Building Regulation Compliance certificate >

With carbon emissions high on the global agenda and the current high cost of fuel, we are all looking for ways to make our homes more energy efficient. In addition, installing energy efficient windows is a legal requirement in order to comply with current Building Regulations.

Windows & Doors >

To incorporate thermal performance, the building regulations regarding the replacement of windows and doors in domestic dwellings were changed on the 1st April 2002 and then amended on the 1st October 2010.

Replacement windows means both the frame and glass is replaced at the same time. If you simply replace the glazing unit only, these building regulations do not apply, and therefore, no Building Regulation Compliance Certificate is needed.

As from the 1st April 2002, a special see-through coating must be applied to the glazing unit of all UPVC double glazed windows. This coating is called a “low e coating”, and is sometimes known by the brand name, such as “K GLASS”. This “low e coating” increases the energy efficiency of the window by helping to reduce warm air leaving and cold air entering through the glazing unit. Measuring the rate of heat loss through a material is called the U-value, and in 2002, glazing units needed to achieve a U-value of 1.8 or below.


On 1st October 2010, the minimum U-value allowed was reduced from 1.8 to 1.6. In addition, a new way of rating the energy efficiency of the whole window was introduced called Window Energy Rating (WER).


This system uses a simple colour coded A-G rating, similar to that used on white goods like refrigerators and washing machines.

Generally speaking, the higher the rating, “A” being the highest, the better the overall thermal performance of your replacement windows and therefore, the greater the savings on your fuel bills.

Today, Certass contractors achieve compliance to the current building regulations regarding the thermal performance of a double glazed window in one of two ways;

  • By achieving a U-value of 1.6
  • With a Window Energy Rating (WER) of band C or above

In addition, compliance with current building regulations B1, L1 and N1, as laid down by law, also includes:

  • Structural stability of the domestic dwelling, for example, using lintels on certain window installations
  • Safety glazing or toughened glass to be used in locations where someone could be injured, for example, patio doors and low level windows
  • Correct ventilation
  • Sufficient opening size for escape in the event of a fire
  • Weathertightness
  • Workmanship and materials


Fabric first is a key to making your home
as energy efficient as possible.

There is no point having a really energy efficient boiler if all the heat goes straight out of the walls, windows, doors and roof. Making the building fabric thermally efficient will greatly reduce the amount of energy required to heat your home.

This is particularly important with solid walls as the heat pass easily pass through to the outside. The installation of external or internal wall insulation to solid walls must meet current Building Regulations.

Indeed, if you make repairs to more than 25% of external walls it is a requirement under Building Regulations to upgrade the thermal performance of external walls (generally excluding conservation areas and listed buildings). So where external render is replaced often the walls should be thermally upgraded.