Replacement Windows and Doors Energy Requirements

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

1. Replacement windows: Maximum U-value of 1.4 W/m²K (whole window, including frame)
2. 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)
3. Roof windows: Maximum U-value of 1.4 W/m²K
4. 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

1. 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
2. CERTASS or other Competent Person Scheme: Similar to FENSA; the installer self-certifies
3. 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

1. Like-for-like replacement of windows or doors in existing frames does not normally require Building Regulations compliance (replacing glass only)
2. Replacing the full window unit (frame and glass) triggers Part L requirements
3. Adding secondary glazing does not trigger Part L requirements

Emergency Repairs

1. Where a window is damaged and requires emergency replacement, the replacement unit should meet Part L standards
2. 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

1. Always use an installer registered with FENSA, CERTASS, or another competent person scheme; otherwise, you will need to apply for Building Control approval separately
2. Check the WER or U-value on the window's product label or certificate before purchase
3. Retain the FENSA/CERTASS certificate; it is required when selling the property as evidence of Building Regulations compliance
4. 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)
5. Consider upgrading to triple glazing (typical U-value 0.8-1.0 W/m²K) for significantly better thermal performance
6. Ensure trickle ventilators are included in the replacement windows; Part F (Ventilation) requires background ventilation equivalent to what was provided by the original windows
7. In conservation areas or on listed buildings, consult the local planning authority before replacing windows; there may be requirements to match the original style