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GBE Retrofit Internal Options (Brainstorm) G#42059

GBE Retrofit Internal Options Brainstorm

GBE > Encyclopaedia > Code > Brainstorm > G#42059

About:

Helpdesk:

  • HiiGuru Ask an Expert 30 minute video call between a customer and BrianSpecMan taking notes and follow up additions to those notes with some analysis.
  • (PS indicates new information not discussed in call)

Prior information

  • Form filled in by customer, 3 internal photographs by customer, floor plans supplied by customer

Description:

  • Terraced Victorian 2 storey house no bay windows, 2 storey original rear extension
  • Floor plans if accurate show Victorian modesty door swings (except in one case) so may be original doors.
  • Existing solid brick external, party and internal partitions
  • Projecting chimney breasts, fireplace closed with air brick at low level
  • One window shown does not look original?
  • Carpet without underlay laid directly on softwood floorboards (carpet left down during works will be remove with all debris after completion) but potentially hiding problems until removed
  • Walls were wall papered covering up damp plaster
  • Evidence of extensive damp at high level.
  • Is there a diagonal line of damp or repair? (not dormer construction, so possibly due to roof/eaves leaking?)

Previous interventions:

  • Any previous internal coving plaster mouldings do not exist in the photos provided.
  • Internal plaster previously applied is new gypsum with some of the party wall may be lime (soft sandy plaster)
  • Ground level Kitchen and neighbour’s property has suffered drain collapse subsidence that has been repaired.
  • Ground level outside has been lowered, filter drain (previously known as French Drain) against external face of wall
  • Chemical damp proof course has been injected and internal wall has been damp proof coated (extent not determined) and gypsum plastered.

Comments on previous interventions

  • Chemical damp proof courses (DPC) were an obligation with grant funding in the 1970’s and no doubt those companies selling and installing it kept on going for decades afterwards.
  • I rarely see or hear about Chemical DPCs today, have they gone out of favour?
  • Today we tend to let solid masonry do their thing and insulate with moisture open materials to allow the moisture out.
  • Filter drains have the potential to allow air drying of the wall below ground, but only if they are well drained.
  • Waterproof tanking of the outside of the wall is a precaution if the filter drain gets waterlogged but prevents the wall drying out.
  • Waterproof tanking of the inside of the wall is a precaution if the filter drain and outside tanking fails but prevents the wall drying out.
  • Chemical DPC is also a precaution if the lower wall gets wet that hinders it drying out.
  • Inspect for any frost damage to bricks and mortar.
  • Gypsum plaster also hinders the wall drying out inwards.

Proposed or current actions:

  • Paper being removed
  • Propose to remove the chimney breasts.
  • Needs new roof and guttering.
  • Proposing to remove gypsum plaster
  • Proposed to batten out and insulate inner face of external wall
  • Considering sheep’s wool as Internal Wall Insulation IWI

Further explorations:

Party Wall Survey, PW Structure Notice, Party wall agreement, Party wall awards

  • The ambition to remove the chimney breasts can lead to damage to the other party’s half of the party wall.
  • Depending upon the dimensions the chimney flues may be interlaced or in two parallel lines.
  • Interlaced flues will make the removal of your side of the chimney breast more challenging.
  • The party wall survey is essential and can include a measured survey, photographs at roof level and internally to record the state of repair and the geometry.
  • Consider what happens and will happen at foundation, ground floor, upper floor, ceiling, attic and roof levels allow to carryout remedial work in all cases.
  • It will form part of the Party Wall Agreement and be used to show the existing, compare with the aftermath and determine any compensation for changes that occur due to the works.
  • https://www.gov.uk/government/publications/preventing-and-resolving-disputes-in-relation-to-party-walls
  • Party walls can be a large heat loss if the adjacent building is unoccupied, but if we assume it is occupied and heated then the heat transfer between houses through the party wall is negligible, however at the external wall junction it may be useful to add insulation to the party wall to reduce the thermal bridge at the party wall/external wall abutment.
  • If the party wall is not insulated it can be exploited for thermal, acoustic and moisture mass, after removing any gypsum plaster consider applying clay or lime plaster, for airtightness with improved acoustics, for thermal mass to hold excess heat and moisture mass to regulate humidity.
  • With the right insulation materials and finishes all these issues can be addressed with one system.
  • Earth and cork granule internal plaster is multifunctional.
  • Diasen’s Diathonite Evolution (PASS) https://greenbuildingencyclopaedia.uk/?p=433

PS Roof coverings and gutter

  • Victorian terraces most often have roofing slates which are thin and relatively lightweight
  • Reroofing can be with the same slates, although some will probably be damaged taking them off.
  • Some additional slates can be obtained from Architectural Salvage Yards
  • https://www.salvoweb.com/salvo-directory/category/all/location/uk/region/all?q=roofing%20slates
  • Replacing roofing slates with heavier concrete or clay tiles will overload the roof timbers unless you replace the timbers too.
  • Timber suffers from creep and will move away from the load over a long time and some details may suffer weather leakage.
  • Avoid switching to metal roofing tiles which will be lightweight but offer no protection from solar gains via the roof tiles.

PS Suspended Floors:

  • Inspect under the carpets asap in case of hidden problems that may need to be addressed sooner rather than later.
  • Inspection will determine the direction of boards and joists any trimming around the chimney breasts and staircase.
  • Work out how the holes will be closed once the chimney breasts are removed.
  • Check for any damp or mould in timbers
  • Upper floor will show up any air leakiness and the need for insulating the floor (thermal or acoustic and at perimeter)
  • Ground floor will show up any air leakiness and the need to insulate the floor.
  • Where you are insulating walls with IWI make sure you address the thermal bridge in the floor zones.
  • Enviroform Solutions Ltd. Https://GreenBuildingEncyclopaedia.uk/?p=4728
  • Thermo-Joist: Foil wrapped aerogel
  • https://prezi.com/dlmqm33k8vgn/copy-of-introducing-enviroform-solutions/

PS Attic:

Consider inspecting and testing the filter drains:

  • Ask the neighbours where the filter drain is drained to, do they have any details, specifications, photos, etc.
  • Ask Local Building Control Office what records they have, determine what approach was taken and the details submitted, inspected and approved.
  • (This work may have been done without BCO involvement; in which case you may be opening a can of worms).
  • Add a few buckets of water to top of filter drain, listen for water draining into drains via inspection chambers.
  • To see if and where it drains, quickly or slowly, remove inspection chamber lids and add a few buckets of water to top of filter drain, see if it drains into surface water or foul water drains.
  • If not, it may be drained to a soakaway in the garden, which may drain slowly, or it may not be drained at all.
  • Lay sheets to collect and separate any different materials removed from the filter drain, to enable reinstatement as designed.
  • Limit the extend of the exploration to limit the risk of trench side collapse.
  • Remove the gravels until you can see the pipe at the bottom of trench and see the outer face of the wall.
  • If the trench is waterlogged it probably is not drained or the drains are blocked.
  • A filter drain needs a pipe at the bottom of the trench, top half perforated bottom half solid, laid to falls to drainage points.
  • The external face of the external wall or the whole trench may be tanked (membrane and/or painted on and all joined up).
  • Inspect for any frost damage to bricks and mortar if visible and above ground below Chemical DPC.

Proposed interventions:

Gypsum plaster:

  • Ideally all gypsum plaster is removed from inside face of external walls to enable the solid brick wall to return to its moisture vapour permeability wall.
  • Gypsum can be removed and replaced with lime plaster or clay plaster which are moisture absorbent and permeable.
  • Or apply IWI system with insulation and finish, all moisture permeable.
  • See Suppliers below

Sheep’s wool as an Internal Wall Insulation (IWI) on inside face of external walls

  • Before using sheep’s wool as an IWI check with the manufacturer’s (or the suppliers) is this a competent application?
  • Was the product developed for this application?
  • Is there manufacturer’s recommendations or British Board of Agrément certificate for this application?
  • If none exists, then this is not a route for a Professional designer/specifier, and I would suggest you err on the cautious side.
  • Consider plant-based fibre insulation products and systems designed to do this that can be fixed directly to brickwork
  • Insulate the walls abutting the external wall to minimise the risk of thermal bridging.
  • If chimney breasts are to remain insulate from external wall to the chimney breast.
  • If chimney breasts are to be removed decide if the whole wall will be insulated or if a step in the wall surface is acceptable.
  • See Suppliers below

Battening out was mentioned:

  • Battening out is often used to create a flat or levelled surface to attach insulation or lining boards but can create a cavity, but a cavity creates a barrier to moisture transport, and a place for ever present mould spores to meet moisture vapour to start growing mould in the cavity unnoticed until it emerges.
  • There are IWI systems available that are fixed directly to the internal face of the external wall, without battening they include a low-density wood fibre against the inner face of brick wall with a dense wood fibre room side with an internal finish; all of which are moisture vapour open and compatible with solid brick external walls.
  • Suppliers of these insulation types will offer to do WUFI calculations to determine the optimum (minimum and maximum) thickness of insulation to reduce the risk of hygrothermal moisture movement putting brick at risk of interstitial condensation, rainwater penetration and frost damage and putting any embedded timber at risk of mould.
  • See Suppliers below.

PS Caution with any remedial waterproofing

  • There are airtight moisture permeable paint on products to allow brickwork to remain moisture vapour open.
  • They are not waterproofing or tanking.

Radiators

  • Avoid placing radiators on external walls and below windows
  • Better to be placed on internal walls to heat the wall and the room rather than heat the sky via the window

Electricity:

  • Economy 7 electricity is provided to the building but it may be time to give up.
  • Economy 7 electricity is cheaper for nighttime electricity, but the day rate is more expensive to pay for it.
  • Economy 7 is only beneficial if there is a lot of energy demand at night, e.g. Night storage radiators, but piped radiators appear in the photographs.
  • Electric Vehicle EV charging is ideally carries out connected to PV panels via battery,
  • Mixergy Domestic hot water heater is internet connected and monitors the price of electricity by the hour and only takes energy to heat water at the lowest cost which can be low, zero or be paid to take it.
  • There are equivalent heating system that do the same storing the energy in a heat store.
  • Mixergy (Blog) https://greenbuildingencyclopaedia.uk/?p=20220
  • Appliance Energy (Checklist) https://greenbuildingencyclopaedia.uk/?p=41788
  • Future-proofing energy bills (CPD) https://greenbuildingencyclopaedia.uk/?p=40685
  • Renewable Energy Ready (Checklist) https://greenbuildingencyclopaedia.uk/?p=41815

PS Window & Door Jambs

Other links

Insulation:

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URL Check 26th July 2019

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