Are heat pumps the defacto heat source for new build properties?

The implications of the 2022 update to building regulations for new and existing homes

What changed in part L?

The headline change to the regulations is a 31% reduction in carbon emissions over the previous iteration of the regulations. This is being driven by a number of different policy changes, the most relevant to renewable heating which we detail below.

Local Authorities will for now retain the ability to set their own local energy efficiency standards (in a change from the consultation).

U values

The approach remains very much “fabric first” with a tightening of the U value requirements. Moreover, these standards now also apply to extensions to existing properties.

New metric - TPER/PER

Under the old Part L Approved Document Dwellings needed to improve upon both the Target Carbon Emission Rate (TER) and Target Fabric Energy Efficiency (TFEE) in order to satisfy Part L.

Under the latest iteration another target has been added that must be complied with: the Target Primary Energy Rate (TPER).

The Target Primary Energy Rate is the maximum primary energy use that will be allowed for in a dwelling or building in a year in order to satisfy Part L, expressed as kWhPE/(m2.year). It is a more holistic measure TER or TFEE that takes into account the upstream processes used to extract energy needed to provide heating and hot water to a newly built building as well as lighting, ventilation, cooling systems and showers.

Using a fossil fuel to heat a home will have a heavy impact on the TPER as the heating will then be a derived from a primary energy source. Heat pumps will score far better, both because they use electricity (not a primary source, but having an energy score derived from its mix of inputs, which are themselves increasingly renewable and thus having a lower energy score than primary fossil fuels) and because they are more than 100% efficient - they use their electricity to generate more heat than could be delivered directly from the electricity itself. 

It’s also worth noting that the loophole that allowed developers to offset the carbon footprint of a boiler with a token solar array has been closed. 

Low flow temperature requirement for new central heating systems

The maximum flow temperatures for a central heating systems is now 55°C where it was previously over 75°C.


Under the Part L 2021 Building Regulations requirements it becomes essential in order to pass SAP to take photographs of each of the dwellings junctions once they are constructed showing continuity of insulation, as well as photographing the installed building services.

These photographs must be clearly labelled, with correct Meta Data showing the time and location of when and where they were taken and must be provided to the energy assessor on the project. 

What changed in part F?

In recognition of the fact that increasing airtightness is a feature of the upgrades to Part L, part F has been updated to ensure a balance of ventilation with airtightness to ensure air quality and prevent mould growth. One key change is that ventilation systems must now have a purge function.

To meet this growing need STIEBEL ELTRON are introducing a new decentralised ventilation product ideal for retrofit situations  - the VLR 70 Trend EU. Contact us today to be notified when launch materials are available.

New part O regulations

Again in recognition of the fact that new buildings are now very highly insulated – and often feature large swathes of glazing that may not be openable - new regulations have been introduced to prevent seasonal overheating issues. 

One of the benefits of heat pumps that can be used to assist in compliance with part O is that they can be used – unlike boilers – to cool as well as heat a building. 


As these changes self evidently favour the choice of renewable heating systems it is likely that they will help to accelerate the drive towards renewable heating in new build homes and major home refurbishments.