Heat pumps in historic buildings : air source heat pump case studies – large buildings

Electrifying heat is key to reducing reliance on fossil fuels for historic buildings. 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. Air source heat pump (ASHP) technology can be installed quickly and has lower capital costs than other heat pump technologies. This makes air source a key technology in the decarbonisation of space heating. This report is a continuation of the previous study ‘HEAG0316: Heat Pumps in Historic Buildings, Air Source Heat Pump Case Studies – Small-scale Buildings’, and focuses on five large historic buildings across 4 sites. In 2022, we commissioned environmental building services engineers, Max Fordham LLP to review the performance of ASHPs in larger historic buildings. The research aligns directly with Historic England’s climate change and sustainability objectives. The four site visits took place between November 2022 and February 2023. The engineers from Max Fordham LLP carried out visual inspections of the ASHP installations and associated heating systems. They also interviewed building users to gauge their opinions on running costs, thermal comfort, noise, cold air plumes 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 challenging. Where data were available, they came in the form of energy bills. This made it difficult to make quantitative comparisons before and after installing the ASHP. The users’ perceptions of running costs are reported, but the information is highly subjective according to each individual’s expectations.