Legislation and U values


  • CE Marking on a product is the manufacturer’s declaration that the product complies with the essential requirements of the relevant European health, safety and environmental protection legislation. Within the UK this denotes compliance with Building Regulations (Part L) and Trading Standards, applicable for external windows and doors covered by the legislation.
  • U-values measure how effective a material is an insulator. The lower the U-value, the better the material is as a heat insulator. If an item requires a U-value then it also needs a CE mark.
  • Psi-values (Ψ-values) measure how much heat can escape through junctions or any other points where the insulation layer stops or changes – e.g. where the wall meets the roof and the floors, window frames, corners etc.

Building Regulations Part L – Conservation of fuel and power

  • Building Regulations (Part L) stipulates that external windows must have a U-value of 1.6 for a renovation project, or 2 for a new build. External doors require a U-value of 1.8.
  • This is an overall U-value of the whole window or door (not just the U-value of the glass), based on: type of timber, centre pane and the Psi value of the spacer bars.
  • Bespoke, conservation grade doors and windows etc. in a listed or heritage building may be exempt from requiring U-values and CE markings.
  • Our U-values are calculated using up to date software, verified by the British Standards Institute (or BSI) – the UK national standards body.

Building Regulations Part Q – Security

  • All accessible doors and windows supplied to new build* properties must be proven to be secure by testing to PAS 24:2012 or other means. (*includes new dwellings created by a material change of use.)
  • Approved Document Q applies to ‘easily accessible’ doors and windows that provide access into the dwelling from outside, access into parts of a building containing flats from outside (i.e. communal entrance doors), or access to a flat from common parts of the building (i.e. flat entrance doors).
  • Easily accessible doors are those within 2 metres vertically of an accessible level surface.
  • Easily accessible windows are those within 2 metres vertically of a flat or sloping roof (up to 30 degrees) or within 3.4 metres of ground level.
  • Secure doorsets and windows tested to PAS 24:2012 will meet the requirements. A doorset that is part of the Secured by Design approved third party accreditation scheme, tested to PAS 24 or STS202 BR2, also meets the requirements.
  • Main doors for dwellings should have the means to see callers, such as clear glass, a door viewer, or a window next to the door. The door should be fitted with a door chain or door limiter.