Part L: A Guide to Energy Efficiency Standards in UK Building Regulations

Part L of the UK Building Regulations focuses on the conservation of fuel and power, or simply, energy efficiency. It outlines the required standards for energy use and efficiency in both new and existing buildings.

Part L is divided into:

  • Part L1A for new dwellings and Part L1B for existing ones.

  • Part L2A for new non-dwellings and Part L2B for existing non-dwellings.

Why is Part L Important?

Given rising energy costs and the urgent need to reduce carbon emissions, Part L is essential in making buildings more energy-efficient and eco-friendly. By improving insulation, controlling heat loss, and promoting renewable energy use, these regulations are designed to reduce energy consumption, benefiting both the environment and homeowners’ wallets.

Key Part L Changes in 2022

Here are the main updates that came into effect in June 2022:

Reduced Carbon Emissions:

  • New-build homes must now produce 31% less carbon emissions.

  • New non-domestic buildings must produce 27% less carbon emissions.

Primary Energy Metric:

  • A new metric, Primary Energy, measures a building's heating efficiency and energy source. This metric accounts for the entire energy supply chain, even considering the power station’s efficiency.

Enhanced U-Values:

  • Minimum U-value standards for insulation in new builds are now 0.18 W/m² for walls, 1.4 for windows/rooflights, and 1.4 for doors.

  • Non-domestic buildings now have a U-value of 0.26 for walls and 1.6 W/m² for windows/curtain walling.

Lower Maximum Flow Temperatures:

  • New and replacement heating systems in all buildings must not exceed a 55°C maximum flow temperature to improve energy efficiency.

Improved Lighting Efficiency:

  • Minimum lighting efficacy standards for new non-domestic buildings are now 80 lumens per circuit watt for display lighting and 95 lumens for general lighting.

SAP10 Assessment:

  • A new Standard Assessment Procedure (SAP10) requires greater insulation and sets a target primary energy rate (measured in kWhPE/m² per year).

Photographic Evidence Requirement:

  • Self-builders must conduct an on-site audit to verify that construction aligns with design plans. Photos must be provided as evidence to the energy assessor and the building control body.

Fix Radio & SymTerra: What Part L is all about?

For anyone looking for a quick podcast to get their head around Part L, listen to SymTerra’s John Ryan with Mark Millar on Fix Radio. Key points covered:


➡️ What Part L is all about?
➡️ When was this brought in and why?
➡️ What other changes should people be aware of
➡️ Upcoming changes or additions we might see in the coming years?
➡️ Where people/builders go massively wrong with regards to regs compliance?

Existing Buildings and Part L

For those renovating or upgrading thermal elements like doors and windows, Part L introduces new efficiency standards to enhance the Fabric Energy Efficiency Standard (FEES):

  • Improved U-values: Walls must now meet a 0.18 W/m²K U-value, while windows and roof windows have a minimum U-value of 1.4 W/m²K.

  • BREL Compliance: A Building Regulations England Part L (BREL) report is essential for certification and includes SAP assessments for both the design and as-built stages.

Failure to comply with Part L requirements could prevent certification, emphasizing the importance of staying informed and compliant.

Why the Part L Changes Were Introduced

The updated Part L standards, effective from 15 June 2022, aim to reduce greenhouse gas emissions from the built environment, which accounts for about 25% of the UK’s carbon emissions. With UK households facing escalating energy costs—up nearly 80% since 2017—these regulations help homeowners cut down on energy bills while reducing environmental impact.

How to Approach Part L Compliance

  1. Find an EPC Assessor: Working with a certified Energy Performance Certificate (EPC) assessor will guide you through the requirements and ensure your project is compliant.

  2. Detailed Planning: Ensure you have detailed architectural drawings and specifications.

  3. Use Approved Construction Details (ACDs): Including ACDs in your design can prevent energy loss through gaps, achieving compliance faster.

  4. SAP Calculations: Before construction, an SAP assessor will input your plans to ensure compliance. Adjustments during the build should be reported to the SAP assessor to maintain compliance.

  5. Final Testing: Near project completion, an air pressure test and SAP calculations are performed, followed by EPC registration.

Frequently Asked Questions

What is an EPC, and why do I need one?

An Energy Performance Certificate (EPC) assesses the energy efficiency of a property, rating it from A (most efficient) to G (least efficient). An EPC is required when selling, renting, or building a property and offers insights into potential improvements to enhance efficiency.

How does Part L relate to other building regulations?

Part L is closely tied to Part F (Ventilation), Part O (Overheating), and Part S (EV Charging). Together, these regulations aim for energy efficiency, reduced fire risks, and a shift toward net-zero targets.

How can I stay updated on future changes to Part L?

Building Regulations are typically updated in April. To stay informed, follow Building Regulation Circulars and check updates on gov.uk.

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

Non-compliance with Part L can prevent certification, affecting the legal completion of your project. The BREL reports (both design and as-built) generated by SAP assessments are critical for compliance.

Are there any upcoming changes to look out for?

Yes, the Future Homes Standard is set for 2025, which will require new homes to produce 75-80% less carbon emissions. Additionally, Part Z will introduce measures for Net Zero by capping embodied carbon emissions in new builds, with key requirements for carbon assessment (Z1) and intensity limits (Z2).

How SymTerra can help you comply with Part L

By using a tool like SymTerra, Part L Photographic Evidence requirements can be met:

Snap Tap and Go, replacing WhatsApp

Capture photo and video updates straight from your phone.

Make short work of reporting, observations, snagging, RFIs, and more.

SymTerra ensures compliance with every photograph across your team and operations, meeting the Part L requirements. Every photo captured is in high definition and resolution. Live photos are time stamped!

Add Additional Detail to Your Photos Directly On-Site

With SymTerra, capture photos that not only meet Part L Photographic Evidence requirements but are also more useful to your team and clients.

Features include instant markup to highlight specific details enhancing your internal project and plot records.

Add Tags & Location

SymTerra location mobile feature example.

Add tags and Location to your Photographic Evidence with SymTerra’s easy to use feature.

Simply press “Add Location” in your SmartNote to capture where the photos are taken using GPS.

Capture Photos Online or Offline to Ensure Continuous Part L Compliance

Reliable photographic evidence is needed at every stage of a project. With SymTerra, take photographs whether online or offline.

These photos can then uploaded and securely stored as soon as you regain connection.

Evidence and Report Easily for All Part L Evidence

Demonstrate compliance with Building Regulation England Part L (BREL) effectively.

SymTerra allows photographic evidence to be captured on site via SymTerra App. Which will then automatically and securely store all photographic evidence on the server, ensuring nothing is missed.

Discover how SymTerra can enhance your Part L compliance process

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