ColdProof

AECB Retrofit Standard for a 1960s detached bungalow in Wrexham

This was a whole house retrofit done in one go, which was certified to the AECB Carbonlite Retrofit Standard. The final space heating demand according to PHPP was around 30 kWh/m2.yr (representing an 86% reduction from baseline), and the team managed to get a good airtightness result (1.015 ACH). The contractor for the job was Jon Day from Myzsa Group, who was responsible for coordinating most of the work. For the walls, this involved insulating the external walls using EPS which required the rafters to be extended at both the eaves and gables, as well as requiring a reconfiguration of the garage roof and a couple of other external structures so that the insulation could pass behind. The cold loft (insulated at ceiling level) was converted to a warm roof that was insulated over / between / under rafters with wood fibre (for which a structural engineer had recommended strengthening a couple of the purlins), the floor had phenolic added over the existing slab, and new windows and doors were installed (which were set on brackets fixed to the outer leaf to ensure no thermal bridging). Thermal bridge modelling was carried out on all junctions to minimise heat loss and check condensation risk. As always with retrofit, there can be some tricky details to resolve in terms of either insulation or airtightness continuity, and in this case the junction between external wall insulation and the pitched roof was a challenge for both – we have written about the airtightness challenge here and our specific solution on a Linkedin post. A heat pump was installed by Integrated Energy which had an operating COP of 4.4, and the MVHR ventilation system was designed by Luft MVHR.