House NI 1960s EnerPHit Upgrade Brainstorm

GBE > Encyclopaedia > Code > Brainstorm > G#16288

House NI 1960s EnerPHit Upgrade Brainstorm
About:

Legend:

Black/grey Questions from client

Green Responses from GBE
When something is blatantly wrong

There are three main areas where I would like your advice on which are the better insulation materials to use:

Roof insulation (responses included here)
Cavity wall insulation (pending)
Under suspended wooden floors (pending)

Project objective

To give you some context, ultimate objective is to meet EnerPHit standard (or as close to as is rational in cost Vs savings terms) – the house needs lots of work, we hope to enjoy 30+ years in it, so feel it makes sense to work to an objective standard as we renovate, with emphasis on high quality insulation installation and good air tightness at every stage.

House was built 1968, and needs lots of updating (metal roof in poor condition, single pane windows, very poor air tightness in general).

Northern Ireland late 1960s House refurbishment to EnerPHit standard

GBE Initial comments are limited to north roof only (but may have strayed a little bit)

Some questions but mostly answers or suggestions and lots of problems to avoid

If anything needs to be better explained, please let me know

Having a ‘whole house plan’ (knowing in advance your final outcome) enables progress without risk of undoing something to complete another

North shallow pitched roof

Metal roof tiles used by house builder for low weight.
Consequence could be: longer roof joist spans and/or smaller sections
Potentially lower capacity to accept heavier tiles, (clay, concrete, slate)
Shallow roof pitch will probably prevent these choices too
Unlikely to be strong enough to accept living roof or hard paving
- (green intensive, brown extensive, blue water retaining, roof terrace)
A sedum mat may be possible if the structure can take the load but it will offer less of the benefits living roofs offer
- Some solar protection and some evaporative cooling from the mat, not from the sedum
- Some water retention in mat and in sedum adding to the loads to be carried
- Three species of sedum are indigenous and drought tolerant

This will take several years, due to budget restraints, so aim is that we do everything to high standard as we move from project to project, with emphasis on using ‘natural’ materials with low-embodied carbon where suitable.

At the moment no reason to consider the following options are not viable choices at this stage.

Bio-based:

hemp
flax
cellulose
wood fibre
others plant fibre based insulation or
sheep’s wool

Mineral:

aerogel

If the metal tile roofing is to be repaired and reused there is no thermal mass to offer solar protection to the interior from solar heat gains

Part of the north roof will still see the sun over the mono-ridge at the chimney wall so parts of the roof will be subject to solar radiation

This would suggest avoiding:

All plastic insulation,
all mineral fibre (stone or glass or slag),
sheep’s wool,
Vacuum Insulated panel,
multi-foils.

This would suggest considering:

Dense Bio-based:

Dense wood fibre boards (Dry manufacture)
Dense wood fibre boards (Wet Manufacture)
Medium flexible density wood fibre squeezable batt
- Squeeze, insert into joist space, release, expand to grip joist sides, span and not slump or fall
Cellulose fibre flake:
- Dry process from below may be impractical in shallow pitch roof
- European methods is to create a ‘compartment’ (boards either side of joists/rafters) dry blow through hole
- Wet process sprayed in from below

Others:

Cellular glass (foamed) board (on top or underside)
Aerogel installed internally below joists
Aerogel attached to outer (top) face of dry lining boarding

Installation from below

Do not use nylon netting fixed to sides of joists, contractors usually end up squeezing insulation under slipping net, but in the hands of a self-builder this may be a risk, but with care may not be an issue.
Consider Insumate multi-wall plastic boards stapled into place
- (a range of permutations to suit different situation)
If you need to maintain a services void in joist depth

We had energy survey done this summer and there is no insulation in cavity walls and very little (50 mm) in ceiling, and even that is poorly installed, with large gaps in places and no air flow.

If you do the work yourself (no skills training but lots of care)
Less need for IR thermography survey afterwards to spot the weaknesses but it may be worthwhile, all the same.
Air-flow through 50 mm gap is commonly required through a pitched roof below the sarking or underlay
Air-flow is commonly achieved in the batten zone above the underlay.
Scottish practice may require ventilation in the counter-batten zone above the sarking (would need to check)
BBA Certification may require different ventilation under metal tile roof, this needs to be investigated.
A malleable metal roof (Lead or Zinc, etc.) would need a vapour barrier and ventilation zone to prevent condensation
Cold roof with insulation between joists are common
Cold roof with ventilation zones in flat roof are avoided today and are very uncommon, I have not specified one for decades.
If you have a gap in the insulation at the top of the joists it creates cold space; if there is no vapour barrier below moist air will enter the gap above the insulation, on a cold day the decking will be cold and then condensation may form on the underside of the decking and drip into the insulation.
I have heard of mechanical ventilation being required in flat roofs if there is a risk of condensation, you should be avoiding that by other means.

The order we’re planning to work in is:

North roof insulation – roof had water damage and needed to be inspected and repaired
Wall insulation (cavity first, exterior insulation later)
South roof
Under floor insulation
Upgrade windows and doors

North roof: more prone to north winds, cold winds (drier than westerly winds?) but can still deliver snow onto the shallow roof.
North winds on shallow roof could push wind driven rain or snow melt water up the roof slops and up between the metal tiles.
If you can identify the manufacturer and the product, check if they have (or had) an BBA Agremént Certificate and get a copy and check if the rules were complied with.
BBACs break the Codes of Practice rules (tiling below normal roof pitches) but set their own laboratory tested rules.
Repairing a non-compliant installation will not help you.
Inspect the metal tiles to see if the profiles (including the dented ones) to see if the profiles offer capillary attraction in the joints which could hold water in between tiles making a water seal.
(lead roofs suffer from thermal pumping, water trapped in the lead laps being pushed and pulled between close lead surfaces by the heating and cooling of the roof by sun and no sun, night and day.
This can lead to moisture being pulled into the insulation or onto the deck below.
Could thermal pumping occur with the dented metal tiles?

Eventual target U-values are:

Image 1 (See right column)

CURRENT STATE

The roof is very low pitch, circa 9 degrees according to my measurements.

If you cannot identify the manufacturer of the metal tiles, check equivalent metal tiles to discover their recommended roof pitches.
If they require steeper than 9 degrees double check if your roof has been installed compliant with any BBA Agrément Certificate or manufacturer recommendations.
FURTHER INVESTIGATION:
- UK’s leading supplier of BBA certified metal tiles show using at 10 degrees

It has lightweight tin tiles over what appears to be the older bitumen covered roof.

I assume you mean a bitumen roofing underlay on counter-battens, on sarking, below battens and below metal tiles
- (this note proved to be a wrong assumption see later notes)
If you are searching for weight savings, consider replacing the bitumen underlay with a moisture permeable wind-tightness layer, but maintain a ventilation zone in the batten zone.
If you find bats do not disturb (£5000 fine per bat)
- contact BCT Bat Helpline: 0345 1300 228
- try to keep the bitumen underlay (wrong assumption not underlay)
- Modern Breathing Roofing Membranes entangle and trap bats.

Image 2 (See right column) North roof, showing living room window and car port

Lead flashings at top of roof against rendered/painted wall and chimney look too low
150 mm normal for rain splash two whole brick courses up, more important with a shallow roof.
There appears to be a vent in the pitched roof near the rendered/painted wall, does it have a sufficiently high upstand?
150 mm is normal.

North facing living rooms are not ideal; no solar gains through glass; maximise the use of the west facing windows for evening solar gains; and minimise reliance upon north facing windows.
North facing windows good or sunlight-free daylight for designer/artist studio
Consider winter shutters or well insulated winter curtains or quilted blankets hung on coat pegs at the glass in winter
Carports are good for the wellbeing of cars, sheltered from rain and allow drier air evaporation of rain and road water.
Not perfect for winter morning starts but early north easterly sun may thaw out the car wind screens for you. North winds may deliver snow onto the car or prevent the car egressing the carport.
Whoops I got side tracked.

Image 3 (See Right column) North roof, showing projecting windows)

Is the triangular flat roof over the projecting windows well insulated (solar radiant and conductivity insulation)?

Image 4 (See Right column) North roof, showing car port and garage)

Decent width garage (inside room to open car doors or have storage either side and above) ditto carport

Image 5 (See Right column) living room, showing fireplace and general layout)

Big windows into the carport is a big heat loss with little other benefit, north light is shaded by carport roof. Car fetishists may be happy with that view, without PH accredited or equivalent windows that will be a cold area on the room’s walls.
Not quite sure what is happening at the line (glazed screen?) (clear, green, white and yellow glazing?) change of level?
Finally got it, middle strip is mirror, glazing above and below
I hope the mirror is well insulated (probably not) ditto the windows (probably not)

Image 6 (See Right column) inside living room, showing decorative beams, before I removed ceiling)

Is that polycarbonate glazing in the bays and the clerestorey glazing or patterned glass?
Green tinted north clerestorey glazing?
All that uninsulated north wall with little visual or light benefits

Image 7 (See Right column) inside living room, showing RSJ, 9 inch joists, and exposed sarking/ply board)

9 inch joist depth is good but not by today’s U value requirements,
especially if you are limited to this zone alone and choose or are driven towards green and low carbon materials.
Consider adding:
- wood fibre or cellulose flake for solar protection in joist zone,
- some aerogel (thin layer internally below joists to boost the U-value)
- and then a services zone if you need it.
Consider running services above or within decorative beam or decorative joist profiles

Image 8 (See Right column) inside living room, showing damp damage to exposed sarking/ply board)

Is the white tide line efflorescence salts from masonry or mould trying to grow?
Whilst this looks very wet for plywood (more understandable if it were chipboard)
I cannot tell from this picture if there is swelling or de-lamination
- if there is then this small affected area of plywood probably needs replacing
- if not then cutting off the water or water vapour supply and drying it out may be sufficient
Judging by the direction of the joists this not at the southerly flashing but it is at a verge wall but it feels like the carport wall not the westerly verge.
- Is high wind pressure building up in the carport and driving moisture into the house through a dry construction joint?
- Or is cold air getting to the bottom of the sarking causing condensation?
An Airtightness test may help understand the problems but you know the location, try to fix the problem and then dry this out and all could be okay again.
The plywood glue lines will act a vapour barrier so developing a vapour open solution may not be practical so the alternative vapour closed construction is safest approach whichever type of insulation used.
Consider adding a vapour control layer internally no matter which insulation you choose
If you are using cold roof with ventilation zone then consider a vapour open construction into the ventilated cavity

Image 9 (See Right column) damage to tin tiles on north roof, (now repaired)

Metal roof tiles may have been damaged by foot traffic (but should be made to be strong enough) leaks are inevitable as overlap seals will not be intact.
Top row of tiles look at same angle as remainder but tide lines suggest the top row have triangular puddles accumulating dust and debris.
Debris collecting at tops of tiles (top and next row) suggests the tiles are set at too low a pitch than recommended.
Check BBA Certificates for the manufacturer or equivalent.

The living room roof had very little insulation, and sarking board/plyboard was water damaged from leaks in tiles, which I’ve now repaired, removing all the plasterboards in the process.

Currently the roof matches the diagram on the below left ‘Conventional Cold Roof’, but without the insulation, or the ceiling!

But I assume the roof is counter-battened and underlay and battened for the metal tiles?
Do you think the roof had already been retrofitted with the metal tiles over 3 layer built-up bitumen roofing?
Is the bitumen you can see built up 3 layer roofing with solar protective aggregate in its top surface?
It probably was not lead roofing or it would have steps in the deck.

Image 10 (see Right Column) 3D images of cold and warm roof

In better detail, a slice through my roof, top to bottom, is:

Lightweight metal tiles (appears to be some form of tin)
Bitumen covering
Wooden decking (not sure if ply or sarking material, or exact thickness)
Nine inch deep joists (let’s say 22.8cm deep joists)
- or 225 mm in building terms, until Brexit overwhelms everything, then 9 by 2 will be back
Plaster board

My guess is that the metal tiles were added to a standard bitumen roof around 20-30 years ago.

In some places, bitumen can be seen between ply boards and between ply boards and walls.

Okay we have come to the same conclusion!
You do not mention (top to bottom) tile battens, underlay and counter-battens
- Are the tiles fixed directly to and through the felt roofing?
- Its a wonder the roof does not leak everywhere
- Nailing through bitumen sheet might make a watertight seal
  - but I would not recommend it
- I would describe this as an incompetent installation without battens and underlay
- The felt roofing could be seen as a second line of defence but it is compromised
FURTHER INVESTIGATION:
- UK’s leading supplier of metal tiles show using a batten over rafters
- They also show underlay and battens
- Your felt roof would need counter-battens on the felt roof, underlay and tile battens
So I wonder if the damp is 20-30 year old leak that prompted the addition of the tiles
Or more recently as a result of a roofer or burglar jumping down from the ridge to the lower roof and squashing the tiles?

If I use 5 cm air gap, I have circa 17.8 cm of insulation available.

I am not sure what the 50 mm air gap is for, if it is not ventilated at the perimeter then it has no purpose other than for heat to escape into, eddy current and dissipate, instead of heating the building occupants.
You have a high and sloping ceiling so you could claim some space below the roof joists to increase the insulation thickness.
This could be done with cross battens and insulation of the same depth or with one of the Insumate systems.

The living room roof is 6 metres wide and 7 metres long.

I’m not currently planning to add insulation-backed plaster boards, but just standard boards.

I have only circa 15 mm thickness, as boards have to fit in narrow gaps between chimney and joists.

I am not sure what the problem is there.
Counter battens with insulation at right angles to the ceiling joist zone insulation minimises cold bridges and potentially closes off routes between any air gaps.
The counter battens offer fixing place for simple plasterboard.
The narrow gaps between joists and walls should be stuffed with thermal insulation.
And any plasterboard on walls could stop below the ceiling joists

Also, I’d like to keep the material mix from inside to outside as simple as possible. If this is misguided, let me know!

The same insulation could be used in joist and counter-batten zones

I plan to put decorative beams backup once the insulation is complete.

Image 11 (See Right column) gap for plaster between chimney and rafters, circa 15-20 mm)

15-20 mm gap to cover with a 12 mm board?

Eventually, I’ll upgrade the outer roof, as the tin tiles deteriorate, with plans to replace with a warm roof implementation, with ideally a green/living roof on top.

Not without strengthening the roof structure first.

But in the meantime, due to budget constraints, I’m planning to implement some form of cold roof setup, with 5cm air gap to allow for ventilation, such as in diagram below.

Roof is currently only vented at bottom, above large window, so air flow is not great. Considering adding abutment vents to top side of roof, near chimney.

You need to reconsider the perimeter flashings (not high enough?) so you could add ventilation at the same time.

When you change your perimeter flashings consider the final warm roof details flashings to avoid the labour intensive chasing for flashings happening twice.

If you ventilate then the insulation does not want to be open surface:

Not glass, stone or slag mineral fibre, open pored,
- air movement will draw heat out of the insulation (and it has no decrement delay)
Foil faced boards (but plastic already screened from choices) (No decrement delay)
Dense fibres will help keep the heat in the material

Image 12 (See Right column) 3D view of sheet roof waterproofing edge detail

4 is not annotated
the air gap is not noted as ventilated or not ventilated

ROOF INSULATION

Below, I have six questions in relation to how best to insulate the roof:

Setting aside target u-values, what insulation type would you recommend for item ‘4’ in the above diagram, and which brands?

Bio-based:

Medium density wood fibre batt, squeezable at edges, but rigid enough to span
- Squeeze, insert into joist space, release, expands to grip joist sides, does not slump or fall

The options I’m considering are:

Flexible wood fibre (natural material, good heat decrement delay, deals well with moisture, good sound insulation, easy to work with, but don’t know if good air tightness is achievable?)
- Medium density squeezable to archive tight fit but may still be air permeable
- Apply a Vapour Control Layer (VCL) for airtightness and vapour control
- With proper ventilation you may be able to use Airtightness layer not vapour barrier
Sheep’s wool (natural material, deals well with moisture)
- No decrement delay
PIR, kingspan TP10 (good lambda values)
- No decrement delay
- Will drive any moisture escaping through the timbers
- Accurate cut to fit is not easy
- Sawing to fit gaps, generates thousands of plastic particles, to escape into the environment
- Consider vacuuming up plastic particles as you progress
- Irish ‘Gap O tape’ can be used to make airtight fit between PIR (Rigid plastic insulation board) and joists
Open-cell spray foam, Lapolla FoamLok (good airtightness, can deal with awkward areas between walls and joists).
- Cannot create the ventilation zone in the diagram
- Can open cell be air tight?
- Is it moisture permeable or can the timbers rot
  - (there is a moisture permeable air-tight one on the market)
- May not be healthy enough
  - (USA some people using spray foam insulation have had to leave their homes because of off-gassing making them ill)
- Take extra special care if bats are present (£5000 fine per bat)

I’m tending towards flexible wood fibre, as looks easy to work with, relatively low embodied carbon, less polluting and can handle some potential moisture.

I am inclined to agree with your conclusion!

Pavaflex looks suitable to me. Open to your recommendation on best material (or materials) to use on this.

Also look at Unger Diffutherm range via Back to Earth

Is 5cm air gap 100% required in your view?

I’m aware of logic of having one (dew point) but in our mild maritime climate, can it be eliminated if certain materials are used?

A condensation check should always be carried out especially in complicated details like this
UK’s way of calculating static condensation checks ignores reality (seasonal, diurnal, fluctuations in heat, cold, moisture)
Consider WUFI or Delphine calculations, via suppliers of ‘pro-clima’ products in Ireland
I am only aware of aiming to have no due points in your construction
Vapour barriers and breather membranes help in vapour tight construction (UK normal practice)
Waterproof membrane on top puts a vapour barrier in the wrong place hence needing the ventilation zone
With a ventilation zone airtightness layer below and wind tightness membrane at the ventilation zone would help
Solar heated flat roofs will drive out moisture if there is somewhere to escape
I have seem many flat roof with no ventilation zone
Do the calculations before deciding

Depending on what insulation material you recommend, should an air barrier or vapour barrier be used?

And if so, where exactly in the layers, and any brand you prefer?

Vapour closed Construction:

Any insulation that is not hygroscopic (Bio-based) should use Vapour Control layer and Breather membranes (UK normal practice) e.g. Mineral wools and plastics
- Vapour resistance on warm side of insulation
- Breather membrane on cold side of insulation (breathing out wards only)
- Internal resistance 5 times greater than external resistance

Vapour open construction:

Goes hand in hand with hygroscopic bio-based materials
- Permits use of hygroscopic bio-based materials
- Airtightness inside of insulation
- Wind tightness and moisture permeability outside of insulation
- Intelligent membranes performance fluctuates with moisture of atmosphere
- Moisture can pass in any direction depending upon conditions

Depending on your insulation recommendation, what material do you recommend I use where a plaster board is typically used?

I see some wood-fibre boards are sometimes used.

Clay boards are used (reed reinforced clay (40 mm thick)
Wood fibre boards with clay or lime plaster skim

How best to fill awkward spaces between joists and walls?

Picture illustrates the problem.

Not foaming insulation (it will shrink later and will not be airtight or thermally insulating)
- Any flexible insulation material
- Ideally the same properties as the remainder of the roof insulation
- Ideally the same product as the roof insulation (use off cuts)

Image _ (See Right column) gap between joists and walls. Wiring will be removed)

The final question may be challenging! Bearing in mind I plan to upgrade the north facing roof in years to come, to achieve better U values.

Is it possible, at that future point, to put in place some form of ‘combi’ insulation setup, which is a hybrid of cold and warm roof?

Mixing cold and warm will be problematic
If you add more later you will need to do a Vapour check analysis now and again later, better to do both now (Whole House Plan) and recheck later when you find another solution.
You will have to beef up the structure at some point, now or later (Whole House Plan)
If there is a ventilation zone in the middle, the top will contribute nothing to the U value
You could consider injecting insulation to fill the 50 mm ventilation zone,
- oh want a tangled web you weave,
- nothing is easy doing this later,
- a third vapour check calculation will be needed for that combination
Even with the ventilation zone in the middle, the bottom could provide the U value, and the top up could provide all the decrement delay.
You could add the decrement delay when the climate has got worse.
But if you use plastics in the bottom to keep it thin, you will have no decrement protection initially
If you use plastics now you have to use vapour-closed construction.
Much easier (but disruptive) is to take the ceiling off and add insulation to another batten zone
Now sense prevails: add a modular removable and replaceable ceiling panel system (using plasterboards and your mock beams decorative cover beads) now that allows you access to add the extra insulation to a new batten zone below the existing roof at a later date.
Modular allows you to move furniture and do this piecemeal as time permits.
Consider all hygroscopic and vapour open and do the vapour check calculations now.

My thinking is, regardless of which insulation I put in now, I don’t want to have to remove it later.

Good Whole House Planning

Also, ultimately I want to achieve a U-value of circa 0.12

Good Whole House Planning

If I use 18 cms of Pavaflex it gives a U value of circa 0.211 W/(m2k)

Does the Building Control Officer (BCO) permit upgrading and not meeting current regulations? …
.. Despite your whole house plan having future ambitions?

Is there any good reason I can’t, at some future point, remove the tiles, remove the old bitumen covered sarking boards, fill the 5cm air gap with flexible wood fibre,

Nice decision, better than my previous proposal

add stiff structural wood (ply for example)

Ply will add a vapour barrier mid way through the construction

and then wood-fibre boards (or PIR boards)

PIR will add greater moisture resistance out side (wrong side) of lots of insulation

to outer later in order to achieve circa 0.15 W/(m2k) ?

Good but not best target (EnerPHit Compliant?)

Then add waterproof membrane over the top. If done right, my guess is that this would remove dew point problem?

Vapour resistant ply and PIR will create or push the due point into the wrong place
Do the calculations first, dynamic calculations are best

No comments beyond here (so far, will look at these at a later date)

Revision table added last page

Final ceiling
1. Cross battens
2. a -Air sealing / vapour barrier or – AMPACK VARIANO
3. b- Airtight supporting structure,
4. supporting structure
5. Insulation
6. Construction waterproofing – Not for building physics AMPACK AERO
7. **Additional Insulation – Minimum 40mm**
8. Closed roof system part – Sealing the gap ≥ 1.5%
9. Closed roof system part – Extensive protective layer
10. Final outer roof covering

WALL INSULATION

I’ve a few questions also regarding best way to insulate the cavity walls.

Wall cavity depth is 50mm. Currently, it has no insulation.

Construction is as below, with estimate U value of circa 1.7:

The house is split level, on a sloping site, with some basement rooms below ground level, with potential for damp to be a problem (basement room below living room).

The house is somewhat exposed to south side, but overall location overlooking Belfast lough is reasonably sheltered being surrounded by large trees. It’s not as exposed to rain and wind as the north coast of Ireland or the West of Scotland for example. The east coast of Ireland is much drier than the west.

The upper story of the house is rendered, which has several large cracks in places. I believe it would be a good idea to repair this right after any cavity insulation is installed in order to reduce risks of water entering the cavity.

The lower story is brown brick.

Image _ (See Right column) south side of house, with rendered top floor and brown brick on bottom floor)

Image _ (See Right column) south side of house, showing cracks in render)

My current view is that it’s best to have some form of cavity insulation, to prevent thermal bypass occurring by air moving through the cavity.

My main questions are around how best to achieve the target u value for the walls, avoiding damp issues within the cavity, generally avoiding potential dampness issues.

Assuming I plan to reach a U value of circa 0.15 W/(m2k), how do you recommend I achieve this?

What material/brand should I use in order to insulate the wall cavity?

I’m considering two different approaches/materials, but open to other suggestions from you.

Assuming it makes good sense to insulate the cavity, the two main options I’m considering are:

Fill entire cavity with ‘Walltite’ (£8k for whole house) and at later point, add exterior insulation in order to achieve u-value of 0.15 W/(m2k). ‘Walltite’ will help with air tightness, will perform if damp and not conduct dampness through the cavity (I believe). My concern is the cost, the high embodied carbon and possible polluting aspect of the materials used (off gassing etc).
1. Fill cavity with beads (to restrict airflow and thus thermal bypass) at cost of around £700, and later add exterior insulation to achieve u-value of 0.15 W/(m2k).

In addition to the above, the next question is what material/brand should I use in order to insulate the exterior of the wall?

External installation options I’m considering:

Cork (natural material, low embodied carbon, non polluting)
- Wood-fibre boards (natural material, low embodied carbon, non polluting, lets walls ‘breath’)
- Expanded polystyrene (EPS) (relatively thin, easy to get local installer)

Where I really need your input is in deciding what materials will best compliment each other here.

I have plenty of space on either side of house, so I’m not too concerned about thickness of the walls.

Problem is, I may have difficultly finding someone locally who installs anything other than EPS for exterior insulation!

FLOOR INSULATION

The ground floor of the house has suspended wooden floors, with good access underneath the house (two feet crawl space from bottom of joists to ground). The joists on ground floor are also 9inches deep, so I have that as a minimum space for insulation, and up to 15 inches in total if needed.

What material would you recommend using in this space?

This is area I’ve given least consideration to, so open to your advice on this.

In general, I’ve done lots of research on insulation over the past few years, but really, it’s brought me to the conclusion that it’s a very technical and complex area and I need professional guidance.

Good for you for trying for so long

Basically, I know enough to realise I know nothing! J

You seem to know more than many architects I know and work with

Much appreciate your expert views in this area,

I would never call myself an expert, X is an unknow quantity and spert is drip under pressure

Conor

Brian GBE

Rev No	Comments	Author	Date
A00	File name FINAL	CMcG	14/11/17
A01	Save as and start response to North roof only initially	BRM	03/12/17
A02	Small refinements on webpage	BRM	09/12/17