Condensation can lead to discolouration of wall surfaces as well as to mould growth…
Condensation is caused by excessive moisture vapour, carried within the air, condensing onto the cooler surfaces within the rooms e.g. typically the wall edge (the reveal) of windows and on wall tiles, mirrors and the like. When the water condenses onto organic materials such as those used in clothing and footwear, mould growth can occur very rapidly. It can also lead to other problems such as dampness within the fabric of the walls and roofs.
Avoiding condensation within the home will be achieved by balancing the following three factors:
generation of moisture vapour
ventilation - background, rapid and mechanical extract
Excessive condensation will occur if this balance is not maintained!
Generation of moisture vapour: Moisture vapour in the home will be generated directly by the occupants e.g. by respiration and indirectly by their activities: clothes drying, washing up etc. Estimates suggest that the average family might produce 7-14 litres per day. The use of a mechanical clothes dryer will considerably reduce the amount of moisture vapour in the air.
Ventilation: Background natural ventilation is provided normally through high level room vents or through narrow grilles located in the top element of the window frames. It is important that these vents are not blocked up.
Rapid ventilation (opening windows) and mechanical ventilation are also usually provided in bathroom and kitchens. Ventilation allows moisture-laden air to be replaced by fresh air.
Heating: Space heating is usually provided by wall mounted radiators, electric storage heaters or underfloor heating. Modern boilers, adequate boiler controls, high levels of insulation and airtightness all play a part in heating the home efficiently.
The problem of condensation can be most severe in winter as the internal surfaces of external walls will be colder (the cooler the surfaces in the home, the more likely it is that any moisture vapour present will condense out on to them). When it is cold, there will be an understandable reluctance to reduce any controllable ventilation in the home e.g. windows may be kept shut. At this time of the year also, clothes are more likely to be dried inside adding to the humidity in the air if a proper clothes dryer is not used. All of this can exacerbate the condensation problems during the winter months.
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