Retrofit of existing housing in the United Kingdom: the carbon reduction possibilities

Feasibility studies were undertaken into retrofitting three examples of social housing stock to meet the carbon reduction targets of the UK government. The results of energy modelling show that the targets cannot readily be met by the combination of passive means and the use of tried and tested technology. On the dwellings modelled up to 50-60% savings in CO2 were predicted using passive measures combined with established solar thermal technology, at a reasonable cost. To meet the full carbon reduction objectives of the programme it was necessary to employ, in addition to the passive measures, innovative PV-T (Photovoltaic Thermal) panels, whose effectiveness is untested over the long term. The addition of PV-T predicted further carbon savings of around 50% - theoretically making the dwellings net generators of electricity, at significant extra cost. The buildings were of medium to low architectural quality and the proposals included the application of insulation to the outside face of external walls – the most effective location for wall insulation. However, this solution, employing external insulation, is unlikely to be acceptable for a significant proportion of UK housing, much of which has a higher architectural or historic value. A key lesson for the retrofit of housing is that, because of both technical and aesthetic considerations, it is highly unlikely to be possible to meet the UK government’s carbon reduction objectives by on-site measures alone.