A Part L Zero Carbon home performance or a Passivhaus?

The energy performance of buildings is assessed through Part L of the Building Regulations. All buildings must meet these standards as well as targets formed through planning policy. The Passivhaus Standard is a voluntary certification that demonstrates a high level of energy performance. However, Passivhaus homes still need to demonstrate compliance with Part L and their performance therefore needs to be set in a regulatory and planning context.

The Passivhaus Standard is typically defined by a small number of energy use targets. Although these are important to the standard; design processes, peer review procedures and construction quality checks mean that following the Passivhaus methodology can result in higher performance buildings than those completed through Part L assessment.

So, what is best for consumers? A Part L zero carbon home performance or a Passivhaus?

The Passivhaus process requires a more involved assessment of a building’s expected energy use performance compared to SAP, the methodology used for Building Regulations compliance. Combined with rigorous auditing procedures and post-construction checks, Passivhaus would clearly be an effective way to reduce the performance gap that is currently reported for Part L homes.

The Passivhaus standard is almost entirely focussed on energy use reduction measures, rather than allowing energy to be offset through the use of renewables or other technologies. Passivhaus therefore should always result in dwellings with much lower energy demands.

However, Passivhaus is an assessment of energy use in buildings and therefore doesn’t align with the metric for national targets, carbon dioxide emissions. Passivhaus developments can struggle to meet the current carbon dioxide targets set by the GLA without the inclusion of low or zero carbon energy generation technologies. The implementation of a Passivhaus standard planning target alone would not encourage renewable energy uptake.

But are the standards even comparable?

Passivhaus is a design approach and quality standard, which results in an energy performance assessment. Part L is an enforcement method for legally minimum building standards. Given the latter’s granularity and accepted error margin it cannot be expected to match the higher Passivhaus building standards.

What’s the conclusion?

A Passivhaus only target would not achieve national climate change CO₂ objectives because it does not contain specific renewable energy generating targets. However Passivhaus does improve overall building performance, evaluation and quality. The Building Regulations and their compliance mechanisms need to up their game if they are to meet the Passivhaus Standard.