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  1. #1
    Join Date
    Jun 2008
    Posts
    100

    Hmm sizing dehumidifier

    I have about 1000 sq ft. of house to dehumidify. Just dampness from the weather. I'd like to get the humidity to 40% if possible, for allergies. I wouldn't be running it below 65 F.
    I was looking at sizing guides online and they differ a lot! One guide is apparently from the EPA. They say for 1000 sq ft you only need 17 pints/day.
    But the allergy buyer's club says 50 pints/day!
    Why would they say 3 times as much? Who's right, for allergies? Is the EPA assuming you don't want to get the humidity down to 40%?
    Also I don't want the fan to run all the time. I had this awful whirlpool device years ago and the fan didn't go off even when the compressor wasn't on.
    thanks
    Laura

  2. #2
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,763
    The EPA may also be thinking about how mech electric a larger unit will use, and that if you get too big of a unit, your A/C will run more often because of the heat it will put into the space/home.
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  3. #3
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428
    Quote Originally Posted by plarian View Post
    I have about 1000 sq ft. of house to dehumidify. Just dampness from the weather. I'd like to get the humidity to 40% if possible, for allergies. I wouldn't be running it below 65 F.

    I was looking at sizing guides online and they differ a lot! One guide is apparently from the EPA. They say for 1000 sq ft you only need 17 pints/day.

    But the allergy buyer's club says 50 pints/day!
    Why would they say 3 times as much? Who's right, for allergies?
    Is the EPA assuming you don't want to get the humidity down to 40%?
    Also I don't want the fan to run all the time. I had this awful whirlpool device years ago and the fan didn't go off even when the compressor wasn't on.

    Thanks Laura
    It all depends on how tight your house is and the Outside Air dew point.

    Does your house currently have A/C?

    What is the existing R.H.?


    A house built in 1907 is a lot different than
    a well sealed one built in 2007 with foam insulation.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  4. #4
    Join Date
    Jun 2008
    Posts
    100
    Quote Originally Posted by dan sw fl View Post
    It all depends on how tight your house is and the Outside Air dew point.

    A house built in 1907 is a lot different than
    a well sealed one built in 2007 with foam insulation.
    The walls are standard 2x4's with 4" insulation. I'm sure it isn't modernly tight. But I think a house in NY state where I am, even one built in 1955 as mine was, is tighter than something in Southern California.
    About 330 of my sq ft is half in the earth because I live on a hill. I don't know how much humidity comes through the walls which are next to the earth.
    It's pretty humid here. There are rainforestish days in the summer.
    I don't plan to use a dehumid. at colder than about 70F though. They lose efficiency fast as it gets colder.
    Laura

  5. #5
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,637
    Quote Originally Posted by plarian View Post
    I have about 1000 sq ft. of house to dehumidify. Just dampness from the weather. I'd like to get the humidity to 40% if possible, for allergies. I wouldn't be running it below 65 F.
    I was looking at sizing guides online and they differ a lot! One guide is apparently from the EPA. They say for 1000 sq ft you only need 17 pints/day.
    But the allergy buyer's club says 50 pints/day!
    Why would they say 3 times as much? Who's right, for allergies? Is the EPA assuming you don't want to get the humidity down to 40%?
    Also I don't want the fan to run all the time. I had this awful whirlpool device years ago and the fan didn't go off even when the compressor wasn't on.
    thanks
    Laura
    If you want good IAQ, <50%RH is adequate. You also need a air change every 3-4 hours. Also the basement should be considered. A good 70 pint/day for <50%RH. Get the best you can afford. The best made is the Santa Fe Compact. It could be set-up to include fresh air and air filtering. More money by lower operating cost and longer life. I work for the company. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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