Draughty or Failing Windows: Repair, Reseal or Replace?
Misted double glazing, draughts, stiff handles and rotten frames: what can be repaired, when only the glass needs replacing, and when a new window makes sense.
Cold draughts, condensation running down the glass and windows that will not close properly are common winter complaints. The good news is that many window problems can be repaired without replacing the whole window, which saves money and disruption.
The quick answer
- Misted between the panes: the sealed unit has failed, and usually only the glass unit needs replacing
- Draughts round the edge: worn seals or hinges that need adjusting
- Stiff or broken handles: often a straightforward part replacement
- Rotten timber: small areas can be cut out and repaired, but extensive rot may mean replacement
- Replacement windows must meet building regulations
Diagnose the problem
| Problem | Likely cause | Usual fix |
| Mist or water between the panes | Failed sealed unit | Replace the glass unit only |
| Condensation on the inside of the glass | Moisture in the room | Better ventilation and heating |
| Draught round the frame | Worn or flattened seals | Replace gaskets or seals |
| Window drops or catches | Worn hinges | Replace or adjust hinges |
| Handle loose or will not lock | Worn handle or gearing | Replace handle or locking mechanism |
| Soft or crumbling timber | Rot | Cut out and splice in new timber, or replace |
| Gaps round the outside of the frame | Failed external sealant | Rake out and reseal |
Misted double glazing
If you see mist or droplets between the two panes that you cannot wipe away, the seal around the glass unit has failed. You do not usually need a new window. A replacement sealed unit can be made to measure and fitted into the existing frame, which is much cheaper than a new window.
Timber windows and sash windows
Timber windows can last a very long time if they are maintained. Small areas of rot can be cut out and repaired with new timber or resin, then painted. Sticking sashes can often be eased, and draught-proofing kits are available for sash windows. In conservation areas and listed buildings, repair is often expected rather than replacement, so check with your council before replacing.
Secondary glazing
Where replacement is not allowed or affordable, secondary glazing adds a second pane on the inside. It can reduce draughts and noise significantly and is often acceptable in older and listed buildings.
When to replace
- Frames are badly rotten, warped or damaged
- Several windows have failing hinges, seals and units
- You want better security and energy performance throughout
- The windows are single glazed and secondary glazing is not suitable
In England, replacement windows must meet building regulations. Installers registered with a competent person scheme, such as FENSA or CERTASS, can self-certify the work. Keep the certificate, as buyers will ask for it when you sell. Replacement windows may also need trickle vents to keep rooms ventilated.
Frequently asked questions
Why do my windows have condensation on the inside?
That is moisture in the room meeting cold glass. Improve ventilation, use extractor fans and keep a steady background heat.
Can you replace just the glass?
Yes. Misted or cracked sealed units can usually be replaced without changing the frame.
Do I need permission to replace windows?
Like-for-like replacements on houses usually do not need planning permission, but flats, listed buildings and conservation areas can be different. Building regulations still apply.
Related guides
- Winter home maintenance checklist
- Condensation, damp and mould
- Winter-proofing: insulation and draught-proofing
- Front and back doors before winter
Send photos of the windows and your postcode, or call 07444 262522.