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  1. #1
    Join Date
    Dec 2018
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    2
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    Old house with high humidity

    I have a 1950's home on the water in Florida. Earlier this year, I had a VS HVAC installed. When it's warm outside, my HVAC dehumidifies just fine. However, during the times when there's no need for cooling, my humidity goes through the roof. 70+%. I've been using an older standalone dehu which will pull out about 5 gal / day when the humidity is high. It stops pulling much of anything in the mid 60%'s though. And when we're away from home, we have to unplug the unit, as there's no one to empty it.

    I'm looking to have a whole house unit installed. It seems Ultra Aire's 120V would fit into our HVAC closet, and I'm not sure if our contractor could make a traditional horizontal unit work in the space without some major "surgery."

    My house is 3200 sq ft, 1950's, with a crawl space (no vapor barrier), and in an area with a high water table. The home is occupied by four people. Would the 120V work for our home? Or do I need to look at a larger unit?

  2. #2
    Join Date
    Apr 2003
    Location
    St. Louis
    Posts
    818
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    High RH goes to low RH. A blower door test will tell you how tight the house is. Have you sealed all pipe and wire penetrations in the crawl space, windows ,doors and attic. If you do some research on dehumidifiers you will find stand alone models are rated at 95% RH and 80*. Whole house are certified at 60%. Contact your electric company they might offer a energy audit that includes blower door test mine came out for $50.

  3. #3
    Join Date
    Dec 2018
    Location
    united state
    Posts
    10
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    mugginess in your home won't be not exactly the outside except if you condition the air in the home. So you have to run the A/C or a dehumidifier continually to change the earth.

    A portion of the things that will help lessen the trading of dampness between the outside and inside is to legitimately protect and air seal your home. Controlling dampness is a piece of this procedure. You state your house is old, so risks are your home is under protected and air fixed. The dehumidifier in your storm cellar is just piece of the arrangement.

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    8,866
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    Sorry about missing your post and my slow response.
    With sand/high water table, a vapor barrier on the earth and blocking the outside air vents in the crawlspace will reduce moisture in the home.

    A Ultra-Aire 120V is a good choice, very high efficiency and a good fan with merv 13 air filter. Important to get connection of the dry air from the dehu to the a/c supply with a return from the open part of the home to the dehumidifier. If you seal the crawlspace and cover the earth, include a small supply to the crawlspace from the dehumidifier. Where in FL is this?
    Let us know how it all works out.
    Regards Teddy Bear
    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"

  5. #5
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    38,651
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    IMO...

    The first thing I would do... is stop the moisture from coming into the crawl space!
    Then re-evaluate the size of de-hum you need.

    What TB says above is good information!
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

  6. #6
    Join Date
    Jan 2019
    Location
    Vero Beach, Florida
    Posts
    36
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    I agree with ga hvac tech. Seal your crawl space!!!
    My next question is when you say variable speed are you talking about the blower or do you have a high end trane xv20 or a lennox xc25 variable speed compressor. Because those you can set up to dehumidify your home with no need for a stand alone dehumidifier.

    If you are dead set on getting a stand alone dehumidifier look into the Lennox healthy climate hcwh070 hcwh090 hcwh120

    You can tie those into your existing ductwork and have them set up to come on when your main unit shuts up. You can control it with an external controller or have it controlled with the onboard controller. Pipe it into the exsisting drain or put it on a condensate pump.

  7. #7
    Join Date
    Dec 2018
    Posts
    2
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    Thread Starter
    First, thank you all for the replies. I'm in the Jacksonville, FL area. In our last home, which was a 1920's home but on drier soil, we had the crawlspace sealed (Clean Space). That worked really well. For this house, we are planning on undertaking a major renovation, and so I didn't want to go through the expense when it would likely be damaged or destroyed once we start renovation.

    As for my current HVAC system, it's a Bryant Evolution (same as Carrier Infinity). It can dehumidify beyond the set temperature, but only to a point. All summer, the indoor humidity was great, although we may have had to cool a bit beyond what we would have normally wanted.

    The real issue is these months where not cooling or heating. The humidity outside stays well about 70%, which means the indoor humidity is at least that.

    Overall, it sounds like a mistake to invest more in dehumidification until I do something about the crawlspace though. Would installing a 6mil visqueen over the earth and sealing the crawlspace vents help significantly? Or look into actually having the crawlspace more professionally sealed as I did in our previous house?

    I'm not opposed to investing what's needed to do things right - I'm just after more comfortable home.

  8. #8
    Join Date
    Jan 2019
    Location
    Vero Beach, Florida
    Posts
    36
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    Have it professionally sealed and then go from there.
    I would have a pressure test done on your ductwork as well. Especially if it’s over 30 years old.

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