Sunsquare: The market leaders in skylight and roof light design and installation


Energy loss is covered in a number of areas within the building regulations, and applies directly to the installation of new windows. As a result, any new project that requires the installation of windows, doors and roof-lights has to abide by the regulations, and this is the case with both domestic and non domestic properties.

Here, we’re going to take a look at the impact the regulations have on windows, rooflights and skylights.

What are the regulations the windows need to comply with?

These are the current standards for any new build:

  • Window, roof windows and rooflights – A Window Energy Rating (WER) of Band C or better, or a U-value of 1.6 W/m2K.

For rooflights, U-values are the most important area to focus on.

Are there any exceptions to the Part B Building Regulations?

In some cases, replacement windows may be unable to obtain the above U-values due to the need to maintain the external appearance of the building’s character - in a listed building, for example.

In these cases, replacement windows will be required to be a centre pane U-value of 1.2 W/m2K. Single glazing, meanwhile, should be supplemented with ‘Low E’ secondary glazing.

(It’s also worth noting that standard double glazed units with low emissivity coating do NOT meet the current values, and a Building Control Surveyor will not sign a Completion Certificate off without proof from the window supplier that the U-values have been met).

U values are probably the most important factor when it comes to rooflights, and need to be taken very seriously.

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Verifying compliance regarding the installer

Whenever a property is bought or sold, the surveyors will ask for proof that any glazing installed after April 2002 is compliant with the building regulations. There are two ways of demonstrating this:

  • A certificate confirming that the work has been carried out by an installer registered under the Fenestration Self-Assessment Scheme by Fensa Ltd, or a person registered by BM Trada Certification Limited, the British Standards Institution, CERTASS Limited or Network VEKA Limited.


  • A certificate by the local authority confirming that the installation has approval under the building regulations.

Any project carried out by a non registered firm - such as a DIY project - will need to be verified by the local council (though this shouldn’t be relevant to architects).

Should Building Regulation approval by the local council be required, payments will need to be made as follows:

  • Per installation up to 10 windows - £85.12 + VAT = £102.14
  • Per installation 11 to 20 windows - £170.22 + VAT = £204.26

Other factors

In addition to the U values and thermal performance, there are a number of other areas the building regulations cover with regards to windows:

  • Means of escape. All first-floor windows and dwellings should have openings large enough to allow people to escape through them in the event of a fire. The typical measurement for this is no less than 450 mm high and 450 mm wide. (This is not a legal requirement as such, but it is heavily recommended for obvious reasons).
  • Ventilation. Building regulations require that all dwellings have adequate ventilation. Replace your windows should never worsen the existing ventilation, and replacements should always have the same - or better - background trickle ventilation. Clear opening sizes must not be any less than the windows being replaced.
  • Safety glazing. It is fairly standard for windows within 800 mm of the floor to be ever type of glass that will break safely - laminated or toughened glass, for example, that we offer as standard at Sunsquare. Consult with your local authority on this, as it can vary depending on the project.

At Sunsquare, we accurately calculate the U-value of each of our BSI Kitemarked rooflights, designing and manufacturing skylights that are easily compliant with Building Regulations due to their impressive thermal performance. Even our fully-insulated upstands provide U-values of just 0.58: not only ensuring your Sunsquare skylight fits perfectly, but ensuring zero per cent chance of dew and damage to the roof membrane. What’s more, we can provide thermal performance certificates for our rooflights.

Want to find out more?

If you want to know more about this or anything else then get in contact

Call us on +44 (0)1284 723377

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