What This Requirement Covers
When windows or doors are replaced in an existing building, the replacement units must meet the energy performance standards in Approved Document L Volume 2 (Existing Dwellings). This requirement applies regardless of whether any other building work is being carried out.
Key Requirements
Minimum Performance Standards
- Replacement windows: Maximum U-value of 1.4 W/m²K (whole window, including frame)
- Replacement doors: Maximum U-value of 1.4 W/m²K (if more than 50% glazed) or 1.0 W/m²K (if less than 50% glazed)
- Roof windows: Maximum U-value of 1.4 W/m²K
- Alternatively, windows can comply by achieving a Window Energy Rating (WER) of Band C or better under the BFRC (British Fenestration Rating Council) scheme
Building Regulations Compliance Routes
There are three ways to demonstrate compliance
- FENSA (Fenestration Self-Assessment Scheme): The installer is registered with FENSA and self-certifies compliance; a certificate is issued and notified to the local authority
- CERTASS or other Competent Person Scheme: Similar to FENSA; the installer self-certifies
- Building Control: A building notice or full plans application is submitted to the local authority Building Control, which inspects the installation
What Counts as a Replacement
- Like-for-like replacement of windows or doors in existing frames does not normally require Building Regulations compliance (replacing glass only)
- Replacing the full window unit (frame and glass) triggers Part L requirements
- Adding secondary glazing does not trigger Part L requirements
Emergency Repairs
- Where a window is damaged and requires emergency replacement, the replacement unit should meet Part L standards
- If a compliant unit cannot be obtained immediately, a temporary repair may be acceptable with the compliant unit installed within a reasonable timeframe
Practical Compliance Tips
- Always use an installer registered with FENSA, CERTASS, or another competent person scheme; otherwise, you will need to apply for Building Control approval separately
- Check the WER or U-value on the window's product label or certificate before purchase
- Retain the FENSA/CERTASS certificate; it is required when selling the property as evidence of Building Regulations compliance
- If you have replaced windows without a certificate, you may need to apply for a regularisation certificate from Building Control (a retrospective approval that involves an inspection and fee)
- Consider upgrading to triple glazing (typical U-value 0.8-1.0 W/m²K) for significantly better thermal performance
- Ensure trickle ventilators are included in the replacement windows; Part F (Ventilation) requires background ventilation equivalent to what was provided by the original windows
- In conservation areas or on listed buildings, consult the local planning authority before replacing windows; there may be requirements to match the original style