Walk-out basement humidity; solutions? (Falls Church: house, buying, living)

[te3tu]

My wife and I just bought a renovated 1950's house in Falls Church with a walk-out basement (which is where our master bed/bath are located). In the first few days (when it was reasonably hot), we actually didn't have a functional AC, so we opened the windows in the basement one night and woke up to serious condensation on the floors. We certainly learned our lesson there and have since gotten the AC fixed and eliminated the condensation problem.

That said, we have still noticed that the basement humidity levels are a good bit higher than upstairs and a bit above the levels we're comfortable with. My digital hygrometer shows consistently between 55 and 60% RH downstairs (and around 45% upstairs, where it's fairly comfortable). Outdoor RH has been 40-45. Nothing is wet downstairs, though we think most things feel damp (although this could just be cold).

We had a few basic questions:

(1) Is 55-60% RH safe/as good as it gets for a walk-out? Based on what I've read elsewhere, this sounds like borderline for comfort, but not worrisome as far as mold/mildew is concerned. We are especially concerned about this because my wife is pregnant, and I want to make sure the sleeping environment for her is as safe as possible.

(2) Is this sort of humidity level/differential worth trying to rectify, and if so, how? We think we have adequate ventilation downstairs, so we were leaning towards the possibility of a whole-home de-humidifier. Is this going to be useful if we have a single-zone AC? We'd like to avoid having a standalone unit in the basement if possible.

(3) Does anyone have any strong recommendations for companies that can evaluate and resolve this sort of situation? I've read some recommendations for AC folks on these forums, but wanted to see anyone had any strong recommendations for this sort of situation.

Thanks so much for your help!

[ACWhite]

Re: 1, no, we have a walkout and routinely get it to 40% with a medium to large standalone dehumidifier.

Although you don't want a standalone unit, it is a much less expensive step that will likely solve your problem, than other options. The AC can probably control the humidity well enough above ground.

If you get water seepage, a sump pump system may be needed. This is a big expense. I can give you company names if you PM me. But from what you have said, a reliable dehumidifier for a few hundred $ is the place to start.

You may have seen this already but if not, it's helpful (and CR claims that problems may occur above 50% RH):

http://www.consumerreports.org/cro/d...ying-guide.htm

[NC211]

We have a walk-out basement as well. Actually, it's an english basement. I know what you're talking about with the increased humidity levels and that feeling of everything feeling "damp" down there, especially during this time of year. Less so during winter.

I bought a sizable de-humidifier from Sears about two years ago. I can't remember the "pint" size of the container, but it's large. The whole unit is probably two feet tall, 18' wide and 12 inches deep. It has fixed the problem. I set it to 50% and let it do it's thing. You can wire up a drain hose straight to a sump pump drain so you don't have to mess with emptying the container, but I haven't done that myself. On hot and humid days (like today), it'll fill up a little over 1/2 of the container with water. I want to say it's a 40 pint size? Every morning I just dump the water and let it run. In a 24 hour cycle, it probably runs a total of 6 hours or so (automatic setting).

It has fixed that "musky" feel in our basement. We have a cat who's bomb-box is down there too. It fixed the odors as well. Highly recommend one!

[airjay75]

I think if you're getting 50-60% relative humidity in this weather without a dehumidifier, you're actually doing pretty good for a walkout basement. I've read multiple places that 60% RH is roughly the number you want to stay under in order to avoid mold and mildew development. I run a dehumidifier in our walkout basement and try to keep that RH around 50% during the summer - during weather like this, I empty the water bucket about every other day. I use an electrical timer instead of the hygrometer function on our dehumidifier - I found the hygrometer on our particular dehumidifier to be very inaccurate. Right now, I have it run for 30 minutes at a time with 60 minute intervals in between (so, roughly, one-third of the time). Short of getting a stand alone dehumidifier for the basement, I think you'd be looking at pretty expensive options to try and lower the humidity in the basement. Of course, if you have water seeping into the basement through the walls or the ground and that's what is causing the higher humidity, that would be a more significant problem.

[NC211]

FYI: I checked mine last night before going to bed. It's a 50 pint Kenmore (Sears) unit. The past 24 hours being the hottest of the year so far with heat index over 100 degrees, it nearly filled up the 50 pint tank in 24 hours. My basement area is roughly 1,100sf and has two entry points (house is built into the side of a hill) - the garage in the front of the house, and the walkout from the back. The garage is where most of my humidity "leaks" come from as kids come and go.

I would look into this route for your basement too. Unless if you're living down there, it probably won't be an issue for you in terms of noise. Just turn it off when you're down there. Turn it back on when you leave. Honestly, I notice a difference in the first two floors of my home when it's on, and when it's not. There is a air-exchange in the basement for the a/c unit that runs those two floors. I think the lower humidity level in the basement (and freshened air) finds it way into the level above via the a/c unit in general.

[LakeLifePA]

We had a full daylight basement that I ran a dehumidifier in 24/7, and it was always very dry. We had a sump pump, and I drained the dehumidifier into that. The good thing about doing it that was that the sump pump got a continual workout even when we would go weeks at a time without rain.

[seiketsu]

This probably wouldn't work if you have a serious humidity/dampness issues, but try buckets of desiccant. I have tubs of DampRid around my house, and that keeps the mustiness at bay. I have yet to turn on my air conditioner this year.