Single glazing runs with water because the glass is cold. The cheap fixes that work, from shrink film to sill strips, and what renters can do without asking.
A single pane of glass is only a few millimetres thick, so on a cold night its inside surface sits close to the temperature outside. Warm, moist room air meets it, cools below its dew point and turns to water.
With single glazing that happens most nights from October to March, and the water runs down onto the frame and sill.
You can't stop single glazing being cold. You can make the inside surface warmer and cut the moisture in the room. Most of the fixes cost a few euro a window.
Make the glass warmer: window film
The best cheap fix is a shrink-film secondary glazing kit. You stick double-sided tape around the inside of the frame, stretch a thin plastic film over it and tighten it with a hairdryer until it's drum-tight and clear.
It works because the film traps a layer of still air in front of the glass.
Still air is a good insulator, so the film's inner surface stays much closer to room temperature, and that's the surface the room air now touches. Less condensation forms, and the room loses less heat through the window too.
A few things to know before you fit it:
- It's for windows you won't open. The film seals the opening section shut until you take it down in spring.
- Test the tape first. On painted timber, try a small piece somewhere hidden. Some tapes lift paint when removed.
- Keep one window per room usable. You still need to air the room, so leave a window you can open, or one with a trickle vent.
- Look for kits sold as secondary glazing film. Hardware and DIY shops stock them each winter. Decorative or solar films are a different product and won't help.
Renting? You can usually do this
Shrink film comes off cleanly with the tape, so most renters can fit it without permission. Check the tape on a hidden spot first and keep the packaging so you can show what you used.
Our guide to damp in a rented house explains what the landlord has to provide, including ventilation in every room.
Deal with the water that still forms
Even with film, you'll get some condensation on the coldest mornings. The aim is to get it off the glass before it soaks into the frame.
A window vacuum pulls a streaming pane dry in a few strokes and holds the water in a tank, so none of it goes back into the room from a wet cloth.
On a house full of single glazing that saves real time every morning.
Cut the moisture in the room
Warmer glass and drier air together are what make the difference. The habits that matter most:
- Keep the trickle vents open, if you have them. The Department of Housing's ventilation leaflet recommends leaving vents open and unblocked, even in winter.
- Air the room every morning. Open a window wide for ten minutes while you get up.
- Dry washing elsewhere. Respond, the Irish housing association, advises against drying clothes indoors where you can avoid it, and against drying towels on the bathroom radiator.
- Pull curtains back in the morning. Curtains drawn tight trap cold, damp air against the glass overnight.
If it's still streaming every morning after all that, the room has more moisture than ventilation can clear, and a dehumidifier is the next step. Our dehumidifier guide covers which type suits a cold room.
Longer-term options
Shrink film is a winter fix. For a permanent one, there are two routes.
Magnetic or fixed secondary glazing fits a second pane inside the existing window. It keeps the original window, which matters in older houses with timber sashes, and it can be removed. If your home is a protected structure, talk to your local authority's conservation officer before changing the windows.
Replacement double glazing solves the cold glass problem completely. When you do it, make sure the new windows have trickle vents. New windows are far more airtight than old single glazing, and without vents the condensation simply moves to the walls. Our condensation guide explains why that happens.