Speaking at Retrofit Live 2015, Colin King, Director of BRE Wales, warns of the harm to houses and health from badly designed and installed external wall insulation (EWI).
One of the country's leading building specialists has warned that the current drive to clad older houses with external wall insulation (EWI) runs the risk of 'trashing the built environment', writes Robert Hine. Colin King, Director of BRE Wales, was speaking on Day 2 of Retrofit Live at CoRE (Centre of Refurbishment Excellence) in Stoke on Trent to an audience of building professionals, manufacturers, academics, and delegates from the social housing and community sectors.
The current government strategy of providing grants for the large-scale insulation of homes primarily to save carbon emissions is misguided, he argued, and is already having unintended consequences because of faulty design, poor quality of workmanship, and lack of regulatory oversight. There is much work still to do before we properly understand just what effect EWI will have on the building fabric in the medium and long term. Some buildings were already suffering serious problems of damp and mould because of shoddy installation work.
Colin and his team at BRE have examined around 2000 brick-built homes with EWI, and none of them could be held as examples of good practice, he claimed. Part of their study involved looking in detail at how walls and other features are constructed, and the effects that different types of brick and building styles have on material properties, such as heat and moisture retention. He was adamant of the need for a comprehensive database of reference values, so that we can more accurately predict the effects of adding an insulating layer to the external wall of any particular building, whether on the outside or the inside.
The Centre of Refurbishment Excellence (CoRE) in Longton, Stoke on Trent, is a non-profit organization that delivers training and supports best practice in the retrofit sector. The building is based on refurbished formerly derelict pottery factory.
Enormous variation in buildings
The work at BRE has shown that properties of buildings vary enormously, even apparently similar ones on the same street. For example, the heat transfer through just a single wall (measured as a U value) can vary over the area of the wall, depending on exposure to the weather, moisture content, variations in construction, ventilation, and so forth. To determine how walls really behave, BRE have reconstructed walls in a laboratory using old bricks and mortar mixes, and tested the effects of adding EWI.
BRE has documented many examples of homes that have had the wrong material applied badly and with little or no attention to detail. This is storing up trouble for the future as a result of cold bridging, moisture retention, and condensation. This will not only cause deterioration of the building fabric, but also could impact the health of occupants, due to damp and mould inside the house. This evidence forms part of a report to government fousing on these 'unintended consequences' of EWI, which has yet to be published.
"Aim for comfort first"
Colin stressed the need to develop the expertise in design and construction required to tackle the challenges posed by installing EWI in older houses. A generic approach, with 'one size fits all', was a recipe for disaster. Each building had its own individual features, including occupants' behaviour, and should be treated as such. Also, a new regime of independent checks would ensure better quality of work. The prime goal should be to make homes more comfortable and economical. Carbon savings would then follow anyway.
"You are a willing audience. In a way you're not the ones I need to be speaking to. It's the ones out there still doing the work that need to listen," he concluded. And of course the clients, who are the ones unwittingly facing the unintended consequences of 'doing the right thing'.