Heat Pumps in Historic Buildings

This project was commissioned by Historic England and carried out by Max Fordham LLP. The research aligns directly with Historic England’s climate change and sustainability objectives.

Electrifying heat is key to reducing reliance on fossil fuels across the heritage sector. No technology is better placed to electrify heat for space heating than heat pumps. The technology is mature, and if the whole heating system is well designed it will deliver comparable running costs to a natural gas system. Ground source heat pump (GSHP) technology can be deployed discretely without altering a site’s appearance, and it delivers excellent efficiency. It is, therefore, a key technology in the decarbonisation of space heating in historic buildings.

The five case study visits took place between February and April 2023. Engineers from Max Fordham LLP carried out visual inspections of the GSHP installations and associated heating systems. They also interviewed building users to gauge their opinions on running costs, thermal comfort, noise and visual appearance. The engineers took as many quantitative measurements as possible, but time constraints and minimising the intrusiveness of site visits meant that most of the findings were qualitative. Assessing running costs was particularly difficult. Where data were available, they came in the form of energy bills. This made it challenging to make quantitative comparisons before and after installing the GSHPs. The users’ perceptions of running costs are reported, but the information is highly subjective according to each individual’s expectations.

The key findings were:

• Closed-loop GSHPs are a viable option for decarbonising heating systems in historic buildings.
• GSHPs are being deployed to decarbonise heating without major work to the existing heating system, particularly where conservation heating is the heating strategy. Further works can follow to help improve the effectiveness and/or efficiency of the heating system.
• Installing a ground collector is disruptive. After the ground is restored, the ground collector is barely noticeable, with only a small number of manhole covers visible.
• Issues with a heating system’s performance are often due to its configuration, not the GSHP itself.
• GSHPs have similar noise levels to other heating system components, such as large circulation pumps. GSHPs are installed inside a plant room, and noise reduction measures are, therefore, more readily available than they are for outdoor air source heat pumps (ASHPs). Acoustics should be considered, but may not require any more attention than those of a fossil fuel system.
• Building users need to have a good understanding of how to use system controls to maximise the efficacy of the system.
• The availability of skilled maintenance contractors was an issue at a number of sites.