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What Causes Condensation?

What Causes Condensation?

What Causes Condensation?

Condensation is caused whenever warm air collides with cold surfaces, or when your home is too humid. The warm, moisture-packed air cools quickly once it comes into contact with a cold surface and releases the water, resulting in liquid droplets.

Daily Tasks that Cause Condensation

We all bathe or shower regularly, but other things we do regularly also cause condensation. Some examples are:

  • Boiling the kettle
  • Cooking
  • Using a tumble dryer
  • Drying clothes indoors
  • Breathing

The average family of 4 will contribute around 4 pints of water per person each day just by doing these tasks, which equals around 100 pints of water vapour every week!  With poor ventilation, this vapour will likely turn into condensation.

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If you Insulate, you must Ventilate

In the days before loft insulation, wall insulation, or even double glazing, this vapour-filled, humid, stale air would have escaped through background ventilation. Ill-fitting doors and windows for example would have allowed this air out, and replaced it with fresher, colder air. If you have ever felt a draught, you’ve experienced this process.

In new builds or renovations that meet building regulations, however, this air cannot escape so easily. With the addition of energy-saving measures such as double glazing, cavity wall insulation and draught-proofing, there is little to no natural ventilation. This leads to a build-up of vapour-filled air being trapped in the property without the addition of proper ventilation.

What Causes Condensation?
A window showing condensation build-up

When does vapour become condensation?

Once the build-up of vapour in the air surpasses the dew point. What is a dew point I hear you ask? According to the Met Office, the dew point is the temperature at which condensation occurs. This depends on the humidity and pressure of the air. At the dew point, the amount of water vapour being condensed equals the amount of water vapour being evaporated.

Condensation occurs when excess moisture in the air exceeds the dew point. This can happen in a number of ways:

  • If a surface temperature is lower than this dew point, you will see condensation form
  • Excess moisture in the air
  • The ambient air temperature of your home

Condensation is more likely to occur when there is more moisture in the air. It is likely that you will notice this condensation first on a window, as warm humid air contact the colder surface of the window and causes water droplets to form.

Ways to Remove Condensation

Adequate ventilation is the only way of preventing condensation. 

To reduce condensation you need to reduce excess moisture in the property. 

You can of course help to prevent what causes condensation in your home in other ways, such as:

  • Wiping down windows/window sills
  • Drying clothes outdoors
  • Opening windows

These methods will likely slow down the build-up of water vapour in the air, however, they will not remove the problem entirely. If you lead a busy lifestyle, you are likely to forget to do these things sometimes, and the British Climate makes this even more difficult.

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Problems Caused by Condensation

When this air is trapped inside, with poor ventilation, we get condensation. While this may not seem like a major problem at first glance, condensation can cause various issues.

Condensation can:

  • affect the health of occupants
  • lower the energy efficiency of the property
  • structurally damage the property
  • visually deteriorate the property

When a property becomes damp, and condensation is allowed to continue, this invites black mould. 

Black mould can cause a whole host of health problems, such as unexplained headaches, fatigue, sneezing, skin rashes and more. You may have just thought yourself prone to these things, without realising black mould had started to take hold in a damp condensation-filled corner.

Condensation can also cause visual deterioration both indoors and out, like visibly damp and mould patches on your walls, carpets and furniture.

Moisture trapped in the structure of your walls can result in corrosion of the plaster, timber rot, cladding rot and other issues, which result in costly repairs.

Finally, due to the impact of condensation on your property, your heating has to work harder to combat these issues, resulting in a higher energy bill. 

How to Prevent Condensation

As we said before Adequate ventilation is the only way of preventing condensation. 

We often overlook ventilation while insulating our homes to make them as warm as possible. However, the ever-increasing airtightness level of new homes and renovations removes the natural ventilation sources.

That is why current building regulations require you to meet certain ventilation standards.

Some ventilation types (like Mechanical Ventilation with Heat Recovery or MVHR) can even save energy by recycling usually lost heat energy back into the fresh air intake.

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