SAP 10.3, HEM… and The Obvious Problem

Paul Bainbridge, Technical Director

Paul’s Greenprints   

We appreciate that alongside our blog from back in March (Part O: Protection from Falling, and the Curious Case of the Easily Accessible Windows), calling this piece ‘SAP 10.3, HEM… and The Obvious Problem’ really does sound like we’re trying to give Harry Potter a run for its money when it comes to thinking up enchanting tales.

But there’s truth to this title, and as you read on, you’ll realise there’s more to this mystery surrounding any upcoming changes to compliance within Part L of the Future Homes Standard in 2025.

With the current planned developments to HEM all being well and good, you might remember that the intention was to release it alongside Part L with proposed reforms to the EPC. However, it’s just not happening. To get to a place from paper to practice will take years. Ideas, consultations, developments… and that’s before we even get started with actually applying everything to our assessments.

With the powers that be accepting this concern, the government introduced SAP 10.3 as an intermediary resource to bridge the transition from SAP to HEM, in the hope that this would minimise any delays or problems. It was hoped that this transition (expected to be 6 months) would allow assessors and developers to make the necessary changes when they were ready and the situation was appropriate.

You might be nodding your head because you already know this, or at least ‘get it’ – and that’s great. But the obvious problem? There’s no way that two different models of software and two different calculations specifically designed to give two different results… can, well, give comparable results. So how can we possibly replace one with the other and not expect issues with the outcomes for developers and home buyers alike?

Let’s illustrate this point to prove the problem:

A dwelling that passes under SAP should pass through HEM, if we’re working on the latter being a suitable replacement assessment model for the former. But this will be very difficult with everything that’s proposed, because for a start, the HEM will be making use of significantly more detail whilst measuring thousands of data points (rather than the existing 12 data points as measured via SAP). In short, we’ll be going from tracking data around energy use from once a month, to once every 30 minutes. Whilst the result under HEM will be more accurate thanks to regularity and efficiency, it won’t give anywhere near the same result as we would have got under its predecessor – which is still, of course, readily in use. Now, the Department for Energy Security and Net Zero (DESNZ) have claimed over and over again that the two assessments will indeed give the same Pass / Fail rating even if the values associated with it are completely different, but the majority of fellow professionals and top voices in our industry – The FES Group included – just don’t see that being a reality. It really is our job to make our clients aware of all angles and expectations, so do keep up with our blog for all future developments, as always.

Of course, these changes should make sense in time and indeed mark progress – we know. But wanting to simply roll out and integrate this switch whilst a set of regulations are already in place just seems unfathomable to us. Add in the fact that there’s also the discussion to reform the EPC, and in theory, it means that a developer could have three houses all built next to each other on one street, and though they’d all be identical builds, all three could be assessed under different measures and therefore certified (or not) with a completely different rating. Surely this is problematic for everyone.

Similarly, we could end up in a situation where some developers are wasting cash by going above and beyond what’s required, yet others will fall short of compliance based purely on when (or with what calculation tool) the assessment on their plot was carried out within the development.

It’s a messy situation, and that’s before we do even talk about – as you expected we would from just a few short sentences ago – the proposed reform to the EPC.

Let’s go back to the three houses on the same street scenario. Given how everything is progressing right now, we could end up seeing those three identical builds throwing out three very different ratings and results to inform their assessments and certifications. In other words, we could theoretically have one dwelling assessed under the existing SAP and the old EPC, one dwelling assessed under the new HEM but the old EPC, and one dwelling assessed under the new HEM and in accordance with the new EPC. This will only ever be confusing for the one person (the home owner) that this was supposed to make it simpler for, so here at The FES Group, it’s not something we’re fully on board with.

We appreciate that our review of this circumstance as written in this blog doesn’t exactly give ‘The FES Group Seal of Approval’, but that’s nothing to do with process or rationale, and absolutely everything to do with timing. The move from SAP to HEM – with or without a reform for the EPC – does indeed move us in the right direction for progress regarding the efficiency and accuracy of assessment. Potentially, the transition could move us away from data that gives ratings based on cost, and instead provide us with data that gives ratings based on emissions. We appreciated that other metrics will come into play here, and of course will also be based on any decisions made from the EPC reform consultation.

Ratings based on cost are quite misleading to the home buyer or resident – as discussed in our previous blog, where we may or may not have mentioned how the cost of having a meth lab in your spare bedroom rather than a home gym can mean your energy bills are going to be significantly higher than your clean-living, treadmill-running neighbour in the house across the street. Cost-based ratings can only ever be estimated, whereas emissions-based data can be proven – and subsequently used by home buyers in the home buying decision-making process (thus making it a fairer assessment for their needs).

It wouldn’t be very ‘us’ to not take a cynical swipe if and when necessary, so we can’t leave this blog without mentioning how much a move to the new assessment model and method would make air source heat pumps look a hell of a lot more attractive than they might otherwise be in reality. This is especially the case where air source heat pumps are currently gaining compliance with B-ratings on EPCs, while some homes powered by gas boilers (along with PV) are reaching compliance with an A-rating. In essence, air source heat pumps currently cost a lot of money to run. They will get better as technology develops, but we can’t escape the fact that electricity isn’t cheap, and so while the pumps use less energy, that energy costs more to begin with. As a result, a cost-based assessment of their use isn’t too tempting to promote. Having said that, there’s no doubt of the dent they make in emissions when assessed and rated purely on that criteria. Low-emission music to the ears of the environmentally conscious buyer, we’re sure.

Our theory here at The FES Group when taking all of this into account is that we should first change the EPC, but perhaps that’s a blog for another time (when we’re likely to get less heat, if you’ll forgive the pun). But what it’s safer and highly more sensible to propose is that we (as an industry) make any necessary or planned changes in line with the next set of regulations, rather than half-way through any existing ones. In short, use this time now to consult, develop, and test the HEM alongside the SAP to make sure it beds in and truly works, then when the next Part L is due (we’re thinking probably 2028), issue the full change right there, right then, rather than attempting to shoehorn in significant changes that cause chaos, confusion, and cost for builders, assessors, and home buyers alike.

When Part L comes in for 2025, there was hope for a six month transition to new ways of assessment under HEM. When that flew out of the triple-glazed window, there was hope purely for a transition at some point.

And now, under the current 2025 Part L? At The FES Group, we’re hoping there’s no transition at all.