Wet sills, fogged glass and water running down a window are the most common complaint we hear from Island homeowners between December and March. It’s worth understanding what’s actually happening, because the instinct — “I need a better blind for this” — is often the wrong answer, and the honest fix is usually cheaper than a new window covering.

Why it happens

Air holds moisture, and warm air holds more of it than cold air. When warm, humid indoor air meets a cold surface, it can’t hold that moisture any more and it condenses — the same thing that happens on a glass of iced water in July. Your window is the coldest surface in the room in winter, so it’s where the water appears first.

Two things decide how bad it gets: how cold the glass is, and how much moisture is in the air. Single-pane and older double-pane windows run colder, so they fog sooner. A busy kitchen, long showers, drying laundry indoors and a house full of people all raise the moisture.

What blinds do — and don’t do

Be wary of any claim that a window covering will “solve” condensation. Here’s the honest picture:

An insulating cellular shade keeps the room warmer at the window, which is genuinely useful for comfort and for heating.
But anything that covers the glass traps colder air behind it. The glass can end up colder than it was, so you may find more moisture on the window — and now it’s hidden behind the blind, where you notice it less until it has been sitting there a while.
Blinds fitted tight inside a recess with no airflow are the worst case for trapping damp against the window.
None of this means blinds cause the problem. It means a blind changes where the water ends up, and shouldn’t be sold to you as a cure for a damp house.

What actually reduces it

In order of how much difference each makes:

Get the moisture out at the source. Run the bathroom extractor during and after showers, use the kitchen hood when cooking, and don’t dry laundry on radiators in a closed room.
Ventilate deliberately. An HRV or a short blast of ventilation in the coldest part of the day moves humid air out. Sealing a house tight and adding no ventilation makes condensation worse, not better.
Keep indoor humidity in a sensible band through winter. If you have a hygrometer, it’s a genuinely useful five-dollar gadget.
Airflow at the window. Open blinds during the day where you can, and leave a small gap rather than sealing fabric tight against the glass.
Only then think about the window itself. Better glazing, or a properly fitted cellular shade on the coldest windows, helps with comfort and heat loss — but they don’t remove the water if the air is wet.

What we’d recommend for a window that fogs every year

Usually a light-filtering or cellular fabric that you open during the day, fitted so it isn’t jammed against the glass, in a room where ventilation has been looked at properly. If a window is badly affected and you’re covering it mainly to hide the problem, tell us — we’d rather have that conversation than sell you a blind that quietly grows mould behind it.

Questions we’re asked most often

Will a cellular shade stop the condensation?

It will make the room warmer and more comfortable, and it may reduce how much you notice, but it won’t stop it if the air in the house is too humid. Fix the humidity first.

Is water on the window a sign the window is failing?

Not necessarily. Fogging between the panes of a double-glazed unit usually means the seal has gone — that’s a window problem. Water on the inside face is a humidity and airflow issue.

Should I leave blinds open or closed on the coldest nights?

Closing them on very cold nights keeps heat in the room, which is the trade-off most people choose. Just keep an eye on the window behind them, and ventilate the house properly in the mornings.

Next step

Call +1 902-314-0877, email [email protected], or request a consultation and we’ll look at the windows and give you a straight answer, including when the honest answer is “a blind won’t fix that”.