Building Standards

Recent record cold winters and continuing rises in fuel prices has lead to greater interest in energy efficiency. For many of us the cost of home energy has leaped up over recent years.

Broxwood’s energy efficient timber windows and doors are designed and manufactured in Scandinavia and Latvia where extreme winter conditions are the norm with temperatures dipping between -30° and -40°.

Due to their extreme winter climate, Scandinavian building standards are much more demanding than the UKs. As a result, manufacturers in Scandinavia and Latvia are continually developing newer, more thermally enhanced products to achieve amongst the best U-values anywhere in the world.

With tough zero carbon targets to meet, rising fuel costs and energy efficiency high on the list of priorities, building standards here are forecast to get much tighter in the UK. It is predicted that eventually all new builds in the UK will be expected to have windows with U-values of less than 1.0 W/m2K.

UK building standards


Visit the Scottish Building Standards website

In Scotland, building standards in relation to windows and doors are a little more stringent than those in England and Wales. Part J of the Scottish building regulations demands the installation of energy efficient double or triple glazing for all replacement windows with a U-value of 1.8 W/m2K or better.

A useful insight to the rules surrounding energy efficiency can be found in the Scottish Buildings Standards Technical Handbook for Domestic Properties

England & Wales

Windows and Doors should comply with Part L of the Building Regulations.

New Build Projects

To determine the U-value required for windows and doors, the Whole Building CO2 Target Emission Rate (TER) must be determined using notional values. The Dwelling Emission Rate (DER) is then determined using actual values and must not exceed the TER. Only with these figures can the U-value for windows and doors be reached. The Building Regulations limit the maximum acceptable whole U-value to 2.2 W/m2K.

Window, roof window, roof light

New build extensions
  • Whole Window U-value 1.8W/m2K or better.
  • Centre pane U-value 1.2W/m2K or better.
  • WER ‘D’ rating.
  • Whole Window 2.0W/m2K or better.
  • Centre Pane U-value 1.2W/m2K or better.
  • WER ‘E’ rating.

Doors with 50%+ internal glazed face area

New build extensions
  • U-value 2.2W/m2K
  • U-value 2.2W/m2K or better.
  • Centre Pane U-value 1.2W/m2K or better.

Other doors

New build extensions
  • 3.0W/m2K
  • 3.0W/m2K

Some buildings, such as those in conservation areas, may be exempt from some of Part L regulations. When replacement windows and doors are used consideration should also be given to compliance with other parts of the Building Regulations notably parts B, E, F, J and part N.

For more information visit:

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Broxwood’s passive house standard timber windows and doors provided the perfect solution for Findhorn’s ecovillage development. Read the Findhorn case study