Bespoke PER UK - Certifiers' Circle Guidance

The Passivhaus total energy metric, aimed at aligning low operational energy buildings with a future all-renewables grid, is PER, or Primary Energy Renewable. It aims to quantify how much renewable energy generation would be required, in a future all-renewable grid, to supply the energy needed at the building.

For most buildings, the standard PER limit will apply. Alternatively, in the case of high occupancy density in residential or office buildings, an in-built calculation within PHPP 10 can be used to set a project-specific criterion. But for some other building uses with a very high energy demand, the standard or calculated limits may not be appropriate. In these cases, the limit value may be exceeded after consultation with the Passive House Institute.

This guidance note from the UK Certifiers' Circle, authored by our Passivhaus Director Gwilym Still, aims to clarify when and how a higher PER limit may be set for Passivhaus certification. It provides answers to frequently asked questions about what PER is, how it relates to other metrics used in the UK, under what circumstances a bespoke PER criterion might apply, and how to check if it does.