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Replacement Windows - Advice from Building Control

Since April 2002, all replacement glazing has come within the scope of the Building Regulations. Since then on, anyone who installs replacement windows or doors will have to comply with strict thermal performance standards.

Reducing energy loss is a key reason for change.

Building regulations have controlled new glazing in buildings for many years but they represent only a very small percentage of our total building stock.

Improving the performance of existing buildings is essential, if we are to meet national and global energy saving targets.

When selling 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 are 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

An estimated 2 million installations of replacement  windows 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 ensure that 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 & Glazing Federation, in association with all key stakeholders, and meets with central Government approval.

A sample of the work of every installer will be inspected by FENSA appointed inspectors to ensure standards are maintained.

FENSA will 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, will need full local authority approval under the Building Regulations.

Local authorities will know of all the approved installers in their areas and will be able to 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.

The basic requirement is:

  • For PVC or wood units 16mm gap low E glass.
  • A wide option in respect of glass and frames is offered and manufacturers details should be studied.
  • Trade off's can be used to substitute lower U values for walls etc. against glass percentage lower than 25%.
  • Attention will be required to ensure that air paths into buildings are sealed by such methods as mastic around frames, expanding foam if suitable, edges of warm deck roofs insulated and sealed, pipe entry to buildings sealed.
  • There are also requirements for ventilation, fire escape and safety glass that the replacement glazing must meet.

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.