Humidifier on Forced Air Furnace


Old 09-02-03, 06:48 PM
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Humidifier on Forced Air Furnace

We live in Buffalo. Winters can be dry, which of course makes it feel colder. We are considering putting a humidifier on the OLD forced air gas furnace. However, our walls and ceiling have blown-in cellulose insulation (no vapor barrier), and I am afraid that the added humidity might soak the insulation from moisture condensing into the cellulose. Is this a valid concern, or should we "just do it"?
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Old 09-03-03, 08:35 AM
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A humidifier will add moisture to the air as a vapor. This vapor can not "soak" anything like insulation. However, as the air cools the moisture can condensate out (turn from vapor to liquid). The condensation is the problem.

You can see this happen when you take a can out of the refrigerator. Warm humid air cools and the water in the air forms droplets on the can. The temperature at which the water condenses out is called the dew point. The dew point depends on the relative humidity (the percentage of water vapor in the air) and temperature of the air.

Your insulation will help keep the air from reaching dew point in the insulation at most outdoor temperatures. However, you will need to adjust the relative humidity down as the outdoor temperature drops (essentially you are lowering the dew point temperature to prevent condensation).

Lowering the relative humidity as the outdoor temperature drops is something that has to be done in all homes. The only difference between your home and mine is the outdoor temperature at which we need to start lowering the relative humidity.

So to make a long answer longer. Yes you can install a humidifier and yes you need to be concened about condensation. Watch for condensation on your windows (this will be the coldest part of the home) and adjust the relative humidity accordingly. This can be done manually, or most manufacturers offer an automatic humidistat that will make the adjustment for you.

Please feel free to call me at (800) 334-6011 or check out our website at if you have any questions.



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