Part L for homeowners: what your installer must comply with
The 2022 Part L uplift changed the rules for replacement windows and doors. Here is what actually applies to your project, and how to spot a quote that ignores it.
The headline rules
Since June 2022, replacement windows in England must achieve a whole-window U-value of 1.4 W/m²K or a Window Energy Rating of Band B or better. Doors with more than 60% glazing must hit 1.4 W/m²K; solid doors must hit 1.4 W/m²K as well. Rooflights are treated separately at 1.6 W/m²K.
These figures are minima, not targets. A reputable installer should be quoting A-rated as a baseline and A+ where appropriate.
FENSA and CERTASS registration
Any company installing replacement windows or doors in your home must either notify Building Control directly or be a member of a Competent Person Scheme — FENSA and CERTASS are the two schemes that cover glazing. Membership means the installer self-certifies compliance and issues you a certificate for your conveyancing pack.
If you sell your home without a FENSA or CERTASS certificate for post-2002 window work, the buyer's solicitor will ask for a retrospective indemnity — which is avoidable.
Ventilation and trickle vents
Part F was updated at the same time as Part L. Replacement windows in habitable rooms must now include trickle vents unless the existing windows did not have them and adding them would be disproportionate. Removing trickle vents to keep sightlines clean is not a valid workaround — it is a breach that will fail Building Control sign-off.
In most cases no, provided the new windows match the style and material of the originals. Conservation areas, listed buildings and Article 4 areas are exceptions — check with your local authority.
Only if your existing windows do not have them and there is a clear structural reason. In practice, on a standard replacement job, they are compulsory.
