Relative Humidity and Why It Matters In Your Home

by Rachel Laurendeau on December 29, 2012

Having the right humidity levels in your house is necessary for comfort, well-being, and to maintain a properly functioning home.

Optimally, relative humidity (RH) levels inside your home should be between 30 and 50 per cent in the winter and can go up to 60 per cent in the summer. If you aren’t sure what the levels are in your home, you can use a simple gadget called a hygrometer to measure them. A hygrometer, sometimes called a humidity sensor or relative humidity indicator, can be purchased for under 50$ at your local home improvement store.

Too much or not enough moisture in the air can create a number of problems for homeowners. Problems with humidity levels in the home occur most often in the winter when we are heating our homes, the windows are closed and ventilation and air circulation are restricted.

When the RH in your home is too high, you can end up with moisture and mildew problems in corners, basements, closets and bathrooms and can end with long-term damage to your home and its contents. Most noticeably, too much humidity can lead to:
• Condensation on windows, leading to water running onto your window frames and potentially rotting them
• Wet stains on walls and ceilings
• Musty smells
• Allergic reactions
• Other on-going health problems

When the RH in your home is too low, you might find ongoing problems, which include:
• Chapped skin and lips
• Scratchy nose and throat, sometimes even nosebleeds or infections
• Breathing problems
• Static and sparks
• Problems with electronic equipment
• General discomfort
• Damage to furniture and other belongings such a musical instruments

• If you have high RH, try finding the sources of humidity and addressing that first (leaky roof, damp basement, too many plants, wet boots…)
• Try running the exhaust fans in the bathrooms and kitchen whenever the moisture levels increase (when showering, boiling water, etc.)
• In the summer, running the air conditioning will reduce humidity in the home or you can use a dehumidifier.
• Installing a heat recovery ventilator (HRV) is an excellent way to reduce high humidity.

• If you have very low RH, this may be caused by cold, dry air seeping in from outside. The best solution would be to improve your home’s air tightness with weatherstripping, caulking and other insulating methods.
• If the problem persists, you may want to use either a stand-alone humidifier or have a humidifier attached to your furnace. (Humidifiers should be used carefully and well- maintained as they can also cause moisture and mold if not tended.)

If you are concerned about the humidity levels in your home, talk to your HVAC specialist to find out if an HRV or whole-home system would be helpful in your particular situation.

Resource: USEPA, CMHC

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