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Research report - The right time for heat pumps in retrofit

Category: Guidance


The right time for heat pumps: Decarbonising home heating in a staged 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 dampness and mould, resulting in poor health outcomes and a cost to the NHS is estimated at more than £1 billion – and heating our buildings is responsible for 23% of the UK’s carbon emissions.

There is an urgent imperative to decarbonise heating in our homes. 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.

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


Moisture and EnerPHit Good Practice Guide. PHT publication January 2024



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PHT Patron Member logo whiteThanks to our Patron members

We are grateful to our Patron members, whose ongoing support has
funded this publication.

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