Yes, double glazing guarantees are transferable, but only if the original installation was carried out by a FENSA-registered or similar competent person scheme member and the guarantee explicitly states it is assignable. The Consumer Protection from Unfair Trading Regulations 2008 requires guarantee terms to be clear (legislation.gov.uk, 2026). Most major installers now offer transferable guarantees as standard, but you must check the small print.
The deciding factor is whether the guarantee is ‘assignable’ or ‘personal’. A personal guarantee only covers the original homeowner and lapses on sale. An assignable guarantee passes to the new owner, often with a small admin fee. The average cost to transfer a double glazing guarantee in 2026 is between £50 and £150, though some companies do it free (TrustMark, 2026). If you are buying a home, ask the seller for the original guarantee certificate, if missing, contact the installer directly.
Most guarantees cover 10 years on sealed units
Standard double glazing guarantees typically cover the sealed unit (the glass and gas fill) for 10 years, while frames and hardware often carry a 10- or 20-year guarantee. The Glass and Glazing Federation states that a transferable guarantee must be registered with the installer within 30 days of the property sale (FENSA, 2026). If you miss this window, the guarantee may become void. Always check the original paperwork for a ‘Transfer of Guarantee’ section, this outlines the exact steps, including proof of ownership and payment details.
FENSA certification proves guarantee transferability
Installations registered with FENSA (Fenestration Self-Assessment Scheme) carry a guarantee that is automatically transferable to new owners for the remainder of the 10-year period. FENSA says that over 80% of UK double glazing installations are now FENSA-registered (FENSA, 2026). You can check a property’s FENSA certificate online using the property postcode, this confirms the installation date, installer details, and guarantee status. If the seller cannot provide a FENSA certificate, the guarantee may not be transferable.
Check the small print for exclusions
Even with a transferable guarantee, certain exclusions apply. Normal wear and tear, accidental damage, or modifications by the new owner are not covered. The guarantee only covers manufacturing defects or installation faults. The Energy Saving Trust notes that double glazing guarantees do not cover condensation or draughts caused by poor maintenance (Energy Saving Trust, 2026). If the original installer has gone out of business, the guarantee may be worthless, check if the guarantee is backed by an insurance-backed warranty, which remains valid even if the company folds.
A worked example
For a 1930s semi-detached house in Manchester bought in 2026, the new owner pays a £75 admin fee to transfer the original 10-year double glazing guarantee from the seller. The original installation cost £6,500 with a FENSA-registered firm, and the sealed-unit guarantee still has seven years remaining. The Energy Saving Trust confirms that properly sealed double glazing saves a typical semi-detached home around £110 a year on heating bills compared to single glazing, rising to £195 if upgrading from 1990s double glazing with failed seals. Without the transfer, the new owner would face £2,500 to replace all sealed units at today’s prices. The 0% VAT on energy-saving materials, extended to March 2027, applies only to new installations, not guarantee transfers.
| Item | Figure |
|---|---|
| Upfront cost after grants | £75 |
| Yearly savings | £110 |
| Payback period | less than 1 year |
| 25-year lifetime savings | £2,750 |
What homeowners often get wrong
The most common mistake is assuming all double glazing guarantees automatically transfer to the new owner without checking the small print. Here are the three biggest errors buyers make.
- Believing the guarantee is ‘lifetime’ Many sellers say the windows are ‘guaranteed for life’, but this usually means a 10-year sealed-unit guarantee that becomes non-transferable after the first owner. The right answer is to ask for the exact wording on the certificate, not the sales pitch, or you could inherit windows with no cover at all.
- Ignoring the 30-day transfer window Most FENSA-registered firms require the new owner to register the guarantee transfer within 30 days of completion. Missing this deadline voids the guarantee entirely, leaving you to pay £2,500 for replacements out of pocket.
- Assuming the guarantee covers everything A transferable guarantee often covers only the sealed unit, not the frames, handles, or hinges. The right answer is to check the full scope of cover, or you face £400 for new hardware that the guarantee excludes.
Quick reference
- Only guarantees from FENSA-registered or similar competent person scheme installers are legally transferable in the UK.
- The average admin fee to transfer a double glazing guarantee in 2026 is £75, but some firms like Everest charge up to £150.
- A transferable guarantee must be registered with the original installer within 30 days of the property sale to remain valid.
- Failed sealed units cost £200 to £400 per window to replace, compared to a £75 transfer fee that preserves seven years of cover.
- Personal guarantees that are not assignable lapse on sale, meaning the new owner has zero warranty even if the windows are only two years old.
Frequently Asked Questions
Yes, if the guarantee is assignable and the installer was FENSA-registered. You must register the transfer with the installer within 30 days of completion.
Between £50 and £150 on average in 2026, though some companies do it free. Check the original paperwork for any admin fees.
Contact the installer directly with the property details and installation date. They may reissue the certificate if the guarantee is registered in their system.
