FENSA is the Fenestration Self-Assessment Scheme. When a FENSA-registered installer fits your replacement windows, they self-certify that the work meets Building Regulations, and you receive a FENSA certificateas proof. That certificate matters most when you come to sell, because the buyer's solicitor will ask for it. Checking an installer is FENSA-registered is one of the simplest ways to protect yourself from a poor deal.
What FENSA actually does
Since April 2002, replacement windows and doors in England and Wales have had to meet Building Regulations, including the Part L energy rules. Normally that would mean involving your local council's Building Control. FENSA exists so a registered installer can self-certify the work instead, which is faster and cheaper. The certificate they issue is the document that says the job complies. CERTASS is a similar competent-person scheme, so some compliant windows carry a CERTASS certificate rather than a FENSA one.
I am FENSA-registered, and I issue a certificate on every job. If a fitter cannot tell you which scheme they belong to, that is your cue to stop the conversation. Self-certification is not optional, it is the law.
Tom Bradley, FENSA-registered installer
Why the certificate matters
The certificate is your evidence of compliance, and it becomes important at two moments. First, it confirms the windows actually meet the Part L energy standards you paid for. Second, and more practically, the buyer's conveyancer will ask for it when you sell. Without it, the sale can stall while solicitors sort out the paperwork. It sits alongside your installer's workmanship guarantee, which is a separate document covering faults rather than compliance.
What happens without a certificate
If windows were fitted after April 2002 with no FENSA or equivalent certificate and no council Building Regulations approval, the work is technically unauthorised. You then have three options: apply for retrospective Building Regulations approval (which costs money and may mean opening up the work), buy indemnity insurance to satisfy the buyer's solicitor, or risk the sale falling through. None of these is pleasant, which is why insisting on a certificate up front is the cheap and easy path.
| Scenario | What it means for you |
|---|---|
| FENSA certificate held | Compliant, easy sale, no further action |
| No certificate, post-2002 work | Retrospective approval or indemnity insurance needed |
| Different scheme (e.g. CERTASS) | Check that scheme's records for the equivalent certificate |
General guidance, not legal advice. Confirm with your conveyancer when buying or selling.
The cheapest mistake to avoid is the dearest one to fix later. Spend nothing now by checking the installer registers the job, or spend hundreds later on indemnity insurance when you try to sell. Easy choice.
Tom Bradley, FENSA-registered installer
How to check your windows are registered
Use the certificate lookup on the official FENSA website: enter your address and it lists any registered installations at the property. If your installer used CERTASS or another competent-person scheme instead, check that scheme's records. Before you buy windows, confirm the installer's scheme membership in writing, and make sure the certificate is part of what you are paying for. Once you have lined up a registered fitter, price the job in the uPVC window calculator so you know a fair figure before the quotes arrive.
Frequently asked questions
FENSA is the Fenestration Self-Assessment Scheme. A FENSA certificate proves your replacement windows and doors meet Building Regulations without needing separate sign-off from your local council, because the registered installer self-certifies the work.
It is your proof that the windows comply with Building Regulations, including the Part L energy requirements. You will usually need it when you sell the house, because the buyer's solicitor asks for it, and missing certificates can delay or jeopardise a sale.
If replacement windows were fitted after April 2002 without a FENSA (or equivalent) certificate or council Building Regulations approval, the work is technically unauthorised. You may have to pay for retrospective approval, or buy indemnity insurance to satisfy a buyer's solicitor.
Use the certificate lookup on the official FENSA website. You enter your address and it shows any registered installations. If you used a different competent-person scheme such as CERTASS, check that scheme's records instead.
No. FENSA certifies that the work meets Building Regulations. A workmanship or product guarantee is separate, usually offered by the installer or backed by an insurance-backed guarantee. You should have both: the FENSA certificate for compliance and a written guarantee for faults.
Not all, but reputable ones belong to FENSA or an equivalent competent-person scheme. Always confirm membership before you sign, because an unregistered fitter cannot self-certify, leaving you to arrange council approval yourself.