Stop Giving the Great Outdoors Free Heating

Your Double Glazed Windows Are Leaking Money — Here’s What to Do

Draught proofing double glazed windows is one of the quickest ways to cut heating bills and stay warmer this winter. Here’s a fast-start summary:

Quick answer — how to draught proof double glazed windows:

Find the draught — run your hand around the window edges, or hold a candle near the frame and watch for flickering
Identify the cause — worn seals, damaged frames, loose hinges, or a faulty locking mechanism
Apply a fix — self-adhesive foam tape or window film for a quick fix; rubber seals, brush strips, or silicone sealant for a lasting repair
Adjust the hardware — tighten screws and realign the locking catch to press the frame tighter against its seal
Maintain regularly — clean and inspect window tracks and hinges every three months to catch problems early

Double glazed windows are supposed to keep the cold out. That’s the whole point. But over time, even good-quality windows can start letting in icy draughts — and when they do, your boiler works harder, your rooms feel colder, and your energy bills climb.

According to the Energy Saving Trust, sealing draughts around windows, floors, and doors can save a typical household around £85 a year in Great Britain. That’s not a huge number on its own — but combine it with a one-degree thermostat reduction (another £90 saved annually) and it adds up fast.

The frustrating part? The draught is often caused by something small: a perished rubber seal, a slightly misaligned latch, or a hairline gap where the frame meets the wall. None of these require a full window replacement to fix.

This guide walks you through exactly where draughts come from, how to find them, and how to seal them — for good.

Relevant articles related to draught proofing double glazed windows:

draft excluder patio door

Why Do Double Glazed Windows Develop Draughts?

It feels like a betrayal when your double glazing starts acting like a screen door. You invested in these windows for their insulation, yet here you are, wearing a scarf in your own living room. Understanding why this happens is the first step toward draught proofing double glazed windows effectively.

Most modern units rely on a sandwich of two glass panes with a layer of argon gas in the middle. This gas is a poor conductor of heat, which is exactly what you want. However, the system is only as good as its weakest link. Over years of service, several components can fail:

Failed Seals: The rubber gaskets (the black strips around the glass) are the frontline soldiers. Over time, they perish, crack, or flatten, allowing air to bypass the glass entirely.
Expansion and Contraction: Materials like uPVC are sensitive to temperature. In the height of summer, they expand; in the depths of winter, they contract. This constant movement can eventually lead to gaps or warped frames.
Mechanical Wear: Hinges and locking mechanisms are moving parts. If a hinge wears down by just a millimeter, the window sash won’t sit flush against the frame, leaving a gap for the wind to whistle through.

To dive deeper into the basics of home efficiency, check out our guide on how to seal air leaks to save energy.

The Role of Window Frame Materials

The material of your window frame dictates how it ages and where the draughts are likely to start.

uPVC: These are incredibly popular but prone to “dropping.” Because uPVC expands and contracts with the seasons, the frame can become slightly misshapen over a decade or two. If you have uPVC units, you might find easy ways to fix drafty upvc windows particularly helpful.
Timber: While beautiful, wood is a living material. It absorbs moisture and can warp or rot if not maintained. This warping creates irregular gaps that standard seals can’t always close.
Aluminium: Modern aluminium frames usually have “thermal breaks” (insulating plastic sections) to stop them from conducting cold. However, older aluminium frames without these breaks create “cold spots” that make the air around them feel like a draught, even if no air is actually moving.
Structural Movement: Sometimes the issue isn’t the window at all, but the house. Small movements in your masonry can open up hairline cracks between the window frame and the wall.

Identifying Failed Glass Unit Seals

There is a big difference between a draughty frame and a “blown” window. If you see fog, mist, or droplets of water inside the two panes of glass, your seal has failed, and the argon gas has escaped.

When a unit is blown, the insulation value drops significantly. While draught proofing double glazed windows by sealing the frame will help with the breeze, it won’t fix the heat loss through the glass itself. In this case, you don’t usually need a whole new window—a professional can often just replace the glass unit (the “IGU”) within your existing frame for a fraction of the cost.

How to Locate the Source of a Window Draught

Before you start sticking foam tape everywhere, you need to play detective. Draughts are sneaky; air can enter at the bottom of a window and exit at the top, making it hard to find the actual entry point.

Here are our favorite ways to hunt down those elusive leaks:

The Hand Test: On a cold, windy day, wet the back of your hand and run it slowly around the perimeter of the window. Your skin is incredibly sensitive to temperature changes, and the moisture will make the “chill” of a draught much more obvious.
The Candle/Incense Test: Light a candle or an incense stick and hold it near the window frame. If the flame flickers or the smoke dances horizontally, you’ve found a leak. Be careful not to get too close to curtains!
The Visual Inspection: Look for daylight. If you can see even a sliver of the outdoors through the closed window, you have a major problem. Also, check for black mould or damp spots, which often indicate where cold air is meeting warm, moist indoor air.
The Listening Test: Sometimes you can hear a draught before you feel it. A high-pitched whistle usually means air is being forced through a very small, pressurized gap.
The Paper Test: Close the window on a piece of paper. If you can pull the paper out easily without any resistance, the seal isn’t tight enough.

For more diagnostic tips, see our article on how to seal window drafts without losing your mind.

Step-by-Step Guide to Draught Proofing Double Glazed Windows

Once you’ve found the culprit, it’s time to take action. Draught proofing double glazed windows is a very satisfying DIY project because you can often feel the results immediately.

Preparation is Key

Regardless of the method you choose, you must clean the area first. Use a mild detergent or sugar soap to remove grease, dust, and old adhesive. If the surface isn’t clean, your new seals will peel off within weeks.

Comparison of DIY Draught-Proofing Materials

Material	Cost	Durability	Ease of Installation	Best For
Self-Adhesive Foam	Very Low	1–3 Years	Very Easy	Small, even gaps
Rubber EPDM Seals	Low	5–10 Years	Easy	Various gap sizes
Brush Strips	Medium	3–5 Years	Moderate	Sliding/Sash windows
Silicone Sealant	Very Low	10+ Years	Moderate	Fixed gaps (non-opening)
Window Film	Low	1 Season	Easy	Reducing heat loss through glass

Temporary DIY Methods for Quick Fixes

If you’re in a rental or just need to survive a particularly brutal cold snap, these temporary fixes are lifesavers.

Self-Adhesive Foam Tape: This is the “bread and butter” of DIY sealing. It’s cheap and easy to apply. Simply measure the gap, cut the tape, and stick it to the frame where the window closes. Be careful not to use tape that is too thick, or you might strain the hinges.
Window Insulation Film: This looks like cling film but is much tougher. You stick it to the frame with double-sided tape and use a hairdryer to shrink it until it’s taut and invisible. It creates an extra layer of still air, acting like “triple glazing.” You can learn more about this in our guide to insulated window treatments.
The Bubble Wrap Method: It sounds crazy, but it works. Spray a little water on the glass and press a sheet of bubble wrap against it (bubbles facing the glass). It stays there by surface tension and provides a massive boost in insulation for zero cost.
Draught Excluders: For the bottom of windows or patio doors, a classic “sausage” draught excluder can block a significant amount of air.

Permanent Draught Proofing Double Glazed Windows Solutions

For a fix that lasts more than one winter, we recommend these more robust options:

Rubber EPDM Seals: These are superior to foam. They are shaped like letters (O, P, or E profiles) and compress when the window closes, creating a much tighter air seal. They are also much more resistant to UV light and weathering.
Silicone Sealant: If you have gaps between the window frame and the wall, silicone is your best friend. Apply a continuous bead along the gap and smooth it with a wet finger. Never use this on the opening parts of the window, or you’ll seal it shut permanently!
Brush Strips: These are essential for sliding windows or sash windows where a rubber seal would create too much friction. If you’re dealing with older styles, check out the ultimate guide to sash window draft strips.
V-Strips (Wiper Strips): These are plastic or metal strips folded into a ‘V’ shape. They spring open to bridge gaps, making them great for windows with uneven frames.

Adjusting Hardware for a Tighter Seal

Sometimes the seal is fine, but the window isn’t pressing against it hard enough. This is often an issue with the “compression.”

Hinge Adjustment: Most uPVC windows have hinges that can be adjusted with an Allen key. If the window has “dropped,” adjusting the hinges can lift it back into its correct position.
Locking Mechanism: Look at the “keep” or “strike plate” on the frame (where the lock clicks in). Many of these are adjustable. By moving the plate slightly, you can force the window to pull tighter against the rubber gasket when locked.
Lubrication: A stiff lock often prevents you from fully engaging the mechanism. A quick spray of silicone lubricant can make the handle turn fully, ensuring all locking points are engaged.

For more specific hardware tips, see our article on draft proof window strips.

Maintenance and Prevention: Keeping the Cold Out Long-Term

Draught proofing double glazed windows shouldn’t be a one-off event. Like a car, windows need a little “TLC” to stay efficient. We recommend a quick quarterly check-up:

Clean the Tracks: Dirt and grit in the bottom track can prevent the window from closing fully. Vacuum them out and wipe with a damp cloth.
Inspect the Gaskets: Run a damp cloth over the rubber seals. If they feel brittle or you see pieces missing, replace them before winter hits.
Lubricate Moving Parts: Use a light oil or silicone spray on hinges and locking bars twice a year.
Gentle Handling: Don’t slam your windows. Excessive force can bend hinges or knock the locking mechanism out of alignment.

Avoiding Common Mistakes in Draught Proofing Double Glazed Windows

While we want to seal the leaks, we don’t want to turn our homes into a plastic bag. Ventilation is vital for your health and the health of your building.

Don’t Block Trickle Vents: Those little plastic vents at the top of your window frames are there for a reason. They allow a controlled amount of air to circulate, which prevents condensation and mould. Sealing them can lead to damp walls and respiratory issues.
Fire Safety: Never apply a draught-proofing method that makes the window difficult to open in an emergency.
Over-Sealing: If you have to put your shoulder into the window to get it to lock, your draught strip is too thick. This will eventually break your hinges or the locking handle.

Energy Savings and Comfort Benefits

Why go through all this trouble? The benefits are more than just financial:

Direct Savings: As mentioned, you can save roughly £85 a year just by sealing gaps.
Thermostat Magic: When your home is draught-free, you don’t feel “cold spots.” This often allows you to turn your thermostat down by 1°C without feeling any difference in comfort, saving another £90 annually.
Noise Reduction: Air carries sound. By sealing air leaks, you’ll notice that street noise, sirens, and wind howling are significantly muffled.
Reduced Carbon Footprint: Using less gas or electricity to heat your home is one of the best things you can do for the environment.

Frequently Asked Questions about Window Draughts

When should I call a professional instead of attempting DIY fixes?

While DIY is great for most issues, call a pro if:

The glass unit is “blown” (internal condensation).
The frame is severely warped or cracked.
The window is difficult to open or close even after lubrication.
You have large gaps in the external masonry around the window. Professional draught proofing for a whole house typically costs around £250, which is a great investment if you aren’t confident with tools. Look for TrustMark accredited installers for peace of mind.

Can I draught proof my windows if I live in a period home?

Absolutely. For heritage homes with sash windows, you can get specialized kits that use discreet brush seals. These maintain the beautiful aesthetics of the window while stopping the “rattle” and the breeze. Secondary glazing is another fantastic option for period properties where you cannot replace the original windows.

Why is my room still cold after sealing the windows?

Windows are only part of the “thermal envelope.” If your windows are sealed but the room is still chilly, you might have:

Loft Insulation Issues: Heat rises; if your loft isn’t insulated to the recommended 270mm, it’s escaping through the roof.
Wall Cavities: Uninsulated cavity walls are a major source of heat loss.
Floorboard Gaps: In older homes, cold air can pull up through the floor.
Chimneys: An open chimney is like an exhaust pipe for your heating. Use a “chimney balloon” or sheep’s wool plug when not in use to save another £60 a year.

If your living room specifically feels like the Arctic, check out our guide on patio door drafts.

Conclusion

At Financefyx, we believe that saving money shouldn’t mean shivering in your own home. Draught proofing double glazed windows is a high-impact, low-cost way to take control of your energy bills and improve your home’s comfort.

Whether you choose a quick fix with foam tape or a permanent upgrade with EPDM rubber seals, the result is the same: a warmer home, a smaller carbon footprint, and more money in your pocket. Don’t let your hard-earned cash leak out through the window frames this winter.

For more ways to keep your home efficient, explore our full range of Energy Saving Tips. Happy sealing!