Do I Need FENSA for Replacement Windows?

FENSA (the Fenestration Self-Assessment Scheme) lets registered installers self-certify that your new windows and doors meet the Building Regulations — without a separate council Building Control inspection. If your installer is FENSA registered, you’ll receive a certificate for the job.

Do you legally need FENSA?

You don’t specifically need FENSA — but you do need to prove the work complies with the regulations. That proof comes either from a Competent Person Scheme certificate (FENSA, CERTASS and others) or a Building Control completion certificate from your council. In practice, using a registered installer is by far the easiest route.

Why the certificate matters

• It’s your evidence of compliance when you sell or remortgage — conveyancing solicitors ask for it.
• It confirms the windows meet the required 1.4 W/m²K (WER Band B) energy standard.
• Registered installers are subject to periodic inspection, which is a quality signal in a sector where that matters.

How to check before you buy

Ask for the installer’s registration number and verify it on the scheme’s website. Every firm you find through our directory shows its accreditations — browse local installers or get quotes and the matched firms will confirm their registration.

Frequently asked questions

Is FENSA the only scheme?

No — CERTASS and other Competent Person Schemes do the same job. Any one of them provides valid compliance evidence.

Does FENSA cover the guarantee on my windows?

No. FENSA certifies Building Regs compliance; the product/workmanship guarantee comes from the installer or manufacturer (often insurance-backed).

What if my installer isn’t registered?

Then the work needs a Building Control application to your council — agree who is responsible for that before work starts.