Actions to decarbonise buildings: a whole life carbon stock assessment

In this paper we develop a whole life carbon stock model to assess the impacts of retrofit in cool-temperate climates. The developed model can explore different retrofit deployment rates to limit emissions of the existing building stock, and be used to develop different pathways which could meet carbon budgets for varying future scenarios. We illustrate the application of the model to the English school stock, comprising approximately 20,000 schools. In applying the model, we find that an estimated school carbon budget is only met with a significant increase in retrofit rates from current ambitions, alongside significant decarbonisation in electricity and material sectors. When retrofit modelling is applied at scale, the aggregated impacts of material consumption are highlighted, and the most stringent carbon budget cannot be met when a whole life carbon approach is taken. Heat pumps and mechanical systems post a significant carbon hotspot due to the use of carbon-intensive materials and regular replacement rates. These systems would therefore benefit from research and development to reduce their impacts. The developed model also allows for a stock level comparison of retrofit to the alternative of demolition and new construction (to different future standards). We show that retrofit provides the lowest whole life carbon solution over the 25 year study period for all buildings, compared to proposed ambitious UK whole life carbon targets.