top of page

What’s SAP-ening with SAP10?

Ahead of the forthcoming changes to Part L of the Building Regulations, the BRE has issued their all-singing-all-dancing SAP 10 methodology.

Though it is very similar to its predecessor, the SAP2012 methodology, there are some interesting changes that are certain to have an impact on how we think about Part L compliance and the ways in which we heat and service new buildings.

It is important to stress that this SAP methodology is not yet in use and will not be brought into use until the changes to Part L come into force (which is rumoured to happen in 2019/2020). However, this preemptive publication of the SAP 10 methodology does give everybody a head start to begin thinking about, and perhaps making considerations for, future designs and scenarios.

We have decided to explore and discuss some of the key points, and the more significant changes that are likely to have the biggest impact.


The most noteworthy difference in methodology is, without a doubt, the change in carbon factor for electricity. More specifically – grid electricity. This will be reduced by 55%, compared with current levels, putting this firmly in the firing line of its gas counterpart.

Though the news is not actually that shocking. It shows the thought that has gone into the methodology. BRE understand that the grid electricity is becoming less and less dependent upon high carbon fossil fuel production and is turning to more renewable sources. Thus, the National Grid itself is in the process of de-carbonising.

The effect of this means that heating new dwellings using electricity as a fuel rather than gas will become more favourable, as it is cheaper to install and may offer a much more efficient route to carbon compliance. This is a particularly momentous change for high rise developments.


Everything comes at a price. The ability to use a lower carbon factor for grid electricity when conducting SAP calculations means the cost reduction benefit of onsite electrical generation, such as our old friend PV (Photovoltaics) and CHP (Combined heat and Power), will have less of an impact than it does with the current carbon factor. Will this result in less PV panels being installed? Possibly, but unlikely. It’s important not to forget that the new Part L compliance will be most likely be more onerous to achieve. So, whilst the above will have an effect, you will probably find that PV will still be required to achieve some local authority targets.


The new SAP methodology will now take into account the number and type of baths and showers used. Previously it has always assumed hot water demand, however flow rates, volumes and whether showers are electric or mains fed will now be taken into consideration. This is a step towards a more real-world accurate assessment, though it could potentially make compliance more difficult as it is likely this will push emissions figures up.


And SAP said, Let there be light: and there was light!

SAP will now take account of the lighting that is included within the dwelling, rather than the basic “how many lights has it got?” approach. This means that the number and types of lights, for example LED, halogen etc will all have an impact. The more LED the better.


As NOVO and many other experts have deliberated previously, the Fabric First Approach is the only way to approach a SAP calculation and Part L compliance. This is aided by the use of improved thermal bridging. Currently, Accredited Construction Details usually have a significant impact upon the calculations. However, in SAP 10, the default thermal bridging figures will be increasing by circa 30%. Accredited Construction Detail, (or ACDs) will be called ‘better case defaults’.

This is to encourage developers to have their own junction details researched and tested, as well as architects and more specifically manufactures of construction systems. This will have a significant impact upon how easy it will be to achieve compliance, and if developers need to develop their own junctions could add significant cost. This is one of the more interesting developments.


There are, of course, a lot more changes that will have an impact upon compliance, however we feel these are the most significant, and that these will be most commonly found across most developments.

Keep an eye on our social media channels. We will be sure to share information as to when the new Part L Building Regulations are realised, and report on how onerous they are for developers to achieve compliance with them.

In the meantime, we feel developers need to be thinking about any future projects and specifically about the changes that have been already highlighted. Essentially, this is an excellent move by the BRE in terms of accuracy and reflections into real-world results.

Further readingSAP Boost for Electric Heating as Grid Decarbonises (via CIBSE Journal) 


bottom of page