SAP and HEM: The Current State of Play
Throughout this year, we have reported on announcements regarding the Home Energy Model (HEM) and SAP, particularly in relation to the Future Homes Standard. With publication of the Standard expected this year, it is worth taking a look at where both methodologies currently stand.
SAP 10.3: Ready to Support the FHS Transition
Development of our Design SAP 10 application to incorporate the SAP 10.3 changes is well underway. Government are finalising some details of the notional dwelling that will underpin the Future Homes Standard, but this is expected to be delivered to schemes shortly. Our updated Design SAP 10 application, with SAP 10.3 changes incorporated, will be released later this year in line with the Future Homes Standard.
In the recent Part L 2025 consultation, the Welsh Government also left the option open to continue using SAP 10 should HEM not be fully ready before Part L 2025 is released next year. This highlights the important role SAP 10.3 can play in providing a reliable framework during the transition period.
Read more about the Welsh Government Consultation here >
The Home Energy Model: Still in Progress
Elmhurst recently provided members with access to a test version of MHCLG’s user interface, built on the FHS wrapper and HEM engine version 0.34. This trial facility gives assessors an early look at what a HEM user interface might feel like and helps them familiarise themselves with the principles. However, as an early-stage tool, it still comes with notable limitations. For example, only generic heat pumps can be modelled, weather files are not yet included, and the compliance targets generated are not reflective of the final Future Homes Standard. Additionally, the final HEM version used for the Future Homes Standard will differ from version 0.34 used here.
Elmhurst are currently developing a new application using the Home Energy Model and Future Homes Standard assessment wrapper. Our application will connect to MHCLG’s Energy Calculation as a Service (EcaaS) facility which will host a version of HEM to be used to calculate compliance with the Future Homes Standard.
Find out more about how HEM works here >
Points Still Awaiting Clarity
While development is progressing, several important areas remain under review: These include:
- The version of the HEM engine that will ultimately be adopted. Currently ECaaS is using version 0.34.
- The final user input requirements within the FHS wrapper. Whilst we are working on our application, we are limited in what we can do until the final user input fields are confirmed.
- The release schedule for the revised PCDB needed for HEM.
- The formation of a conventions group to ensure consistency across the industry
Wales and Scotland
For Part L 2025 in Wales, HEM is expected to be used for compliance, which will require a new wrapper. It is not yet confirmed whether this will run through the MHCLG EcaaS service. In Scotland, HEM is also expected to be adopted in the next update to Section 6 of the Domestic Building Standards.
What This Means for Assessors
The announcement earlier this year that both SAP and HEM could be used for compliance initially created some uncertainty across the industry. As we move closer to the launch of the Future Homes Standard, it is clear that HEM still requires further development before it is ready to be used at scale.
SAP 10.3 will be ready for immediate use. This provides assessors with a familiar, trusted methodology that can be relied upon as soon as the Standard is published. For the industry, this continuity means there will be no gap in compliance tools: assessors will be able to deliver robust, accurate assessments while preparing for the longer-term transition to HEM.