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One of the most frequent complaints among Canadian homeowners, regardless of the age of the house, involves moisture. Too much moisture in a house causes condensation and frost on the windows in the winter, and creates musty odours in basements and closets all year long. More importantly, dampness creates mould growth, which can lead to serious health problems for the home's occupants, and ruin clothes, carpets, furniture and other possessions.

Solving a moisture problem in a home can be as simple as turning on the fan in the bathroom, or as complex as installing new windows, insulation or ventilation systems.

In new homes, drying construction materials in the house can release up to 2,250 litres (500 gallons) of water during the first year. In older homes, common causes of moisture include poor insulation at exterior wall corners, wall and ceiling junctions and in finished basements. Roof leaks at chimneys, flashings, skylights and eavestroughs are often the source of the problem, as are foundation leaks and plumbing leaks, particularly at toilet bases and under sink drains.

But there are many other potential sources for moisture and the mould it may cause, and some are easy to eliminate.

For example, turning on the bathroom fan during your shower will send all the moist air outside instead of throughout the home. Make sure your bathroom fan is vented outside and not into an attic. The same goes for your clothes dryer -- it should be vented outside. If you commonly dry clothes in the house on a line, try taking them outside. Dry your firewood outside too.

Indoor pools, hot tubs, greenhouses, and even house plants and aquariums can also raise the humidity level in a home.

Another frequent problem is that equipment such as humidifiers, dehumidifiers, air conditioners, and heat-recovery ventilators are not properly maintained and instead of helping the situation, they encourage mould growth.

Natural Resources Canada says it's a good idea to know the level of relative humidity in your house if you are experiencing moisture problems. It suggests that you buy or borrow a hygrometer and watch the changes in relative humidity that occur throughout a typical day in different rooms of the house during the heating system.

A humidifier should not be used in a house unless the relative humidity drops below 30 per cent, and that humidity should not exceed 55 per cent in winter. Levels lower than 30 per cent aggravate skin allergies and respiratory infections, while higher levels increase the spread of mould, bacteria and virus.

Another way to combat mould growth is by keeping air circulating in out-of-the-way areas, by pulling furniture and stored items away from exterior walls and basement floors, and by keeping closet doors ajar. NRCan suggests keeping drapes and curtains open, making sure that warm air registers are not blocked, and setting the furnace fan to run continuously.

Also, of course, direct water away from the house through downspouts and landscaping.

If the easy solutions don't help, it may be time to look at some serious changes to the home. Adding insulation at the exterior wall corners, wall and ceiling junctions and in finished basements may help. Increased ventilation is also an option. A bathroom fan with a dehumidistat set at 45 per cent relative humidity or less is an option. It must be capable of continuous mechanical operation, and for that reason must have a low noise rating.

Other more expensive solutions may include installing a heat-recovery ventilator, which provides the home with a continuous supply of fresh air from outside, while venting the stale indoor air to the exterior. It also transfers heat from the outgoing warm air to the incoming cool air. But NRCan notes that when outdoor conditions are mild and damp, such as in coastal areas or rainy spring days, ventilation won't be very effective at removing moisture. It suggests that a good way to help your home "dry out" after summer is to leave windows open on warm, dry fall days. That helps move the moist air outside before winter arrives.

When the frost is on the windows, they are often the first things to be blamed -- and sometimes when they are replaced, the problem still remains. However, if you've tried all the above ways to reduce moisture and you still have a problem, it may be time to replace old windows with high performance, low-e windows. The best ones are filled with inert gases to provide extra energy efficiency. As an option to replacing windows, sometimes adding weatherstripping or window film can help.

For more information, contact Canada Mortgage and Housing Corp. or NRCan.

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