FENSA and CERTASS are the two main Competent Person Schemes for replacement windows and doors in England and Wales. A registered installer can self-certify that your new windows meet Building Regulations and lodge the certificate with your local authority, without a separate building control application.
Which scheme your installer uses matters far less than the fact that they are on one. Here is what the certificate proves, why it matters, and what to do if yours is missing.
Points to take away
- The certificate proves your replacement windows meet Building Regulations.
- FENSA and CERTASS do the same core job. FENSA is windows and doors only. CERTASS covers more.
- No certificate is a problem at sale, fixed with indemnity insurance or a retrospective application.
- The scheme certificate is separate from the installer’s own guarantee. Keep both.
- Check the installer is registered before you book, using each scheme’s online checker.
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What the certificate proves
Replacement windows and doors are notifiable building work. They have to meet Building Regulations on:
- Thermal performance (Part L): the window must not lose more heat than the current limit, usually shown as a minimum energy rating or a maximum U-value.
- Ventilation (Part F): background ventilation, normally trickle vents, must be maintained or provided.
- Safety glazing (Part K): toughened or laminated glass in and near doors, low-level windows and other critical locations.
- Means of escape: at least one openable window of a set size in habitable rooms above ground floor.
A Competent Person Scheme installer signs off that the job meets all of this and registers the certificate with your council, usually within 30 days. You get a copy for your records.
FENSA vs CERTASS: the differences
| FENSA | CERTASS | |
|---|---|---|
| Established | 2002 | 2006 |
| Scope | Replacement windows and doors | Windows, doors, plus conservatories, roofline, insulation |
| Assessment | Random post-installation inspections on a sample of members’ work | Installer self-certification with regular company audits |
| Certificate | Building Regulations compliance certificate | Building Regulations compliance certificate |
| Insurance-backed guarantee | Available through the scheme | Available through the scheme |
There is also a third scheme, Assure. All three produce a certificate a conveyancing solicitor will accept.
Why you need one
The certificate rarely matters day to day. It matters when you sell.
A buyer’s solicitor runs standard enquiries and will ask for the FENSA or CERTASS certificate for any windows replaced since 2002. No certificate means the work is technically unauthorised, which can hold up or reduce an offer.
The certificate is not the guarantee
Two separate documents, often confused.
- The scheme certificate (FENSA or CERTASS) confirms Building Regulations compliance and is held by the council.
- The guarantee is the installer’s own promise to put right faults in the windows and the fitting, commonly for 10 years, and commonly backed by an insurance policy so it survives the installer going out of business.
Ask for both in writing before the balance is paid, and store them together.
What if my windows have no certificate
Common on windows fitted by a trader who was not scheme-registered, or where the paperwork is lost.
- Indemnity insurance. A one-off policy, usually £20 to £100, that covers a future buyer against the council taking enforcement action. It does not confirm the work is compliant, only that a buyer is protected. Solicitors accept it routinely.
- Retrospective application (regularisation). Apply to building control, who inspect what they can and issue a completion certificate if it passes. More thorough, more expensive, and any non-compliant work has to be corrected.
For a job done in the last few weeks with a missing certificate, go back to the installer first. They can usually still lodge it.
How to check an installer is registered
Before you book, search the company on the FENSA or CERTASS website checker by name or postcode. Ask which scheme your certificate will come from, and confirm the guarantee is insurance-backed. Our guide to comparing double glazing quotes covers the other things to check on a quote.
Get a free quote and we will match you with vetted installers who are scheme-registered and will provide a certificate.