Blog June 2014
I am on the Committee of our local group to develop a Neighbourhood Plan
And we are discussing if the existing Conservation measures are popular.
As the housing stock is almost 100% solid brick wall construction, I have brought up the subject of external solid wall insulation, and produced the following note for residents to appraise their options;
NOTES RE EXTERNAL INSULATION TO BACKS OF HOUSES
Current wall construction of solid brick wall and plaster has a very low insulating value so if you want to save energy it is wise to check your insulation options, loft insulation and double glazing being the first measures to take in improving the energy performance of your home.
The government are trying different methods of encouraging people to do this and one of their new measures will be to offer new home owners a voucher worth £6k to install wall insulation.
If you upgrade your walls to current standards you can improve its performance by seven times, however technically it is not a straightforwards matter. External wall insulation is better technically, but it will alter the house appearance and needs to be detailed carefully. Internal wall insulation cannot provide a complete lining and where there are gaps problems arise.
Currently neither render nor external insulation is allowed on the brick front walls and nor on the rear or side brick walls above the Ground Floor in the Conservation Area. Generally fronts of houses should not be painted either, to protect the appearance of the facing brickwork, but the backs can be, which has been done a little, breaking up the homogeneity of the rear poorer quality stock brickwork.
We are suggesting to tighten control at the fronts of houses but to loosen them at the back, so any wall insulation to the fronts of houses should be internal, and we want to know regarding the backs of houses
- firstly if residents want the freedom to paint the external walls,
- and/or if you want to be allowed to install rendered external wall insulation,
Any changes to the existing policy needs to be added to our Neighbourhood Plan, so please respond. It was felt that not enough information was available when discussed at the local meeting so here are some notes to inform you.
In a typical red brick house, if there is no rear ground floor extension, this measure to the back walls of the house would reduce your heating bill by about a third. Looking at the bills of a typical house, this may be up to £300pa currently
Here is a list comparing the alternative of internal insulation;
Internal Wall Insulation
• Can be undertaken on a room by room basis.
• Doesn’t affect external appearance so the homogeneity of the existing brickwork will remain
• there is a loss of thermal mass increasing the response times to the change in temperature and but also reduces the likelihood of condensation on internal wall surfaces
• no extra maintenance
• Minor reduction in room size, difficult if it impacts on a perpendicular door width
• Disruptive and inconvenient
• Any pipes and electrical outlets on external walls will also need to be re-routed, especially in bathrooms and kitchens
• requires skirting boards, door frames and external fittings to be removed and reattached
• can make it hard to fix heavy items to inside walls – although special fixings are available
• Thermal bridging problems, at floor, wall and ceiling interfaces likely to cause rotting of concealed timbers built into the structure. Detailing of window reveals can be especially challenging
• As the brick part of the wall is insulated from the heating there is a loss of heat and cooling storage in the brickwork, and the loss of thermal flow into the building fabric results it in staying colder and wetter for longer periods reducing further its thermal value with increased risk of frost damage to external faces.
• Requires a vapour barrier applied to original wall which then prevents building fabric from breathing via the internal face.
External Wall Insulation
• Least disruptive for occupants and existing finishes and easier to install.
• Has no effect on internal building services.
• Overcomes thermal bridging.
• Does not reduce floor area
• Renews external appearance
• Improves weatherproofing and sound resistance
• Fills cracks and gaps in brickwork reducing draughts
• Reduces condensation on internal walls and can help prevent damp (but will not solve rising or penetration damp)
• Finish is durable and designed for the lifetime of the building
• Prolongs building life
• Aesthetically pleasing
• Low maintenance
• Extensive range of finishes and colours
• Hard renders systems may not allow for the moisture and vapour movement associated with traditional buildings built in lime mortar, therefore causing cracks that can allow moisture ingress, but a polymer additive makes is flexible
• Needs a render specification which allows the building fabric to breathe via the external face.
• Detailing around openings, at eaves and at d.p.c level requires careful attention to ensure that vulnerability from rainwater is eradicated, and appearance is acceptable; higher spec phenolic insulation which is thinner and 7% more expensive, and would be required to assist.
• Any external fittings; pipes boiler flues, lights &c will need to be removed and refitted
• Increased thickness of wall may cause junction problems needs careful detailing to be visually acceptable
• Changes the appearance, losing the homogeneity of the rear terrace unless all do it.
• Access issues relating to installation, particularly if there is a ground floor extension to scaffold over.