Research Report - The right time for heat pumps in retrofit

Published: April 2024
v 1.2 issued June 2024

The UK has some of the worst performing housing stock in Europe. Too many homes suffer damp and mould, resulting in poor health outcomes and a £1 billion plus cost to the NHS – and at the same time, heating our buildings is responsible for nearly a quarter of the UK’s carbon emissions. There is an urgent imperative to decarbonise heating in our homes, but we also need better housing that is more comfortable, healthier and cheaper to run.

Simply replacing a gas boiler with a heat pump can reduce carbon emissions by around 77%, but it does not address the effects of poor building fabric and ventilation on health and comfort. Enabling heat pumps and fabric to work in synergy to maximum effect could deliver, not simply "fabric first" – but the “people first” choice.

This paper explores the implications of installing an air source heat pump at different levels of fabric improvement by modelling some typical retrofit scenarios, using PHPP to estimate energy demand and hence running costs. It aims to answer the question “when should you install a heat pump in a staged retrofit?”, and thereby help clients and designers to make informed decisions in developing an optimum retrofit plan.