9 ways to prevent condensation on windows inside your home

Prevent condensation on windows inside and out, for clear panes – with or without a dehumidifier.

How to stop condensation
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Condensation on windows – on or in-between panes – isn't pretty but, alas, it's something most of us have to deal with – no matter what types of windows you have and, whether we're in an old home or living it up in a small and damp(ish) small apartment.

And no, it's not just reserved for wintertime either. Condensation on inside windows is actually different from other forms of dampness, such as rain and rising damp. It is water released when air is cooled to its dewpoint temperature and unable to carry so much moisture as vapour – the opposite process to evaporation.

So this can happen indoors whenever warm, damp air comes into contact with colder objects, like windows. And all that excess water can in turn lead to unsightly and unhygienic mold or even to wood decay...

Condensation on window panes and mould caused by condensation on walls

Condensation has formed on windowpanes (left); condensation-related mould on walls (right)

However, a few simple measures and tweaks to your lifestyle can often successfully get the moisture balance back in your home to prevent future condensation on inside windows.

Douglas Kent, technical and research director for the Society for the Protection of Ancient Buildings (SPAB), gives us his expert guidance and insights on the causes of condensation in houses and how to avoid them. 

How to prevent condensation on windows

In homes, old or new, simple lifestyle changes that lower humidity and/or keep surface temperatures above dewpoint will be more practical and a less expensive long-term solution than installing whole-house ventilation systems. Try these tips below:

1. Ventilate

The key is to generate less moisture but some is of course inevitable so, open windows where you can and avoid draft-proofing those in kitchens and bathrooms. 

This is especially important if you live in a small, open-plan flat without an efficient extractor fan or air bricks, as there's nowhere for all the moisture to go. So, open the windows often, especially when cooking, and crack them open while you're in bed. 

Ensure also that lofts, floor voids and redundant chimneys are well ventilated and avoid foam treatments on the underside of roofs that can cause timber decay.

2. Monitor heating

Increased heating can maintain surfaces above dewpoint, especially if run constantly at a low level rather than intermittently. Lagging cold pipes may prevent surface condensation, as can improved insulation levels. 

So to stop condensation from forming is to keep your heating on a low setting throughout the colder months. Temperature fluctuations, especially the temperature plummeting around dawn, are very often responsible for condensation forming on windows. The trick is not to blast your home with hot air for short periods of time and leave it cold the rest of the time. An even, continuous low heat setting is better.  

3. Start cooking with lids

If ventilation is a little poor in your home and in the kitchen more specifically, try and cook with lids on to stop the steam escaping so much.

4. Dry clothes outside

Weather-permitting of course, but damp laundry in an unventilated room is a recipe for water droplets on those windows of yours (and a musty smell as a result of that).

5. Keep humidity in its place

Close kitchen and bathroom doors when in use to trap humidity in its tracks.

6. Keep dryer vents clear

Keep vent tumble driers to the outside if not of the condenser type. And, be sure to clean your dryer vent often to keep it doing its job efficiently.

7. Turn down your humidifier

If you're using a humidifier, and condensation has recently become a problem, try to turn it down for short periods at a time until you see an improvement.

8. Or, choose a dehumidifier 

Those in Victorian properties or more trad homes wouldn't be without one of the best dehumidifiers around as older homes are more prone to damp and condensation. Try the other methods ahead of investing. 

You might not want a dehumidifier running at night in a bedroom, but if you pop yours on after you get up and time it to switch off an hour or so later, it'll stop condensation and its effects from becoming a problem. And in case you were wondering, dehumidifiers use very little energy (much less than tumble dryers) to run, so you won't see a hike in your energy bills. 

9. Open drapes

Keep drapes open to stop trapping moisture and heat on the window panes. This will stop wet drapes also which is never nice.

Why do I get so much condensation on the inside of my windows?

This is all due to the moisture levels in your home but it could also be that the moisture is managing to seep through between both window panes as the sealant is old and worn. If it's quite saturated, consider replacing your windows or the sealant. Otherwise, you should be able to sort it out using the above tips.

Is condensation on windows normal?

It is totally normal, condensation can arise when more moisture is produced – often from cooking or washing. Insufficient ventilation is the main cause, for example, due to double-glazing, blocking of flues and air bricks, or incorrect installation of roofing underlay.

Condensation occurs mostly in winter, but can appear throughout all seasons depending on your home and climate. And might first be noticed when water droplets form on hard surfaces, or mold appears on absorbent finishes. 

What is known as ‘interstitial’ condensation occurs within the building materials and elements. For example, if a wall is covered with an impermeable barrier or renders that doesn’t allow moisture to pass through the wall naturally.

If the condensation problem you have seems to be more than one you can solve yourself, it will be worth employing an independent chartered surveyor or consultant (not a contractor with a vested commercial interest); they can carry out a more detailed investigation if required.

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Douglas Kent

After beginning his career as a chartered surveyor, Douglas soon specialised in building conservation. In 2000 he joined the Society for the Protection of Ancient Buildings (SPAB) where he now holds the position of technical and research director.