Contact Us
Member Login

Your cart is empty




Welsh Government issues long awaited response to the Part L review


On 25th March 2021 the Welsh Government published its long awaited response to the Part L consultation which closed in March 2020. Since its release Elmhurst has been busy analysing the consultation outcome, and has put together a more detailed look at the response and confirmed changes to Building Regulations.

Part L 2025

In the initial consultation it was proposed a home in 2025 would have 75-80% lower carbon emissions than current Part L standards. The expected form of heating would mainly be heat pumps and heat networks, with traditional fossil fuel fired boilers phased out. Welsh Government has now confirmed this will be the expected standard for a home built to the Part L in 2025.

It was confirmed the review on Part L 2025 will be launched in 2023. This was brought forward from the initial proposal due to the urgency of action needed to tackle climate change.

Part L 2021

As part of the transition to the Part L 2025 it was proposed to have an interim change to Part L standards for new dwellings. Welsh Government have now confirmed this is due for implementation in Spring 2022 and will include the following changes.

Energy Efficiency Standards

In the original consultation it was proposed to introduce three compulsory metrics for compliance based on Primary Energy, Carbon Emissions and Cost in the form of the Householder Affordability Rating. Welsh Government have confirmed these metrics will be implemented, with a minimum EPC rating of B for all new homes in Part L 2021.

Two levels of uplift over current Part L were proposed; a 37% reduction or 56% reduction in carbon emissions. As expected the 37% uplift has been chosen for Part L 2021.

Finally fuel factors will also be removed from Part L 2021. These are no longer required as electricity is less carbon intensive than mains gas, and it is no longer deemed appropriate to ease compliance for Oil and LPG heated homes.

Minimum standards for Fabric and Services

For Part L in Wales the Fabric Energy Efficiency standard is not adopted, therefore the minimum standards for building fabric are tighter than other regions. The following minimum standards will be required for thermal elements in Part L 2021;


Element Part L 2021 standard
External Walls (Houses) 0.18 w/m2k
External Walls (Flats) 0.21 w/m2k
Party Walls 0.2 w/m2k
Roofs 0.13 w/m2k
Floors 0.15 w/m2k
Windows 1.4 w/m2k
Rooflights 2.2 w/m2k
Doors 1.4 w/m2k
Air Permeability 8 m3/m2/hr @ 50 Pa


The suggested minimum standards for building services have also now been confirmed and has seen a slight improvement in standards for heat pumps and light fittings over the standards proposed in the consultation.


There is some good news for Air Tightness Testers as the proposal to remove sample testing and therefore conduct a test on every new home has been implemented into Part L 2021. This also applies to small sites which currently can avoid air tightness testing if compliance with the energy efficiency standards is achieved using a score of 15 m3/m2/hr @ 50 Pa.

In order to encourage the use of appropriate ventilation for air tight homes, SAP will not show any savings for a test score lower than 3 m3/m2/hr @50 Pa if mechanical ventilation is not used. Whilst Elmhurst agrees that inadequate ventilation for air tight homes causes issues with air quality, we did not agree that artificially limiting the air tightness in the SAP engine was the best way to implement this. We believe this could increase the performance gap and the energy ratings may not be a true reflection of the performance of the dwelling.

Finally as expected the PULSE method of air tightness testing will be introduced as an alternative to the existing blower door test. Further details of PULSE can be found here.

Improving Compliance, Performance and Providing Information

In the Part L consultation a new industry standard report, known as the BRWL (Building Regulations Wales Part L) report was proposed. This will be implemented in Part L 2021, although the format of it may still be subject to change before the final approved document is issued.

One of the more significant proposals was the requirement to provide photographic evidence of the construction of the dwelling to building control bodies, OCDEAs and the home owners. This has been confirmed in Part L 2021 and items such as ground floor perimeter insulation, ground floor to wall junction detail, window positions in relation to cavity closers and space/hot water heating systems, will need to be photographed during the build process. Currently no restrictions have been made on who can take the photographs. This is an important change and all stakeholders will need to fully understand the requirements to ensure it is implemented successfully when Part L 2021 commences.

Transitional arrangements

The current building regulations allow for entire sites (sometimes numbering hundreds of plots) to be built to older versions of regulations, if a single dwelling makes a start within a year of depositing the building regulations application. Whilst there is some logic to this in regards to consistency of specification and budgeting, it does result in homes being built to standards as much as ten years old sometimes. This is fundamentally wrong and something which Elmhurst has lobbied Government to change for years.

For Part L 2021 the site wide approach to transitioning across regulations will change to a plot specific approach. Therefore, plots that do not start within the reasonable period of the regulations application, even if on the same site, would need to be built to the latest standards. This will need careful management from all industry stakeholders to ensure the correct regulations are applied and enforced.

In the Stage 2A consultation it was proposed to set the reasonable period at a length of 2 years. We await the consultation responses to see what Welsh Government will confirm for this proposal.


Elmhurst’s On Construction Team Leader, Jason Hewins, commented; “In summary the detail of the Part L response is mostly what we expected and lobbied for in our consultation response. It will be interesting to see how the minimum EPC rating of B for new homes affects developers particularly in electrically heated homes. The increase in air tightness testing, improved compliance procedures and plot specific transitional arrangements are welcomed and we look forward to seeing these implemented in 2022. Elmhurst will keep members updated with further insights shortly to ensure everyone is prepared for the changes to regulations in 2022 and beyond.”

Read the full response to the Part L consultation here.