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Humidity is the amount of moisture or water vapor 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 vapor to indoor air through routine household activities like cooking, showering, bathing, doing laundry and dish-washing. More moisture can enter your home from the surrounding soil through a basement or crawl space.

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 (see below). Some of the problems are no more than nuisances, while others could be far more serious. They often occur during the heating season when our windows are closed, and indoor air circulation and ventilation are reduced.

HUMIDITY PROBLEMS
		Too Much Humidity	Too Little Humidity
Typical Symptoms		Condensation on windows Moldy bathroom Musty smells Allergic reactions	Chapped skin and lips Gaps in Hardwood Floors Checking or cracks in Hardwood Floors Static and sparks Problems with electronic equipment
Long-term Effects		Damage to the house and Hardwood Floors Ongoing allergies Other health problems	Continuing discomfort Damage to furniture and Hardwood Floors

Diagnosing the Humidity Problem Instead of guessing whether or not your customer may have a humidity problem inside their house or down the road, 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 relative humidity indicator) can measure the humidity level in their 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, exactly what action.

Relative Humidity
Humidity is normally measured as relative humidity (RH). RH is a 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 vapor 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.

Using Your Hygrometer
Your Hygrometer will show the relative humidity (RH) in your house. Although the RH will not be exactly the same throughout the home, it can be moved around in the house from time to time.

Don’t place the 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 your Hygrometer does not produce instant results. It may take up to 30 minutes to provide a stable reading in a new location or to adjust to sudden changes in relative humidity.

Humidity: How Much Is Too Much, How Much is Too Little? Experts have developed rules of thumb to help homeowners make decisions regarding humidity levels in their house. 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. The National Wood Flooring Association says that 35% to 55% is the acceptable range, but always check with the Hardwood Flooring Manufacturer’s recommendation.

Rules of Thumb
To prevent window condensation during the heating season, the recommended indoor RH is 30% to 50%. When it is below -10°C (14°F) outdoors, recommended indoor RH is 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.

In summer, you can reduce house humidity levels with the use of a dehumidifier or by running an air conditioner. In winter, a house that is too wet usually has some high moisture sources (for example, a damp basement, roof leaks, many plants). Deal with these problems first. If high humidity persists, you may need to make simple changes in your family’s habits, such as remembering to open or close doors or windows. Or, you can install equipment, such as exhaust fans in bathrooms or a heat recovery ventilator (HRV), to remove excess humidity.

Very low indoor RH levels in the winter may result from cold, dry air leaking in from outside. In this case, sealing up the house by weather-stripping and caulking will improve humidity conditions indoors and may reduce your heating bills at the same time. Always check to see if you switched your humidifier from the Summer setting to the Winter setting. Also you can switch your thermostat to the ON position instead of the Auto position. This will keep the air flow moving and the humidifier to keep putting moisture into the home.

If low humidity problems persist, despite air-tightening the house, consider the use of a humidifier. Humidifiers — both stand-alone humidifiers and humidifiers attached to your furnace — will increase indoor RH levels. But if they are not installed, used and maintained properly, they 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. The good news is, if you have a humidity problem, it can usually be controlled.