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The HEM-line blog
The Home Energy Model (HEM) is a new way of forecasting the energy performance of residential buildings in the United Kingdom. In the coming years, HEM will replace the Standard Assessment Procedure (SAP) for generating Energy Performance Certificates (EPC) and checking compliance with Part L / Section 6 of Building Regulations.
HEM is currently in development. When it is approved for use, this blog will include tutorials and advice for how to use the new calculation tool.
While we're waiting, you can browse through this archive of my LinkedIn articles, covering changes to Building Regulations, Energy Performance Certification, national planning policy, and everything in between.
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Elmhurst Cardiff Conference 2026
Plenty of thoughts still to digest after last week's Elmhurst Wales Conference in Cardiff.
Great speakers, great venue, and very well organised. Top marks!
Jon Ponting
Oct 41 min read
Tweaks on the way for SAP10.3
Just six months to wait until the new Part L (the Future Homes Standard) goes live in England.
Five changes to the new methodology are under review with a fix expected before the end of the year. In some cases, these changes could affect existing SAP10.3 results.
Jon Ponting
Sep 302 min read
Part L 2026 - Revisions
If you’ve already downloaded your own copies of the Future Homes Standard and Future Buildings Standard (Part L 2026), do it again! There’s been some amendments.
Nothing too serious, just a few corrections and clarifications. All the big headlines (such as amount of PV and fossil fuel free requirements) remain the same.
Jon Ponting
Sep 271 min read
Part L 2026 PV requirements - FAQs
Since the new Approved Document Part L (the Future Homes Standard) was published, there's been uncertainty about the specifics of the new PV Functional Requirement.
We now have answers to some of those Frequently Asked Questions from the MHCLG.
Jon Ponting
Sep 131 min read
WholeHouse in action
Last week, I dusted off the hard hat to see a WholeHouse development taking shape in Somerset.
The concept of WholeHouse has been bubbling away for a few years, so it’s great to see it’s being successfully applied to a real construction site – in this case, by Galion.
Jon Ponting
Aug 301 min read
SAP10.3 Oddities: Exhaust Air Heat Pumps
To comply with the Future Homes Standard, most new homes will require a heat pump. Apartment complexes might look at Exhaust Air Heat Pumps, but it seems the new SAP10.3 calculator isn’t so keen on those. I've been down a SAP rabbithole to find out why.
Jon Ponting
May 312 min read
SAP10.3 Oddities: WWHRS
We’ve had a few weeks to get under the bonnet of SAP10.3 to understand what a Future Homes Standard compliant home looks like, and we’ve uncovered a strange quirk which works against WWHRS.
To unpick what’s going on in the new SAP methodology, I met up with two of the biggest suppliers of Waste Water Heat Recovery Systems (WWHRS) in the UK: Showersave and ReCoup, at the Keystone Group offices in Derbyshire.
Jon Ponting
May 242 min read
SAP10.3 Oddities: Low Air; Don't Care
SAP10.3, which checks homes are compliant with the Future Homes Standard, does a very strange thing with air leakage results. You could have an air test of 1.5 or 4.5, and your fabric performance (FEE) won't change.
Logically, a house with a better air tightness will lose less heat, so you’d expect the fabric performance to score better. That’s always been the case in previous versions of SAP.
Jon Ponting
May 172 min read
New Part L for Wales (Extensions and Non-Resi)
Part L2 (2026) in Wales introduces Photographic Evidence for non-domestic buildings.
Also, a new tier of requirements has been added to the Consequential Improvements rule for residential extensions in Wales, bringing a touch of Future Homes Standard to the renovation market.
Jon Ponting
May 142 min read
New Part L for Wales (Onsite generation)
Here are some further details about the changes to Approved Document Part L (Wales), which closely follows the Future Homes Standard targets which apply to England, but are scheduled to come into force three weeks earlier; being applied to new building sites from 4th March 2027. This post focuses on the new requirement for onsite energy generation.
Jon Ponting
May 122 min read
New Part L for Wales (Targets and Notional)
This revised Approved Document Part L will apply to any building work where the relevant building inspector accepts applications from 4th March 2027.
Any unstarted buildings on existing sites after 4th March 2028 will need to meet the new regs, regardless of when the site was submitted.
As with the current Part L, most of the English (UK) and Welsh versions are identical, but there are a few curveballs developers need to be aware of.
Jon Ponting
May 102 min read
FHS Launch - Impact on EPCs
With the Future Homes Standard set to go live across England next March, housebuilders will need to design in PV panels and install heat pumps to the vast majority of new buildings.
That’s going to have a positive impact on Energy Performance Certificates... for now.
Jon Ponting
Apr 82 min read
FHS Launch - The gas boiler 'ban'
We’re told the Future Homes Standard will require most new homes to use heat pumps. That’s most, not all.
So does that mean there’s scope to sneak through the occasional gas boiler under the new Part L?
No. For two reasons...
Jon Ponting
Apr 52 min read
FHS Launch - Mandatory solar panels
One part of the Future Homes Standard has grabbed the media’s attention more than most: Mandatory solar panels on all new homes. But how will these new regs work in practice?
Jon Ponting
Apr 12 min read
FHS Launch - Fabric performance
Now the Future Homes Standard and Part L (2026) have been published, we can begin unpicking what compliance looks like for new building sites across England.
Changes to the fabric performance targets are under the spotlight this morning, or lack of changes may be more appropriate.
Jon Ponting
Mar 292 min read
FHS Launch - When does it apply?
When will the Future Homes Standard apply?
For most developments, we have a full calendar year to get ourselves ready. The new Part L goes live on 24th March 2027.
This is defined as the date the developer submits documents (initial notice, building notice, application with full plans) to the relevant building authority.
If paperwork is submitted and accepted before 24th March, the site can built to the 2021 (current) regs.
Jon Ponting
Mar 262 min read
Future Homes Standard Update for Wales
The Senedd has published its response to last year's Approved Document Part L consultation, confirming new energy standards for building sites from 2027.
Strictly speaking, FHS doesn't apply in Wales, but this news broadly follows what we're expecting from the UK Government in the coming weeks.
Jon Ponting
Mar 92 min read
Is 2026 the new 'Autumn 2025'?
The Government's standard response about the release of the Future Homes Standard has changed recently from 'Autumn 2025' to 'in the coming months'.
Jon Ponting
Nov 13, 20251 min read
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