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Condensation on a Roof Window – An Avoidable Issue We Don’t Need

Condensation Roof Window

Condensation on a Roof Window – An Avoidable Issue We Don’t Need

We see it all the time in our lives. If you have a mirror in your bathroom and have used your shower, you will notice the mirror ‘fog up’. You may also see it if you are cooking in the kitchen and notice the same thing happening on your windows and when it comes to roof windows, it is no different. In fact if you have a roof window in an area like a kitchen or bathroom, you may notice condensation much more frequently.

To put your mind at rest, this is not uncommon. Condensation is noticed more often on roof windows and flat roof windows because warm air rises. This is because the molecules in warm air are much further apart than molecules found in cool air. As a result, this makes the warm air less dense than cool air and will rise above it.

This natural phenomenon is also much more common in new build homes, but will eventually dry out by a significant amount in the first few years. Ventilating your home and circulating air throughout will go a long way to prevent it from happening and if you aren’t mad keen on letting cold air into your home during the winter, dehumidifiers are a great help too.


One of the issues that condensation on a roof window can cause is the common misconception of a leak in your roof. After all, the roof window is covering a hole in your roof and it is easy to worry that the window is faulty and is allowing rain or snow to make its way into our homes, but more often than not, condensation is the issue, which can be aided with ventilation or dehumidifiers.

However, the real worry that crosses our mind is when we notice the leak coming through the ceiling as opposed to the window. In some cases, the installer hasn’t used membrane or insulation between the window and the rough opening made for it. Because warm air rises, the moisture comes into contact with the underside of the flashing kit and then drips back through the roof between the frame and opening, which gives the appearance of a leak. An installer using membrane or insulation between the window and rough opening should prevent this.

A common question now may be ‘my roof window is not in a bathroom or a kitchen, but there is still a lot of condensation. Why?’ and the answer is relatively simple. Bathrooms and kitchens are normally the biggest contributors, but when we exhale, we also release warm air and combine that with cleaning and excess moisture from bathrooms and kitchens that manage to escape into other rooms, it can soon ‘fog up’ your windows.

You may notice that it is much more prevalent in Winter than it is in Summer and this is because the warm air expelled from showering, cooking or even breathing is so much warmer than the natural air surrounding your property. Warm air also carries larger amounts of water than cold air and once it attaches to a cold surface like a window pane, it begins to convert back into water.

There are various ways to combat condensation and the inevitable fright you first get when you see it dripping from your roof window or around it. Ventilating your homes and using dehumidifiers are a very common practice, but cooking with lids on your pots and using ceiling fans to push the warm air back down so that it doesn’t allow condensation on your window.

lid on boiling pot

Ventilating your home as often as possible will not only reduce the amount of excess moisture in your home and allow you to sleep at night without thinking your roof is leaking, but it will also prevent the build up of mould, which some can be extremely harmful to us. Certain tasks like opening your blinds or curtains or using exhaust fans in your kitchen or bathroom are also a big help.

The truth is when installed correctly, roof windows can be an extremely beneficial addition to your home. Regular natural daylight offers many health benefits to us along with minimising the risk of mould, but ventilation is also beneficial for this reason whilst offering an additional option for expelling warm air from your home.

RoofLITE roof window

We carry an extensive range of roof windows from RoofLITE+ and VELUX, all with fantastic benefits and features that benefit the homeowner and installers with quicker installation times than previous generations. If you would like to know more about our these products and how they can change your home, please contact our sales office via telephone, e-mail or live chat.

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