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Thread: Whole home dehumidification with a twist - All concrete construction, no ducting...

  1. #1
    Join Date
    Jan 2022
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    Whole home dehumidification with a twist - All concrete construction, no ducting...

    I live in Puerto Rico, where it's warm all year long. Unfortunately, where my house is located is also *EXTREMELY* humid. We also don't normally get much wind through here, due to living in a valley. So it's basically warm, humid, stale air. When we first moved in here, we tried living with the windows open 24x7 and not using AC, but we ended up with mold on literally all of our possessions. So we installed ductless mini splits throughout the house. In Puerto Rico, HVAC guys default to throwing in way oversized units, because most people here aren't using the AC to dry out the air, but rather to cool off quickly. I actually had to talk our HVAC contractor down in every room, and what we ended up with is still oversized, I think. We have one large unit downstairs to cool/dry the living room, dining room, and kitchen. And then upstairs 4 bedrooms, each with their own unit, though one bedroom (My office) we keep turned off all the time, because it's just too much for the space - The air from the other bedrooms cool this room fine.

    Anyway, because this is an uninsulated concrete house, in the winter months when it stays in the mid 70s, the ACs basically don't run at all. This of course causes the humidity to build up and we end up with 90+% humidity in the house. We run a portable unit downstairs, but it requires emptying 4-5 times per day. In the night it fills up and stops running, and by morning we're back to 80%. It's a never ending struggle.

    So what I'm trying to find is some way to dehumidify the entire house, that doesn't rely on ductwork, because I have none. I have no problem making holes in the concrete to go outdoors for drainage or fresh air intake, but I don't have a feasible way to install ducting. However, my stairwell is located in the middle of the house on an exterior wall, so I could feasibly install a unit there and maybe have it do an adequate job.

    Basically I'm just looking for options here. I have no idea what to do, but the humidity indoors is out of control. Even during the summer months, we have to crank the AC just to keep it dry-ish indoors (60% or so), but we would much rather have it a bit warmer if possible.

  2. #2
    Join Date
    Jun 2003
    Madison, WI/Cape Coral, FL
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    How many sq.ft. of home are you cooling? Number of occupants? Suggest 76^F, 50%RH target.

    Start by setting up your a/cs to remove max moisture. Use the highest quality air filter available which slows air flow and increases moisture removal. Measure the inlet/outlet temp/%RH of the air flowing through your cooling cools. This will tell us about how well your a/c is setup and the opportunity to improve. You still need to have supplemental dehumidification during the evenings and rainy days. A well setup a/c removes 3 lbs. per hour of moisture per ton. To avoid excess need for dehumidifiers, adjusting the a/cs cooling coil temperature is important.

    Fresh air and locating the dehumidifier(s) with fresh air in the home will be the critical task.

    Get the measurements on the a/c operation and the answer to rest of the questions above to start this process.

    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"

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