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What is the Most Common Cause of Condensation

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What is the Most Common Cause of Condensation

By Ruth MacEachern

Product Manager

Jul 31, 2023

Did you know that each day, every person in your home is responsible for approximately two and a half litres of water vapour being released into the air in your home. This water vapour can be held in the air until it comes into contact with a cold surface where it will condense into droplets of liquid. This condensation can cause problems like damp and mould to develop that can negatively affect your health and cause major damage to your property.

What household activities release the most water vapour into the air

In terms of the amount of water vapour that they release per person, the following are the household activities which contribute most to condensation problems in the home:

Bathing or showering

A hot bath or shower is by far the largest source of water vapour in the average home. Although water in a bath is present for longer, giving it more time to evaporate, a shower agitates the water more which means that both can release up to 1.7Kg of water on average.

Drying clothes on a radiator or an indoor tumble dryer

Drying clothes on a radiator or an unventilated tumble dryer can be a major contributor to the amount of moisture in the air of your home. An average towel might contain a full kilogram of water when wet, and if all of this evaporates into the air, it can be a big part of the amount of condensation you will see. Even a tumble dryer with a condenser will release some water into the air. It is much better to dry clothes outdoors – as well as being cheaper and better for the environment too.


It might come as a surprise to many people, but simply breathing can be a major source of the water vapour that leads to condensation. Each day we inhale and exhale approximately 14,000 litres of air, and when we exhale, some water vapour is released – as you can see if you breathe out onto cold glass. Over the course of a day, the average person will breathe out approximately 400g of water vapour. When you see condensation on your bedroom windows in the morning, the most likely cause is the water vapour that you have exhaled during the night!

Cooking on the hob

If you do not use a lid on the pan when boiling water on the hob, a considerable amount of water vapour can be released. Cooking pasta for 10 minutes can release approximately 100g of water vapour into the air.

Using a washing machine or dishwasher

Even at low temperatures, a washing machine can still release quite a lot of liquid into the air. Over the course of an average wash, between 25-50g of water vapour is released.

Boiling a kettle

When you use a kettle to boil enough water for two cups of coffee, approximately 10g of water evaporates and escapes into the air.

Reducing water vapour

There are some simple steps you can take to reduce the amount of water vapour in your home such as ensuring that you cook with pan lids in place and avoid drying clothes indoors. Sleeping with a window open can also help – provided that you don’t suffer from hay fever or live in a noisy or polluted area.

The only truly effective way to reduce condensation is to improve the ventilation in your home which will help more of the moist air to escape. Modern extractor fans in your kitchen, bathroom, and other rooms with high moisture content such as a WC or utility room will prevent as much steam escaping into other rooms.

If you have persistent problems, or live in an area with high radon levels, a whole house ventilation system such as Positive Input Ventilation (PIV) systems such as EnviroVent ATMOS may be more appropriate, as this will disperse fresh filtered air throughout your home to displace the humid and stale air.

Read more about ways to reduce condensation in your home >>

Find out more

If you are worried about the amount of condensation in your home, and the problems with damp and mould that it can lead to, we can help. Our ventilation specialists can visit your property to conduct a free home survey that will identify the main sources of moisture in the air so that you can plan the best way to reduce it.

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  • 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

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