When planning to replace existing windows or add new windows to a property (e.g. as part of an extension), it is vital that you know about any relevant planning rules and building regulations. For example, restrictions are likely to apply if your house is in a conservation area, is a listed building, or is subject to Article 4 Directions. These remove permitted development rights, meaning that you will need planning permission. Contact your local planning authority to check.
Building regulations and building control
If you are using a professional window installer, the installer should be responsible for ensuring that the new windows comply with current building regulations, and for gaining permission from the appropriate Building Control Service where applicable. Make sure that the installer is registered with a relevant Competent Persons Scheme, and on completion of the job will issue a certificate confirming that the installation complies with building regulations. Several such schemes are recognized under building regulations:
- FENSA (Fenestration Self-Assessment Scheme) - set up by the Glass and Glazing Federation and other industry bodies; issues certificates of compliance on behalf of their registered installers, which can be located via the FENSA website
- Certass ('Certification and self-assessment) - also issues compliance certificates for registered Certass contractors, a list of which is available on the Certass website
- BSI (British Standards Institution) - operate a Kitemark scheme for certified installers
For the DIY or self-build enthusiast, the installation must be approved by the relevant Building Control Body, either the local authority or an approved inspector. Areas to consider include not only the performance of the windows themselves, but also safety glazing, ventilation and fire safety. Check with your local planning authority at the outset of any project. The Planning Portal website gives more useful information.
Although not nearly as effective as window replacement, fixing a secondary frame and panes inside the existing window reveal is a cheaper option. Indeed for buildings in a conservation area where the original features must be retained, this may be the only choice. Any secondary glazing system should fulfil the following points:
- opens to enable access to existing window
- ideally at least 100 mm from existing window
- extend existing window cill if necessary to ensure good seal
- existing window remains unsealed to allow venting of condensation to the outside
- use low-E glass for improved performance of secondary glazing