- Moisture in the home



The most often talked about problem in homes is moisture and how to get rid of it. Moisture usually becomes a problem as soon as the weather starts to turn cold and we close up the doors and windows. When all the windows and doors are closed the moisture within your home begins to look for other places to vent i.e. our bathroom fan, range hood or fireplace. If you do not have or use any of these ways of venting excess moisture, you may begin to find the excess showing up as condensation on windows or as stains on ceilings. Walls inside closets, bathroom tiles and walls as well as basement storage areas will show signs of dampness and staining. Moisture causes odours to linger in crawl spaces and basement rooms allowing fungus and mildew to grow. This is particularly discomforting to any people with allergies.


1. Any home with or without a window in the bathroom should have a bathroom exhaust fan controlled by a DEHUMIDISTAT moving air at an average rate of 105 cubic feet per minute. (see operation of a Dehumidistat at the end of this article)

2. FORCED AIR FURNACE: If a forced air furnace has only a single speed blower motor have a conversion made to a two speed motor allowing air to be circulated 24 hours a day 365 days a year throughout your home. Two speed motors operate your blower at 1/3 the R.P.M. when the burner is off still pressurizing the home by blowing the unwanted moist warm air out open windows etc. If after installing a two speed motor you start to feel drafts at some of your floor registers you should consider installing a HOYME DAMPER. This is installed on the inflow cold air duct and the combustion air duct on your furnace and prevents cold air from coming into the home through the heating system when the burner is off.

3. ELECTRIC or HOT WATER HEATED HOMES RADIANT or CONVECTION With these types of heating systems it is very important to have the best exhaust ventilation system you can afford as you do not have a forced air flow within the home moving the air. You should install a HEAT RECOVERY VENTILATION SYSTEM - HRV - to control moisture and air quality as well as recover some of the warm air being exhausted from the home.

4. BATHING & SHOWERS Bathroom fans that require manually turning on and off should be left on for a minimum of one hour after bath or shower use. This can be accomplished by installing a one hour timer - simply remove the single pole on/off switch and replace with the timer. This allows you to go about your day and the fan will shut itself off at the end of the hour.

5. MOISTURE (CONDENSATION) ON WINDOWS This is the first sign of too much moisture (relative humidity) in the home. When this happens venting must begin. A too high moisture content in your home will increase your heating costs because your heating system will have to heat the excess moisture before you get a comfort level. The drier the air the easier it is to heat.

6. DEHUMIDISTAT A dehumidistat is a device to operate a ventilation system such as a bathroom fan or an HRV (Heat recovery ventilation) to exhaust the excess humidity out of your home. The setting of this unit is determined by the outside air temperature (see chart) Outside Air Temperature Inside Humidity Setting (home at 20 degrees C. - 68 F)

0 to -12 C. 40%
12 to -18 C. 35%
19 to -24 C. 25%
25 to -30 C. 20%
-31 or below 15%

For more information on moisture and how your home works write for a free booklet entitled CONSUMERS GUIDE TO KEEPING HEAT IN available from:

Energy Publications
c/o Canada Communication Group,
Ottawa, Ontario
K1A 0S9
Fax: (819)-994-1498
Phone: 1-800-387-2000

Article courtesy of: Shell Busey

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June 21st, 2024