Introduction
The building regulations is a mechanism to ensure that buildings are constructed and renovated with energy efficiency at the forefront of the building planning and building work process. One important area that assists in ensuring that building work is conducted with efficiency in mind is Part L of the Building Regulations, which sets out the legal requirements for the conservation of fuel and power in buildings and to building control bodies across England.
It is imperative to understand Part L from the perspective of planning a renovation within existing dwellings, developing commercial new builds, working with local authority, or whether you are a professional in the construction industry.
In this blog, we will highlight areas that Part L covers, why it is so important for new builds, renovation and existing dwellings, and how to ensure compliance.
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Just What is Building Regulations Part L?
Building Regulations Part L forms one of the technical documents of the pertinent to us that Part L focuses on heating and hot water systems.
Part L and the Building Regulations are statutory instruments made under the Building Act 1984. Specifically, Part L deals with the energy performance of buildings, with the aim of reducing carbon emissions and improving overall energy efficiency. Therefore, the documents look into such things as appliance efficiency and insulation to ensure CO2 emissions are minimised.
It is divided into two main volumes:
- Volume 1: Dwellings – covering new and existing homes.
- Volume 2: Buildings other than dwellings – covering commercial and public buildings.
The most recent updates to Part L came into effect on 15 June 2022, with amendments incorporated in 2023. All these changes form a broader part of the UK’s strategy to meet net-zero carbon emissions by 2050.
The Purpose of Part L Building Regulations
The overall goal of Part L is to reduce the energy demand of buildings, whilst ensuring that they are constructed or renovated in a way that reduces or minimises heat loss and maximises energy efficiency.
This includes:
- Improving building thermal insulation and thermal performance.
- Enhancing the efficiency of heating systems.
- Encouraging the use of low-carbon technologies such as heat pumps and solar panels.
- Reducing the air leakage rate and improving airtightness.
- Promoting on-site renewable energy generation.
Key Requirements of Part L
1. Thermal Performance Standards
Part L sets minimum standards for the thermal performance of a building with an obvious focus on walls, roofs, floors, windows, and doors. The thermal performance is expressed in term of U-values, which measure how well a building element resists heat flow. The lower the U-value, the better the insulation.
I.e. the maximum U-value for walls in new dwellings is 0.18 W/m²K, while for roofs it's 0.11 W/m²K.
2. Primary Energy and Carbon Emissions Targets
New builds must meet primary energy and CO2 emissions targets. These are calculated using the Standard Assessment Procedure (SAP) for dwellings and SBEM (Simplified Building Energy Model) for non-domestic buildings.
In 2022, an update was introduced with a 31% reduction in carbon emissions for new homes compared to previous standards, this is seen as a stepping stone towards the Future Homes Standard in 2025 which we will touch upon later in this blog.
3. Air Tightness and Ventilation
The regulations state that buildings must be constructed to limit uncontrolled air leakage rate, which can lead to heat losses. Air pressure testing is required for most new buildings to demonstrate compliance.
Similarly adequate ventilation must be provided to ensure good indoor air quality, which is addressed in Part F of the Building Regulations.
4. Low-Carbon Heating Systems
Part L encourages the use of low-carbon heating technologies, such as:
- Air source heat pumps and ground source heat pumps
- Solar thermal systems
- District heating networks
Gas boilers and gas-fired water heaters are still permitted but must meet high efficiency standards.
5. Energy Performance Certificates (EPCs)
All new buildings must be assessed and issued with an energy performance certificate, this certification rates the building’s energy efficiency on a scale from A (most efficient) to G (least efficient). This is a legal requirement for selling or renting a property and building owners should be aware of this.
Compliance Pathways
There are two main ways to demonstrate compliance with Part L:
1. Follow Approved Document L
Approved Document L provides detailed guidance on how to meet the requirements of Part L. Including specifics on insulation, heating and hot water systems, and construction methods. Examples of approved documents include approved document L1B and approved document L1A.
2. Alternative Compliance Methods
If a developer chooses not to follow the Approved Document route for Part L building regulations compliance, they must demonstrate compliance through robust alternative evidence, such as bespoke energy modelling or third-party certification.
Why Part L Matters
1. Environmental Impact
UK Buildings are responsible for around 40% of the UK’s energy consumption and critically 30% of carbon emissions. Improving energy efficiency and encouraging renewable technology uptake is crucial to meeting climate targets.
2. Cost Savings
Energy-efficient buildings could be cheaper to run overtime with lower heating and electricity costs.
3. Market Value
Homes and commercial properties with high energy ratings could be attractive to buyers and tenants, potentially increasing property value.
Building Regulations - Common Challenges and Solutions
❌ Poor Design Coordination
Solution: Involve energy assessors and building control early in the design process to ensure compliance.
❌ Misunderstanding of Regulations
Solution: Take the Approved Documents and consult with building control officers early in the process.
Looking Ahead: The Future Homes and Buildings Standards
Part L is a stepping stone toward the Future Homes Standard (FHS) and Future Buildings Standard (FBS), which are expected to come into force in 2025. These will require:
- Zero-carbon ready homes
- No new gas boilers for new builds
- Further reductions in energy demand
Conclusion
Part L of the Building Regulations has a vital role in the energy performance of buildings in the UK. It sets clear standards for insulation, heating, space heating controls and energy use, reducing carbon emissions, and helping to create more sustainable homes and workplaces.
To learn more about the future regulations and standards such as the future building standard, subscribe to our newsletter.
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