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  1. #1
    Join Date
    Jul 2008
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    10

    heat pump or gas furnace for lower humidity?

    I have a small (960 sq ft) house that has had some moisture damage and mold inside the walls. I have addressed the causes of the moisture, removed the drywall, and will be replacing damaged studs. I would like to keep humidity at a minimum to prevent re-growth of mold in the future.

    There is currently no HVAC at all. I know that an air conditioner and a gas furnace will both dry out the air. Does anyone know if a heat pump will dry out the air in winter? If so, how does it compare to a gas furnace as far as dehumidication?

    Any advice will be greatly appreciated. Thanks.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    HP, or gas furnace, in winter time will have teh same humidity in the house, if the furnaces combustion air is coming from the outside air.

    Was the moisture damage from winter humidity, or summer humidiy.
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  3. #3
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    Jul 2008
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    Was the moisture damage from winter humidity, or summer humidiy.
    It was from water coming in from leaks in roof and vinyl siding. The house was vacant for about a year before I bought it.

    But it is in Atlanta where the humidity is fairly high. The house is well shaded by a huge tree in the summer. Also, here in Atlanta we occasionally have very rainy winters.

    HP, or gas furnace, in winter time will have teh same humidity in the house, if the furnaces combustion air is coming from the outside air.
    I'm assuming that the intake vent would be inside the house. Is that different from the combustion air? I am not technically knowledgeable about this stuff.

  4. #4
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    Jan 2004
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    Lancaster PA
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    You may be confusing the return air and the combustion air.

    Return air. The air that is heated or cooled and circulated in the house to condition the house.

    Combustion air. The air that is mixed with a fuel for the fuel to burn, and then exhausted to the outside.
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  5. #5
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    Jul 2008
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    HP, or gas furnace, in winter time will have teh same humidity in the house, if the furnaces combustion air is coming from the outside air.
    One of the bids I've received is for a Goodman AFUE GMV95 variable-speed gas furnace.

  6. #6
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    Jul 2008
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    10
    HP, or gas furnace, in winter time will have teh same humidity in the house, if the furnaces combustion air is coming from the outside air.
    The unit will be installed in the attic, so I am assuming that the combustion air would be coming from inside the attic.

    Are you saying that the HP and the gas furnace would have the same humidity in the house as each other, but lower than the outside air?

    or

    Humidity in the house will be the same as the outside air, regardless of HP or gas furnace?

  7. #7
    Join Date
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    Location
    Lancaster PA
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    The indoor humidity will be the same weather a HP, or gas furnace.
    The amount of fresh air coming in to the house will have more effect on the indoor humidity then which unit you use.

    What size 95% furnace.
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  8. #8
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    Jul 2008
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    What size 95% furnace.
    2 ton.

    Another guy quoted me for a 45 Mbtu Goodman but did not specify model number or efficiency.

  9. #9
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    Jan 2004
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    Lancaster PA
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    Since you fixed the walls. I'm guessing you improved teh insulation. And decreased the amount of fresh air leaking into the house.

    A load calc would be best to know what size HP, or furnace you need. But either should be fine for your winters.

    What are your electric and gas rates.
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  10. #10
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    Jul 2008
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    Gas is $1.49 per therm this month (but rates fluctuate widely since deregulation) plus about $20 per month in fees whether i use any gas or not. If I go with electric, I will go with an electric stove and water heater and cancel gas service.

    Electric is currently about 8.5 cents per kwh.

  11. #11
    Join Date
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    Lancaster PA
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    Your gas rate is relatively low.
    A HP is cheaper until about 30* or so, depending on HP termal balance point. Then the gas furnace is cheaper to operate.
    not including your 20 a month gas fee.

    Once that is added, the HP is cheaper.
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