Double glazing is meant to be airtight, so a window that whistles or feels cold at the edges is telling you something has worn. Before you consider replacing the window, check these things in this order.
1. Close the window and look at the seal
Walk round the window and run a finger along the rubber. Is it hard, flattened or pulled out of its groove? If so, a new seal is the answer.
2. Try the handle and hinges
Most uPVC windows have adjustable hinges and keeps, designed to pull the sash tight against the seal. If the window does not close firmly, a quick adjustment with an Allen key can fix it. Look for small adjusting screws on the hinges and the keeps on the frame.
3. Replacing the rubber gasket
- Pull the old gasket out of its groove, starting at a corner.
- Wipe the groove clean and dry.
- Measure the groove width, and compare the shape of the old seal with the new one.
- Press the new gasket into the groove with your thumb, starting at a corner and working round without stretching it.
- Leave the ends slightly long and push them together, as rubber shrinks back a little.
A replacement uPVC gasket is far cheaper than a new window and takes no tools.
4. Seal the frame to the wall
If you can feel moving air around the outside of the frame, the gap between the frame and the wall may need a flexible sealant. Clean the gap, apply a bead of sealant and smooth it with a damp finger.
5. Seasonal fixes
For a window you cannot adjust, such as an old sash in a rented flat, a clear window tape or a brush strip is the seasonal answer. You can fit it in the autumn and peel it off in the spring.
6. Know when to stop
If the sash is warped or the frame is rotten, no seal will cure it. A window specialist can advise on repair or replacement.
A word about condensation
Fixing draughts changes the airflow in a room. Make sure you keep trickle vents open, ventilate when cooking and bathing, and use extractor fans, so you do not trade a draught for condensation.