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About Your House
CE 01

Measuring Humidity In Your Home

Do You Have a Humidity Problem?

Straight Facts About Humidity

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. And more moisture can enter your home from the surrounding soil through a basement or crawlspace.

When Is Humidity a Problem?

We need humidity for our comfort and health. But too much or too little humidity can produce a host of difficulties for householders. Some of the problems are no more than nuisances; others could be far more serious. Many are familiar to Canadians, often occurring during the heating season when it is very cold outside, our windows are closed, and indoor air circulation and ventilation are reduced.


Humidity Hassles

  Too much humidity  Too little humidity 
Typical Symptoms  Condensation on windows  Chapped skin and lips 
  Wet stains on walls and ceilings  Scratchy nose and throat 
  Moldy bathroom  Breathing problems 
  Musty smells  Static and sparks 
  Allergic reactions  Problems with electronic equipment 
Long-Term Effects  Damage to the house and contents  Continuing discomfort 
  Ongoing allergies   Damage to furniture and other items 
  Other health problems   

Diagnosing the Humidity Problem

Instead of guessing whether or not you have a humidity problem inside your house, why not find out for sure?

A small, inexpensive and easy-to-use instrument called a hygrometer (sometimes referred to as a humidity sensor or a relative humidity indicator) can measure the humidity level in your house and confirm whether the house has too much or too little humidity. Once you know for sure, you can decide whether any action is required and, if so, what to do.

So You Want To Buy a Hygrometer?

The two types of hygrometers that are most suitable for household use are mechanical hygrometers and electronic hygrometers. For most households. either type will perform satisfactorily if properly used and calibrated.

Hardware stores, department stores, building supply stores and electronics stores often carry hygrometers. In fact, hygrometers are usually sold wherever you would buy a room thermometer. Hygrometers and room thermometers are often combined into a single piece of equipment.

Using Your Hygrometer

Your hygrometer will show the relative humidity (RH) in your house. Although the RH will not be exactly the same throughout your home, one hygrometer per house is usually sufficient. You should place it where the humidity symptoms are most obvious, in the room that you are most concerned about, or where your family spends the most lime. Because hygrometers are small, they can be moved around in your house from time to time.

Don't place your hygrometer near a radiator, a heat register or a chimney, or in any other location where it could be affected by direct heat.

Remember that a hygrometer does not produce instant results. It may take up to two hours to provide a stable reading in a new location or to adjust to sudden changes in relative humidity.

Relative Humidity

Humidity is normally measured as relative humidity (RH). RH is percentage that indicates the amount of moisture in the air relative to the maximum amount the air can hold at that temperature. For instance, when air at a given temperature contains all the water vapour it can hold at that temperature, it has a RH of 100%. If the humidity exceeds 100%, moisture will begin to condense from the air. If the air contains only half the water it can hold at that temperature, the RH is 50%.

Warm air can hold more moisture than cool air, so that the RH of a sample of air will change as the temperature changes, even though the actual amount of moisture in the sample air does not. For example, as a sample of air cools the RH rises.

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.

Recommended indoor RH: 30% to 50%

When it is below 10oC outdoors, recommended indoor RH: 30%

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 low indoor RH levels in 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 excessive moisture and mold in your home.

The 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.

Other useful Canada Mortgage and Housing Corporation information

Moisture and Air: Problem and Remedies


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