Humidity is the amount of moisture or water vapour in the air. You, your family, and your pets produce moisture when you breathe or perspire. Even your indoor plants produce moisture. We add water vapour to indoor air through routine household activities: cooking, showering, bathing, doing laundry, and dishwashing. More moisture can enter your home from the surrounding soil through a basement or crawl space.

Humidity: How much is too much, or too little?

Experts have developed rules of thumb to help homeowners make decisions regarding humidity levels in their houses. The limits should be used as guides only. Acceptable or comfortable humidity levels will actually vary from season to season, from house to house, and even
between rooms in the same house.

Rules of thumb

To prevent window condensation during the heating season, the recommended indoor RH is 30 per cent to 50 per cent. When it is below –10°C outdoors, recommended indoor RH is 30 per cent.

Taking action

Humidity can be controlled. If the relative humidity in your home is too high, you can reduce it; if it is too low, you can increase it. This may require simple changes in your family’s habits, such as remembering to open or close doors or windows. Or you may need to install equipment, such as exhaust fans in bathrooms or kitchens, to remove excess humidity. Very lowindoor RH levels in the winter may be due to cold, dry air leaking in from outside. Sealing up the house by
weatherstripping and caulking will improve humidity conditions indoors, and may reduce your
heating bills at the same time. Humidifiers—both stand-alone appliances and devices attached
to your furnace—can be useful for increasing indoor RH levels. But remember that humidifiers, if
not installed, used and maintained properly, can also be sources of excess moisture and mold in
your home.

Final Analysis

Humidity levels in your home can be too high or too low. In either case, problems can result.
A hygrometer can provide the information you need to determine whether you have a humidity
problem—but it must be accurate to be useful. If you have a humidity problem, it can usually be controlled.


Source: http://www.cmhc.ca/