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  1. #1
    Join Date
    Dec 2009
    Location
    Central Massachusetts
    Posts
    9

    Default Forced Hot Air Heating Drier Than Other Types?

    Recent visit to the doctor we got talking about dry skin. He asked if we had a forced hot air heating system, saying it tends to cause dryness more than other types. I've heard this before and got wondering if there's any truth to it or simply fallacy.
    With a radiator, hot water or electric type system, there will be air flow over it as heat will tend to rise and circulate around the room, just slower air movement than with forced hot air circulation. I can understand if one were to stand over a heating register in the direct air flow it would tend to dry out something faster, but generally I can't feel the air flow in a room when the system is heating.
    I do run humidifiers in the house and it's usually about 35-40%.

  2. #2
    Join Date
    Feb 2010
    Location
    Iowa, Quad-Cities area
    Posts
    129

    Default Re: Forced Hot Air Heating Drier Than Other Types?

    When cold outdoor air comes into a heated home (air exchange),forced air system or not; ie: electric baseboard or a boiler/hot water type system, it will have a drying effect.
    You have probably heard of people that get a home too tight and will have to introduce outdoor air to reduce the excess moisture.
    I had a customer that installed hi-eff. furnaces. No problem. Then he added attic insulation. No problem.
    Then he had new windows installed. Bam, he called with major excess humidity issues.
    Soultion: We added a large fresh air pipe to his return air and that's all it took to eliminate the excess moisture.

  3. #3
    Join Date
    Jan 2010
    Posts
    163

    Default Re: Forced Hot Air Heating Drier Than Other Types?

    Of itself, FAH is no dryer than any other type of heat. As your other poster said, the drying of air happens during the heating season when outside air is mixed in with the heated indoor air. This is because, as the temperature of air rises, its relative humidity goes down, since warmer air can contain greater amounts of moisture.

    FAH can cause a somewhat higher level of infiltration of outside air if the system is not balanced--that is, unbalanced airflow to various rooms will result in those rooms being either pressurized or de-pressurized. This increases air infiltration or exfiltration, either condition will ultimately result in more outside air being brought into the house.

    But, the humidity levels in your house of 35-40% are considered healthy. You might be able to go as high as 60% without causing excessive condensation on cool surfaces. Experiment with this to find the right balance.

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