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4th October 2017

How To Reduce Condensation, Damp & Mould In Your Home

condensation-damp-mould.jpgWhat causes condensation, damp and mould?

Condensation occurs when excess warm moisture in the air (steam or water vapour) comes into contact with a cold surface and turns into water.

If condensation is allowed to settle on a surface for over six hours, then the perfect condition for mould is created... This can cause patches of mould to form, often appearing on windows, at the corners and edges of rooms, on walls and behind furniture such as sofas, wardrobes and cupboards, and is worse in winter.

There are three main causes of condensation:

  • Too much moisture in your home
  • Too little ventilation
  • Cool temperatures

Everyday activities cause condensation, such as cooking, showering/bathing and drying clothes indoors. Through the daily routine of showers, baths, boiling kettles, cooking, drying clothes and breathing, a family of 4 will contribute approximately 4 pints of water per person a day, equal to over 100 pints of water vapour a week, which has to end up somewhere...

Before the days of double glazing, wall and loft insulation this humid, stale air would find its escape route through ill-fitting windows and doors, lofts and so on. It would be replaced by fresher, colder air or to you and me - a draught!

At this time of year it becomes particularly apparent, as people dry their clothes indoors, increasing the relative humidity of the air, and also start to switch on the heating while keeping windows firmly shut against the cold. This behaviour increases the humidity in properties. Condensation will form if the Relative Humidity (RH) rises above 70%.

If a property is fully insulated and the windows are double glazed, the original draughts that once removed the excess moisture we produce during our everyday lives are locked in.

Any activity in the home which creates steam - such as cooking, showering and drying clothes indoors - will cause condensation to occur, unless there's adequate ventilation.

You can take some simple steps to reduce condensation, helping to prevent damp and mould.

TIP: Dry your windows and window sills every morning, as well as surfaces in the kitchen and bathroom that have become wet. Wring out the cloth rather than drying it on the radiator.

Condensation prevention will help ensure that your property remains damp and mould free and save you having to spend more money in the future having to continuously remove condensation.

How to reduce condensation

Many people will choose to open a window to remove condensation within the home, the problem with this is that the weather outdoors tends to have more moisture and a higher humidity than indoors which will cause more condensation problems once you close the window. Having humidity levels of 50% or higher in your home can damage your property and can make allergies and asthma problems worse.

These four steps will help you reduce the condensation in your home. They amount to a request for you to change the way you live in the building and to be aware that your actions cause the problem:-


1. Produce less moisture by changes in your lifestyle

  • Cooking: Cook with pan lids on and turn the heat down once the water starts boiling. Only use the minimum amount of water for cooking vegetables.
  • Washing clothes: Hang your washing outside to dry if possible. If you have to dry clothes inside, don't put washing on radiators or in front of a radiant heater, instead hang it in the bathroom with the door closed and a window slightly open or extractor fan on. When using a tumble dryer, make sure you vent it to the outside (unless it is the new condensing type).
  • Washing: Shut the bathroom door when you bathe/shower so as to not spread vapour. When filling your bath, run the cold water first then add the hot water - this will reduce the steam, which leads to condensation, by 90%.
  • Bathroom extractor fan: Never turn them off because they are noisy! Check if your fan is robust enough - place a sheet of 80grm paper over the vent grill when the system is "on" and if the paper sticks then the fan is operating well - if the sheet falls then perhaps your fan is not robust enough...
  • Sleeping: Once awake in the morning immediately open windows to vent vapour and leave open until you leave for work.
  • Window frames: Frames with "trickle-vents" are ideal and should never be closed. The frames themselves must be of the "thermal break" type whereby inner surfaces are not directly in contact with the outside and so cold is not conducted through the frame.

2. Increase ventilation to remove moisture

  • Some ventilation is needed to remove moisture as it is being produced. Keep a small window or vent open when there is moisture in the room (also leave trickle-vents open).
  • Keep kitchen and bathroom doors closed to prevent moisture escaping around your home, even if your kitchen or bathroom has an extractor fan. Doing this will stop the moisture reaching other rooms, especially bedrooms, which are often colder and more likely to get condensation.
  • Ventilate your kitchen while cooking, washing up or washing by hand, and for about 20 minutes afterwards. Use your cooker extractor hood or extractor fan, or keep the window slightly open.
  • Ventilate your bathroom for about 20 minutes after use by opening a window or using the extractor fan - they are cheap to run and very effective.
  • Ventilate your bedroom by leaving a window slightly open overnight or use trickle vents, if fitted, in your windows. But think about security if you're leaving a window open.
  • If possible, place wardrobes and cupboards against internal walls where there is less risk of cold and damp from outside (if against cold outside walls then leave an airspace behind them).
  • Open doors to ventilate cupboards and wardrobes - try not to overfill them, as this reduces air circulation. To reduce the risk of mildew on clothes and other stored items, allow air to circulate round them by pulling them a little way out from the walls.

3. Heat your home a little more

  • When the whole house is warmer, condensation is less likely.
  • The best way to combat condensation forming is to keep an even, low temperature throughout your property for long periods of time. Turning the heating up for a couple of hours twice a day can make condensation worse, so try to keep a balance throughout the property. Where possible, try to heat the whole house. If you have central heating, set it to provide background warmth in all rooms, including unused rooms.
  • You need some ventilation to let the air circulate. But take care not to over-ventilate in cold weather, as it will make your home colder and make condensation more likely. It will also increase your heating costs.
  • Variations in temperature will soak-up or release condensate and so when heating is turned off (after bedtime perhaps) the air cools and releases its vapour just at a time when you are breathing vapour all night in one spot - your bedroom. This is why it's beneficial to open windows as much as possible and especially in the mornings.

Will a dehumidifier prevent condensation?

Dehumidifiers are a temporary solution to moisture problems - the drawback with these units is that they are only effective in the room that they are placed, they need to be emptied on a daily basis and they consume electricity.

The most effective way to prevent condensation in the home is with a continuous source of fresh air. Good ventilation of kitchens when cooking, washing or drying clothes is essential along with a source of ventilation in your bathroom to remove moisture from taking a shower or bath.