Wet windows every morning from October to March are one of the most common complaints we hear from homeowners across Dublin and Ireland. Condensation on windows is not just a nuisance. Left alone it stains paint, rots timber sills, feeds black mould around the frame and is a sign the room is colder and damper than it should be.

The good news is that most window condensation can be reduced sharply with a few changes to how the house is heated and ventilated. The rest comes down to the windows themselves. This guide covers both, starting with the quick fixes and finishing with the point at which replacing the glazing is the only thing that will actually solve it.

Key Takeaways

Condensation forms when warm, moist indoor air touches a cold surface. In most Irish homes the coldest surface in the room is the window.
Where the water sits tells you the cause: inside the glass means a humidity or cold-glass problem, between the panes means a failed sealed unit, outside means the glazing is working well.
Steady heating, ventilation while cooking and showering, and drying clothes outside or in a vented dryer will cut most inside condensation.
Single glazing, blown double-glazed units and old aluminium frames will keep condensing no matter what you do. Those need replacing.

Why Do Windows Get Condensation?

Air holds moisture, and warm air holds more of it than cold air. Everyday living in an Irish home puts a surprising amount of water into the air: a family of four produces roughly 10 to 15 litres a day through breathing, cooking, showering, boiling kettles and drying clothes indoors.

When that moist air meets a surface that is cold enough, the moisture drops out as water droplets. That temperature is called the dew point. The inside face of a window is usually the coldest surface in the room, so it is where the water appears first. Older or poorer glazing has a colder inside surface, so it condenses sooner, more heavily and for more of the year.

Ireland’s mild, damp climate makes this worse than in drier countries. Outdoor humidity is high for most of the year, so ventilating with outside air does less to dry the house than it would elsewhere, and houses are heated intermittently, so surfaces cool right down overnight.

Persistent condensation is one reason damp is so common in Irish homes: 21.2% of people live in a dwelling with damp, leaks or rot in window frames or floors, according to Eurostat. Our Irish damp and mould statistics page has the national figures.

The Three Types of Window Condensation

1. Condensation on the Inside of the Glass

The most common type. Water beads on the room side of the glass, heaviest at the bottom and in the corners, usually first thing in the morning and worst in bedrooms and kitchens. The cause is a combination of too much moisture indoors and a glass surface that is too cold. Everything in the next two sections is aimed at this type.

2. Condensation Between the Panes

Misting or water trapped between the two sheets of glass in a double-glazed unit means the seal around the edge of the unit has failed and the insulating gas has been replaced by damp air. No amount of heating or ventilating will clear it. The sealed unit has to be replaced, and if several units on the same house have gone, the frames are usually near the end of their life too. Our guide to telling the age of your double glazing helps you judge which it is.

3. Condensation on the Outside of the Glass

Dew on the outside of the window on a cold, still morning is actually a good sign. It means very little heat is escaping through the glass, so the outer pane is cold enough for outdoor moisture to settle on it. It is common on new triple glazing and clears by itself once the sun is up. It causes no harm.

Quick Fixes You Can Make Tonight

Heat the House More Evenly

Blasting the heating for an hour in the morning and evening and letting the house go cold in between is the worst pattern for condensation. Surfaces cool right down, then moist warm air hits them. A lower, steadier background temperature keeps the glass above the dew point for longer. In bedrooms, avoid turning radiators off entirely.

Get the Moisture Out at Source

Run the extractor fan while cooking and for 15 minutes after, and use lids on pans.
Run the bathroom fan during and after every shower, and keep the bathroom door closed so the steam does not spread through the house.
Dry clothes outside, in a vented or condenser dryer, or in one room with the window open and the door shut. A single load of washing drying on radiators releases around two litres of water into the house.
Keep lids on fish tanks and don’t overwater houseplants.

Let Air Circulate at the Window

Heavy curtains and blinds pulled tight against the glass trap a pocket of cold air and stop warm room air reaching the window. Leave a gap, or open curtains and blinds during the day. Move furniture and beds at least a few centimetres away from external walls and windows.

Ventilate, Briefly and Purposefully

Ten minutes with windows fully open at opposite ends of the house does more than leaving one window ajar all day, and loses far less heat. If your windows have trickle vents, keep them open through the winter. Our guide explains why trickle vents should stay open in winter. If they don’t have vents, see whether trickle vents stop condensation and mould.

Wipe It Off

Until the cause is fixed, wipe wet glass and frames every morning with a squeegee or microfibre cloth. It stops the water soaking into sills and seals and starves mould of the damp it needs. If mould has already taken hold on the handles or frame, see how to remove mould from window handles.

Longer-Term Fixes

Dehumidifier

A decent compressor dehumidifier in the worst-affected room will pull several litres of water a day out of the air and is the quickest way to prove that humidity, rather than the window itself, is the main problem. If a dehumidifier stops the condensation, the house has a ventilation issue. If the glass still streams, the window is too cold.

Continuous Background Ventilation

Trickle vents in the window frames give a constant, controlled trickle of fresh air without opening the window. They are now required on new and replacement windows in Ireland under the building regulations, and can be added to most existing uPVC and aluminium frames. See how trickle vents are installed in windows in Ireland.

Warmer Glass

If the glass is the cold surface, the permanent fix is to make it warmer. Modern double glazing with a low-emissivity coating, argon filling and a warm-edge spacer bar has an inside surface several degrees warmer than a 20-year-old unit, and triple glazing warmer still. That single change moves the glass above the dew point on all but the coldest mornings. Compare the options on our double glazed and triple glazed windows pages.

Does Triple Glazing Stop Condensation?

Triple glazing greatly reduces condensation on the inside of the glass, because the inner pane stays close to room temperature. Homeowners who move from single or early double glazing to triple glazing usually see morning condensation disappear from the glass altogether.

Two honest caveats. First, triple glazing does not remove moisture from the air. If the house is producing more water vapour than it can vent, that moisture will condense on the next coldest surface instead, often an external wall corner or behind a wardrobe. Ventilation still matters. Second, triple glazing can produce more condensation on the outside of the glass on cold, clear mornings, for the reason explained above. That is harmless and clears quickly.

Whether triple glazing is worth it for your home depends on more than condensation. Our full guide covers the pros and cons of triple glazing for Irish homeowners.

When Replacing the Windows Is the Real Answer

There are four situations where no amount of heating and ventilating will stop the condensation, because the window itself is the problem:

Single glazing. A single pane of glass is almost as cold inside as outside. It will condense every cold night in an occupied room.
Blown or misted double-glazed units. Once the seal has failed, the unit has lost its insulating value and will fog internally as well as condense on the inside face.
Old aluminium frames without a thermal break. The frame itself conducts cold straight through and streams with water even when the glass is dry.
Rotten or warped timber frames that no longer seal, letting cold air wash over the inside of the glass.

If your home fits one of these, replacement glazing is the fix, and it usually solves the cold-room and noise problems at the same time. Our guide to fixing cold and noisy rooms in older Irish homes covers what to expect, and our window replacement cost guide covers what it costs.

Frequently Asked Questions

Why is there condensation on the inside of my windows every morning?

Overnight the room cools, the glass becomes the coldest surface, and moisture from breathing and the day’s cooking and washing settles on it. Steadier heating, less indoor moisture and a warmer glass surface are the three fixes.

Is condensation on windows a sign of damp?

It is a sign of high indoor humidity, which will lead to damp and mould if it continues. It is not usually a sign of rising or penetrating damp in the walls, which shows as staining rather than droplets.

Does opening the window stop condensation?

Briefly opening windows fully to swap the air helps a lot. Leaving one window slightly open all day cools the room and does little. Trickle vents give the best of both.

Why is there condensation between the panes of my double glazing?

The sealed unit has failed. The unit needs to be replaced. If the window is more than 15 to 20 years old, check the rest of the frames before replacing units one at a time.

Do new windows stop condensation completely?

New double or triple glazing stops condensation on the glass in nearly all normal conditions. It cannot remove moisture from the air, so a house with a ventilation problem still needs that addressed.

Can I put anti-condensation film on my windows?

Secondary film kits add a small amount of insulation and can reduce condensation on single glazing in the short term. They are a stopgap, not a fix, and they cannot be used on windows that need to open for ventilation or escape.

Final Verdict

Start with the free fixes: steadier heat, extractor fans, no clothes on radiators, curtains off the glass and a proper ten-minute air change each day. If the windows still stream after that, the glass is too cold, and the permanent fix is modern double or triple glazing with warm-edge spacers and trickle vents built in.

Expert Windows surveys homes across Dublin and Ireland and will tell you honestly whether your condensation is a ventilation problem or a window problem. Request a free survey and quote for uPVC, aluminium or AluClad replacement windows.

How to Stop Condensation on Windows in Irish Homes