In my basement, it’s been kind of damp, with what appears to be moisture condensing on the cold slab floor. I think this is the more likely culprit than soil moisture coming up through the floor, because when I moved some items that were on the floor, it was dry beneath them. According to my temp/rh meter, the dewpoint in the basement is about 68F right now, and the floor and cold water pipes are considerably colder than that.
Eventually I may finish the basement, in which case I would consider the foam insulation solution promoted in a not too distant issue of FHB.
In the meantime, is my best option a mechanical dehumidifier? I’ve got sticker shock on the price of the units, and am concerned about the operating cost, but also don’t want all of my tools etc. to get damaged by the high humidity. And I suppose the insulation described above would not help my problem with humidity in the basement, just condensation on the floor/wall.
I’ve got some pipe dream about ducting hot attic air into the basement to pick up the moisture, but I’ve ruled that out as impractical. Any sort of passive dehumidification ideas out there?
Thanks…
Alec
Replies
I've got some pipe dream about ducting hot attic air into the basement to pick up the moisture, but I've ruled that out as impractical. Any sort of passive dehumidification ideas out there?
If you are letting any hot air in there now, that may be contributing to the problem. Warm air condenses as it contacts the cooler air and surfaces. Keep those windows closed tight.
I run a 30 pint dehumidifier on a setting of about 1/2 on the dial during the summer months. I dump a good 3 or 4 gals a day.
A good unit is around $200.00 I believe. I'm guessing it cost $10-15 a month to run it if that.
Eric
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Any sort of ventillation will generally work, so long as it's warmer outside than in, and not pouring rain. Set up an exhaust fan in a window on one end, and an inlet vent through a window on the far side. Ideally, add ducts on both ends so that air goes in/out at floor level.
It is not the temp, but also the humidity level.Nowever if you blow in enough air to warm the place it it might help. But then you get a hot house.Here are the Minneapolis and Boston dewpoints for yesterday.http://www.wunderground.com/history/airport/KMIC/2005/6/27/DailyHistory.html
http://www.wunderground.com/history/airport/KBOS/2005/6/27/DailyHistory.htmlWith the dewpoin running 70 F it is will be hard to dry out a basement with that air.
You're right, the hot attic air, even though it would have a much lower RH than the ambient air, will still have the same dewpoint. Dehumidifier it is, I suppose.
Home Depot has a 13 pint dehumidifier for 150 dollars.
Are we there yet ?
But you get condensation because the temperature drops lower than the dewpoint. By circulating warmer air you do two things:-- Stagnant air that has picked up additional humidity from the floor/walls is moved out.-- Stagnant air in corners that has dropped to near-earth temps (50 degrees) is replaced with warmer air.If it was just a matter of the outside dew point you'd get the same condensation upstairs and down. It's the fact that the air in the basement is cooled by the walls/floor, plus it picks up any moisture wicking through the walls/floor that causes the problem.
Do you have central air?
If you do, open a duct in the basemeent. The AC will dehumidify the air somewhat.