Read the latest news & industry developments

Read the latest news & industry developments



What are Part L Building Regulations and How Do They Affect Me?

Hugh Franklin

21st November 2023


Building Regulations

If you’re involved in a construction or renovation project, you’ve probably come across references to Part L Building Regulations. These crucial standards are part of UK building regulations, ensure energy efficiency in residential and non-residential properties, and play a significant role in the government’s aim to reach net zero.

Understanding Part L Building Regulations


Part L Building Regulations, also known as the Conservation of Fuel and Power regulations, are set out by the UK government to control the energy efficiency of new and existing buildings. These regulations aim to reduce carbon emissions and combat climate change and are divided into two categories: Part L1 for dwellings and Part L2 for non-domestic buildings.


  1. Part L1 Building Regulations apply to new dwellings (L1A) and existing dwellings undergoing extensions or material alterations (L1B). These regulations cover aspects such as insulation, heating efficiency, air tightness, and the use of renewable energy sources.
  2. Part L2 Building Regulations are divided into new non-domestic buildings (L2A) and existing non-domestic buildings(L2B). They encompass similar principles as Part L1, with additional considerations for commercial and public buildings, such as lighting efficiency.


Updates to the Regulations


First published in 2014, Part L building regulations, like all regulations, continue to be adapted and updated.


In 2021 the regulations went through their most significant changes, which saw a tightening on the emissions allowed from new builds and looked to reduce the gap between the calculated energy efficiency during the planning phase of construction and the actual efficiency once completed. 

Impact of the 2021 Part L Building Regulations


The following are the most noticeable changes in the 2021 Part L guidelines compared to its 2014 predecessor. More stringent testing, higher energy efficiency rates or the building and U-values of the materials used. Below are just a few highlights that our customers need to be aware of-


1. All new homes need to produce 31% less carbon emissions.

Under the 2021 edition of Part L, all new homes must produce significantly fewer carbon emissions than previously allowed under older editions.


2. All new dwellings require air permeability testing

Previously under the old Part L regulations, ‘sample’ air permeability testing, also known as Airflow testing, was allowed on larger developments. This is no longer the case; every new build dwelling requires testing. This change can make a difference if not adequately planned for in advance and can add significant delays and costs to the completion of a project.


3. A 2-point reduction in air permeability

Not only has there been a change to how larger developments test their air tightness, but the regulations have become stricter. In England and Wales, new dwellings must have an air permeability under 8 m3/hr. m2 @50Pa a reduction from the previous 10 m3/hr. M @50Pa. This is expected to be even more stringent when The Future Homes Standard is introduced in 2025. AeroBarrier UK tests and treatment can achieve an amazing 0.6m3/hr @50Pa air permeability, ensuring you are going beyond the current and future regulation changes.


4. Photographic evidence is now required.

The new update requires all buildings to have photographic evidence showing that the correct procedures have been followed during construction. If no photographic evidence is provided, default values will be used for the work. This might not seem like a big deal, but the default values can significantly differ from what you would expect and may mean that the building needs to be signed off by building control without significant remedial work.

How can Areobarrier UK help?


At AeroBarrier UK, we offer a simple solution that provides the proper airflow test now required by Part L and an instant and complete solution to any leaks within the building’s envelope and the relevant certifications. So you can help complete your construction work without the stress of missing deadlines and provide your customers the most energy-efficient home possible. 


What is the main purpose of Part L Building Regulations?

Part L Building Regulations aim to reduce carbon emissions and improve energy efficiency in residential and non-residential buildings. They are critical to the UK’s efforts to combat climate change and reach net-zero emissions.

What happens if I don’t comply with Part L Building Regulations?

Non-compliance with Part L can result in fines and enforcement action, such as an order to make necessary changes to the building. It can also negatively impact the building’s value and its potential for sale or lease.

What does the term ‘U-values’ refer to in the context of Part L Building Regulations?

U-values measure the amount of heat that can pass through a material. They are used in Part L regulations to assess the energy efficiency of elements such as walls, floors, doors, and roofs. A lower U-value means better insulation and better energy efficiency.

How is compliance with Part L Building Regulations checked?

Compliance is typically checked by local building control bodies, either local authorities or approved inspectors. They review plans before construction and inspect the building work at various stages. Additionally, new regulations as of June 2022 mandate that builders conduct an on-site audit to confirm that the design details in the plans have been constructed, and photographs must be taken as evidence

Are there exceptions to Part L Building Regulations?

Certain types of buildings, like temporary buildings, workshops, and non-residential agricultural buildings with low energy demand, are exempt.

Discover how you can achieve & exceed airtightness with AeroBarrier.

Discover how you can achieve & exceed airtightness with AeroBarrier.

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