Condensation - 1 in 5 UK properties affected

Condensation is a significant problem in the UK, affecting one in five properties. This common problem is the consequence of high humidity in a building, and most commonly occurs between October and April.

As homeowners switch the heating on, dry their clothes indoors and take hot baths and showers (all while keeping the windows firmly shut against the cold), condensation issues can escalate. Air can only hold so much water before it condenses on cold surfaces, which normally occurs above 70% relative humidity (RH), causing damp patches on walls and around windows. This can result in the growth of mould in these areas.

Most condensation problems can be solved with good ventilation. A family of four will on average produce 14 litres (24 pints) of water vapour each day, so keeping a house correctly heated and well ventilated is an important part of preventing condensation. Efforts to keep homes warm can lead to unexpected condensation if ventilation rates are reduced.

Condensation can become a problem when home owners insulate the walls and roof of a property and the windows are double glazed. While insulation is good for warmth, it can eliminate the draughts which once removed excess moisture. Homeowners can suddenly experience condensation and may even find the timbers in their loft become mouldy.

When a surveyor inspects the problem, it is often found that in fitting additional layers of insulation in the loft, the natural eaves ventilation has been blocked. Warm air and water vapour naturally pass through the ceiling into the loft space, where it mixes with cold air and condenses. This causes the loft to become damp to the point where it can rain inside, creating substantial damage with significant repair costs. A similar effect may be seen if water tanks are left uncovered and water evaporates. Some home owners may find that these effects are only found on the side of the roof that is in the shade, as it is the cooler part of the house.

Here are five top tips to prevent condensation issues in the home:

1. Don’t use a de-humidifier
De-humidifiers merely mask the condensation problem and do not address the real cause. They can require frequent emptying and stop once the collector is full. Moreover, they’re invariably noisy and can be costly to run.

2. Ventilate the house
Where possible, ventilate the house to let the build-up of water vapour escape, particularly if you’re drying clothing indoors. If you have double glazing, then keep the trickle vents open. When cooking or boiling a kettle in the kitchen, or using hot water in the bathroom, close the doors and put the extraction fan on to prevent the moisture entering colder rooms.

3. Central heating
When you turn the central heating on, heat the whole property on a low heat rather than leaving some rooms cooler and susceptible to condensation. ‘Yo-yo’ heating does not warm the fabric of the building and reduce the risk of condensation forming.

4. Regular maintenance and advice from property surveyors
Regular maintenance is key to preventing ongoing issues. Identify any problem areas when they occur and seek professional advice to address them immediately. Property owners should always seek the advice of property care specialists when evaluating the causes of their specific condensation issues, as every situation is different.

5. Consider installing a Positive Input Ventilation (PiV) system
Property surveyors may recommend the installation of a PiV system, that will help to ventilate the building by diluting and displacing the damp air. From installation, the unit gently ventilates the home with fresh air, which is pushed back down into the house and redistributed.