What to do if PVC windows start letting in air

Introduction

If you feel a draft or hear wind whistling around PVC (uPVC) windows, the seal may be compromised. Air leakage reduces energy efficiency, increases condensation risk and makes indoor climate uncomfortable. This guide explains how to identify the cause, what repairs you can do yourself, and when to call a professional.

Quick checks to start with

• Inspect the sealing gasket around the sash for cracks, flattening or aging.
• Run your hand along the perimeter of the closed sash to detect drafts.
• Paper test: close a sheet of paper in the sash; if it slides out easily, there’s a gap.
• Check that the sash sits evenly in the frame and there’s no sagging or misalignment.
• Check the handle position — windows often have micro-ventilation and full-close modes.

Common causes and DIY fixes

1. Loose or misadjusted hardware

• Signs: sash doesn’t press tightly against the frame; whistling along an edge.
• Fix: adjust the locking points and hinge screws with a hex key or screwdriver. Turn in small increments and test the seal.

2. Worn or deformed gasket

• Signs: visible cracks, loss of elasticity, leaking air along the entire perimeter.
• Fix: replace the gasket. Remove the old seal, clean the groove, measure the profile, order the correct EPDM seal and fit it evenly.

3. Handle/lock pressure settings

• Signs: window appears closed but not pulled tight to the frame.
• Fix: ensure the handle is fully engaged and check the strike plate positions to increase compression if necessary.

4. Sagging sash or warped frame

• Signs: uneven gaps, difficulty closing the window.
• Fix: tighten fixing screws, adjust hinges. Significant sagging usually requires a specialist.

5. Blocked drainage and dirt

• Signs: moisture or water at the bottom of the frame.
• Fix: clean drainage holes and gasket channels; remove debris so moisture doesn't accumulate and damage seals.

When to call a professional

• If you’re unsure about the diagnosis or adjustments.
• If the gasket or frame needs complex replacement or is non-standard.
• If hinges are damaged or the sash is heavily sagged.
• If DIY attempts don’t stop the draft.

A pro can measure frame geometry, evaluate overall tightness, and replace hardware or seals correctly.

Maintenance tips to prevent air leaks

• Inspect seals annually and clean gasket grooves.
• Lubricate hardware and hinges once a year with appropriate lubricants.
• Recheck pressure settings after seasonal temperature changes.
• Avoid aggressive cleaners on rubber seals.

Quick winter measures

• Replace worn seals before cold season.
• Use sealing tape or textile strips as a temporary fix, not a permanent solution.
• Recheck windows after storms or strong winds.

FAQ

Can I replace the gasket myself?

Often yes for standard profiles: measure the groove, buy the right EPDM seal and fit it. Non-standard profiles or damaged grooves require professional help.

How much does repair cost?

Costs vary: simple adjustments are inexpensive; gasket and hardware replacement cost more. Exact price after on-site inspection.

Will tightening screws always help?

Often it does, but if the gasket is worn or the frame is warped, further repairs are needed.

Conclusion

Air leakage in PVC windows is common but fixable. Start with simple tests and adjustments: paper test, gasket inspection, hardware tuning. Replace seals when needed and contact a professional for complex issues — correct repair saves heating costs and extends window life.