The worry of winter condensation

Crisp, autumn mornings and dark, chilly evenings as the nights draw in, signal the start of the all too familiar ‘condensation season’, which commonly occurs between October and April. Water trickling down windows, cold walls that are damp to the touch and possibly mould growth in corners or around windows are all signs of a potential condensation problem.

Condensation is chiefly a winter issue, as we have the perfectly understandable wish to keep a property warm and draught free, so close windows. This reduces the ventilation and moist air inside builds up. External walls and windows are usually colder than internal areas. The Relative Humidity (the amount of water vapour the air can hold at a given temperature) rises above 70% and condensation forms on these cold surfaces at what is called the ‘Dew Point’.

Inadvertently, we don’t help the situation either. The daily rituals of showers or baths, boiling kettles, cooking pots simmering on stoves or simply trying to dry washing inside if it’s too wet for it to be placed outside, all add moisture into the warm air of our modern, draught free homes. On average a family of four will produce 24 pints (14 litres) of water vapour in a single day!

There are a few simple steps you can take to help minimise condensation:

• When cooking try and keep lids on pots and pans, close the kitchen door and open the window for a while to allow the moist air to escape
• Hang damp washing outside whenever possible. Placing it in a bathroom with the door closed and window open is an alternative if you have enough room
• When bathing or showering, keep the door closed and when you’ve finished ventilate the bathroom with the window open and the door closed for at least 20 minutes
• Don’t put large items of furniture such as wardrobes or sofas right up against cold outside walls. Allow space for air to circulate around them
• Try to regulate temperature in your property. Maintain a constant low level background heat even when the house is empty, to help ensure no rapid temperature changes and keep wall surfaces warm.

The moisture that is still produced in our daily lives needs to be able to escape, so keeping a home correctly heated and well ventilated is an important step in helping to prevent condensation and its associated issues.

Remember condensation will form if Relative Humidity rises above 70% and for every 1°C drop in temperature there is a 5% rise in Relative Humidity.