Guide to UK Building Regulations for Windows

Homeowners in the UK must comply with building regulations when installing new or replacement windows. Read our handy guide to help you understand what you need to know about installing windows to comply with UK law.

What are the UK building regulations for windows?

Building regulations are the legal guidelines that ensure new and replacement windows meet safety standards, are energy efficient and provide adequate ventilation.

Building regulations ensure that people are kept safe and energy consumption is lowered. They also ensure sufficient ventilation to keep your home healthy and mould-free.

Where can I find full details of UK building regulations for windows?

You can see the approved documents here.

Here is a summary of the UK building regulations for windows.

Part L: Conservation of Power

This explains the requirements for energy efficiency. New windows must have a U-value of no more than 1.2 W/m².K and a Window Energy Rating (WER) of B or better. Replacement windows must have a U-value of no more than 1.4 W/m².K and a WER of B or better.

U value refers to the amount of heat loss and

WER rating refers to the overall energy efficiency of a window.

Part B: Fire Safety

The regulations set out the vital fire safety measures for windows. Habitable rooms require a window large enough for emergency escape.

Measurements for the opening part of a new window must be a minimum of  0.33 m2 and 450 mm in height or width. New and replacement windows in habitable rooms must be able to open to provide emergency escape.

Part F: Ventilation

New and replacement windows are required to provide adequate ventilation. Background ventilators, trickle vents, or openable windows are accepted solutions.

Ventilation ensures homes are kept free of excess moisture, improves air quality and reduces the risk of mould.

What British Standards (BS) are relevant to Windows?

British Standards (BS) provide technical guidance on the design, manufacture and installation of windows, ensuring they comply with the UK building regulations.

BS EN 1279-2:2018 –includes glass in buildings, insulating glass units, and evaluation of conformity/product standards.

BS 8213-1:2016 – covers windows, doors and roof lights. In particular, it describes performance and outlines the classification for weather-tightness, ventilation, heat transfer and safety in use.

BS 7950:1999 – outlines the security requirements of windows for domestic applications, including doors and shutters.

What else do I need to know when installing new or replacement windows?

After installation, you must get a Building Regulations Certificate of Compliance. This is covered by a FENSA certificate (Fenestration Self-Assessment Scheme Assessment), which a qualified professional must provide. If you are given a FENSA certificate, you are not required to get a separate Building Regulation Certificate of Compliance for new or replacement windows.

The easiest way to get a building regulation certificate is to use an approved installer registered as competent under the government-approved Competent Person Scheme, showing they have the necessary skills and expertise to comply with building regulations. They will be able to issue you with a Building Regulation Certificate of Compliance.

Alternatively, if you install windows yourself or use someone who is not approved, you must apply for a Building Regulations Certificate from Building Control at your local authority. First, you will submit a building notice to the Building Control Body, and next, a Building Control Officer will inspect the windows. If the windows pass inspection you will be issued with a Building Regulation Certificate of Compliance.

Why do I need a Building Regulations Certificate of Compliance for New and Replacement Windows?

1. It has been a legal requirement since 2002.
2. When you decide to sell your home, you will be asked to supply the certificate, which many mortgage lenders require before proceeding.
3. Warranties on windows will only be valid if building regulations are followed and a certificate is obtained.
4. You will be unsure whether your windows meet safety and energy requirements. The certificate provides peace of mind.

Don’t worry if you are unsure about building regulations for new and replacement windows. Our expert team can ensure that all new windows, supplied and fitted by our professional installers, meet UK building regulations. Get in touch with us at Colne Valley Windows to find out more.