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Are you plagued by condensation in your home, peeling wallpaper and mould growth.  Ever wondered what it is, better still getting rid of it?  Then read on.

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Condensation - Introduction


Condensation can be a real menace, causing pools of water to appear on the window ledges, misty glass, mould growth and peeling wallpaper.  Under certain circumstances condensation can even cause structural damage.  Given all of these irritating and potentially harmful effects, it's understandable why so many homeowners are at their 'wits end' when it comes to trying to prevent it.

Before controls can be introduced an understanding of condensation and why it occurs is helpful and necessary when trying to identify the problem, and to ensure a correct diagnosis. The good news is, that condensation can be effectively controlled, if not eliminated.  But first, the nature of the beast must be understood.

Before looking at condensation in the home, it would be an advantage to look at what happens in the natural water cycle of the earth and atmosphere. 
All air contains moisture in varying quantities in the form of water vapour. Warm air naturally rises so that when it reaches a colder region in the atmosphere the temperature of the air drops, causing the vapour it contains to condensate. But what does this actually mean? Well, it simply means that the water vapour that the air contains is returned to its original liquid state as a result of cooling, forming water droplets as clouds. In clouds, these water droplets collide to form raindrops. By means of the rain the moisture is returned to the earth so by creating a continuous cycle to occur.
The important point to understand here is that temperature is the governing factor; ‘the water vapour that the air contains is returned to its original liquid state as a result of cooling’. As already mentioned, all air contains moisture in varying quantities, but the amount of which that it is capable of carrying is dependant on the air temperature, warmer air can carry more moisture, than cooler air. This means that moisture that is comfortably carried when warm will saturate the same volume of air when cooled. When this situation occurs, it is known as having reached 'dew point'; the air contains all the vapour it can at that particular temperature. Further cooling will induce condensation.

This process also takes place in the home where saturated air containing moisture produced within the home is returned to its original liquid state; condensation.  Moisture is produced by such things as cooking, bathing and washing and can quickly accumulate until the air contains all the vapour it can at that particular temperature. At this stage, the air, heavily ladened and struggling to contain the vapour will quickly condense or liquify by further cooling.  In the home, further cooling occurs by it coming in contact with a cold surface such as a pane of glass or a cold wall.
Rooms more likely to produce high levels of moisture are the kitchen and bathroom.  It is also important to realise that because warm air can carry more moisture, the higher the room temperature, as in a kitchen for example, where cooking is in progress and while moisture is being produced, the larger the potential content (humidity) of the air and the resulting condensation.
Moisture can also travel from its source very often a warm room, to a cooler area such as a hallway or bedroom where it is more susceptible to condensate due to the cooler temperature. 

Condensation in The Home
Despite the fact that our homes are sheltered by the walls and a roof, the water cycle process will still continue as long as the conditions are present for it to exist, resulting in condensation. As a consequence, in the home, this natural process that otherwise helps to sustain life can become a problem.  We cannot prevent what is after all a natural process, but by understanding, we can introduce controls into our homes that will break the cycle, so by preventing the resulting condensation.

Condensation can be caused by any one of, or a number of the different conditions listed below.

  • Inadequate heating 
  • Poor ventilation
  • Cold surfaces  
  • Poor insulation
  • Blocked, un-ventilated fireplaces and flues
  • Cold Bridges
  • Generation of moisture

The following pages all relate to condensation

Relative Humidity
The Need For Ventilation and Extraction Fans
Fire Places and Flues
The Roof Space




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