I am finishing a 24oo sq ft house with finished basement (poured walls, slab, with high-end waterproofing on exterior of poured walls–asphalt and bubble-wrap attached to turn water reaching wall down into special collection pipe at base of wall and running out at downhill grade. It has been a very wet season here in Atlanta, from drought to 9-inch surplus rainfall this calendar year. I am still a week away from getting permanent power that will enable HVAC startup. Problem is wet walls and wet floors, especially the lower 2 feet and the first 1-2 feet of floor slab on the side with the tallest poured walls (10 feet). I am convinced it is condensation, not seepage. I am told I need a dehumidifier. I intend to wait until I see the effect of running the AC for a while but what if that doesn’t stop the wet. How do I size a dehumidifier? How important would it be to put it into the existing system? vs a stand alone unit?
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If the house is new, I wouldn't get too excited just yet. Some of the moisture could be from the concrete curing.
Are the gutters on yet? If not, the groundwater may not be getting away from the house.
Maternity is another word for eternity.
Boss Hog's got a good point. But you have wetness now. Dehumidifiers are sized in pints/day, under ideal conditions. Bigger is better. Sears offers up to a 50 pint one. I buy them used when I find them and keep a couple of spares around.
A dehumidifier puts out hot, dry air. If you can handle adding hot air to the house you don't need to add it to the existing system. I'm the only one I know who designs dehumidifiers as part of the air system, mostly due to the type of houses I deal with where condensation is a real factor and AC is unnecessary. I want the hot output air to be tempered by the heat exchanger before getting into the house. If you don't utilize a heat exchanger, there's no point in putting it in the system other than to blow dry air all around the house. And if you do that, your dehumidifier will probably be grossly under-sized.
Assuming a typical house, you want, if anything, a stand-alone in the basement, preferably drained into a floor drain. If your basement gets enough AC it won't be an issue. If you have 7.5A to spare, think about hurrying things along. Dry is nice and it smells a whole lot better. You'll also feel better knowing for sure that it was condensation.
*I forgot to mention that I find a 40 pint works for our open plan 20,000 cu ft but a 50 pint works better.
PAHS Designer/Builder- Bury it!
Edited 7/10/2003 12:57:56 PM ET by VaTom
yeah,
Dehumidifiers are cheap, and available at many sources.
depending on the area you're concerned with you can buy anywhere from a 15 to a 50 pint/24hours unit.
Edison (a Canadian company) has a clever design whereby you can just locate the unit over a floor drain and it will drip straight down.
Whirlpool's units require a garden hose hook-up to run it over to a drain, and there is always about a quart of water left standing in the build-in bucket. Kind of dumb design, in my opinion. These are best used as a "empty it yourself, every day" kind of design.
Other makers have variations in between these two extremes, as far as 'self draining' goes, so check out what's available near you, and cheap.
$100 ~ 150 should buy you a good one for your needs. I think they are great things to have in ANY basement because the cooler surfaces down there tend to condense out water vapor from the humid summer air in almost any home (of course, AC helps this, but it does not totally eliminate it, especially when doors are left open by kids and so on).
Hope this helps,
Norm
Thanks a lot for good info.
We used a smaller size dehumidifier in our damp basement, letting the hose drain into our sump pump. This way it ran constantly, so we finally had to shut it off. Our electric bill was shocking. Be prepared for a large electric bill the longer you run your dehumidifier.