What is condensation

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What is condensation?

Condensation forms because the moisture in the air can no longer be held as a vapour, so returns to liquid form.   This occurs when warm moist air comes into contact with either cooler air or a cooler surface. ‘Dew point’ describes the temperature when air containing a given quantity of moisture vapour will condense onto that surface.

While condensation is obvious when it occurs on impermeable surfaces – most commonly window glass, cold-water pipes and ceramic tiles- it will also form on any surface, which is at, or lower than, dew point. The presence of condensation on more absorbent surfaces (such as paint, plaster or wallpaper) becomes obvious when disruption, damage or mould growth forms on that surface.

Mould growth is a typical sign of chronic condensation and occurs as spores, which are always present in the air. These spores find water (condensate) and organic material (dirt and grease) that support their life cycle. Mould is a significant health risk to asthmatics, anyone with other respiratory conditions, the very young and elderly people.

The high humidity levels associated with condensation also enables house dust mites to flourish. The droppings from these microscopic creatures as well as mould spores can cause allergic reactions which are also linked to the onset of asthma.

For those concerned with condensation in buildings, the quantity of water vapour in the air and the temperature of surfaces within buildings are two key issues

How to recognise condensation

Practically, diagnosis of condensation cannot be just visual. Measurement of temperature, humidity, ventilation and consideration of insulation qualities and heating patterns need to be undertaken.

However, typical signs of condensation to look out for are:

  • Misty wall surfaces;
  • Water staining and streaking on walls, particularly in bathrooms and kitchens;
  • Patches of damp with no obvious edges
  • Mould growth on wall surfaces, around external wall openings and in areas of low circulation or poor ventilation.

What action is required?

Double glazing and improved insulation means we have warmer homes, but unless a property is adequately ventilated, it can become damp. We ask all tenants to ensure that our properties are sufficiently ventilated by taking a few simple precautions stated below in order to avoid condensation and the build-up of damp.


Open bedroom windows when you go to bed at night; a 10mm gap will do. If it really is too cold to do this, wipe the condensation off the windows first thing in the morning, but please do not put the cloth you used on the radiator to dry as this will create more condensation.


Ensure full use of extractor or ventilation fans. Where these are not provided, open a window after bathing or showering to give the steam and damp air a chance to escape. Wipe windows, walls and mirrors to remove condensation (a microfibre cloth is the most efficient means of doing this), and dry the shower tray or bath. Keep the door closed while the bathroom is in use to prevent the steam escaping to other parts of the house


When cooking, cover pans. Use extractor or ventilation fans where provided. If you do not have an automatic kettle, take care to ensure it is not left boiling. These precautions will help to reduce steam and therefore moisture in the air. Keep the door closed while the kitchen is in use to prevent the steam escaping to other parts of the house.

Living areas

Where there are chimneys, do not block them up. If a wall appears to be damp, do not put furniture right up against it; allow some circulation of air.


Make sure that any ventilation bricks or openings in the building are not obstructed.


Keep glass as clear of condensation as you can. Wipe away any moisture that has formed using a soft cloth. Leave open any ‘trickle’ vents in double glazed units. Get into the habit of opening windows to keep the moisture content in the air down and to air the property whenever you can.


Avoid drying clothes on radiators. Tumble dryers should be vented to the outside, unless fitted with a condenser.


Provide a reasonable level of heating (no less than 10°C in an unused area, or 16°C if in use); cold rooms are susceptible to condensation. Remember, the best way to heat a room and avoid condensation is to maintain a low level of warmth throughout the day rather than to turn the heating off while you are out and put it on at a high level when you return back home.

Portable Heaters

Portable gas and paraffin heaters can create a significant amount of damp and condensation within properties. Please do not use these types of heaters

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