but systems are available for shallow and pitched roofs
Living roofs can provide solar protection due to thermal mass:
Living roofs can provide evaporative cooling of water from soil or gravels and from some plant leaves.
Living roofs do not normally provide added thermal insulation (other than in the water reservoir layer); that is provided by the conduction thermal insulation needed by the underlying roof.
New methods of creating living roofs are being researched.
Living roofs can also provide solar shading.
Living roofs can also provide solar reflection to add to the albedo effect.
See Also:
GBE Checklist
GBE Jargon Buster
GBE CPD: JQ37 Living Roof Specification
GBE Lectures: Elements: (27.1) Flat roofs
GBE Lectures: Elements: (27.2) Pitched Roofs
Research underway:
New methods of creating living roofs are being researched now that may provide insulation within the build-up using hygroscopic plant materials benefiting from evaporative cooling.
Living roofs and solar panels are often good bedfellow, mutually supportive.
Solar panels are often mounted on frames setting them at an optimal angle; this allows the panels to have cooler undersides, helping with PV efficiency.
This arrangement creates shaded spaces behind and below the panels, with varying levels of light leakage at the edges and full sun in front of the panels.
Plants grown from seeds dropped with bird poo as fertiliser inhabit brown roofs.
Brown roof plants inhabit spaces behind, between and below panels.
Brown roof plants providing some shade, cooling effect and evaporative cooling to panels.
As long as plants do not overshadow panels they are complimentary.
See Also:
GBE Checklist
GBE Jargon Buster
GBE CPD: JQ37 Living Roof Specification
Panels should ideally all face south but south +or- 30 degrees is okay.
South-westerly is preferred south-easterly since the day warms the longer the sun has been around.
Ideally roof needs to have pitched roof orientation to match.
The roof’s pitch, i.e. angle of roof slope above horizontal, is important, ideally orthogonal (right angle) to the angle of the sun.
Since the angle of the sun varies all year and all day roof pitch is less important.
Even a panel laid flat on a roof will have generate renewable energy, but less than the optimum.
Panel spacing becomes important in solar farms one row must not overshadow the next row in winter.
Solar farms can be ground or roof based.
Tables exist showing percentage of output for different orientation and pitch, compared to optimum
If ST panels are for domestic hot water they need to face the sun all year but are likely to be most effective during summer and less so in winter.
Domestic hot water used at hand wash bowls, sinks and dual supply washing machines is used in non-domestic buildings too.
If ST panels are for space heating they need to face the sun in winter at lower sun angles so they should be placed more vertical.
It’s suggested these be attached to walls not roofs, and are suitable on the lower, steeper slope of mansard roofs.
Some argue there is insufficient heat in winter, but they can contribute beneficial heat as part of a pre-heat strategy.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: T15 ST Solar Thermal panels
GBE Robust Specification
BIRE is argued to be most appropriate, meaning solar panels are incorporated in building construction replacing roof coverings not sitting above them on support frames.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: T15 ST, V10 PV, and T15 & V10 PVT.
GBE Robust Specification
ST panels are likely to be enclosures with heat absorbing panels laying on thermal insulation in a sealed enclosure. ST panels glass should minimises external reflection, maximises sunlight entry, maximises internal reflection, to minimise heat egress, maximising performance.
The right insulation needs to be adopted then conducted and radiated heat from the hot panels should not pass through the bottom of the enclosure.
If the heat stays in the panel it won’t enter attics, rooms in roof or bedrooms below to add to overheating.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: T15 ST,
GBE Robust Specification
PVs are known to diminish performance when hot; they rely upon ventilation below the panel to keep them cooler.
BIPV panels are likely to be a simple panel replacing the roof tiling fixed over the battens and roofing felt.
This results in a tight ventilation labyrinth below the panel within the batten zone and above roofing felt.
Once PV panels are solar heated they will reradiate from their underside through roofing felt or BRM to heat up spaces below.
In order to overcome this heat build up, a number of options exist:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: V10 PV
GBE Robust Specification
PVs are known to diminish performance when hot; they rely upon ventilation below the panel to keep them cooler.
BIPVT panels incorporate ST panels below PV panels.
Once PV panels are solar light/heated they will reradiate from the underside into the ST panels to heat it up.
The ST panel will take the heat away to:
All of this will potentially offer some overheating protection to the space below the roof.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: T15 & V10 PVT
GBE Robust Specification
If the building, roofs, glazing and panels all face in the right direction to capture solar light/heat this helps to enable solar light/heat gains.
However the presence of land, buildings, trees or tall bushes, if they are high enough into the sun’s path, can block the sun’s rays.
If they are coniferous they are likely to block the sun’s rays in the summer and winter.
However if they are deciduous they shade buildings in summer, their leaves will fall in autumn, allowing ray’s to reach their targets in winter.
Sunlight passing through a tree canopy between breeze-driven fluttering leaves will fall as dappled light, which is regarded as delightful.
Dappled light reduces the amount of solar light/heat gain but can still cause intermittent glare.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Service Providers: Solar Access surveys
Sun’s rays beam down onto buildings hitting roofs, rooflights, roof windows, walls, windows and doors (glazed or not).
The heat of the sun lands on the outer surfaces of the opaque parts of the building or passes through the glazed parts falling on floors and walls of interiors beyond the glass.
What happens next depends upon their method of construction and materials at their external and internals surfaces.
These descriptions often confuse the general public, and it is worth a moment of our time.
I have see “Why would you use a cold roof, why not insulate?” in online forum.
Its not about insulation or not, its about where the insulation is positioned.
A cold, pitched roof will have the insulation at the horizontal ceiling.
Cross ventilation of the roof void will occur above the insulation in the attic space.
In winter with house heating on roof timbers and the attic space are therefore cold whilst the rooms below are warm.
A better description might be a Winter Cold Roof.
A warm, pitched roof will have the insulation at the sloping rafters.
The cross ventilation must occur above this insulation within the batten zone of the covering.
There would be no need for insulation at the ceiling level.
In winter with house heating on the roof timbers, the attic space and the rooms below are therefore warm.
A better description might be a Winter Warm Roof.
I just (04/08/2015) read in an eNewsletter from a fastener manufacturer:
“Traditional cold roof constructions are giving way to their opposite – the warm roof. This method of construction delivers a host of extra benefits and is now commonly believed to be the single best roofing option for the changeable climate of the UK.”
On the face of it that sounds possible, but UK mainstream construction does not understand the different properties of thermal insulation materials, i.e. Conductivity thermal insulation v solar radiation resistant thermal insulation.
So that statement can be wrong if you choose the wrong insulation types.
I just (04/08/2015) read in an eNewsletter from the same fastener manufacturer:
“In a recent article we revealed the many benefits of warm roof constructions and some of the many factors that need to be considered during the complex and delicate process of design and specification.
features and benefits of these superior Warm Roof Batten Fixings include:
They too do not understand the difference between Conductivity thermal insulation and solar radiation resistant thermal insulation.
Using any of the products listed, all conductivity thermal insulation, summer hot roof overheating will occur.
Whilst high decrement delay materials, not listed above, in their place, summer cool roof will occur.
“Environmental Awareness – A building installed with warm roofing will use substantially less energy than before, reducing carbon footprint”
I am not sure how they come to this conclusion, but:
“100% glazed facades without solar shading is like dating-site sex without protection: lots of it, a lot sexier, but bloody irresponsible” based on quote by Robin Nicholson
100% glazed does mean 100% air-conditioned, air conditioning has very high energy and carbon demands, generates heat waste, needs Voltage Optimisation and Legionella health and safety maintenance regimes in place and costs lots of money to run.
Very High OPEX, very High TOTEX
By others:
Passivhaus Webinar: Passive House Windows for Mediterranean Climates https://youtu.be/YHg4Pt1M5Tw via @YouTube via twitter @JMenendez
Letting Agents have begun to dictate architectural style of commercial offices to let, yet again.
On the basis that it’s easy for them to let 100% glazed facades and those who can, want an easy life.
In reality developers want the best net to gross ratio to charge for the largest rentable floor area; profitable low CAPEX
So developers prefer 25 mm glass instead of 300-500 mm of masonry.
It is allegedly desirable by tenants to have 100% glazed unrestricted views.
And in reality every tenant knows they suffer from:
The solutions include:
prisms to reflect sunlight but permit daylight.
tubular insulation that blocks high angled sun but permits low angled sun
Generating heat internally
Make the building look less attractive when they are all set at different heights and angles and if they are distorted or damaged.
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GBE Products:
prisms to reflect sunlight but permit daylight.
tubular insulation that blocks high angled sun but permits low angled sun
GBE Robust Specification
Heavyweight wall construction including:
Will soak up heat of the sun’s rays on outer faces of walls, the heat won’t reach the interior of the building and so has little effect upon the internal temperature.
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GBE Products:
GBE Robust Specification
In a recent HCA conference on Overheating
One speaker consistently used Rejection where I would prefer to hear Removal
He used:
I prefer:
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#HCAOVERHEATING
@HCAUK
However if walls are not masonry but timber or light metal framed with light claddings, then the sun’s rays will have a very different effect.
The same effect occurs on timber or metal-framed roofs.
Sun’s rays falling on the cladding will warm the cladding, depending upon the materials of the cladding it will then:
Reflect
Refract
Absorb
Convection
Conduct and/or
Re-radiate
…the heat outwards to air or inwards towards the core construction, attic or interior spaces causing overheating.
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Building Regulations require permanent ventilation to allow any moisture build up in attics to escape.
Eaves ventilation is a simple method it allows wind pressure to pass through the roof via eaves on both sides.
Ventilation needs to occur at the eaves and other perimeters: gables and parapets or abutments to ensure cross flow.
Ventilation may also be needed up the slope or at the ridge to address hot air rising.
Historically 1 to 3 finger wide gaps were used at eaves and verges.
Plastic parts were invented for predictable, dedicated and deliberate roof perimeter ventilation and costs rose.
Roofing underlays are designed to catch any rainwater entering under tile or slates, shingles or shakes.
Roofing underlays were made of bitumen impregnated natural fibre meshes and are heavy to carry to the roof.
BRMs are moisture permeable but rainwater and air tight, they are lightweight and easy to carry to the roof.
BRMs were introduced and considered as a low cost alternative to perimeter ventilation for moisture release.
However the second serendipitous benefit of roofing underlays and eaves ventilation is releasing heat, but this has been forgotten.
Ventilation for overheating roofs remains an important issue.
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GBE Products: H60-H69 Roofing Felts
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Various membranes are used to manage risks of condensation in construction in different ways, by:
For vapour-closed construction: (Common in UK design thinking and construction application)
For vapour open construction: (Common in EU design thinking and construction application)
All membranes need integrity at overlaps, junctions, abutments and if the construction is not layered then also at services interfaces.
Vapour barriers are notoriously badly sealed at services interfaces and in some cases only lapped at overlaps.
Air and wind tightness membranes are significantly better served by a comprehensive set of adhesives, sealants, tapes and grommets.
These accessories must all be as competent as the membranes, especially when subjected to daily and yearly cyclical overheating and cooling, moistening and drying cycles, all trying to destroy the integrity of those seals.
There is PhD research that suggests combining BRMs without eaves ventilation does not work.
There is PhD research that suggests BRMs are incompatible with bats roosting in roofs
The subject of a future GBE Issue paper.
In Europe they have developed ‘Intelligent’ airtightness and wind tightness layers whose moisture permeability varies with atmospheric conditions: in winter more closed, in summer more open.
So called ‘Intelligent membranes’ perform differently in different weather conditions:
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GBE CPD: P14 Airtightness of Building Elements:
GBE Products: P14 Air/Wind tightness systems, membranes and accessories
GBE Robust Specifications: JP14 Air/Wind tightness systems Specification & Guidance Notes.
The construction was water and water vapour permeable without damp proof courses and damp proof membranes and air leaky with airbricks, air leaky windows and under floor ventilation to:
Reduce risk of moisture vapour build up
Reduce risk of mould
Supply fresh combustion air to open fires and boilers
Supply cool air to food storage
Today with higher expectations of life style we do not like drafts:
Windows are more airtight to avoid drafts
Windows are more energy efficient to reduce down drafts and improve comfort conditions
Vapour barriers are commonplace (but should be added to old buildings with caution)
Breather membranes are essential if vapour barriers are used
Fitted carpets are commonly added (higher risk of asthma)
But hardwood and laminate flooring is also popular
Fridges and freezers are normal
Balanced flues are commonplace reducing drafts and improving comfort conditions
Increasing costs of heating and carbon reduction targets mean we need to be more energy efficient.
Airtightness measures will be applied but we need to be aware of these historic objectives, construction methods and materials when designing new interventions in old building to ensure we do not get things wrong.
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We are now encouraged to reduce air leakiness of construction which is the same as improve airtightness of construction.
The Building Regulations Approved Document L (‘Part L’) is woefully inadequate and so is the construction sector in delivering against them, generally.
The current pass level is 10, whilst a library with a better score of 8 is unusable in windy weather due to wind noise and papers fluttering and being blown off tables.
Passivhaus energy design standard requires a pass rate of:
Balanced flue boilers provide dedicated combustion air supply.
Fridges and freezers provide dedicated food cooling and freezing.
Well insulated and ventilated pantry has been
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GBE Products: Passivhaus and EnerPHit accredited products, Or Equivalent Products,
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GBE Code: Design Standards
GBE Code: Briefing Tool
By others:
The risk associated with increasing airtightness include:
Everybody that understands how to make high performance competent buildings knows they the building needs to do most if not all the work and services should do the bit the building cannot achieve.
When we fail to invest and build cheaply we become heavily reliant upon services.
When we build somewhere in between we insulate to a level that sees a significant reduction in energy demand and a low level services intervention.
Building fabric should be as competent as possible.
We should be using air and wind tight membranes, tape, sealants and grommets to maintain the integrity of membranes at changes of direction, junctions, boundaries, and service pipe penetration crossings.
Ventilation should be deliberate and purposeful, not unintended or fortuitous.
Passivhaus and EnerPHit require mechanical ventilation with heat recovery to be installed.
It is required to be low level, high performance, high efficiency, high heat recovery,
Mechanical ventilation with heat recovery works well in winter to reduce heating to close to zero.
MVHR must be easily visibly and appreciably controllable:
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GBE Products: P14 Airtightness systems
GBE Services: Passivhaus and EnerPHit MVHR
GBE Robust Specification
Simplification is desirable, simplification of service pipe penetrations through proofing membranes, avoiding the need for fire, acoustic and thermal proofing and air resistant grommets and sealants that may be prone to premature failure.
Avoiding out of sequence working and high risk of late arrival of services components interfering with completion of damp proof membranes, other proofing barriers, floor wall or roof construction and finishes.
Simplification is desirable, simplification in building walls, cutting chases, inserting conduit, rendering in, plastering over and painting walls and then feeding cables through conduit.
Skirting board convector heating: heating pipes running above the floor and in front of the walls, behind skirting covers with ventilation slots.
An alternative approach is to layer the construction and services so none of those complications occur.
Dado linings and hollow skirting and dado sections creating places for wiring outside of the wall thickness.
Timber framed walls with a second lining and batten zone inside of the wall creates a place for services without compromising vapour barriers and airtightness membranes.
The batten zones created need to be insulated or they become a route for thermal bypass and heat loss to space where it was delivered by the services.
Thermal bypass allows heat to move to other parts of the building where they may build up and lead to overheating.
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GBE Products: P20, T32 & T99 Skirting board convector heating
GBE Robust Specification
GBE CPD: Design to Reduce Waste
Hot or hot and humid spaces are beneficial for roosting bats and maternity roosts in particular.
Hot dry spaces will ensure that timbers never reach high moisture content levels and not become vulnerable to rot.
Hot spaces can be a source of renewable heat.
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GBE Products: Q53 Bat boxes, Bat entrances,
GBE Robust Specification
GBE CPD: Bats Beds and ZEDs
GBE Library: Bat and Bird Book
GBE CAD: 3D Cutaways
The labyrinth of battens and counter-battens below tiles or slates is a potential source of renewable heat
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GBE Case Study: Scottish project that extracted 8 degrees heat from below slates for preheating hot water in winter
GBE Case Study: TSB Retrofit for a Future project in Peterborough.
GBE CPD: TSB Retrofit for a Future project in Peterborough.
Historically tiling underlay was not used and roofs ventilated easily between the tiles, creating a breezy, dark but magically illuminated roof space.
Alas underlays were introduced to minimise risk of wind blow rain entering the roof and falling on the ceiling and insulation, instead the rain would be channelled to the eaves to discharge.
But roofs immediately change to airtight except for the continuous eaves 50 mm gap:
Additional measures need to be in place to deal with wind-washing at the eaves.
In Scotland softwood sarking boarding is applied over the roof timbers this made sure the stronger winds had little effect on the interior, the roofing underlay is applied over counter-battens over the softwood sarking.
I have not entered a Scottish roof space to feel if they are any cooler due to the decrement delay by the softwood, it may only have limited effect.
Additional ventilation of the attic is necessary because they overheat in summer.
Perimeter moisture ventilation potentially provides ventilation to remove the solar heat gains.
However this is not normally sufficient and more has to be done.
Ideally there is also ventilation at the ridge or on the slopes to release rising hot air.
But more importantly, sufficient ventilation is needed to deal with significant solar heat gains.
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GBE Materials: Softwood, Sarking, Battens and Counter-battens
GBE Products: P10 Dense wood fibre insulation board
GBE Robust Specification
The usual means to protecting cold water in storage tanks from frosts in winter in attics, is thermal conductivity insulation wrapped around the sides and over the top of the tank and no thermal conductivity insulation below the tank platform, allowing heat from the accommodation below to pass through the ceiling to the underside of the tank platform to warm the soffit of the platform and hence the tank and the contained water.
The thickness of insulation to tanks is usually insubstantial, compared to ceiling insulation.
There seems to be little interest in this insulation and the bulk of the water may justify it being ignored.
In reality the crucial part of this system is to insulate between the perimeter of the tank platform and the ceiling or the heat lost from the accommodation below just spreads out from below the platform to the whole attic space and cross ventilation will remove the heat.
This is a substantial source of heat loss from the accommodation below in winter, 3 times the area of heat loss through uninsulated loft hatches; and a substantial route for heat gain to the accommodation below adding to summer overheating.
If solar radiation resistant thermal insulation is required to the ceiling then the same insulation type should be applied to the perimeter of the tank platform and to the cold-water tank.
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GBE Checklist
GBE Jargon Buster
GBE Materials: Softwood, timber panel products
GBE Products: P10 cold water tank thermal insulation, tank deck perimeter insulation,
GBE Defect Analysis: Water storage tank Insulation
GBE Robust Specification
The usual means to protecting top floor accommodation from air leakage and heat loss to attics in winter, is thermal conductivity insulation between ceiling joists and over ceiling joists.
The risk is that no thermal conductivity insulation is installed above the attic access hatch, allowing heat from the accommodation below to pass through the hatch into the attic and cross ventilation will dissipate the heat.
This is a substantial source of heat loss from the accommodation below in winter, and a substantial route for heat gain to the accommodation below from summer overheating in the attic.
Attic hatches should also be weather stripped and latched to pull the hatch tight to the weather stripping and preventing air pressure buffeting lifting the hatch.
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GBE Materials: Softwood, timber panel products
GBE Products:
GBE Defect Analysis: Water storage tank Insulation
GBE Robust Specification
Access for inspection and maintenance of:
All these need walkways or crawl-ways installed above increasingly thick thermal insulation.
Storing possessions in the attic is commonplace and the structural design of roofs always requires the timbers to be sized to carry a 25 kg/m2 load.
Once attics have been insulated at flat ceiling level the storage space is lost.
There may be a temptation to a reuse the attic for storage in which case problems occur:
Products are now available to create raised access ways and storage platforms above thick insulation.
They include:
They solve one aspect of the possessions-in-situ problem:
The other aspect of the possessions-in-situ problem:
The stilts and the air space within section profile potentially make a thermal bridge through the insulation for 2/3rd of the insulation depth where it is warmer in winter keeping the heat in.
The stilts and the air space also provide a route down for solar heated attic air to penetrate towards the space below.
Plastic stilts with H profile maintain air paths within web spaces small enough that they are unlikely to get insulated when insitu, without a labour intense process.
50 x 50 x 5 mm stilts occurring at 1200 x 600 mm centres is:
50 x 50 mm softwood stilts may be:
Potential improvement to these systems include:
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GBE Checklist
GBE Jargon Buster: Repeating Thermal Bridge
GBE Materials: Softwood, timber panel products
GBE Products:
GBE Defect Analysis: Water storage tank Insulation
GBE Robust Specification
A common repeating thermal bridge is where e.g. stilts bridge a layer of insulation in an element.
As this occurs regularly throughout the element, i.e. the ceiling, this is deemed a repeating thermal bridge and must be accounted for in the U Value calculation for the element by making the appropriate corrections.
See Also:
Building Regulations Approved Document L1A.
Luminaires are often fitted to ceilings by cutting a whole in the ceiling and the luminaire is fitted flush with the bottom surface and projecting above.
Most luminaires are not thermally insulated to maintain the integrity of any ceiling thermal insulation, and can create a thermal bridge between the warm room below and the cold floor, attic or roof above.
Some luminaires are not airtight enclosures, sometimes deliberately to ensure there is no heat build-up in the luminaire which may reduce the life of the light-bulb or even the luminaire; connecting the space above and below.
Air passing through a luminaire will carry heat and moisture vapour, reducing the energy performance of the building.
For high performance buildings it is essential to reduce air leakage and heat flow.
Luminaires will occupy the space of insulation above the ceiling so extra insulation will be needed above the surrounding insulation.
Moulded airtight housings are made to fit over the top of luminaires to make them airtight and stop heat flow.
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In the last 5 years there has been significant improvement in the kit and software so analysis can now be more accurate, focussed, purposeful and intentional.
Normally IRT is most often used for detecting heat loss from buildings but can also be used for detecting heat gain.
IRT can also be used in:
IRT from outside looking at external faces of the building, shows heat escaping through the building fabric, analysis will look for hot spots and other anomalies.
External view heat loss IRT is normally carried out at night after the fabric is cooled down from solar gains to avoid misleading information. Examples:
Interpretation of IRT images can be misleading and analysis of the building materials at anomalies in daylight is essential to check materials and there relative emissivity.
In the wrong hands IRT can be a misleading method for testing for overheating.
IRT can also be used for detecting heat gain.
External view heat loss images taken in the day will be misleading for a number of reasons:
Normally IRT is most often used for detecting heat loss from buildings.
IRT from inside looking at internal faces of the building show heat escaping through the building fabric, analysis will look for cold spots and other anomalies.
IRT can also be used for detecting heat gain.
IRT can be used internally looking at internal faces of the building to show heat entering through glazing and building fabric.
The heat source for IRT internal surveys of heat gain is the sun.
Internal views may well show up shadowing by adjacent buildings and trees
A recent ‘tweet’ showed an internal view of an external door during the prolonged heat wave across Europe.
But the more revealing views would be:
These images are likely to show hot ceiling, hot walls, hot roofing.
This publication was written with the help of the ZCH so unlikely to be anything different here.
I found the same issues raised by ZCH repeated, but one item caught my attention.
Case Study 4 BRE test houses made to British and Swedish building standards.
My own analysis of the BRE survey:
Infrared Thermography:
Simulated heat gains:
Solar gains:
I remember an architect including a window in an attic, the contractor thought the architect was nuts, as they do.
Upon completion he asked the architect permission to include a window in every attic he builds in future, which of course was granted.
The opportunities and advantages of having a window rather than just a vent in an attic are numerous:
A room below a well-insulated attic should not suffer from excessive heat loss via attic window trickle vents in winter.
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GBE Products: L10 Windows, Roof windows
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Attic glazing could be a window, rooflights or roof window; it could be in gable walls, dormer or roof slope.
Ideally it would be placed on the northern slope or gable to maximise the daylight without sunlight.
If north is not available, choose eastern slope, dormer or gable for morning sunlight, to minimise solar light/heat gains.
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GBE Products: L10 windows, rooflights or roof window
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Windows, rooflights and glazed doors will allow some of the suns rays in, reflecting or refracting some light and heat.
Then the same effect as a greenhouse comes into effect the wavelength of light changes and heat will not readily escape back out through the same glass.
So the heat builds up making the space inside hotter.
In summer this is a problem, in winter this is an advantage.
Some of the built up heat will conduct back out through the glazing and opaque construction.
In addition to the change in light frequency keeping heat inside glazing in greenhouses and buildings:
High performance glazing often includes low emissivity glass, designed to reflect heat back into buildings.
The combination of overheating and low-E glass can exacerbate the problem to increase or persist longer.
One translucent insulating glazing/cladding manufacturer, with optional glazing performances, regularly downgrades the U Value and omits Low E characteristics in rooflights over spaces if there is no heating or cooling and insufficient ventilation and risk of overheating.
Design criteria is evolving as software sophistication enables it.
By others:
Passivhaus Webinar: Passive House Windows for Mediterranean Climates https://youtu.be/YHg4Pt1M5Tw via @YouTube via twitter @JMenendez
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GBE Products:
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Internal solar shading, inside of the glass, comes in a variety of forms:
Internal solar shading is effective at stopping summer sunlight, but they have already permitted the sun’s heat inside.
Internal solar shading ideally needs to be combined with ventilation to remove that heat.
This ventilation could be via the windows, doors, and trickle vents dealing with the problem at the point of source.
If heat is not lost at point of source, then spaces need cooling using passive, active or mechanical ventilation.
If at all possible and in all cases, we should be avoiding air conditioning.
One manufacturer makes reversible perforated blinds silver on one side black on the other:
Inward opening windows will clash with internal shading.
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GBE Products: N10 Reversible perforated blinds
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GBE Services: Shutter refurbishment and upgrades
Venetian blinds can be used effectively when contained within double glazed or double casement windows.
The blind is controlled room-side with cleverly included pull cables.
The blind is enclosed so never gets dusty and remains untouched, undamaged and of consistent appearance.
The blind provides choices between: privacy v view, darkness v daylight, shade v sunlight, coolth v heat.
If the blind is between casements the void could be ventilated to the exterior.
Encapsulated blinds do not clash with inward or outward opening windows
This is a multi-functional, cost effective solution that could survive value engineering, cost cutting and substitution.
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GBE Case study: Elizabeth Fry student accommodation, UEA, Norwich.
GBE CPD: L10 Windows
GBE Products: L10 Windows with encapsulated blinds
GBE Robust Specification
Once inside the sun’s rays will fall on the adjacent floors and walls within eyesight of the sun.
If the floors are made of any of the following then the floor will soak up the heat:
Floors will absorb heat over sun bathed surface areas, gradually warming from the exposed face into the thickness.
Heat absorption will continue until it reaches saturation point or it reaches any insulation layer
Heat absorption will stop when sun’s path moves out of eyesight of the floor area and there is no more heat to add.
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GBE Lectures: Elements: (23) Floors
GBE Products:
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Low thermal mass floor surfaces prevent heat absorption into the finish or substrate (base) to varying degrees and less advantage can be taken of solar light/heat gains.
Insulating screeds and insulating concrete or alternative concretes will not heat up as much as dense concrete.
Timber floors:
Carpets with or without underlays
Raised Access Platform floors hide the supporting thermal mass floors away from the sun’s rays.
Spaces below platform floors used as plenum spaces could exploit thermal mass if the ventilation is designed to deposit heat in the floor and purge it at another time, but that needs a level of coordination between disciplines, not often seen.
Suspended ceilings hide the supporting thermal mass floors away from the sun’s rays.
Spaces above suspended ceilings used as plenum spaces could exploit thermal mass if the ventilation is designed to deposit heat in the floor and purge it at another time, but that needs a level of coordination between disciplines, not often seen.
Steel trough permanent formwork soffits of composite steel and concrete floors prevent exploitation of thermal mass of concrete floors from below
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GBE Lectures: Elements: (23) Floors
GBE Products:
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The same applies to any adjacent sun kissed walls, if the walls are made of cement, lime, gypsum or clay render, plaster or finish they will absorb heat to varying degrees depending upon thickness and density and their substrate (background); however insulating or light plasters and renders will not absorb as much as dense.
If the wall is dry-lined with:
By virtue of the isolation framework, levelling battens, counter battens or dabs the board is substantially isolated from the background, dry-lining boards can absorb the heat but will not be able to pass it on into the substrate material so have restricted mid-term effect.
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GBE Jargon Buster
GBE Lectures: Elements: (21) Walls
GBE Lectures: Elements: (22) Partitions
GBE Products:
GBE Robust Specification
In social media I spotted an autoclaved aerated concrete block manufacturer noting the hottest day on record and smugly asking how many people complaining about the overheating were living in timber framed houses.
This needs taking apart and understanding, it might assume…..:
Conclusion:
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GBE Jargon Buster
GBE Lectures: Elements: (21) Walls
GBE Lectures: Elements: (22) Partitions
GBE Products:
GBE Robust Specification
Thermal mass works at different time scales:
Serviced heat stores are a separate set of solutions.
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GBE Jargon Buster
Heat has to be absorbed by the surface into the material and on into the thickness.
Thermal mass is not well exploited when it is small in area and thick.
Thermal mass is most effective when it is large in area and thin: walls, floors and ceilings are potentially effective.
Steel trough and concrete composite floors will not absorb heat from below
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GBE Jargon Buster
GBE Lectures: Elements: (21) Walls
GBE Lectures: Elements: (22) Partitions
Mid term elemental core thermal mass works at weekly, monthly or seasonal scale, progressively warming from winter to summer and cooling from summer to winter.
Heat has to be absorbed by the surface into the material and on into the thickness.
Over the year the average daily temperatures rising towards summer, will raise the temperatures of the element cores offering thermal inertia.
Opening windows to cool a space will only cool the air (if the outside air is cooler) once the windows are closed the exposed thermal mass will rewarm the space rapidly.
See Also:
GBE Lectures: Elements: (21) Walls
Long term external thermal mass works at inter-seasonal time scale.
Thermal mass of subsoil around a buried or bunded building is exploited; no thermal insulation is used between building and subsoil.
Thermal insulation is located beyond the subsoil so that heat can be stored in the subsoil around, behind, above and below the building.
The summer heat warms the building fabric and then passes through the floor and walls into the subsoil.
Heat can penetrate the right types of soil at about 1 meter per month; 6 months of heating will warm 6 meters of soil.
Insulation needs to surround and corral 6 meters of subsoil.
Ground water movement could remove the heat so that needs to be considered in the geometry of the insulation.
The geology (subsoil types) and topography (surface profiles) of some geographical areas (locations) are better than others:
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GBE Checklist
GBE Jargon Buster
GBE CPD: Zero Energy Building
GBE Products: E20 Below ground conductivity thermal insulation
GBE Robust Specification
Serviced heat stores are a separate set of solutions and come in a variety of formats
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GBE Jargon Buster
GBE CPD: Zero Energy Building
GBE Products: Heat store systems
GBE Robust Specification
When we had a domestic hot water cylinder fail it needed replacing the service agreement meant British Gas were called out to do their best.
The rather battered foam insulated cylinder was replaced with a new thickly insulated package with polyethylene sheath surrounding mineral fibre conduction thermal insulation and copper cylinder.
British Gas pays millions on endless TV advertising persuading us they are the right people for the job
The Engineer promptly informed us that he did not believe in thermal insulation on domestic hot water systems:
Pipe lagging or lack of it is another source of heat adding to the overheating problem.
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GBE Jargon Buster
GBE Products: Y50 Pipe insulation and Cylinder insulation
GBE Robust Specification
Hocketon Housing Project (HHP) has an effective Heath Robinson solution for domestic hot water.
HHP use a 1m3 plastic drink container as a heat store (usually contained in a metal cage for transport) with 300 mm conductivity thermal insulation surround to keep it hot.
The heat store being well insulated, avoids overheating the house (which is itself well insulated and could readily overheat if this heat was not well contained).
The water inside is the heat store is held at 40 degrees C the temperature the hot water will be used at, avoiding using more energy than necessary to heat the water to a higher temperature, and avoiding adding cold to be able to use it.
Investigate the heat source: no ST panels visible, PV & Wind turbine were added later, did the MVHR provide excess heat?
A separate pipe passes through the heat store, domestic cold water passes through the pipe, heat transfers from the heat store into the cold water, domestic hot water is passed along well insulated short pipes to the kitchen sink, ?washing machine?, wash basins and shower.
Pipe runs are not buried in construction (in or under concrete floors, under ceramic tiles, in blockwork walls) but adopting the layered construction approach.
Pipes are inside the spaces, boxed into ducts and very well insulated, accessible to repair, maintain and upgrade.
Pipes do not pass through vapour barriers, breather membranes, damp proof membranes, and thermal insulation; do not make air leaks or thermal bridges.
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GBE Jargon Buster
GBE Products:
GBE Robust Specification
GBE CPD: Hocketon Housing Project (HHP)
Heat stores have evolved from rocks to salt to phase change materials including waxes.
Today vessels with the right recipe of wax for optimum energy storage and release are used effectively.
They are added to energy management systems that monitor inputs (renewable heat and renewable energy) and demands (heating and hot water) and optimise the use each is put to.
Whenever there is excess heat to requirements it can be put into the heat store by passing the heat through pipes running through the storage media and transferring heat to the media.
When there is insufficient heat to match demands the process can be reversed and the heat drawn out of the storage media.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: T50 & Y21 Heat stores for central heating
GBE Robust Specification
As some begin to make competent buildings (Passivhaus, EnerPHit, Minergie and SuperE) the high levels of thermal insulation means heat loss is down to a minimum.
The next slice of the energy consumption cake that needs to concern us is hot water.
We need to insulate the domestic hot water pipes and vessels to similar levels of efficiency or their heat might tip the balance to create overheated buildings.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products:
GBE ToolBox: Passivhaus, EnerPHit, Minergie and SuperE,
GBE Robust Specification
Pipe lagging or lack of it is another source of heat adding to the overheating problem.
Historically (1960’s housing for example) hot pipes were buried in screeds and run in floor and attic voids without insulation squandering excessive amounts of hear where it was not needed, added to overheating, or was lost to the atmosphere.
In winter heat loss to the building fabric will potentially warm the interior of the building but just as easily warm the voids in the construction or the atmosphere.
In summer heat loss to the building fabric will potentially warm the interior of the building when you least require it.
Today pipe runs should not be buried in construction (in or under concrete floors, under ceramic tiles, in blockwork walls) but adopting the layered construction approach.
Pipes carrying hot water buried in construction lose heat into that construction, rather than deliver it the intended location.
The only exception to this is deliberate under-floor heating where the pipe is cast-in to transfer heat to the fabric effectively.
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GBE Jargon Buster
GBE Products:
GBE Robust Specification
Pipe lagging or lack of it is another source of heat adding to the overheating problem.
Domestic hot water pipes are often long runs between cylinder and bathrooms and kitchens in poorly planned house layouts.
These uninsulated pipe runs mean we run a lot of hot water from cylinders towards taps before the hot water arrives, as soon as the tap is turned off, the long run of pipe filled with hot water then looses its heat into the construction, ducts or voids or to the atmosphere.
Today British Gas Engineers replacing hot water cylinders are only obliged to insulate the first meter of pipe from the cylinder.
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When lagging is so labour intensive and costly it makes sense to consider alternatives.
When pipe insulation is often pre-manufactured to be small section and consequentially ineffective, alternatives should be considered.
Filling a duct space including getting around the back of the pipes is easier than lagging the pipe.
Filling the duct space offers greater insulation to resist heat loss,
Creating filled voids with no air movement and no eddy currents stops thermal loss to the voids and dissipation.
Every little loss of heat helps to minimise the cumulative overheating from many sources.
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The Construction shows where National and International Plumbing Apprentices of the year competitions occur, judge their skills on their pipes but never on their insulation work.
Donated appliances and materials are never the water saving or energy saving varieties or versions.
This may be indicative of the curriculum content and the skills acquired.
Multi-skilling of tradesmen is severely frowned upon by the skills councils, who control the curriculum of apprentices.
Multi-skilling is allegedly eroding the skills of any one tradesman.
And maybe it is all about protectionism looking after jobs?
They do not want multi-disciplined low skilled tradesmen out there.
But the system we have adopted does not control cowboy builders.
This does not prepare our workforce for reality and the enormous programme of work under Energy Company Commitment (ECO) if it has not been killed off and GreenDeal if it ever starts.
Our workforce is discouraged from carrying insulation with them when they know they will be opening up ducts, floors, walls and roof to find uninsulated pipes.
Instead they are expected to do their plumbing and electrics then close up the ducts ignoring uninsulated pipes and uninsulated voids that potentially create thermal bridges.
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Lagging in prevalent use in the 1960’s was made of loose woven hessian strips; it is ineffective as conduction thermal insulation.
There was very little of it (thickness) and it was labour intensive to wrap around a pipes if unrestricted and almost impossible if against a wall or floor, so the temptation to do very little of the pipe (length) was real.
If inspection happened it would only occur for those parts easily inspected, the vast majority remaining uninsulated.
In domestic buildings the specifications might well ask for insulation on domestic hot water and heating pipes but very few people police it and it does not happen.
Speculative housing developers know the pipes will not be insulated even if specified, they do not want to pay for something they are not getting; so they do not specify it, do not get it and do not pay for it.
The DIY market sells extruded hollow foamed plastic or rubber conduction thermal insulation for small size pipes.
And the pipe runs are predominantly inaccessible.
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In commercial buildings the specifications require insulating and identification labelling of pipes carrying heat or coolth amongst others.
Inspection is likely to happen so it might be fair to assume insulation happens, at least where it is on show and easily inspected.
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Since hot water and heating services are a significant source of heat that can contribute to overheating, it is recommended that they be designed to be more accessible, insulate able and upgradable, than has been common to date.
Service ducts behind walls or between serviced rooms are commonplace in offices.
Services ducts could become common in homes but they may be smaller to suit the nature and content of the services required.
Integer house at BRE campus has:
BedZED has:
Hollow voids created need to be insulated or they become a route for thermal bypass and heat loss to spaces where it was not delivered by the services.
Thermal bypass allows heat to move to other parts of the building where they may build up and lead to overheating.
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Adding conduction thermal insulation or acoustic insulation into ground and upper timber floors and accommodating services is simple enough except the physical action is fiddly.
For a long time now nylon meshes have been stapled to the tops of joists and slung between the joists creating a hammock to fill with insulation.
But if you watch anybody installing them your will observe a fault that develops as the job progresses.
The first few joist spaces work okay but as they progress across the floor they push down on the mesh to create the required depth in the current hammock, and the insulation in the first and subsequent joist spaces progressively rise above the joist zone.
What is happening is the nylon mesh is pulled and slips through the staples shortening the length one side of the staple reducing the capacity of the hammock.
When the softwood boards are relayed the insulation above the joists becomes compressed and ineffective.
Ineffective insulation allows heat or coolth to transfer more readily and overheating can happen more easily.
There are rigid scored and foldable sheets that can be stapled into place to support the required thickness of insulation without the risk of slipping and compressing, thus allowing effective conduction thermal insulation.
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Urban areas are characterised by:
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Trees provide shading from the sun’s heat and can cool the air below the canopy.
There may be an element of evaporative cooling below the tree canopy.
Car parking below trees allow the cars to avoid overheating
Seating below trees provides respite from oppressive heat
Trees in gardens can shelter a south and west elevations and patio to avoid hot spots
Trees in large numbers helps to increase the extent of these advantages
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BRE has a test laboratory that includes hear sources representing humans; they are black-coated cylinders with open top and bottom and 100 watt light bulb mounted internally.
Other information sources say a human is equivalent to 80 watts and a bald headed male is 100 watts.
The amount of heat varies according to size, age, health, amount of clothing and activity:
A young couple moved into a Passivhaus and found it was a little cool so they bought a dog/had a baby: sorted.
Canary wharf towers with 10,000 occupants generate 1,000,000 watts of heat, let alone IT equipment and Solar gains.
Every day living requires use of many appliances, some essential others non-essential, some continuous and others intermittent, some on or of and others on sleep mode.
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See Also: All rooms, Living rooms, Kitchens/Utilities, Bathrooms
Computers
Monitors:
Printers/Plotters
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Televisions generate heat when on (say 8 or more hours of the day)
Video, DVD, Blue ray, Set top boxes, recorders,
Digital radio: is high-energy consumption
Wood burners:
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Fridges and freezers
Cookers are intermittent, powerful and used all year
Microwaves use less energy and generate less heat than cookers.
Kettles generate short bursts of heat and intense steam,
Clothes Tumble Dryers:
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Baths & Showers:
Toothbrushes:
Hair dryers:
Hair curlers/straighteners
Under floor heating:
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When BedZED’s ZEDfactory analysed the future climate and the necessary response to it they made recommendations and a checklist of actions, they included:
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Hot and warmer air rises and colder air falls.
Eddy currents can be formed where the hot and cold replace each other.
Living rooms which have stairwells rising to upper floor landings provide the opportunity for warm or hot air to rise and escape from the room to the landing.
In summer upper floors are likely to be warm or overheating due to radiant solar gains passing through the roof into attics and upper floors.
Hot air entering through lower floor windows can rise in the room and escape up the stairwell to add to the landing and upper floor overheating.
In winter colder air in the upper floors can leak down to the lower floor via the stairwell to create cold draughts and thermal discomfort for the occupants.
Introducing door, screen, partition or insulated curtain lobbies around stairwells can help to overcome heat or coolth transfer up or down.
Adding rooflights or windows at the upper floor landing can release overheated air from landings, help with cross ventilation when used with upper floor room open windows and open doors between rooms and landing.
Once the upper floor landing heat has been released via windows or rooflights on the upper floor, heat from the connected spaces on the lower floors can rise up the open stairwell and be released.
The action of warmed air on lower floors escaping to upper floors and out through rooflights or windows or vents is known as the stack effect.
Stack effect gets is name because it mimics the effect of a heat rising from a fire in the grate up and out of the chimney stack.
Stack effect is reliant upon the warmed air rising being replaced with more air which can be warmed and rise.
This effect can be used to cool the whole house in summer.
Conversely heat loss in winter from those rooflights and upper floor windows can cool the upper floors and cool air can fall through the stairwell and be replaced by warm air from lower floors.
Rooflights and windows over stairwells should ideally be very good insulators for winter and if required be protected with solar shading in summer.
Porches project outside the house volume
Lobbies will be within the house volume and may be inside of the front or rear door
Porches and lobbies protect the front and rear doors from weather and wind
Porches on the sunny side of the house can capture heat of the winter and summer sun and feed it into the house
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Recent statistics indicated that 80% of UK conservatories are heated
This suggests that conservatories are either:
Conservatories often have no roof ventilation and some side ventilation or just the doors
Building Regulations require that conservatories be separated from the house by doors and windows
One solution is to glaze the conservatory with translucent multi-walled insulating plastic glazing that:
Another solution is to decorate the adjacent room with a mural of the interior of a conservatory with the views.
Jacuzzis in Conservatories
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Balconies in the heating season are often cold and damp.
Pigeons or gulls often overtake unused balconies.
Balconies are often used as storage for bikes and other durable goods.
Glazing them in can make them more useful as extra living space and more useful as storage space.
Glazing in a balcony on the south and southeast sides may lead to overheating.
Glazing in can be with sliding glass/sashes that will change the character of the balcony and restrict airflow
Glazing in with hinged glass panes that move aside retains the character of the balcony and avoids risk of overheating
Balconies could be used for secure external clothes drying, but blustery wind conditions may make this impractical.
Glazing in will help with reducing blustery wind conditions and encourage balcony clothes drying removing the risk of humidity adding to the overheating.
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Especially in urban and high-density developments, inadequate provision is made for clothes drying.
Today we do need secure provision because of the risk of theft; internal drying does that for you automatically.
EcoHomes does and Code for Sustainable Homes did included requirements for external and/or internal clothes drying.
Internal drying options includes lines hung over baths, not ideal by any means if you want to bathe at the same time.
Internal clothes drying will add to internal humidity that will add to any overheating, so ventilation becomes important or external drying needs to be considered.
Enclosed but ventilated balconies can provide secure external weather protected ventilated clothes drying.
Sunspaces can also offer secure external weather protected ventilated clothes drying.
An alternative for tight sites is to include a small portion of their storage area as a dedicated internal clothes drying and airing cupboard.
The finishes must acknowledge the wet clothing that may drip and will evaporate into this space.
This cupboard heated by radiator like a bathroom towel radiator, with controlled ventilation and heat recovery.
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Sunspaces have been used:
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The sunspaces have high thermal mass materials and finishes to floor and wall between sunspaces and house
High performance triple-glazed Low-E windows to the house and double-glazed Low-E glazing to the sunspace
They create an inside-outside space for outdoor activities in sheltered conditions
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The sunspaces have high thermal mass materials and finishes to floor and wall between sunspaces and house
High performance triple glazed Low-E windows to the house and double-glazed Low-E glazing to the sunspace
They create an inside-outside space for outdoor activities in sheltered conditions
The sunspaces are mostly successful however the top floor flats do have a problem with overheating:
Precast concrete roof provides the decrement delay needed to stop heat entering through the roof
The sunspace does not have solar shading at the very top and this leads to overheating in the sunspace
This also leads to solar penetration of the upper windows and overheating of the top floor flat.
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At Integer House the sunspace is more like a greenhouse in a garden with garden paving and gravels between inside.
The wall between the sunspace and the house is timber weatherboarding so there is significantly reduce thermal mass on show to exploit.
The house windows may be double-glazed and sunspace single glazed and aluminium framed reducing efficiency.
The glazed slope has internal louver blinds that are digitally controlled and when it started, controlled by and at the whim of visitors to the website via the Internet.
There is no occupant so there is no heat-capturing regime in place.
The top floor of the house has one room open to the sunspace it overheats and there is no way to insulate it from the sunspace so there is no escaping the overheating other than to not use the space.
Most recently the sunspace glazing has been changed to orange coloured PV glass
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Initially tenants did not understand the sunspaces but once moved in and exploring how to use them, they found they did not want to live without them.
At Swaffham the sunspace is a reception, atrium, café, exhibition area.
There is no separation at the line between the sunspace and the offices; it is broken, open, with corridors leading to spaces on the north side on all levels.
The line between offices and sunspace is expressed timber framed and plasterboard, so there is no thermal mass on show to exploit.
It is not known if the partitions next to the atrium are conductivity or radiation thermally insulated.
The partitions between the office space and sunspace may or may not be insulated and if insulated may have conductivity thermal insulation but not likely to have solar radiation resistant thermal insulation.
The sunspace is glazed with aluminium framing reducing efficiency, on timber structure.
The glazed slope has external translucent roller blinds that are automatically controlled responding to sunlight.
There is no heat-capturing regime in place.
There is no ventilation opening for heat removal and introducing of coolth in replacement air.
The upper floors are exposed to the sunspace it overheats and they overheat, there is no way to insolate them from the sunspace so there is no escaping the overheating other than to not use the spaces.
This building was designed to fail or value engineered, cost cut or substituted and built to fail.
When the building funding dried up EEDA East of England Development Agency moved in and fitted air conditioning.
An environmental burden from then onwards.
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Keyworth House has an 8 storey atria on the south side, 100% glazed in full view of the sun with no solar shading.
The glazed wall is aluminium curtain walling with fixed glazing and low level 2 replacement air intake vents and revolving door, there are no obvious air vents in the top of the glazing.
Backing onto the atrium is 8 storeys of office spaces that are used as staff rooms, computer design suites, design studio and toilets.
The exposed wall face to the atrium is plasterboard spandrel panels and glass windows; the floor is ceramic tiling, so negligible thermal mass on show to soak up the heat.
These office spaces have open able windows on to the atrium with internal sun-blinds.
A corridor links these offices with classrooms on the north side, it has 6 storeys of class rooms and 1 storey of studio/exhibition space extending up to the 8th storey.
The Atrium is filled with mid day solar light/heat and the highest levels overheat since there is not obvious means to loose the heat at the top.
The offices facing the atrium are bathed in solar light/heat with internal binds that will heat up and the only mean to lose that heat could have been to open the windows to the atrium, but there is no coolth there.
The atrium heat passing though the opaque and glazed wall to the atrium also warms the offices.
The open able windows to the atrium can only introduce hot air to the rooms; they have exposed thermal mass to floor soffits that is insufficient for the purpose.
These rooms are unusable for all intent and purposes in sunny weather and are only used by the most determined students and lecturers.
Doors from these offices to the corridor can be left open to alleviate the overheating by thermally polluting the corridor and potentially on to the teaching spaces beyond on 6 floors and studio/exhibition space on top floor.
This building was designed to fail or value engineered, cost cut or substituted and built to fail.
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Penny Poyser’s TV series ‘No Waste Like Home’
Recent purpose made student accommodation had adopted an approach akin to Hotel access cards on locks:
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Historically the RIBA discouraged Architects from revisiting building to review their performance, thus avoiding the risk of being sued for incompetent buildings.
This approach meant architects and engineers could design poor performing buildings, never find out and continue to repeat their failings.
Government Soft landings is better known as Soft landings.
Yet another attempt by Government to get better results from the construction industry, where facilities management is now seen as a major contributor to building sustainability.
Mechanical & Electrical contract specifications increasingly call for bespoke computer controlled Integrated Building Energy Management Systems (IBEMS) that often are not handed over adequately to the Facilities Managers.
Facilities Managers (FM) are often not qualified to operate sophisticated IBEMS and often resort to turning the controls off and running the buildings manually.
Soft landings was introduced to create a prolonged hand over period where the designers:
Coincidentally Building Information Modeling/Management (BIM) is FM driven, requiring better computer models of the buildings to be handed over with built in O&MM information.
COBie is the FM classification system required in BIM to deliver the FM information in a consistent format.
Soft landings should include Post Occupancy Evaluation to check if the users are satisfied with conditions.
BSRIA created Soft landings.
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(GBE BRM ’14 – ‘15)
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A building being created for a software house, they went bust close to completion of construction, leaving a constructor with a building needing to be completed and a building needing a new tenant or owner.
Suffolk County Council took on the task and completed it as their-own new head quarters, but needed to remodel it to suit their needs.
The Facilities Manager is being proactive and finding solutions to problems.
One side of the fully glazed building overheats due to solar light/heat gains; whilst the other side is cold.
Exploiting the under-floor heating pipes they now take the heat from the south hot side of the building, absorbed into the floor, collected by under floor heating pipes working in reverse and move it to the cold north side of the building, heating that side, keeping more of the staff happy more of the time.
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The demand for energy and resource efficiency has lead to the adoption of communal and district heating in domestic developments.
The challenges include:
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The demand for energy and resource efficiency has lead to the adoption of combined heat and power in communal and district heating in domestic developments.
Fuel is burned to generate heat to turn water to steam to drive generators to create electricity.
The heated steam is recycled but in many cases it’s cooled back to hot water then reheated to steam.
The cooling back to water wastes energy and CHP combined with Communal or District Heating uses the waste heated steam or waste heated water to circulate to buildings with a heating demands and replaces burning more fuel.
In the heating season excess heat can be put to good use for room heating and domestic hot water.
However in summer the demands are lower, no heating needed but domestic hot water still required
The boiler is usually in a separate energy centre so overheating of housing units is not normally an issue.
Excess heat generated in summer risks being wasted or dumped.
Options exist for using the excess heat
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Heating pipes are distributed through blocks of flats via vertical ducts usually within communal stairs and/or horizontal ducts in communal corridors above ceilings.
Following an immature standard: Heating flow pipes deliver at 80 degrees C and return pipe at 50 degrees C.
The 30 C degrees of heat has to be lost to the building, predominantly via radiators and inevitably from insulated and uninsulated pipework.
Radiators need to be very efficient at delivering heat to the rooms.
Insulation to pipework, bends and valves need to be continuous, competent and efficient at preventing heat loss.
Ideally the duct needs to be insulated, not just the pipes, not providing air in which eddy currents can move freely to dissipate heat
Insulating ducts as well as pipes is not seen as normal practice and unlikely to happen.
In reality the insulation to pipes is insufficient for 30 C degrees and these loses heat the horizontal and/or vertical ducts.
Pipes below floors lose heat to the floor/ceiling voids/ducts and they then heat the floors above.
Communal corridors are often long and connect to stair cores with self-closing fire doors, so cannot lose heat readily and suffer from excessive over heating in winter.
Hold-open devices on fire doors with automatic release on fire alarm, may help to release this heat
The heat from corridors may be sufficient to heat some unheated flats.
Ventilating vertical ducts at the top and bottom to loose heat is possible, horizontal ducts are more difficult.
Smoke ventilation provision is often adopted to help release excess heat.
Performance specification requiring the return to be no more than 50 degree C means the installer will remove, or not add, all insulation on the return pipe to loose as much heat as possible in the corridors.
But we should be designing systems that do not deliver more heat than is needed and never have to loose heat.
Possible solution to this problem:
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A control interface within a home that comprises a heat exchanger, which transfers heat from the community heating network to the individual home’s internal heating and/or hot water distribution system.
These deliver heat at 80 degrees C in the flow pipe and leave the house at 50 degrees C in the return pipe
This is a permanent source of heat for heating and hot water in winter and heat for hot water in summer.
This is a permanent source of heat contributing to potential overheating.
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In some cases it was felt necessary to heat communal stairwells and corridor spaces.
Under floor heating in screeds or below ceramic tiles were adopted leading to overheating.
But as was described before, communal distribution pipes are already providing heating to the corridor slabs
Under floor heating is unnecessary.
Heat loss from flats may well be sufficient to heat communal corridors and stairwells.
Solar light/heat gains to glazed stairwells should be sufficient to heat stairwells on sunny days in winter,
Solar light/heat gains to glazed stairwells will overheat in summer and should be avoided.
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Compartment walls between communal corridors or communal stair cores and houses, flats or maisonettes
These walls may have an uninsulated cavity; they offer an escape route for heat, through one leaf into the cavity.
The cavity will then act like a chimney and the heat rises to the highest point, then warms both leafs of the wall and then heat spaces beyond, leading to potential overheating.
A potential solution is to fully fill the cavities of these walls with convection thermal insulation to stop air movement.
This potentially conflicts with acoustic insulation function of these walls.
Choosing the right insulation material that deals with both thermal and acoustic performance is the answer.
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Passive ventilated offices are an ambition for designers but a nightmare for services engineers
Its not rocket science either.
Atria offer stack effect ventilation and cooling opportunities if there are:
Open plan offices adjacent to the atria need to have windows at the building perimeter.
Stand back and hey presto it works.
Alas in numerous cases it did not, some of the floors worked and others stayed static leading to humidity, stale air and overheating.
Mechanical Engineers do not like passive ventilation of open plan offices with atria and insist upon mechanical ventilation creating a permanent energy demand.
Upon investigation the lowest floors do benefit from the cooling stack effect but as their heated air enters the atria it passes the edges of the floors above and traps the hot air on those floors preventing it from entering the atria.
There is a simple solution that probably needs active Building Energy Management System BEMS to control it.
The perimeter vents or windows will probably be opened wide by the occupants, if they are all set the same then the problem occurs, the top floors will open their windows wide and nothing happens no cooling effect.
What is needed is for the windows to be regulated so the top floor has the windows open widest and the bottom floor open least, the middle floor open to a middle setting.
Now all three floors can compete on level terms for the cooling effect of the atria stack effect, all three sets of hot air escape from the floor edge, none overpowering the other.
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There is a reasonable assumption that overheating can be solved by ventilation.
This is on the basis that glazed area solar heat gains are greater than potential heat loss through building fabric and glazing; removing heat in the air could help, but this ignores:
Ventilation can either be passive (preferred), active (preferred), mechanical (if you have to), or (at worst) air conditioning.
This assumption may be true but with increasing services energy costs we have to focus on getting buildings to do most, if not all, of the work themselves.
“Fabric First” & “Build Light, Insulate Right, Solar Tight”.
Only then should services be employed to deal with any shortfalls that cannot be met by competent and effective building fabric alone.
“Build Tight, Ventilate Right”.
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In the UK we are regulated to reduce energy demand, by Building Regulations Approved Document L (Part L).
Part L focuses on thermal conductivity of floors, walls and roofs:
Sadly our regulations are wholly inadequate to:
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The above issue relate to keeping heat inside, cold outside and apply to the winter heating season.
What UK Regulations fail to engage with is summer (cooling season) solar light/heat gains and risks of overheating.
Sadly our regulations are wholly inadequate to:
Solar light/heat gain through opaque building fabric
Radiation resistant thermal insulation
Decrement delay.
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There is provision within the Building Regulations Approved Document L to use Standard Assessment Procedure (SAP) software and Appendix P.
We are informed that this was not intended to check for overheating, but it is often assumed to do so and is used for this purpose.
It requires a cost benefit analysis to justify change and this can be avoided or fudged to ignore the issue.
Passivhaus Planning Package (PHPP) software is capable of doing an overheating check, but it is not as robust as it might be hoped.
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(extract from NHBC/ZCH Understanding overheating Where to Start NF44)
The overheating check in SAP is used to assess the risk of overheating and demonstrate compliance with Criterion Three (limiting the effects of solar gains in summer) of Approved Document L1A.
The SAP tool considers the effects of solar gains, external temperature, geographic location and the thermal properties of the construction itself (for instance thermal mass).
However, the tool has limited ability to deal with the complex interactions between the contributing factors that are described in this guide and, being a compliance tool, it does not offer the designer any diagnostic information to remedy a ‘high risk’ of overheating.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Equations
GBE Data Sets
GBE Calculators
GBE Toolkit
Heat movement, heat loss and its reduction works in a number of different ways, some uses conventional thermal insulation and others use other material properties:
Virtually all insulation materials in the UK market have this characteristic, but with varying levels of performance.
Properties needed include:
Material include:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: Aerogel, VIP,
GBE Robust Specification
Most insulation materials in the UK market do not have solar radiation resistance in abundance.
Those that do have varying levels of performance.
Properties needed include:
Materials include:
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GBE Checklist
GBE Jargon Buster
GBE Products: P10 Dense wood fibre, cellular glass
GBE Robust Specification
Some insulation materials in the UK market have this characteristic and have varying levels of performance.
Properties needed include:
Materials include:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products:
GBE Robust Specification
Solar radiation resistant thermal insulation around a lightweight building will reduce solar heat gain keeping interiors cool in summer.
No solar radiation resistant thermal insulation in lightweight construction, permits summer solar light/heat gain/entry.
Whilst solar radiation resistant thermal insulation has conductivity insulation characteristics as well, these are not as effective as conductivity-only thermal insulation; but the thicknesses required for solar radiation resistance will exceed the thickness required for conductivity.
If you combine solar radiation resistant and conductivity insulation, in lightweight construction, then use more solar radiation resistant and less conductivity insulation; not the other way round.
Conductivity thermal insulation around a lightweight building, lightweight roof or heavyweight building will reduce heat loss keeping interiors warm in winter.
Solar radiation resistant insulation around a lightweight building or lightweight roof will reduce heat loss keeping interiors warm in winter.
Solar radiation resistant thermal insulation is more expensive than conductivity thermal insulation and you need more of it, for a competent building.
Conductivity thermal insulation without solar radiation resistant thermal insulation in lightweight construction is incompetent construction.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Radiation resistant thermal insulation, conductivity thermal insulation
GBE Robust Specification
On the assumption that my opinion is correct:
Conductivity thermal insulation without solar radiation resistant thermal insulation in lightweight construction is incompetent construction.
As designers begin to know this and ignore it, they too become incompetent.
Quantity Surveyors that ‘Value Engineer/Cost Cut’ away from competent, with client or project team approval, take no responsibility.
Design and Build or General contractors will continue to substitute or surreptitiously substitute and make your buildings incompetent, don’t sign off stage payments (equals approval of surreptitious substitutions) without checking first.
Consider using a Declaration of Conformity signed by the Contractor/Subcontractor’s Directors, that they have not substituted conductivity insulation in place of solar radiation resistant thermal insulation.
Consider Building Performance Contracts with draconian fines for incompetent buildings.
See Also:
CBx Seminar on Energy Performance Contracts
GBE GBS A90 Appendix DofC Declaration of Conformity
“There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man’s lawful prey.”
John Ruskin (1819-1900)
Don’t compromise on CAPEX and suffer at the hands of OPEX, TOTEX is the answer.
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GBE Jargon Buster
GBE Calculators:
Can Facilities Managers manage overheating if they do not have data?
Many companies are now offering better information from your buildings operation so you can identify where for example:
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GBE Checklist
GBE Jargon Buster
GBE Products: Monitors, Meters, Controls
GBE Servers: Energy Data Service Providers
GBE Robust Specification
UKGBC & Innovate UK event Measuring Energy and Indoor Air Quality Innovation Showcase
Combining no solar radiation resistant thermal insulation with ample conductivity thermal insulation in the same lightweight building or lightweight roof construction will lead to solar heat getting in, not being able to get back out, leading to overheating.
QED.
GBE believes this to be the primary cause of the majority of cases of summer overheating in top floor lightweight roof and wall construction accommodation.
There are many other secondary causes of summer overheating that exacerbate the primary cause.
Fiddling with the secondary causes won’t help until you have fixed the primary cause.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Radiation resistant thermal insulation, conductivity thermal insulation
GBE Robust Specification
Warehousing is vulnerable to solar heat gain and overheating.
Few will see the overheating because it remains at high-level due to thermal stratification.
Ventilation at high level can remove it in summer.
In winter ventilation equipment at high level can push hot air downwards and circulate the air, neutralising the stratification.
Simple fans can achieve this when ceilings are not high.
Warehouses are usually made of lightweight steel frame and thin metal cladding with the wrong choice of thermal insulation type and material.
Glass wool was swapped for stone wool for fire performance in warehouse construction, now it needs to be swapped for:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation, fire insulation
GBE Robust Specification
Food warehousing kept at lower temperature is particularly vulnerable to this solar heat gain problem.
Nobody will see the overheating because it is neutralised by the chilling equipment working all year round and working harder on sunny days, with this insulation strategy.
Food warehouses are usually made of lightweight steel frame and thin metal cladding with the wrong choice of thermal insulation type and material
Glass wool was swapped for stone wool for fire performance in warehouse construction, now it needs to be swapped for:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation, fire insulation
GBE Robust Specification
Retail warehouses are vulnerable to this solar heat gain problem.
Retail warehouses are usually made of lightweight steel frame and thin metal cladding with the wrong choice of thermal insulation type and material.
Glass wool was swapped for stone wool for fire performance in warehouse construction, now it needs to be swapped for:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation, fire insulation
GBE Robust Specification
Food retail will have areas of cooler air adjacent to chilled and frozen food cabinets
Food retail will have cold storage areas back-of house
Pitched or flat roofs with the wrong insulation strategy will permit solar heat gain.
Nobody will see the overheating because it is neutralised by the chilling equipment working all year round and working harder on sunny days, with the wrong insulation strategy.
Glass wool was swapped for stone wool for fire performance in warehouse construction, now it needs to be swapped for:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation, fire insulation
GBE Robust Specification
If there is mid-term thermal mass in the core of the roof above habitable top floors then this may protect the spaces from overheating, as long as night-time cross flow and/or passive stack ventilation purging is possible, to cool down that thermal mass.
Sunspaces without solar shading at the south side of buildings connected to top floor accommodation can contribute to overheating and may make cross ventilation more restricted.
If there is internal short-term thermal mass between attic spaces habitable space below with ventilation in the attic and habitable spaces below then overheating may be reduced or alleviated.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: K11 high thermal mass boards forming attic floor above insulation
GBE Robust Specification
GBE Case study: BedZED.
GBE Lectures: Pitched roofs
The plastic thermal conductivity insulation sector promotes reduced thickness to achieve required U values.
And we are all too keen to adopt these reduced thicknesses in our building elements.
Thin conductivity insulation means thin walls so we can continue to build with roughly 300-400 mm walls.
Thin external wall construction allows developers to squeeze more houses on a site.
This reduced thickness is all about conductivity resistance and ignores solar radiation resistance.
Thin conductivity insulation has been restricted to foamed plastic insulation but other materials are increasingly available in the market including:
Conductivity thermal insulation is acceptable in heavyweight construction.
Solar radiation resistant thermal insulation is essential in lightweight construction.
Lightweight construction needs to be thicker to accommodate solar radiation resistant thermal insulation
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation
GBE Robust Specification
GBE Lectures: External walls
Glass wool insulation used for conductivity thermal insulation currently has a large market share it is cheap.
There will always be a temptation to use cheap insulation, but beware the risk of overheating.
Plant based fibre insulation used for solar radiation resistant thermal insulation currently has a small market share it is expensive.
You may be tempted to use a combination of conductivity and solar radiation resistant thermal insulation to reduce costs.
If this is the case then sufficient solar radiation resistant thermal insulation to achieve the decrement delay, should be determined first, then the remaining thickness of conductivity insulation, in combination, to achieve the required U-value.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation
GBE Robust Specification
GBE Equations, GBE Datasets, GBE Calculators
GBE Lectures: External walls
GreenSpec Case Study: bere:architects’ Larch House is the UK’s first zero carbon (code 6), low cost, Certified Passivhaus, built as prototype social housing and launched at the 2010 National Eisteddfod for Wales.
The characteristics of the different insulations include:
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation
GBE Robust Specification
GBE Equations, GBE Datasets, GBE Calculators
GBE Lectures: External walls
Firstly do not use hydrophobic conductivity insulation (mineral wool) in:
Unless you carryout hydro-thermal moisture movement analysis over time
Research opportunity: if mineral wool (hydrophobic) and plant based (hygroscopic) insulation are used in the same system, will the moisture vapour or condensate migrate towards the hygroscopic and be absorbed into the fibres?
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation
GBE Robust Specification
GBE Equations, GBE Datasets, GBE Calculators
GBE Lectures: External walls
If the solar radiation resistant insulation is in the outer position and the conductivity thermal insulation is in the inner position:
If the conductivity insulation is in the outer position and the solar radiation resistant thermal insulation is in the inner position:
If the solar radiation resistant insulation sandwiches conductivity thermal insulation:
If the conductivity insulation sandwiches solar radiation resistant thermal insulation:
Conclusion:
Research Opportunity:
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GBE Checklist
GBE Jargon Buster
GBE Products: P10 Solar radiation resistant thermal insulation
GBE Robust Specification
GBE Equations, GBE Datasets, GBE Calculators
GBE Lectures: External walls
GreenSpec Case Study: bere:architects’ Larch House is the UK’s first zero carbon (code 6), low cost, Certified Passivhaus, built as prototype social housing and launched at the 2010 National Eisteddfod for Wales.
Modern Methods of Construction (MMC) tend to include:
Can include: all services, fitted furniture and equipment
More skilled workers are required in the factory in weather-free, controlled temperature, comfortable, ergonomic working conditions.
Processes include: Line Production, Lean Production, Just In Time (JIT) Logistics, KanBan
Benefits include: greater productivity can occur with less waste and packaging.
Installing, fitting, testing, calibrating, commissioning of services can be done in the factory
Different skills are needed on site for handling, assembly, final connections testing and commissioning and final closing in finishes.
There is a preoccupation with thin construction and the MMC world are seduced by this issue as well.
Structural Insulated Panel Systems (SIPS) are an example of thin MMC.
Thinner conductivity thermal insulation usually comes from stronger k-values requiring less thickness to meet U value targets.
Stronger k-values usually come from petrochemical based conductivity thermal insulation including:
Structural, conduction thermal insulation bonded to Orientated Strand Board (OSB) sheer resistance planes; all you need is a cladding and a lining and all is well; except no solar radiation resistant thermal insulation to protect from overheating.
Brickwork outer leaf to SIPS will help to protect the walls and rooms beyond from overheating.
But SIPS roofs need solar radiation resistant thermal insulation to protect the attic and top floor accommodation from overheating.
None of the SIPS building systems offer additional solar radiation resistant thermal insulation as part of their standard specification.
The Technology Strategy Board (TSB) (Now Innovate UK) ran the Retrofit for the Future (RftF) competition to refurbish housing to achieve 80% energy and carbon reduction.
Many eras of housing, their materials and construction types were included across the UK to get a good representative set to convert and monitor for 2 years.
Amongst the projects was a proposal to digitally scan the rooms as the survey, send the survey to a shipping container outside with Computer Aided Design (CAD) software to design the interior fit out, its files sent to Computer Aided Design Computer Aided Manufacturing (CADCAM) milling equipment to cut the panels, mark their location on each panel, then the panels are transferred to the house to achieve an accurate fit out in 90 minutes.
Subsequent projects in the GreenDeal programme have adopted the idea to fit out a house in a day.
However the material they have chosen are thin petrochemical foamed plastic, moisture resistant, conductivity thermal insulation and these are placed on the inside face of the solid external walls separated with battens leaving a cavity.
The insulation will stop heat that would otherwise drive outwards through the wall and drive out moisture,
One company has promoted its activity on line and has 1000 properties to process.
Thick walls are not the end of the world, in fact they will probably help avoiding the end of world for human occupation.
Thick wall panels came in the form of Insulated Structural Panel Systems (ISPS).
Manufacturers or ISPS think of 400-600 mm panels as nothing special.
Hollow structural framed and lined panels filled with non-structural thermal insulation in quilts or batts or loose filled with wet or dry flake or fibre.
Thicker conductivity thermal insulation usually comes from weaker k-values requiring greater thickness to meet U value targets.
Weaker k-values come from mineral, animal or plant based conductivity thermal insulation including:
But a bonus of plant based conductivity thermal insulation is they are effective solar radiation resistant thermal insulation too.
Effective solar radiation resistant thermal insulation in roof and wall panels will protect the interior from overheating.
Another IMC is Cross Laminated Timber Panel (CLTP) framed and Insulation in-filled panels.
These use Hemp-lime or Straw bales as infill with lime render outside and lime plaster inside.
Hemp-lime and lime would be problematic if applied insitu on site due to the slow setting and strengthening time so the innovation comes from complete finishing of the panels off site
All applying, setting, curing, hydrating, hardening, drying, strengthening of wet trades, materials and finishes can occur off site avoiding delays and simplifying in-sequence work.
Other advantages of plant based thermal insulation are:
The GreenDeal (now withdrawn), Energy Company Obligation (ECO) (now shrinking) and other recent grant funded retrofits have to work within a regulatory confines.
British Standards Institution (BSI) Publically Available Standard (PAS) PAS 2030 is there to regulate these works.
PAS 2030 requires competent materials, products, equipment, installers providing applications backed up by recognised guarantees or warranties.
The Micro-generation Compliance Scheme (MCS), Energy Technology List (ETL) of approved technologies, materials and installers exist.
Such lists appear restrictive and big players can afford approval processes whilst alternative materials are less likely to be included.
These schemes are left vulnerable to limited choice of approved, sometimes inappropriate and incompetent materials on offer and being installed.
See Also:
GBE Checklist
GBE Jargon Buster
GBE Products: P10 Radiation resistant thermal insulation
GBE Robust Specification
GBE CPD: GreenDeal, Methods, Materials,
GBE Links: ECA, ETL, MCS.
We used to teach about this characteristic in University in the 1970’s but materials were not available in the market place.
Today they are, in Europe the problem has been understood and they have developed the products to address it.
The Greens are bringing these products into the UK and promoting their use.
There are numerous suppliers: http://www.greenspecdownload.co.uk/index.php?cID=631
However the UK market obsessed with Fiduciary rules; mainstream construction is not interested in investment, or in climate change, so the problem remains unresolved and the solution remains a fringe benefit.
See Also:
GBE Checklist
GBE Jargon Buster: Fiduciary rules
GBE Materials & Properties
GBE Products: P10 Radiation resistant thermal insulation
GBE Robust Specification
GBE Suppliers
GBE Installers and Applicators
Those in the know describe solid wall brick or stone buildings (Prior to 1919) as ‘hard to treat’.
The walls do not have cavities to insulate so walls need to be insulated either externally or internally.
Historic buildings in conservation areas may have architectural details that discourage or complicate external insulation.
The same buildings may also have internal details that discourage and complicate internal insulation.
In these buildings without these complications external wall insulation (EWI) is usually the simplest, safest and best option, subject to the details.
Because of brick or stone, these walls already provide protection from radiant solar light/heat, so should avoid overheating, insulation used need only be conductivity thermal insulation.
But it needs an airtight outer finish or it could suffer convection losses and wind washing heat out of its surfaces.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification
GBE CPD: Retrofit Historic Fabric
GBE Lectures: Elements Walls
Buildings are never simple and often have external services and other construction that complicates and compromise the installation of External Wall Insulation (EWI).
Soil and vent pipes, rainwater downpipes, Gas and Electric meter cupboards, Gas pipes, Cable TV and Broadband, Overhead Power or Telephone cables, Balanced flues, Flues, extract fans, TV Ariel, Satellite Dishes and cables, external lights and CCTV, waste pipes and gullies with raised curbs in the pavement next to the wall, etc.
Other building junctions include: attached outhouses, bin stores, garages, carports, conservatory, porches, bay and oriel windows, eaves and verge details, ground level details, etc.
Under Energy Company Obligations (ECO) there are often template specifications and details for standard applications on uninterrupted wall surfaces and internal and external corners and abutments at edges, roof eaves, gable verges and ground level.
There may also be standard details for the services and abutments encountered, but often with a provision ‘when practical’ and these details may be compromised in the standard specification and details.
There are solutions that are expensive materials, but are not yet well known or widely known in the industry.
Ideally the services are removed and replaced outside of the thickness of the new insulation, but these solutions are beyond the skills of the Insulation installers.
The ECO companies do not want to engage services contractors or the whole process starts getting expensive.
Pricing of the works is often hurried to meet artificial deadlines, with robust safety margins and profits built in.
When the works is carried out the standard details which are labour intensive, time consuming and costly, are avoided and the insulation stopped and started either side of services with a working space for installation, creating massive gaps in the insulation and thermal bridges through the walls.
These Thermal bridges will lead to internal condensation in the vicinity of the services, mould will form where the condensation occurs.
Mould leads to asthma, a burden on the NHS; potentially toxic mould, uninhabitable buildings, irretrievable possessions, un-demolish able buildings, no-entry building sites.
Condensation can lead to embeded timbers becoming saturated, leading to rot and potential structural failure.
Solutions to the problems described above are being developed all the time but we may not always be aware of them.
For the reluctant ECO installer there are thin insulation solutions for external services:
Aerogel thin and high performance conduction thermal insulation bonded to weather resistant cladding boards.
These are cut to negotiate services supports and installed behind the services across the width of the services and applications/installation zone, abutted and weather-proofed to the EWI.
These materials are not cheap but the avoid the condensation, mould and other subsequent risks.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification
GBE CPD: Retrofit Historic Fabric:
GBE CPD: GreenDeal: Targets Tactics Techniques
GBE CPD: GreenDeal: Manner Methods Materials
GBE CPD: GreenDeal: Rhetoric Risks Remedies
GBE Lectures: Elements: (21) Walls
When insulating internally or externally existing ‘breathing’ solid walls need a ‘breathing’ insulation.
Gypsum plaster or cement render should be removed to permit breathing and moisture transport
Clay based and cork granule insulated renders and plasters are available that offer:
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification
GBE CPD: Retrofit Historic Fabric
GBE Lectures: Elements (21) Walls,
GBE CPD: Materials Render,
Other types of walls are likely to include cavity walls (Post 1919), which by inference are ‘easy to treat’.
But if easy means filling cavities with insulation then they will only ever be ‘easy to treat inadequately’.
My interpretation of ‘treat’ here means in terms of meeting carbon reduction targets.
50 mm cavities filled with 50 mm of insulation is wholly inadequate.
With brick, stone or blockwork in outer and inner leaves, walls already provide protection from radiant solar light/heat.
To avoid overheating, the insulation used need only be conductivity thermal insulation but no harm done by choosing solar radiation resistant thermal insulation as long as the thickness deals with the conductivity requirement.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification
GBE Lectures: Elements Walls
Starting with an uninsulated cavity wall you have a number of options in where you insulate the wall.
It could be entirely inside, some inside, some in the cavity and some outside, but never entirely outside.
Some permutations work but uninsulated cavity with insulation outside will not, because external insulation would be redundant.
Since cavities are at least in theory ventilated, all heat loss will occur in the cavity and external insulation will do nothing to change that.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification
GBE Lectures: Elements Walls
GBE Calculators:
U value and Interstitial Condensation Calculators,
Hydro/Hygro thermal moisture movement calculators: WUFI, Delphie
Compartment walls between:
Houses, maisonettes or flats; including top floors, rooms in roof and attics
Communal corridor or stair risers and houses, maisonettes or flats
Not long ago whilst monitoring new homes it was discovered that uninsulated cavity party walls where leading to overheating in attics and passing heat through roof tiling to the sky.
Heat loss through only one leaf of bricks or blocks, one half of the cavity wall, will enter the cavity,
This can happen from one or both sides at the same time
The cavity acts as a chimney and the heat rises to the highest point in pitched roof or the top floor under a flat roof
This then heats the 2 leafs of the cavity wall then heats the spaces beyond
The spaces beyond may be attic space or it may be room in the roof or top floor flat, or upstairs in maisonette
This will add to heating or overheating of any spaces
Overheating communal spaces can use the cavity to loose heat
The cavity can move the heat to other locations with overheating potential
The Building Regulations have been revised to avoid problems in future homes but problems remain in existing.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification
GBE Lectures: Elements Walls
Terraces of houses in a conservation area or the external face is ornate may be difficult to insulate easily.
The Floors may be timber so offer no thermal mass to exploit.
Using internal insulation to external walls will cover up the existing thermal mass in the walls.
Internal loadbearing walls of brick and plaster may offer a little thermal mass
Internal partitions of timber stud, lath and plaster offer a little thermal mass
Internal partitions of solid timber and plaster skim offer a no thermal mass
New partitions of timber stud and plasterboard usually offer no thermal mass
The solid party walls are the only remaining opportunity for thermal mass, if exposed.
Cement render should be left on to use its thermal mass
Gypsum plaster may need to be removed to ensure the brick wall thermal mass can be exploited, but risk reducing acoustic performance of the party wall.
High density clay plaster could be added to offer thermal mass as well as airtightness and moisture mass.
We are encouraged to provide large glazed areas on the south elevation (facing south + or – 30%) this is:
In summer we need to balance summer glazed area solar light/heat gains with one or two options:
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification
GBE Lectures: Elements Walls
GBE Calculators: U value v G value calculators
Comes in the form of either or a combination of:
Cross ventilation:
Stack effect:
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification
GBE Lectures: Air Movement Through Buildings Series
GBE Case Study: BRE Environment Building
Often a passive ventilation system with a special rotating cowl
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products: U10 Active Venting systems
GBE Robust Specification
GBE Lectures: Air Movement Through Buildings Series
Building Regulations address airtightness of building fabric in particular eternal envelop (walls, roofs and occasionally floors)
Building Regulations targets are wholly inadequate and do not show any signs of improvement despite initial promises.
A building with an airtightness level of 8 is described as noisy, draughty and unusable in windy weather.
Building Regulation permit levels of up to 10 and constructors can achieve anywhere between reported 0.1 and 27.
Building fabric should be as competent as possible.
Ventilation should be deliberate and purposeful, not unintended or fortuitous.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products: P14 Wind and air tightness systems
GBE Robust Specification: P14 Wind and air tightness systems
GBE Lectures: Air Movement Through Buildings Series
Architects worried that occupants will create condensation and mould conditions, considering making construction air-leaky to reduce risk.
Air leaky construction could also help with overheating if the heat can escape in the air egress.
However the same will apply in winter and occupants will have to pay to keep homes at comfortable temperatures.
For many millions that are already classified as in fuel poverty this is not a sensible solution.
Instead buildings should be airtight to control heat loss and purposefully passively, actively or mechanically ventilated to manage moisture build-up and control indoor air quality.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Products:
GBE Robust Specification: Wind and air tightness systems
GBE Lectures: Air Movement Through Buildings Series
A development of stack effect passive ventilation system: where exhaust air ducts pass through intake air ducts via a heat exchanger that allows transfer of heat-only from one to the other whilst airflows remain separated.
E.g. Ventive systems are designed to retrofit into existing brick chimneys.
Summer bypass is essential in these systems to avoid overheating.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Lectures: Air Movement Through Buildings Series
GBE Products:
GBE Robust Specification
Developments of active ventilation system where exhaust air ducts pass through intake air ducts and allow transfer of heat only from one to the other whilst airflows remain separated.
Summer bypass is essential in these systems to avoid overheating.
See Also:
GBE Jargon Buster
GBE Checklist
GBE Lectures: Air Movement Through Buildings Series
GBE Products:
GBE Robust Specification
Comes in a wide range of formats, locations and purposes:
See Also:
GBE Jargon Buster
GBE Checklist
GBE CPD: Solar Shading, Alternative Solar Shading
Fixed eaves overhangs, porches, Porte cochere, veranda, balconies, etc. positioned outside of and above windows or glazed doors acting as solar shading to prevent summer solar light/heat of opaque parts or entering glazed parts.
See Also:
GBE Jargon Buster
GBE Checklist
GBE CPD: Solar Shading, Alternative Solar Shading
GBE Products: L15 Solar Shading, Alternative Solar Shading
GBE Robust Specification
Whilst living walls are excellent to look at, they are often an environmental conundrum.
If irrigated:
They offer:
NB: They can annoy architects if they cover up their precious details.
Nature does its own thing.
Birds nesting in them might poo on your pavement, get used to it, don’t ban the birds.
See Also:
GBE Jargon Buster
GBE Checklist
GBE CPD: L15 Solar Shading, Alternative Solar Shading
GBE Products:
GBE Robust Specification
External solar shading is used outside of glazed openings to prevent summer solar light/heat entering.
Positioned and configured to permit winter solar gain, with added challenge of glare and perimeter overspill protection.
Brise Soleil comes in different formats: (the flowing relates to UK, northern hemisphere,
Cantilevering from the wall above the glazed part shading from high level summer solar light/heat:
Vertical in front of the glazed parts:
Vertical and set a distance from the glazed part:
Blinkers: cantilevered from the wall and beside the glazed part:
Northerly bries soleil: is ineffective, architectural frippery, is a waste of money and suggests incompetence.
Same solar treatment on all elevations: is architectural frippery, ¼ is a waste of money and suggests incompetence.
See Also:
GBE Jargon Buster
GBE Checklist
GBE CPD: L15 Solar Shading
GBE CPD: L15 Solar Shading alternatives
GBE Products:
GBE Robust Specification
They know a thing or two about overcoming overheating in tight urban spaces
The details of architectural facades reveals a lot
Balconies are often placed on both sides of a corner of a building
Balcony balustrades are perforated to allow air passage
External ‘French’ doors open inwards and wide to allow airflow across corners through two sets of doors
Internal blinds are passed through the door openings and draped over the balcony balustrade
The sloping blinds provide:
See Also:
GBE Jargon Buster
GBE Checklist
GBE CPD: Solar Shading, Alternative Solar Shading
GBE Products:
GBE Robust Specification
With addition of pivoting supports allowing blades to be angled to suit sun’s location, orientation or angle of projection.
May be driven by motors to acknowledge panning sun’s path across sky and time of year.
May be controlled by learning software that remembers sun’s position at different times and seasons.
Can be used to exclude sunlight but maximise daylight entry.
Bouncing light off surfaces of blades can absorb ultra-violet (UV) light.
See Also:
GBE Products
GBE Robust Specification
External shading outside of glazing prevents summer solar light/heat reaching and entering windows, rooflights, roof windows, etc.
Not deployed in winter to permit solar light/heat gain and sometimes deployed to reduce glare.
Outward opening windows may clash with external blinds.
See Also:
GBE Jargon Buster
GBE Checklist
GBE CPD: L15 Solar Shading Alternatives
GBE Products: N10 External blinds, Awnings, Umbrellas
GBE Robust Specification
Not to be confused with solar shading but sometimes they are combined with solar shading.
Solar shading to lower casements and light shelf to upper casements of same window
They occur some distance down from the top of a window creating a ‘shelf’.
Light shelves can be internal and/or external of the glass.
They reflect sunlight and/or daylight into the building.
Bounce light off top surface of a horizontal light coloured and reflective surface, sometimes glass or water.
The light passes through the upper window frame, onto the ceiling or soffit of the floor or roof.
This bounces the light deep into the section of building, increasing light levels furthest from windows.
In addition to the light, heat from the sun can pass through as well and then heats the interior.
Windows opening inward and outward should not clash with light shelves.
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GBE Products: L15 Light shelves
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GBE CPD: L15 Solar Shading
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In exceptional circumstances the roofs may also be protected by external brise soleil.
In UK it is commonplace for roof plant areas to be shielded from view from below and adjacent.
In France it is commonplace for roof plant areas to be shielded from view from below, adjacent and above with metal grilles over the whole roof area, that have the potential to become solar shading as well as visual barriers.
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GBE CPD: Alternative Solar Shading
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GBE Image Bank
Exceptionally pitched roof are shaded
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GBE CPD: Solar Shading, Alternative Solar Shading
GBE Products: L15 Pitched roof solar shading
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Case study: Grand Designs: galvanized expanded metal mesh on pitched framing above profiled metal roof.
Another term is Thermal Lag (Time delay or lag, not pipe lagging/conduction thermal insulation).
Decrement delay is time it takes for radiant heat to pass through an element of external envelop of buildings.
The time it takes to hit the outside surface, to pass through it and come out of the inside surface.
High thermal mass materials usually but not always have the characteristic.
Conductivity thermal insulation can have the characteristic but most insulation materials do not.
Solar radiation resistant thermal insulation is conductivity insulation that does not perform very well, its high density makes it absorb heat and slows its passage down for an extended period.
Materials with decrement delay characteristics:
Materials not offering decrement delay:
Materials appearing to have decrement delay (under radiant heat source tests) but after a short period reach full saturation and then heat flows:
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GBE Products: P10 Radiation resistant thermal Insulation Products
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GBE Equation: Decrement Delay
GBE Dataset: Decrement Delay
GBE Calculator: Decrement Delay
Water can be ice, water or moisture vapour (steam), it goes through 2 phase changes to manifest in 3 phases.
Changing phases requires heat energy transfer to occur.
For water to turn to moisture vapour requires heat in the water to be released from the water.
Phase change materials are selected for the greatest capacity to absorb, store ‘latently’ and release heat at phase changes.
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GBE Products: K13 Phase Change materials,
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The same occurs in a moist building material for it to dry requires heat to be lost from the material.
Hence buildings feel colder during or after rain or other precipitation (snow, rain, mist, fog), when wind is drying buildings.
If walls are damp from previous rain then some absorbed heat will warm moisture and evaporate it.
Moisture vapour will be driven inwards and outwards, cooling the wall.
If the wall has a cavity then some moisture will evaporate into the cavity, it being ventilated will remove moisture from cavities and cool the walls.
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Water penetration through outer leaves of cavity walls will run down inner faces of outer leaves.
If cavities are fully filled with conductivity thermal insulation the outer face of mineral fibre insulation will become moist. Full fill cavity insulation needs to be hydrophobic (rejects water from its fibres or into its air spaces).
Moisture entering the outer face of insulation will occupy air spaces between fibres in insulation, preventing it from its optimum performance in the moistened thickness.
Mineral fibre’s conductivity insulation performance is quoted at different moisture content levels.
Waxes are popular for this purpose.
Early products in the market were metal cassettes filled with wax.
Plasterboards with wax pellets in the mix came next.
Today GRP equivalents using plant fibre and plant resin make up honeycomb boards containing wax and/or clay recipes pellets in the cells.
(E.g. EBB products & lehmorange products).
Phase change materials offer lightweight buildings similar properties to high thermal mass buildings.
Today 10 mm of PCMs in board format can have equivalent thermal mass of 120 mm of concrete.
Use of PCMs could reduce the thickness of thermal mass walls.
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GBE Jargon Buster
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GBE Products: K13 Phase Change Materials
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Brick, stone or concrete are materials exhibiting thermal mass, it is one contributing factors making up solar light/heat protection and decrement delay.
A recent building in Austria with
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GBE Case Study: 2226 Austrian building
The Victorians knew a thing or two about building, which we can adopt in today’s high performance buildings.
When using thick walls deep reveals at windows can lead to high contrast glare.
To overcome glare, sloping window reveals can soften the contrast by letting daylight or sunlight spread onto sloping reveals.
Victorians like the French only 20 miles away on the other side of the channel (and all the way to the Mediterranean sea) use shutters to windows to provide solar shading in the summer and thermal insulation in the winter.
Victorians used shutters internally in a cooler climate.
French mostly but not exclusively use shutters externally in a hotter climate.
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GBE Services: C51 & L10 Window Shutter refurbishment
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GBE Library: EH Study of Window upgrades in Glasgow
Thick walled buildings may be okay on low-density developments but may not be practical on small urban sites.
Reducing thickness of thermal mass walls by replacing some with phase change materials could offer the best of both worlds.
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For phase change materials to be effective they need to absorb heat and have the means to release the same heat to be able to absorb more heat at a later time.
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The cross-laminated timber panel (CLTP) school building on the BRE Campus that was later converted into medical centre includes a computer server cupboard.
The computer server is left on long periods of the day and gets hot and continues to push out heat.
The cupboard is lined with PCM lining boards, they absorb the heat of the server.
If the server was turned off at night then the PCM could lose its heat and then the following day the server could be turned back on and when heat builds up the PCM absorb the heat again.
But the habit of leaving servers on overnight means the PCM cannot lose heat, so they cannot be available to absorb more heat the following day.
The server cupboard could have been naturally ventilated the server providing the heat to start the stack effect.
The ventilation system could have included heat recovery to reuse the heat elsewhere.
The ventilation of the server cupboard could have saved the expense of the PCMs.
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GBE Jargon Buster
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GBE Products: K13 Phase Change Material Boards
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WWF Living Planet Centre Woking
The incorporation of PCM boards within barrel vault roof construction needs to be better understood by me at least.
If a PCM board is located towards the top of the roof element is it there to capture solar heat gains and prevent them entering the building?
If a PCM board is located towards the bottom of the roof element is it there to capture convected heat from below and remove it from the building?
When a PCM boards absorbs heat and reaches saturation point does it then start to radiate, convect or conduct any of its heat?
Could the upper level PCM absorb solar radiation heat and when saturated then reradiate or conduct it downwards?
If reradiated or conducted downwards would appropriate propertied thermal insulation help to prevent this?
If reradiated downwards does the inner plywood lining offer any resistance to reradiated heat?
It is light coloured rather than dark, which might help; it is unfinished and matt which might not.
During the June/July 2015 hot days the building experienced overheating and staff on the upper open plan floor chose to work on the lower floor when possible.
The client and design team are in discussions trying to understand the problem and come up with solutions.
The client is aware of this document on the NGS website and plans to investigate it further.
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R Research Opportunity:
Academic research or manufacturer’s data needed to understand PCM action when heat saturated
If there is sufficient thermal mass, absorbed heat and time then building fabric can act as a ‘thermal flywheel’.
The thermal mass absorbing heat at a time of plenty to release it later when the sun’s heat is gone for the day.
Releasing heat to rewarm rooms, potentially into the evening, can avoid needing to turn heating appliances in winter but can be a problem in summer.
The first mention of heating, suggest this is a winter (heating season) only issue.
In reality solar heat gains in summer usually result in overheating and solar heat gains in winter can be beneficial.
The areas of glazed openings on different elevations will influence the size of the problem and/or benefit.
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Once high thermal mass elements have absorbed excess heat from spaces, they need to be cooled to allow it to continue to offer this service the following day.
During daytime under floor heating pipes with cooler liquid drawing heat from floors can move heat towards colder parts of the building.
Overnight perimeter vents can be opened and colder night air can pass over surfaces of thermal mass to cool it, ready for the following day.
Concrete hollow cores plank floors can be cooled using air passed through the hollow cores (E.g. Termodeck)
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GBE Image bank: BRE Environment Building, etc.
GBE Case study: Elizabeth Fry student accommodation, UEA, Norwich.
Windows can be opened both sides of a double sided building with clear routes available from one side to the other.
Prevailing winds can push external air into and through the building, pushing internal air out the other side.
If the external air is cooler than the internal air then the cooler external air passing through can flush out the warmer internal air.
If any internal thermal mass is on show and has been exploited it will have absorbed any excess heat.
The cool external air can flow across the surface of the exposed thermal mass and cool it, eventually purging the heat out of that thermal mass.
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Windows that open wide and allow uninterrupted flow of air are best.
Side hung casements are good.
Mid point vertical or horizontal pivot windows are good
Projecting swivel windows can be good
Inward or outward opening windows may clash with any internal or external solar shading.
Windows that slide down and up are good.
Vertical sliding sashes are good.
Make sure vertical sliding sashes are not painted solid and ironmongery still works
You may wish to consider upgrading the sash windows to reduce permanent air leakage due to loose fit sashes.
A window is available where the whole casement moves outside of the face of the wall, it allows vertical (heat driven) or horizontal (wind driven) ventilation on 4 sides whilst maintaining the <100 mm safety gap.
Security is a major issue if the occupant needed to leave the house and wanted to continue to purge.
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GBE Products:
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GBE Library: EH in Glasgow: Upgrading windows
GBE CPD: Retrofit Housing
Because air intake vents (AIV) replacement air vents (RAV) are often automated, they can be open when it is windy outside.
Wind baffles can be added to restrict drafts affecting occupants, they may then make the AIV or RAV less effective or even ineffective.
Buoyancy of hot air in stack effect situations should overcome resistance and draw air in and drive it out despite the baffles.
Buoyance and stack effect ventilation needs a building section that has uninterrupted route from entry to heat source to exit, to be effective.
Cross flow ventilation may find baffles a restriction.
Cross flow ventilation needs a building section that allows uninterrupted cross flow from one side to the other.
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GBE Products: U10 air intake vents (AIV) replacement air vents (RAV)
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Tilting inward bottom hung windows:
Tilting outward top hung windows:
ROSPA rules preventing children falling through windows mean opening restrictors will prevent the windows being opened wider then 100 mm at the extreme and less in the triangles at the sides.
Building Regulation’s ambitions with purge ventilation is to clear moisture vapour and smells.
The same issues apply to opening doors; different problems apply to sliding doors.
Windows that do not open:
High thermal mass materials can be warmed by solar heat gain during daytime.
In the air layer adjacent to the building (say 1-3m) the air will be warmed to quite high temperatures.
When the same materials are adjacent to windows, then the air outside the window will be warmed by these two thermal masses during summer days.
Air drawn in though the window for cross ventilation or purging will be pre-warmed and offer no cooling effect.
The pre-warmed air will add extra heat to the interior leading to overheating instead of cooling or purging.
People do not use purge ventilation using opened ajar windows due to:
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GBE Products: L10 Secure Purging Windows
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An alternative to windows promoted by ZCH literature is vents associated with windows and doors
The may consist of window like construction and may even be included as a casement or glazing substitution
The will have internal open and close able well-insulated and weather-stripped blanking panels.
They will have insect resistant perforated metal sheet or mesh to allow air to pass through.
Being perforated/meshed the air passing through may not be too windy to disturb interior objects, papers, etc.
Being of narrow dimension will not be passable by burglars, offering security whilst ventilating.
Can be open when the external air is cooler
With at least one vent on both sides of a building and can permit cross flow for purging of heat.
Ideally each room would have its own vent.
Can be closed if the external air is static or hotter than internal
Can be opened for normal ventilation, purging of humidity or smells.
Can be left open overnight, can be used for ground floor or basement flats.
Case Study:
Seminar building at the Innovation Farm near Cambridge:
BRE Environment Building:
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GBE Products: L10 Secure Purging vents
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GBE Image Bank: Seminar building at the Innovation Farm near Cambridge,.
When buildings overheat:
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GBE Defect: Heat activated polymer migration from phthalate plasticised PVC resilient flooring coved and capped skirting into adhesives leading to failure of waterproofing in wet rooms and easy clean corners in hygienic rooms.
World FM reported on SOM Architect’s Post Occupancy Evaluation (POE) survey report, May 2015, including a recent survey of building occupants in many businesses, in many sectors.
The striking issue was that whilst almost all issues scored fairly well, thermal comfort was consistently the worst scoring topic of all with very low satisfaction scores.
See Also:
Library: http://www.som.com/ideas/research/post_occupancy_evaluation_survey_report
Staff’s reduced capacity to concentrate on tasks
Reduced productivity of workforce
Staff absenteeism
Ineffective buildings lead to loss of workforce
Air conditioning uptake in homes:
Today: 3% (B&Q sell them for DIY)
2050: 50% predicted (exacerbating the problem for those without)
Increased: energy consumption, costs, and carbon generation.
Failing: to meet carbon targets.
More European fines to UK Government, paid for by our dwindling tax reserves, so achieved by more reduced public services and July 2015 diversion from Zero Carbon targets.
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GBE Products: U10 Passive, active or Whole House Ventilation Systems
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Indoor air pollution:
PM, SO2, NO2, CO, O3, VOCs, Radon
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GBE Products: IAQ fixed monitors; hand held detectors
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Heat stroke
Heat exhaustion
Heat syncope
Heat cramps
Death
Residents who are at home during the daytime experience significantly greater overheating exposure with implications for their health and wellbeing.
Elderly over 65 years (hit significantly by 2003 heat wave)
Chronically ill
Socially deprived
Low income
14-30th August 2003 heat wave: 70,000 extra summer deaths in Europe (Peer reviewed statistics quoted in Wikipedia)
https://en.wikipedia.org/wiki/2003_European_heat_wave
SE France hardest hit with 14,802 (60% excess deaths)
2003: 2091 heat wave deaths/annum UK (17% excess deaths) HSQ 2005
0-64 years old: 236 (11% excess deaths); 65-74 y o: 74 (3%); 75+ y o: 1,781 (23%); London: & SW: 1063 (65%)
2050: 7000 heat wave deaths/annum UK (predicted)
Compared with:
2012/13: 31,000 Excess Winter Deaths (EWD) (UK)
2013/14: 18,200 (EWD) (UK)
2014/15: >40,000 (EWD) highest in 15 years (UK)
2014: 4200 air pollution deaths/year London-wide
2014: 2.4 million people in fuel poverty (paying more then 10% of income on heating) (UK 2013 official statistics)
2014/15: 1,084,604 people in food poverty received three days’ food up 19% on previous year.
(The Trussell Trust UK’s largest network of food banks)
2015: 2380 Number of deaths after benefits withdrawn
27/08/2015: Europe is having a heat wave (Spain’s worst in 30 years; >8 weeks) (Malta > 4 months)
UK is almost unaffected by this 2015 heat wave.
How many will die this year? Will this be another wakeup call? Will it be ignored? “Oh no, its just weather”.
Moving the must vulnerable occupants away from the most, into the least, vulnerable properties, helps.
The building that are made vacant can then be refurbished in the ways described here.
Do not move less vulnerable occupants into the most vulnerable buildings, you just make them unwell and more vulnerable later.
We will risk the occurrence of Fuel Poverty problems at both ends of the year
We risk needing affordable warmth and affordable coolth.
Well we already have the problem.
Government already pays winter heating allowance every year instead of insulating their buildings once.
Will this get the chop next to afford the MPs 11% pay rise and the gambling banker bonuses?
An estimated 20% of houses are vulnerable or already overheating
How long before society demands summer cooling allowance to be paid to the most vulnerable?
This paper started before the HCA UK, ARCC, EPSRC conference: ‘Overheating and IAQ in new housing’
I will update this when the seminar papers are published and I think of anything else.
Follow Twitter handles and hash tags:
@HCAUK @ARCCCN
#HCAOVERHEATING #IAQ
http://www.gov.uk/housing/design-and-sustainability http://www.arcc-network.org.uk
So what? Now what? Data sheets: http://www.arcc-network.org.uk/sowhat
Event organisers were encouraged to develop and publish Contract/Specification Performance Requirements
GBE will republish them.
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© GBE NBS BrianSpecMan aka Brian Murphy 2015
© GBE NGS ASWS Brian Murphy aka BrianSpecMan *
29th May 2015 – 8th November 2019
© GBE NGS ASWS Brian Murphy aka BrianSpecMan
11th June 2015 – 27th August 2017