SAP 10 / Part L 2021 – Myth Busters

Myth #1 – A 150mm cavity is required

This is dependent on the insulation you are using. A better performing insulation will require a smaller thickness to meet compliance.

For example, 90mm of a high-performance PIR board with a 10mm air gap can achieve the same results as 150mm wool insulation.

Myth #2 – I can no longer build with a gas boiler

Under the new building regulations gas boilers must be accompanied by some form of renewable energy to meet compliance. This is most commonly solar PV.

When carrying out the SAP calculations we will outline the minimum solar PV requirements to meet compliance.

The best alternative to this is Air Source Heat Pumps – which often do not require additional renewable technologies to meet compliance. Our team can present both options as part of our SAP service.

Myth #3 – Gas is out, electric boilers & radiators are in

This is a very common misconception.

Standard electric heating can be viable for some projects; however, its running costs mean that it is not a viable option without installing renewable technologies alongside it.

This means it will often not be viable, particularly for dwellings with limited roof space for solar panels.

Myth #4 – I must commission bespoke thermal bridging calculations

Generally, following a standard set of thermal bridging details is fine.

However, for more unique construction types such as SIPs, steel/timber frame or unusual masonry details – a bespoke set would be required.

This is because SAP can no longer pass with default PSI values, as was sometimes the case under the old regulations.