Part L + O Overview

Part L + O Overview

What is Part L 2021?

Welcome to our Part L and O hub

Changes to Part L of the Building Regulations in England, including the supporting Approved Documents, are expected to have a significant impact on glass and glazing products in residential and non-residential buildings. High performance, energy efficient glass and windows are expected to play a crucial role in delivering nearly zero energy buildings (nZEB) in the UK.

The consultation process was undertaken in stages, beginning in late 2019 and ending on 13th April 2021,and it is important that our industry understands the opportunities these new requirements will bring. On 15th December 2021, the Government published the 2021 editions of the supporting Approved Documents Part L (conservation of fuel and power) and Part F (ventilation) of the Building Regulations for new and existing buildings, as well as the new regulation (Part O) addressing the risk of overheating in new homes.

The confirmed timeline for these regulatory changes are as follows:

Date Action 
From late 2019 to April 2021 Consultations completed on:
  • Future Homes Standard
  • Overheating in new dwellings
  • Energy efficiency standards for work carried out in new and existing dwellings
  • Energy efficiency standards for new buildings other than dwellings
  • Energy efficiency standards for work to existing buildings other than dwellings
15th December 2021 Publication of new Approved Documents Part L, F and O
15th June 2022 Part L, F and O come into force

Through our hub, we will report on the changes to Part L in England, as well as the regulatory requirements in Wales, Scotland, Northern Ireland and Ireland.

If you have any questions on the new regulatory requirements and what the implications might be for glass, please complete our online contact form, selecting 'Architect' or 'Trade' as the Nature of Enquiry and 'Part L' as the Enquiry Type.

Hand in hand with Part L are the compliance tools such as Standard Assessment Procedure (SAP) and Simplified Building Energy Model (SBEM). Although the tools contain default values for windows, they do tend to be generic and conservative. We would encourage all designers to use manufacturers' values in these programs and real window sizes and orientations to realise the contribution that energy efficient windows can make. Our Spectrum online calculator can be used to quickly determine the g value and centre pane U value for our range of thermal insulation and solar control glass.

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