How to Cure Condensation

Condensation is most immediately obvious as a ‘misting’ of windows at night and, in serious cases, as water streaming down on to window sills. It is caused by warm, moist air meeting a cold surface.

All air in a house contains a certain amount of moisture (water vapour), but at any one temperature there is a maximum amount it can contain an amount known as saturation. The saturation level depends on temperature – the warmer the air, the more water vapour it can have.

If warm, moist air meets a cold surface such as a window or wall, it is cooled to a point – the dew point – where the amount of water vapour present is too much and the excess condenses out on the surface as water droplets.

Condensation is probably the number one problem in houses – and much of it has been caused by our desire toinsulate and draught-proof in order to reduce fuel bills. In Victorian times, when houses were well ventilated (in fact, draughty) and heat­ing was provided by cheap solid-fuel fires, condensation was an unknown problem. In modern houses with central heating and equipped with good loft insulation and comprehensive draught-proofing, condensation can happen in all sorts of places

Room Condensation

– windows, walls, inside fitted wardrobes and, more seriously, inside bricked-up chimneys and inside the loft space. Curing it is not always easy.

Curing condensation

Unless you understand the causes of con­densation and how all the potential cures interplay, you will never be able to deal with the problem effectively. Unfortu­nately, there are a great many reasons why condensation occurs. In simple terms, it depends on four main factors – the surface temperature of walls, windows and so on; the amount of heat you put into your house; how much ventilation you provide and how much moisture you produce.

Basically, to cure condensation, you have to warm the affected part of the house or reduce the amount of water vapour in the air, or both. But in practice it is not quite as simple as this: you have to get the right balance between the four main factors and, to make things even more difficult to work out, all four are individually quite complicated.

You may obtain the solution to a con­densation problem by changing one fac­tor, but in many situations it may be desirable (or necessary) to change two or more. For example, a condensation prob­lem on the inside surface of an internal wall may be remedied by:


  • increasing the heat input to the room
  • increasing the thermal insulation of the wall
  • applying a lightweight lining (insulated or uninsulated) to the inside surface of the wall
  • increasing the ventilation of the room
  • using a dehumidifier.

Before making any decision about which way to solve a condensation problem, consider all the options, taking into account cost and whether the solution will be effective in the short or long term.

Filed Under: Home & Maintenance


About the Author: Jason Prickett loves to write about home maintenance and stuff you can do yourself instead of hiring any professional. His step by step guides will assist you in completing your home maintenance tasks.

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