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What Causes Window Condensation?

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What Causes Window Condensation?

By Ruth MacEachern

Product Manager

Mar 06, 2024

It is a sight that we have all seen.  When you wake up on a cold winter morning and open the curtains, instead of a clear view of your garden, you see windows covered in droplets of water.  Condensation on windows might seem like a small issue, but if it isn't dealt with, it will lead to bigger problems down the line.

What causes condensation on windows?

Every day, we breathe more than 15,000 times, and it is that breath that makes up a big part of the condensation that you see on your windows in the morning.

The amount of water vapour in when we breathe is obvious on cold days – when you breathe out what seems like clouds of steam.  The reason you can see the vapour on a cold day is that the air temperature is sufficiently low for the water in your breath to condense, however that vapour is always there – even on a hot day.  You can test this by breathing out once on a windowpane, and you will see the water vapour condense almost instantly.

Even though your your breathing slows down when you sleep, the amount of water in your breath does not change, and on cold nights, when that moisture laden air comes into contact with the cold glass of your windows it condenses to form beads of water that you will see in the morning.  You breeathe thousands of times each night, and even though not every drop of water ends up on the glass, enough will to cause a build-up.

What are the problems with window condensation?

Like all types of condensation, if you do not act on window condensation, it can lead to damp.  If the moisture is allowed to run down onto your windowsills and settle, it can form small pools of water that will eventually soak into surrounding walls and wood causing damp patches and rot.

Damp is a problem anywhere in the home, but in bedrooms it is particularly harmful.  Damp can lead to the growth of dangerous black mould which can affect your health and cause severe allergic responses.

Tackling Window Condensation

The first step to handling condensation on your windows is simple – wipe them down each morning to prevent the water from having an opportunity to settle. 

Wiping down windows each morning can be a bit of a chore, but it is important in preventing damp.  But it is important to remember that it is not a permanent solution.  If you really want to prevent window condensation and protect your home from damp, it is important to look at ways of reducing the humidity in your air.

One of the reasons why humid air builds up in our bedrooms at night is that there is less airflow in the evenings.  During winter we will normally have windows closed throughout the night, and without people moving in the house, the air gets a chance to become still, so it is more likely to come into contact with the cold surfaces where it condenses.

The only solution to window condensation is to install a ventilation system in your home that works day and night to keep air moving around.  Modern Positive Input Ventilation systems work by drawing fresh filtered air into your home from outside to replace the moist air.  This reduces overall humidity and because the air is constantly moving, it no longer has the chance to cause condensation.

If you are worried about the potential health risk of having damp in your bedroom, then book a free home survey from one of our local specialists.  They will be able to assess your current needs and recommend a solution that will reduce condensation immediately.


Need help with condensation, mould or damp problems?

One of our local experts will contact you to learn more about your problems, offer free expert advice and make recommendations for a permanent solution.

During the free survey we will

  • check Assess any condensation, damp or mould problems in your property
  • check Take readings of the relative humidity levels
  • check Identify any underlying problems and make recommendations for a permanent solution

Arrange a FREE Home Survey now