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Condensation: how to use ventilation to control condensation and damp

By Rebecca Milligan

Condensation on windows is a pain to live with, and can be a precursor to more serious damp problems. We spoke to ventilation company Envirovent's Phil Harrison for advice on how to control it.
Condensation on a window

Condensation is caused by high humidity. We all create moisture in our homes through cooking, boiling kettles, showers, and even breathing. On average, a family of four will create more than 100 pints of moisture each week. Unless your property is well ventilated, that moisture can’t escape.

Condensation is a problem for increasing numbers of homeowners, as we all try to make our homes more energy efficient. Measures to keep heat in, such as double glazing, cavity wall insulation and loft insulation, can keep more moisture in, too.

This is less of a problem in summer months, when you can have windows open. But in winter, many people end up with condensation on the windows, particularly when the temperature drops outside. If left untreated, condensation can cause damp, mould and damage fixtures and fittings.

If you think you need a professional to help you banish condensation from your home, search our site for a qualified electrician or a ventilation specialist who has been endorsed by Which? Trusted Traders.

How to prevent condensation

Whether you want to prevent condensation or help treat the condensation already affecting your home, there are three main types of action you should consider.

  1. Insulation: while this might seem counter-intuitive, it’s still important to keep your walls warm. Moisture forms when warm air hits a cold surface – this is why condensation appears on windows or a cold surface that hasn’t been well insulated. Decent insulation prevents moisture appearing on walls and ceilings.
  2. Heating: warm air holds more moisture than cold air. Keeping your heating on constantly at a slightly lower temperature warms the fabric of your house more efficiently than blasting the heating for short periods of time. It’s also more environmentally sound and cheaper.
  3. Ventilation: ensure that there’s a good flow of air through your house, so moisture can escape. Air bricks, window vents, extractor fans and ventilation systems can all help increase ventilation.

Our Which? guide to dealing with damp gives more guidance about different forms of damp in your home.

Installing a ventilation system

Probably the most effective way to reduce the moisture in the air is to increase the airflow through your property. While you can open the windows in warmer weather, installing a proper ventilation system can provide a more long-term solution.

A ventilation system uses a unit that will filter the air, pushing fresh, filtered air into your property. Whole house ventilation units gently ventilate the home from a central position on the landing in a house, or the central hallway in a bungalow, to transform a stagnant and stale atmosphere into a fresh, healthy and condensation free environment.

Working in unison with vapour/humidity tracking fans in the bathroom and kitchen, the system will provide the ventilation required to prevent condensation and resulting mould growth.

Each property is unique in its design, layout, the number of people living there, and how they use the space This means specialist ventilation companies, such as Envirovent, will need to visit your property to recommend the best ventilation system for your home's needs.

There are, however, some general rules that apply.

  • Ensure you have good working ventilation in wet zones, ie kitchens and bathrooms. Envirovent's Domestic Network Manager Phil Harrison recommends using vapour-tracking fans that kick in when they sense excess moisture.
  • Phil also recommends ‘positive input ventilation’ – a system that pushes more air into your property to reduce the percentage of the moisture in the air. This works on the same principle as using air to clear your windows in your car.
  • Reducing the moisture levels in your property using clean, filtered air will also improve the general air quality. Dust mites thrive in moist conditions, so filtered air can be particularly beneficial for people with asthma and other allergies.

Costs for ventilation systems vary depending on the property and the product being fitted. Phil says that, on average, a full system costs around £1,000. The fitting itself will usually take about four hours, and should be done by a qualified electrician.

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