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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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HEM Deepdive: Colours
I’ve been digging into areas of the Home Energy Model which us humble SAP assessors have never had to bother ourselves with previously.
One of the new questions HEM asks is:
What colour is the house?
It asks, because black surfaces absorb more heat than white surfaces.
Jon Ponting
Oct 262 min read
HEM Deepdive: Obstacles
With the Home Energy Model edging towards its official release, I’ve been playing with some of the new inputs to understand how impactful they are on a dwelling’s energy performance.
The first section that will be unfamiliar territory to SAP assessors is Obstacles.
Jon Ponting
Oct 182 min read
New SAP Feature: Electric Showers and WWHRS
A new feature has been unlocked in SAP!
We can now attach Waste Water Heat Recovery systems to electric showers.
The shower has to be an approved Modulating Instantaneous Electric Shower.
Jon Ponting
Oct 112 min read
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
The roll-out of EPC Reform in Scotland
The Scottish Government has released more info about new-style EPCs, including a new go-live date. Unsurprisingly, they've delayed the launch until 2028.
Soon, Scottish EPCs will start displaying three A-G ratings instead of one.
Domestic properties will be ranked using heat retention (fabric performance), heating system efficiency and energy costs.
Jon Ponting
Sep 62 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
NPPF 2026
The National Planning Policy Framework (NPPF) was updated last week. Have we all had a chance to read through and pick out our favourite bits?
In terms of energy performance, there are four policies that grabbed the lions-share of my attention.
Jon Ponting
Aug 232 min read
Mandatory EV chargers in Wales
EV chargers will soon be mandatory on new building projects across Wales.
The Welsh Government consulted on this a while ago, following in the footsteps of the UK Government’s Approved Document Part S which launched in 2021.
Details of the Welsh Part S can be found here… they haven’t announced a launch date yet.
Jon Ponting
Aug 161 min read
Nerding and birding
Combining two of my favourite past-times.. nerding and birding!
While exploring the Ceredigion coastline in mid-Wales, we stumbled upon the Dyfi Osprey Project.
This was a great opportunity to tick osprey in the bird book, but also, check out this setup which is proudly on show in the visitor centre... Nine Tesla power banks with plenty of onsite PV.
Jon Ponting
Aug 91 min read
Scotland Section 6 and PassivHaus consultation
The Scottish Government has published new proposals for changing Section 6 of the Technical Handbooks to create a ‘Scottish equivalent to the PassivHaus standard’.
A public consultation on these changes is open until 16th October 2026.
Jon Ponting
Aug 23 min read
HEM Deep-Dive: Energy Flex
Data from a Home Energy Model studying three 48-hour snapshots of energy flex in a small house.
The fabric performance meets Future Homes Standard, but this model uses direct heating (panel heaters) and direct electric immersion (instead of a heat pump).
The model includes a PV array (4kWp), a 5 kW battery, and an immersion diverter.
Jon Ponting
Jul 293 min read
London Plan 2028 - Consultation
The London Plan, which sets strict planning requirements for building projects across the Capital, is having its five-yearly makeover.
The consultation is open until October 15th 2026, with adoption expected in early 2028.
Jon Ponting
Jul 262 min read
Why doesn't the UK embrace domestic air con?
Our recent weather has shown, once again, that UK homes don’t deal well with long hot spells. This time though, discussions about domestic air conditioning seems to have cranked up a level.
Jon Ponting
Jul 192 min read
HEM Deep-Dive: Thermal Mass
Is it better to build our homes with a low thermal mass and lightweight materials, or use dense materials to create a high thermal mass?
I've built a HEM model to look into this.
Jon Ponting
Jul 153 min read
Boiler Upgrade Scheme increased to £9k
The UK Government is upping the stakes with the Boiler Upgrade Scheme by increasing the heat pump grant to £9,000 for homes running off oil.
Jon Ponting
Jul 121 min read
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