5% off orders over £1000 with checkout coupon '5off'

Understanding U-Values

If you are a first timer to buying a rooflight, you may be wondering what U-Values actually mean?

Quite simply this is the measure of heat that is transmitted through a building part – in the case of rooflights, through the glazing.

They are also known as the ‘overall heat transfer co-efficient’ and the higher the number value is signifies the more heat that is being lost, meaning it is less energy efficient.

A lower value means that insulating properties are greater and therefore ultimately more energy efficient and better for the environment.

How the U-Value is Calculated

The U-Value is determined by the material used, its depth and positioning. When we manufacture our rooflights they are made up of several components, each of which have different properties in relation to heat transference.

A number of factors need to be considered when identifying the U-Value, including:

  • How each property conducts heat
  • The external and internal resistance of each component material

An equation of these values is used to determine the overall U-Value.

Our Rooflights

Please see below the table which shows the technical information on the U-Values of each of the different skins of our range of rooflights:

Double Skin2.6 W/m²KAs installed
Triple Skin1.8 W/m²KAs installed
Quad Skin1.4 W/m²KAs installed


Within the UKs building regulations, U-Values are covered by Part L and this sets out a maximum U-Value for modern building work.

If you have any further questions in relation to U-Values or our rooflights, please do not hesitate to get in touch either by calling 01670 821166 or email us directly at info@directrooflights.co.uk.