Cold air coming through window gaps is common in UK homes, especially in older properties or during windy weather. Even small gaps can make a room feel noticeably colder and push up heating costs.

But draughts aren’t just a comfort issue — they can also contribute to condensation and mould by creating cold surfaces where moisture settles.

If you’re also seeing window condensation in winter, it’s worth understanding the wider moisture picture in our guide on How to Stop Condensation on Windows.

This guide focuses on identifying the exact source of the draught and sealing it properly — without accidentally blocking ventilation or causing other issues.

Why Cold Air Comes Through Window Gaps

Over time, window seals compress, shrink or peel away. Frames can shift slightly with age and temperature changes.

Common causes include:

Worn or flattened rubber seals
Gaps where foam or brush seals have degraded
Misaligned closing mechanisms
Warped timber frames (older windows)
Poorly fitted secondary glazing

In many cases, the window itself is sound — it’s the seal around it that’s failing.

Is This a Serious Issue?

Usually not structurally serious — but it can:

Make rooms uncomfortable
Increase heating costs
Create cold spots that encourage condensation
Lead to rattling in windy conditions

If you’re getting visible rainwater inside, that’s more urgent than a simple air draught.

It’s also important not to confuse “cold glass” with a draught. Glass will naturally feel cold in winter — that doesn’t automatically mean there’s a gap.

What to Check Before Fixing Anything

Before applying any seal, identify exactly where air is entering:

Feel around the frame on a windy day
Use a tissue to spot airflow movement
Check whether the window closes firmly all the way around
Look for cracked, flattened or missing seals
Identify whether the gap is at the opening edge or between frame and wall

Also check you’re not sealing drainage (weep) holes on uPVC frames — these are designed to let water escape.

Accurate diagnosis prevents wasted effort.

How to Stop Cold Air Coming Through Window Gaps

Step 1: Identify the Exact Gap

Work slowly around the frame. Note where you feel airflow — hinge side, closing side, bottom edge or corners.

The solution depends on the type and size of gap.

Step 2: Choose the Right Type of Seal

Different gaps require different sealing materials. Too thin does nothing. Too thick prevents proper closure.

For a breakdown of options, see:
Best Window Draught Seal Strips (UK)

Choosing the correct thickness is more important than choosing the strongest adhesive.

Step 3: Clean the Surface Properly

Wipe down the frame so adhesive seals bond correctly. Dust and damp reduce adhesion and cause premature peeling.

Allow the surface to dry fully before applying any seal.

Step 4: Apply the Seal Neatly

Apply in a continuous line where possible. Avoid stretching foam seals tightly — they can shrink back later.

Press firmly but evenly.

Take your time. A neat fit improves durability.

Step 5: Test Closure and Adjust

Close the window gently.

It should shut firmly without force. If you have to push hard, the seal may be too thick.

The window should lock securely and sit evenly in the frame.

How Draughts Connect to Condensation

Cold air entering through gaps lowers the temperature of the window frame and surrounding surfaces.

Colder surfaces increase the likelihood of condensation forming — particularly in bedrooms and living rooms overnight.

Sealing draughts properly can:

Improve comfort
Stabilise surface temperature
Reduce condensation risk

However, sealing alone won’t fix heavy condensation. If moisture levels are high throughout the home, ventilation and humidity control need addressing (see How to Stop Condensation on Windows for the full guide).

Common Mistakes to Avoid

Using a seal that’s too thick
Sealing over drainage/weep holes
Applying seals to damp or dusty frames
Trying to fix a misaligned window with seals alone
Blocking intentional ventilation points

Sealing everything tightly without airflow planning can worsen condensation problems.

When to Stop DIY and Seek Help

Stop and investigate further if:

The window won’t close or lock properly
The frame is cracked or badly warped
You’re getting water ingress rather than just air movement
The surrounding plaster shows signs of damp

Those issues may require adjustment, repair or professional assessment.

Final Reassurance

Draught sealing is one of the most effective “small jobs” you can do to improve comfort in a UK home.

You don’t need to replace your windows to feel a difference.

When you:

Identify the gap correctly
Choose the right seal thickness
Apply it neatly
Maintain sensible ventilation

…most people notice a room feels calmer — less cold air movement, fewer rattles, and often less condensation too.