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Originally published Friday, February 25, 2011 at 7:01 PM

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A primer on proper home humidity levels

Homefix: Dwight Barnett answers home-improvement questions. This week's topic is on humidifying your home.

Scripps Howard News Service

Q: I have a question about what the proper humidity should be in our home. I have several thermo-hygrometers in our house. Our home doesn't feel too dry in the winter. We have a portable humidifier in our bedroom just to add a little moisture during the winter, and we enjoy the soothing hum of it. Our house stays anywhere from 30 percent to 40 percent in the coldest part of winter. Is that OK?

Also, I've had a heating and air company out to get a quote on installing a humidifier on the gas furnace. They told me that the space around our furnace wouldn't accommodate a regular humidifier, but they recommended a steam humidifier due to the smaller size of the unit. What is your take on a steam humidifier?

A: It would be difficult to raise indoor humidity levels above 40 percent when the room temperature is around 68 degrees of mechanically heated air. The warmer the air, the more moisture the air can hold, and 68 degrees may feel warm, but it's not like summertime temperatures.

If you can remember the 90-degree summer days, you know that there is also a corresponding high humidity level, because the warmer air holds moisture.

What I have been told over the years is that the preferred wintertime level inside the home should be anywhere from 40 percent to 70 percent relative humidity at 68 degrees when the outside temperature is 30 degrees or less.

Indoor humidity levels beyond 70 percent create an environment in which mold spores can gain a foothold in your home. Fortunately, the air conditioner dehumidifies and cools the air at the same time.

It has been my experience that humidifiers connected to ductwork present the possibilities for rust or corrosion that can damage either the ductwork or the furnace. Proper maintenance can prevent this type of problem from occurring.

I encourage my clients to add humidity by using in-room steam-producing humidifiers or vaporizers. Remember to shut off the humidifier in the summer so that the air conditioner is not overworked as it removes moisture from the air.

Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home-improvement questions at Sorry, no personal replies.

(Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home-improvement questions at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 286, Evansville, IN 47702, or e-mail him at Please include a SASE with your questions.)


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