Why Your Windows Are Condensing – And What to Do About It

Noticed water droplets forming on your windows—especially in the mornings? You’re not alone.

Condensation is one of the most common window complaints we hear from homeowners in Newcastle. It can make your windows look foggy, dampen sills, and even lead to mould or peeling paint if left unchecked.

At Windows and Doors Newcastle, we’ve helped hundreds of customers deal with condensation on and around their windows. In this guide, we’ll explain exactly what causes it, when it’s a sign of a bigger problem, and what you can do to fix or prevent it.

What is condensation?

Condensation happens when warm, moist air meets a cooler surface—like your window glass. When that air hits the cold pane, it can’t hold as much moisture, so it releases water droplets.

It’s a natural process. And in many cases, it’s simply a sign that there’s a lot of moisture in the air and not enough ventilation.

But not all condensation is equal. Where it appears on your window tells you a lot about the cause—and whether you need to take action.

Let’s break it down.

1. Condensation on the inside of your windows

This is the most common type, and it forms on the room-facing side of the glass.

You’ll usually see it:

• In the morning, especially after a cold night
• In rooms with poor airflow like bathrooms and kitchens
• On colder glass surfaces (especially single or older double glazing)

What causes it?

• Cooking, bathing, and drying clothes indoors
• Poor ventilation or blocked vents
• High indoor humidity from everyday living
• Windows or frames that aren’t insulated well

Is it a problem?

Occasional light condensation isn’t unusual—especially in winter. But if it’s happening every day, running down the glass, or causing black mould or damage around the frames, it’s a sign your home has too much humidity or not enough ventilation.

What to do about it:

• Open trickle vents or slightly crack a window
• Use extractor fans in kitchens and bathrooms
• Dry clothes outside or use a vented tumble dryer
• Run a dehumidifier if moisture levels are high
• Add thermal blinds or curtains to reduce surface cooling
• Upgrade to modern, energy-efficient double or triple glazing

We often see customers in Newcastle solve the issue with a simple ventilation change or a window upgrade that uses warm-edge spacer bars and better seals.

2. Condensation between the panes

If you see mist or droplets inside the glass unit, between the two panes, that’s not normal. It means your sealed unit has failed and moisture has leaked in.

You’ll notice:

• A misty or foggy look that never goes away
• Water droplets or haze that shift as the temperature changes
• Loss of clarity or visibility through the window

What causes it?

• Broken or deteriorated seals around the glazing unit
• Poor manufacturing or installation
• Age—most double glazing lasts 15–25 years
• Temperature or pressure changes over time

Is it a problem?

Yes. This type of condensation means the insulating gas (like argon) has escaped, and the window has lost its energy efficiency. It won’t keep out the cold properly, and it can lead to further moisture damage over time.

What to do about it:

• The glass unit will need replacing
• In most cases, the frame can be left in place, and only the sealed unit is swapped
• Upgrade to A-rated or A+ rated units with warm-edge spacers for better long-term performance

At Windows and Doors Newcastle, we carry out sealed unit replacements regularly. It’s fast, affordable, and a great way to restore insulation without a full window replacement.

3. Condensation on the outside of your windows

This one surprises people—but it’s actually a good sign.

If you see condensation on the external side of your double or triple glazing (usually early in the morning), it means your windows are doing their job.

The outer pane is so well insulated from indoor heat that it stays cool overnight, allowing morning dew to settle.

What to do about it:

Nothing at all. It will usually evaporate by mid-morning once the sun warms the glass. If it bothers you visually, you can use a soft cloth to wipe it away—but it’s not a fault.

When is condensation a sign of window failure?

Not all condensation is serious, but here are the warning signs that suggest it’s time to take action:

• Moisture between the panes that won’t go away
• Mould or damp patches around the frame
• Condensation on windows even when rooms are well ventilated
• Wooden frames that feel soft or damp
• Visible damage to seals, gaskets, or sills

If you’re not sure, we’re happy to inspect your windows and tell you exactly what’s going on.

How to reduce condensation long-term

Here are the most effective steps we recommend for Newcastle homes:

Improve airflow

• Open windows briefly every day to let moisture out
• Install or unblock trickle vents
• Use extractor fans during and after cooking or showering

Reduce indoor humidity

• Avoid drying clothes on radiators
• Keep lids on pots when cooking
• Use a dehumidifier in damp-prone rooms

Upgrade old glazing

• Replace single-glazed units or early double glazing with A-rated windows
• Consider triple glazing in north-facing or high-moisture rooms
• Choose warm-edge spacer bars and Low-E glass

Maintain seals and frames

• Check for gaps or cracks in sealant and caulking
• Replace worn gaskets or broken vents
• Keep drainage channels clear to prevent water build-up

Final thoughts

Condensation is a common issue in Newcastle homes—especially during colder months. But understanding what’s causing it (and where it’s forming) helps you take the right action.

Most of the time, it’s easy to fix with better ventilation or a quick repair. In other cases, it’s a sign your windows need upgrading to something more efficient.

At Windows and Doors Newcastle, we offer free assessments and honest advice. Whether you need new glazing, better ventilation, or just a few small fixes, we’ll help you sort it without pressure.

Book a free window health check

If you’re dealing with misty glass, mould, or excess moisture, contact Windows and Doors Newcastle for a free inspection.

We’ll check your glazing, explain what’s happening, and give you straightforward solutions to keep your home dry, warm, and comfortable.

Clear windows, clear answers—every time.