Condensation – Why have I got it & What can I do?
Condensation is dampness caused by water in the atmosphere. It is often first indicated by the presence of mould growth, which requires pure water for its growth and condensed water is pure.
In the home, excessive moisture builds in air as a result of daily activities such as washing, drying clothes, showers, cooking and simply humans breathing! When this moist air finds a cold surface with a temperature at dew point or below, the moisture condenses to leave the surface damp. Condensation often appears at low levels on wall surfaces where the wall is cooler, often where there is also limited air movement to remove saturated air. The appearance of this moisture profile is often mistaken for rising damp.dehumidifier reviews and buying guide.
Condensation is a problem because if left untreated it can lead to mould growth on walls, ceilings, clothes and furnishings, and can also lead to rotting of woodwork.
Important numbers to consider when assessing condensation are the relative humidity of atmosphere (RH) and the dew point. Relative humidity is the amount of moisture held in air, expressed as a percentage of the saturation point of that air. Dew point is the temperature at which moisture in air condenses to form dew.
Dew point is important to understand in relation to condensation. The greater the amount of moisture in air, the higher the dew point. Therefore, where lots of moisture in being released into the atmosphere, from power showers, boiling kettles, etc, the easier it is for dew point to be reached.
As an example, if relative humidity in a room is 50% (a fairly ‘normal’ figure) and room temperature is at 21 degrees Celsius, the dew point is as high as 10 degrees Celsius. When there is lots of human activity causing increased RH in a building, it is more likely that the dew point will be reached.
Where condensation is occurring on the lower parts of walls, there can also develop a cycle of condensation in that area: Air coming into contact with the cold surface reaches dew point and deposits water. This cold air falls to the floor and pushes up warm air into its place. This warm air reaches dew point and deposits moisture, and so the cycle continues. The atmosphere in the room is becoming more dry as that area of wall acts as a dehumidifier, however this is creating dampness on the wall.
Why is condensation now such a common cause of dampness?
In times gone by, buildings were more draughty. Open fires and gaps around windows and doors meant that moisture from daily causes could exit the building and be replaced with new, drier air. However, improved heat (and therefore air) retention in properties, by for example closing chimneys and installing airtight UPVC windows and doors, has lead to increased likelihood of high humidity levels inside. The following are some examples of causes:
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