Residential retrofit in the climate emergency: the role of metrics

This paper examines whether current residential retrofit metrics are fit for purpose and if they can help deliver swift and significant cuts in carbon emissions. Information is presented on metrics used for a variety of UK and European Union building and building retrofit standards and evaluation and assessment tools. An analytical approach is developed that offers a simplified set of four key aspects of metrics: scope, headline measurement, normalisation factor and timescale. This helps to unpack the complexity of metric design. However, choice of metrics is not simply a technocratic issue, because their design is not value free. Two examples where metrics form the basis for policy-making for retrofit and energy use in buildings are described: UK Energy Performance Certificates and the Energiesprong approach to deep retrofit. Use of multiple metrics improves their fitness for purpose and is already established practice in some standards and policy. Metrics in common use omit many aspects of energy use in buildings. New metrics are required that can take account of the whole life of a building, the time profile of retrofit, or the ability of the building to be flexible as to when energy is used.

Policy relevance

• Existing and new metrics can contribute to the transformation of the building stock. They have real-world impacts on buildings, those retrofitting them and their occupants.
• Retrofit metrics embody values and views about how retrofit should be undertaken.
• Unpacking metric design and considering scope, headline measures, normalisation factors and timescale separately can help inform better policy decisions.
• There is no one ideal metric for building retrofit—many policies and standards use multiple metrics.
• A focus on carbon metrics only for retrofit can lead to missing opportunities for high-quality building fabric. Energy metrics remain important.