Most people assume draughty uPVC windows are a sign the frames need replacing, but that’s rarely the case. More often than not, the problem comes down to something small, a worn rubber seal, a locking pin that’s shifted slightly out of position, or a gap where the sealant around the frame has started to crack. Whatever the cause, knowing how to stop draughts from uPVC windows is something most homeowners can handle themselves, without spending much money or calling anyone out. In many cases, a few simple tests and the correct solution and application in the correct location are all that are required.
This guide covers exactly that: why draughts happen, how to find where the cold air is getting in, and six practical steps to sort it out properly.
Why Do uPVC Windows Let in Draughts?
uPVC windows are built to last, but over time, everyday use and fluctuating temperatures can cause small issues that let cold air in. Here are the most common reasons:
- Worn or perished rubber seals: The rubber gaskets around your window frame compress and crack over the years, losing their ability to form a tight barrier.
- Misaligned hinges: When hinges loosen or drop slightly, the window sash no longer sits flush against the frame, leaving a gap along one edge.
- Faulty locking mechanism: If the handle or locking points don’t pull the window in tightly when closed, air can sneak through even when you think the window is shut.
- Dropped sash: On older installations especially, the sash can drop over time, opening up a visible gap between the frame and the glass unit.
- Gaps between the frame and the wall: Sometimes the issue isn’t the window itself but the area where the uPVC frame meets the surrounding brickwork or plasterwork. As the sealant shrinks or the expanding foam wears down, gaps can form to allow cold air to penetrate.
Even a tiny gap can make a noticeable difference to the temperature in a room, and the longer it’s left, the worse it tends to get.
How to Check Where the Draught Is Coming From
The first step in figuring out how to stop draughts from uPVC windows is knowing exactly where the cold air is getting in. Fortunately, it’s pretty straightforward to check.
On a windy day, slowly run your hand around the edges of the closed window, along the frame, the handle side, and the hinge side. If you feel a stream of cool air anywhere, that’s your problem spot.
A lit candle works just as well. Hold it near the window edges and watch the flame. If it flickers, air is coming through at that point.
You can also try sliding a piece of paper between the sash and the frame. If it moves freely without any resistance, the seal isn’t doing its job properly, and that’s almost certainly where your draught is coming from.
How to Stop Draughts from uPVC Windows: 6 DIY Fixes
Once you’ve found the source, here’s what you can do to fix it.
1. Adjust the Locking Pins
This is often the quickest fix and the first thing worth trying. The locking pins, also called cams or espag points, sit along the edge of the window and pull it tight against the frame when you turn the handle. Over time, they can shift out of position, meaning the window closes but doesn’t seal properly.
To adjust them, open the window and look at the locking points along the sash edge. Most have a small Allen key socket, usually 2.5 mm or 3 mm. Turning this adjusts how far the cam sticks out, which in turn affects how tightly the window pulls in when locked. Make small adjustments and test the seal after each one. Don’t over-tighten, as that can make the window difficult to close.
2. Adjust the Hinges
If the draught is mainly on the hinge side of the window, the hinges are likely the issue. Loose or worn hinges allow the sash to drop slightly, which opens up a gap that locking adjustments alone won’t fix.
Most uPVC casement window hinges have built-in adjustment points, and an Allen key is usually all you need. Try tightening the top hinge slightly and loosening the bottom one to lift a dropped sash back into position. If the hinges are visibly damaged or have worn beyond adjustment, replacing them is the better option. New hinges are available at most hardware and home improvement stores and can be easily obtained for a very low price, but bring one of the old ones to ensure you’re getting the right size.
3. Replace the Rubber Seals
The rubber weatherstripping around the window frame is what creates the airtight barrier when the window is closed. Once it cracks or flattens, it can no longer form a proper seal, and draughts get in.
Replacing it is a straightforward job. Pull out the old seal; it usually sits in a groove around the frame, clean the channel, and press the new rubber seal into place. It comes in a metre-by-metre length from most DIY or glazing suppliers, so take a piece of the old seal with you to ensure that you match up the profile correctly.
4. Apply Fresh Silicone Sealant
If there are gaps between the uPVC frame and the surrounding wall, fresh silicone sealant is the answer. This is normal; the sealant will shrink and crack over time, and it just needs to be replaced periodically.
Scrape out the old sealant fully, clean the area with a damp cloth, and apply a fresh bead of uPVC-safe silicone along the gap. Smooth it off with a wet finger or a sealant tool and leave it to cure for 24 hours before exposing it to moisture. It is an inexpensive solution which can have a significant effect, particularly at the point where the frame connects to brickwork or plasterwork.
5. Add Weatherstripping or Draught Excluder Strips
If adjusting the window hasn’t fully closed the gap, adding self-adhesive foam or rubber weatherstripping around the frame is a good next step. It remains on the inside of the frame, and when the sash is shut, it will create pressure in the frame against the sash to fill any empty spaces. It is readily available at any hardware store, and it is easy to apply.
For windows you don’t plan to open during winter, draught-sealing tape is another option. A clear and self-sticking film which easily peels away in the spring and stays in place during the colder seasons, trapping cold air out.
6. Fill Gaps Between the Frame and the Wall
Where the window frame meets the brickwork or plasterwork, expanding foam is the right fix if the gaps are on the larger side. When the foam is completely cured, cut it flat and seal with a silicone sealant bead or seal with uPVC trim for a more finished look. Silicone sealant alone is generally sufficient to seal smaller spaces.
What About Draughty uPVC Doors?
It also applies to uPVC doors. If cold air is entering at the base, then installing a new threshold seal or draught excluder strip will resolve the issue. If there are draughts around the sides or top of the door, inspect the rubber strip around the door frame; if it is cracked or squashed, it will need to be replaced. If there is a visible gap when the door is closed, it’s also a good idea to adjust the hinges.
DIY Fixes vs When to Call a Professional
The majority of draught problems with uPVC windows are easily dealt with at the property. However, sometimes it’s better to hire a glazing professional.
| Situation | DIY or Professional? |
| Locking cams need adjusting | DIY |
| The rubber seal needs replacing | DIY |
| Hinges need adjusting | DIY |
| Hinges are damaged or corroded | Professional |
| Condensation between the glass panes | Professional |
| The frame is warped or poorly installed | Professional |
| The windows are over 20 years old | Consider replacement |
If, after all the above, you are still getting cold air through the frame, then the frame itself might be warped, or the original installation may have been incorrect. That’s when a professional glazier is worth calling in. A condensation between the panes is a different problem; this indicates that the sealed glass has failed in some way and requires replacement, not repair.
If you’re based in Glasgow or the central belt of Scotland and you’d rather have an expert take a look, Trade uPVC Windows Glasgow offers a free, no-obligation measurement and consultation. They manufacture and fit their own REHAU uPVC windows, so there’s no middleman, and every installation comes with a 10-year product warranty. You can reach them at info@tradeupvcwindows.co.uk or call 07723 363366.
How to Prevent Draughts Coming Back
Once the draught is sorted, a little routine maintenance will keep things that way going forward.
Clean and lubricate the hinges and locking mechanisms once or twice a year with a silicone-based spray
- Inspect the rubber seals each autumn and replace them at the first sign of cracking or wear
- Check the external silicone around the frame every couple of years and top it up where needed
- Keep the drainage holes along the bottom of the frame clear so water doesn’t build up and damage the seals
None of these tasks takes long, and they’re far easier than dealing with a draughty house all winter.
FAQs
How do I know if my uPVC window seals need replacing?
If you can feel cold air around the edges of the closed window or if the rubber is visibly cracked, flattened or peeling from the frame, it’s time to replace the seal. It’s a simple job, and the materials are inexpensive.
Can I fix how to stop draughts from uPVC windows myself?
Yes, in most cases you can. Adjusting the locking pins, replacing worn rubber seals, applying fresh silicone, and adding weatherstripping are all straightforward DIY jobs. You will need an Allen key, a tube of silicone sealant, and may need some replacement silicone sealant that you can purchase at a hardware store.
How do I adjust uPVC windows to stop draughts?
Open the window and look for the locking cams along the sash edge; they usually have a small Allen key slot. These adjustments will tighten the window when they are made. If the draught is on the hinge side, then the hinges can also be adjusted as above.
Why are my uPVC windows draughty even though they’re fairly new?
New windows can still have draughts if they weren’t installed correctly, if the frame wasn’t sealed properly against the wall, or if the locking mechanism wasn’t set up to close tightly enough. If the windows still have a warranty, it’s worth contacting the installer again.
Is it worth replacing draughty uPVC windows?
If the frames are old, warped, or repeatedly causing issues despite repairs, replacement is often the better option. The energy savings are significant in modern uPVC windows compared to older windows, and can be seen in their increased thermal performance and seal.
Final Thoughts
Draughty uPVC windows are a frequent occurrence, but one that is often more easily tolerated than avoided. Whether it’s adjusting the locking pins for a tighter close, replacing perished rubber seals, or resealing the frame with fresh silicone, there’s almost always a straightforward fix. And if you’ve worked through everything and you’re still not getting results, a glazing professional can usually sort it out in a single visit.The main thing is not to leave it too long. Even small draughts add up over a winter, pushing your heating bills up and making your home less comfortable than it should be. A bit of time spent on how to stop draughts from uPVC windows now will pay for itself many times over before the cold weather is done.
