A UPVC window that lets in cold air when it's closed is failing at its most basic job. The good news is that the cause is almost always identifiable and fixable. Here's a systematic way to diagnose where the draught is coming from.
Is It Coming From the Glass or the Frame?
The first step is to identify whether the draught is coming through the glass area or around the edges of the window sash. Hold your hand flat against the glass and move it slowly to the edge — you should feel the draught intensify as you approach the seal or hinge area. Glass that feels cold to the touch but has no air movement around the edges may simply be radiating cold (normal in older double glazing) rather than leaking air.
Perished Rubber Seals and Gaskets
The most common cause of draughts in UPVC windows is perished or hardened rubber seals. UPVC windows have two sets of seals: one around the glass unit (the glazing gasket) and one around the sash frame (the weather seal). Over time, both types harden, crack, or pull away from the frame, creating gaps through which cold air enters. Seal replacement is a straightforward and affordable repair that immediately improves the thermal performance of the window.
Window Not Closing Properly
If the window isn't pressing the seals firmly against the frame, cold air will get through even if the seals are in good condition. A dropped sash, worn friction stays, or failed locking points that don't fully engage will all reduce the compression on the seals. The fix here is mechanical — repairing or replacing the hinges, friction stays, or locking mechanism so the window closes tightly.
Failed Pile Seals
Some UPVC windows — particularly older ones — use a brush-type pile seal around the sash rather than a full rubber gasket. Pile seals compress over time and eventually stop providing an effective seal. They can be replaced as a length of seal material pushed into a slot in the frame, but getting the right profile is important. A professional UPVC engineer will carry a range of seal profiles to match most window types.
Gap in the Glazing Bead
The glazing bead is the strip of plastic that holds the glass unit in the frame. If a glazing bead has cracked, bowed outward, or pulled away from the frame, it creates a gap through which cold air can enter behind the glass unit. Replacing a glazing bead is a quick repair — the old bead is levered off, a new one is cut to length and snapped into place. The Glass Guardian provides draught diagnosis and repair across Birmingham and the Black Country.
Need a UPVC Repair in Birmingham or the Black Country?
The Glass Guardian provides fast, affordable UPVC window and door repairs across Birmingham, Dudley, Walsall, Wolverhampton, and the surrounding area. Call for a free quote.