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What causes condensation on windows in summer

If you’re noticing a film of condensation on the inside of your windows during summer, either as a thin film of mist or larger droplets of liquid, you’re no doubt wondering what the cause is.

Your first thought will probably be that something is wrong, either with your home ventilation or with your windows themselves, when the real source of the problem is actually caused by excessively high indoor humidity levels.

First, what is condensation?

The everyday air around us is naturally filled with tiny invisible droplets of water called water vapour.

When those tiny droplets come into contact with a cool surface – such as the inside of your windows – the invisible droplets of water condense to become larger visible droplets: condensation. 

So what causes condensation on windows in summer?

It’s actually a result of high humidity levels in the room. In the summer months, the air inside your home is often cooler than the air outside, especially if you’re fortunate enough to have air conditioning.

That’s when the moisture in the indoor air makes contact with the window, causing the moisture to liquefy. When the outdoor temperature reaches 20 degrees or higher, indoor humidity levels should be at about 35%.

With too much indoor humidity, the moisture in the air can cause dangerous moulds and mildew to flourish which can damage furniture, wallpaper, paintwork, floors and brickwork. 

How to avoid condensation in the summer.

Controlling the condensation on your windows in summer means reducing the humidity – the moisture levels – in your home, and the most effective way to do that is with adequate ventilation.

Dry clothes outside when possible. If you use a tumble dryer, make sure it’s vented to the outside. And always use the extractor fan when you’re cooking or bathing. 

Condensation inside a double or triple-pane window?

This won’t clear up by reducing the humidity levels in your home simply because it’s often a sign that the gas between the panes has leaked out through a tiny hole or crack. In other words, it’s time you replaced your window. 

Which brings us neatly to the many benefits of upgrading to The Residence Collection of replacement windows or doors, just one of which is trickle vents, which are designed to allow fresh air to trickle into the house and circulate, whilst letting stale, polluted air out.

Trickle vents provide permanent ventilation and improved air quality, besides being a draught-free and more secure way to create a healthier and more comfortable living space.

At Residence Collection, our entire range of windows are designed to allow for your home to ventilate while maintaining the temperature of your property, whilst appearing traditionally beautiful.

Start your Residence Journey today! Download one of our brochures or find your local Residence Collection installer using our handy search tool.



At Residence Collection, we have a range of colours available and can offer everything from timeless classics like Grained White to modern favourites such as Eclectic Grey. Don’t forget, we also offer a dual finish that allows you to find windows and doors that look as good from the inside as they do outside.