Government consultation opens on home energy assessment

Critics say Home Energy Model (HEM) lacks ambition and fails to address key measures, such as reducing carbon emissions from construction

The government has announced an open consultation into the Home Energy Model (HEM), which will replace the Standard Assessment Procedure (SAP), the primary tool for gauging the energy efficiency of domestic properties. 

The HEM – created as part of a three-year research project with the Department for Energy Security and Net Zero and the Building Research Establishment (BRE) – will be implemented in 2025 as part of the Future Homes and Buildings Standard (FHBS).

One of the FHBS goals is that new domestic properties must have 75-80% lower carbon emissions through the adoption of low-carbon alternatives to gas central heating.

The HEM has been designed to support different applications where energy performance assessments are required. It can also model energy performance for every half-hour of the year, enabling better representation of smart technologies and storage.

Gillian Charlesworth, BRE Chief Executive said: “This is a significant milestone on the road to achieving net zero across the UK’s housing stock. BRE has worked closely with government since SAP was introduced and we are excited about the potential for ambitious policies and programmes for low-carbon homes, which the latest version will support.”

However, the plans have received some criticism. Simon McWhirter, Deputy Chief Executive at the UK Green Building Council (UKGBC), the membership-led industry network on the sustainability of the built environment, said it shouldn’t be described as a "future" standard. 

“Having already shattered industry confidence with repeated green rollbacks, the government has opted for the least ambitious option that would deliver ‘future’ homes from 2025 at a lower standard than many homes already built today,” said McWhirter.

“We’re disappointed that, despite such a long delay in producing this draft standard, the government still hasn’t included measures to reduce the embodied carbon emissions from construction. Nor has it moved to tackle flood risk or end the huge water waste from new builds.”

“An obvious step for government is to encourage Passivhaus in the UK via tax or planning incentives until we have 100,000 certified examples.”

David Coley, Professor of Low Carbon Design and Head of the Energy and the Design of Environments Research Centre at the University of Bath, said the key question wasn’t the method but a focus on “what we are trying to achieve – low-energy homes”.

He said: “Any unpoliced, unresponsive method will have two central issues. First, it can be gamed, not necessarily in a nefarious way, but people will target points and find unintended optima. Second, it might, on average, match prediction with reality, although SAP was poor at this, but for the homeowner it needs to work at the level of each and every house.

“We already have a perfectly good standard that solves both these issues: the Certified Passivhaus [an international design standard combining high standards of comfort and health with reduced energy use from buildings]. To me, an obvious step for government is to encourage Passivhaus in the UK via tax or planning incentives until we have 100,000 certified examples.

“At this point, the industry will have learned how to build low-energy buildings that deliver for the consumer and reduce any increased costs to near-zero. Future consumers will then be able to make an informed choice, and an informed choice is not an option they currently have.”

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