Heat Pumps in Historic Buildings

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 entire heating system is well-designed, it will deliver comparable running costs to a natural gas system.

Water source heat pump (WSHP) 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 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 WSHP installations and associated heating systems. They also interviewed building users to gauge their opinions on running costs, thermal comfort, noise, and visual appearance.

The key findings were:

• Closed-loop WSHPs are a viable and readily available option for discreetly decarbonising heating systems in historic buildings.
• When used for conservation heating, WSHPs can operate efficiently with existing radiators and pipework.
• Many historic stately homes are located close to a body of water, because this was a priority when they were built. WSHPs are, therefore, particularly suited to these buildings. When a body of water is available nearby, a WSHP system can be a more discreet solution than an air source heat pump (ASHP) system and a more straightforward installation than a ground source heat pump (GSHP) system.
• Issues with a heating system’s performance are often due to its configuration, not the WSHP itself. The open-loop system at Site 2 was the only one that experienced significant difficulties extracting heat from the source.
• Closed-loop WSHPs have similar noise levels to other heating system components, such as large circulation pumps. They are installed inside a housing in a plant room, and noise reduction measures are, therefore, more readily available than they are for outdoor 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 WSHP system.
• The availability of skilled maintenance and installation contractors was an issue at a number of the sites.
• Safe and effective maintenance options and a good understanding of the water source are essential when designing an open-loop WSHP system.