Replacement windows: FENSA

From April 2002, all replacement glazing now comes within the scope of the Building Regulations. Anyone who installs replacement windows or doors must comply with strict thermal performance standards.

One of the main reasons for the change is the need to reduce energy loss. The Building Regulations have controlled glazing in new buildings for many years, but they represent only a very small percentage of our total building stock. It is also essential to improve the performance of the much larger numbers of existing buildings if we are to meet increasingly stringent national and global energy saving targets.

When the time comes to sell your property, your purchaser's surveyors will ask for evidence that any replacement glazing installed after April 2002 complies with the new Building Regulations.

There will be two ways to prove compliance:

  • A certificate showing that the work has been done by an installer who is registered under the  FENSA  Scheme.
  • A certificate from the local authority saying that the installation has approval under the Building Regulations.

The FENSA scheme

It is estimated that around 2 million installations of replacement glazing happen every year. If all of them went through the normal Building Regulations application process it would place an enormous burden on local authorities. It is essential to have a way to ensure that the work is done properly without an unreasonable increase in the administrative and financial burden on installers and property owners. The answer is a scheme which allows installation companies that meet certain criteria to self-certify that their work complies with the Building Regulations.
The scheme is known as FENSA, which stands for Fenestration Self-Assessment. It was set up by the Glass and Glazing Federation, in association with all key stakeholders, and meets with central Government approval. A sample of work of every installer is inspected by FENSA appointed inspectors to ensure standards are maintained. FENSA also inform local authorities of all completed FENSA installations and issue certificates to householders confirming compliance.

Any installation done by a firm which is not registered to self-certify, or done as a DIY project by a householder, needs full local authority approval under the Building Regulations. The council knows all the approved installers in the area and can identify unauthorised work very easily.

You should note that you, as the house owner, are ultimately responsible for ensuring the work complies with the Building Regulations. Before you sign a contract to buy replacement glazing, be sure to ask whether the installer is able to self-certify. If not, either they, or you, will need to make an application to the council for approval under the Building Regulations and pay any relevant charges. 

Download a Guidance Sheet on Replacement Windows (PDF, 48KB)