Just exactly how much, and how quickly, can we reduce carbon emissions from heating England’s new and existing homes – and can we justify the embodied carbon emissions of the materials and products used? The AECB takes a deep dive into the figures using their simple PHPP-based building stock modeling tool as Andrew Simmonds and Lenny Antonelli chart the group’s recent work with Tim Martel and Green Party energy policy advisor Tony Firkins.
Policymakers expect the building industry and home owners to make deep cuts in their energy use to dramatically lower greenhouse gas (GHG) emissions because perhaps, at least in theory, reducing emissions from buildings is seen as easier than in other areas – such as decarbonising the UK’s heat supply and industrial sector.
The thinking goes that if you retrofit existing homes so they use ‘much less energy’, and construct new buildings so they use ‘almost none’, you can dramatically cut the sector’s heating energy needs, and therefore CO2 emissions. Then alongside taming heat demand we can decarbonise the UK’s heat supply (this is going to be very challenging). But is it really that straightforward to decarbonise England’s homes, and how can we validate or improve policy assumptions underlying these aspirations?
The AECB decided to try to add up the main CO2 emissions related to heating, improving and constructing England’s housing stock, as well as factoring in the need to emit CO2 to invest in retrofit materials and products – the ‘Carbon Burp’. The model also factors in: the rate of dwelling demolition and conversions from non-domestic buildings; the rate of building new homes; the number of listed buildings unlikely to be significantly improved; and the levels of building regulations and new build & retrofit energy performance being aimed for. This initiative is in essence an informed, ’back of the envelope’ exercise intended to be thought provoking and useful. The fully referenced spreadsheet is available for those who want to check the method and the figures. If there is sufficient demand the AECB will run an interactive webinar on this piece of work.
The intention was to keep the model as simple and transparent as possible, with all assumptions and key numbers clearly stated. They wanted to be able to adjust basic input data and change key assumptions easily to allow ‘sensitivity testing’ – to get a feel for what factors are more important, which are less so, and even inform fine-tuning for policy.