How to Improve the Insulation of PVC Windows and Doors

Even fairly recent PVC windows can let air through if the gaskets have aged, the sashes are out of adjustment or the junction with the wall was neglected. Before considering replacement, several fixes can restore good insulation.

1. Find the leaks

On a cold, windy day, run the back of your hand or a candle along the sashes and frame: a draught or flickering flame reveals a leak. A thermal camera, used by some tradespeople, gives a precise picture of cold spots.

2. Replace the gaskets

Sash gaskets harden over time. On most PVC profiles they sit in a groove and are easy to replace, as long as you get the right reference. A new gasket often eliminates draughts on its own.

3. Adjust the sashes

Modern window hardware has adjustment points, especially eccentric cams that increase or reduce closing pressure. A sash pressed firmly against its gasket makes the window much more airtight. It is a quick job for a joiner.

4. Seal the junction with the wall

This is often the weak point. If the seal between frame and masonry is cracked or missing, air flows around the window. Depending on the case, the outer sealant is redone, a suitable foam is injected or an airtight membrane is fitted on the inside.

5. Upgrade the glazing

If the glass is old, replacing it with low-emissivity, argon-filled double glazing with a warm-edge spacer noticeably reduces losses, provided the frame can take the new thickness.

6. Do not forget the front door

Check the threshold seal and fit an automatic drop seal or brush strip if needed. The threshold is a common cold spot.

7. Use your shutters

Shutters closed at night in winter create an extra layer of air in front of the window. It is a simple, often underrated gain.

Mind the ventilation

Making windows airtight must never compromise fresh-air supply. Never block trickle vents linked to mechanical ventilation: they are essential to avoid damp and condensation.