Exhaust Air Heat Pumps in Part L 2026

EAHPs are currently struggling to enable Part L 2026 compliance calculations for typical apartments, with only a single product producing positive results. We expect that this will change after further testing and manufacturer updates.

EAHPs provide low carbon heating and hot water with an additional benefit of some cooling making them useful to address Part O requirements. Their performance to mitigate overheating is linked to both their ventilation rate and cooling capacity.

Development with longer programmes should maintain compliance on their risk registers as the impact and release of Home Energy Model (HEM), which will replace SAP 10.3, is still unclear. EAHPs may perform better or worse under the new methodology, and compliance position could shift once HEM is released.