The Part L update, or ‘uplift’, is a shift in the energy efficiency requirements of the Part L Building Regulations. This blog post provides a comprehensive overview of the key changes and how they impact new build projects.

What are the Part L Building Regulations?

They came into effect in June 2022 and are now acting as a stepping stone to help the construction industry adapt to changing regulations and low-carbon heating, as we move towards The Future Homes and Building Standard coming into effect in 2025.

The Approved Document L of the Building Regulations outlines the updated energy performance requirements for dwellings. The government’s uplift in the energy efficiency standards for new homes requires more efficient building fabric (insulation and air tightness) and building services (heating, hot water, lighting, etc).

These new Part L building regulations will apply to individual dwellings rather than developments. This will ensure that as many homes as possible are built to these updated standards.

For a dwelling to be registered under the current regulations, a building notice must be submitted by June 2022 and work must commence by June 2023. Dwellings that are registered or commence work after these dates will have to comply with the updated standards.

What is The Future Homes and Building Standard?

The Future Homes and Building Standard is a set of standards that reinforce the Building Regulations. They ensure that new homes built from 2025 will produce 75-80% fewer emissions than homes delivered under the current regulations.

The part L building regulations 2022 update is a move towards this change. It aims for all new homes in England to produce 30% fewer carbon emissions. In addition, new commercial buildings, such as offices and shops, will have to cut emissions by 27%.

There are also changes to Part F and a newly approved document – Part O. This will look at mitigating the risk of overheating in new homes.

What to expect for Part L Building Regulations

Fabric energy efficiency  

The Fabric Energy Efficiency metric will be improved, with the regulations adopting the ‘full FEES’ target. This will likely require improvements across numerous areas of specification compared to Part L 2013.

Primary energy

The new primary energy target will be adopted, considering the efficiency of a dwelling’s heating system as well as upstream energy uses e.g., power station efficiencies, fuel transportation, and conservation. Achieving this standard will therefore depend on the fuel source utilised for space and water heating. On-site energy generation will also be considered.  

CO2 emissions

Part L 2021 will adopt a 30% uplift in CO2 emission standards compared with Part L 2013. This is considered an appropriate interim step prior to the introduction of the Future Homes Standard in 2025.

Minimum standards for fabric and fixed building services

Updated minimum U-Values for thermal elements will be adopted constituting a relatively minor improvement on current minimum standards. The worst performing building services products will no longer be able to be specified, with updated standards set for boilers, heat pumps, cooling systems, and lighting.

U – Values

U-Values measure how effective a home’s fabric is at preventing heat from transmitting between the inside and outside of the home. The lower the U-value the better, as this means heat is less able to quickly transmit through your home.

U-Values are to become required as a minimum in the Future Homes Standard, and at a slightly more stringent level under the proposed ‘Zero Carbon Standard’. This also applies to air tightness.

The proposed new levels published in the government’s response to the most recent Future Homes Standard consultation are:

Updated U values Part L update
Updated U values Part L update

Air Tightness Testing

Sample testing will no longer be permitted. All dwellings will need to be pressure tested for air tightness.

The new maximum target for air tightness is <8m3/(h·m2)@50Pa, which is a 2-point reduction from the current maximum of 10. This is going to drop again to <5m3/(h·m2)@50Pa when The Future Homes and Buildings Standard comes into full effect in 2025.

This stricter, more airtight target will allow for low-temperature heating systems such as air source heat pumps to be viable and meet the reduced carbon emissions targets.

Changes to part F (ventilation)

With new build air tightness getting ever lower as new regulations come in, controlling the air flow in, out, and throughout the house through controlled ventilation becomes more important. Therefore, choosing the correct ventilation method is key to achieving the required air changes to maintain air quality.

Dwellings that achieve an air tightness score of <3m3/(h·m2)@50Pa or below will be required to install continuous mechanical ventilation, centralised or decentralised. However, fan flow rates have not actually changed under the new regulations.

Passive stack (system 2 ventilation) and Positive input ventilation (PV) has been removed altogether and natural ventilation without the aid of mechanical extracts has been given higher targets for Equivalent Areas for background ventilators. 

Thermal Bridging Details

Government-approved construction details will be removed meaning specific thermal bridging details or bespoke calculations will likely be required to pass the SAP calculations.

 SAP10 and Part L Building Regulations

The Standard Assessment Procedure (SAP) is computer software used to model and estimate a dwelling’s annual energy consumption to produce an EPC (Energy Performance Certificate). Until now modelling has been done using a dated version of the software, SAP2012, which has hardly changed since its release in 2013.

Since 2012 a lot has changed, especially in relation to technology, construction, and the greening of the UK’s electricity grid. For example, since 2013 the UK’s electricity grid has almost tripled its proportion of renewable energy inputs from 14.9% to 43%, a factor which is not yet reflected in SAP.

SAP10, therefore, represents a modernization of the current calculation methodology. Updating and introducing new inputs will have a significant impact on the EPC result, making them more reflective of a dwelling’s energy consumption and creating a different approach to design and specification.

SAP 10 was announced by the government back in 2018, but no deadline has ever been confirmed. However, since then SAP 10.1 has been produced and a newer version 10.2 is currently being reviewed. It is anticipated that SAP 10.1/10.2 will finally arrive along with the updates to the Part L building regulations.

SAP Evidence Requirements

To address the performance gap there will be a greater requirement for evidence for the SAP calculation. The SAP assessor and developer will be required to sign a BRIEL (Building Regulations England Part L) compliance report as well as provide photographic evidence throughout the build process.


The Part L Building Regulations 2022 update represents a significant step towards a more sustainable future for the construction industry. By understanding these regulations and incorporating best practices like air tightness testing, construction professionals can ensure their projects meet compliance standards.

What’s Next?

Ensure that your project meets air tightness standards. The current maximum target for air tightness is <8m3/(h·m2)@50Pa. Achieve compliance and ensure optimal energy efficiency with our professional air tightness testing services. Contact us today for a free consultation to discuss your specific project requirements.

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