Gas and Oil Home Heating Furnaces - Dehumidifier in crawlspace

A friend of mine just installed a dehumidifier in his crawlspace after noticing excessive moisture. He has a vapor barrier and proper venting, but with the high humidity in the air he still has a problem. My situation is not as bad, but I did notice some light mold on a few of the joists. I am thinking of adding a dehumidifier as well. He closed up his vents (plans to insulate them next )and drained to the outside with adequate pitch. With a little PM to make sure the drain stay clear, it sounds like a plan to me. Any other thoughts?

Originally posted by Bartj
A friend of mine just installed a dehumidifier in his crawlspace after noticing excessive moisture. He has a vapor barrier and proper venting, but with the high humidity in the air he still has a problem. My situation is not as bad, but I did notice some light mold on a few of the joists. I am thinking of adding a dehumidifier as well. He closed up his vents (plans to insulate them next )and drained to the outside with adequate pitch. With a little PM to make sure the drain stay clear, it sounds like a plan to me. Any other thoughts?


The dehumidifier is always a good idea......try shedding some light on the situation. Mold grows in cool dark places. :cool:

Bartj:

A dehumidifier is a good idea but is not a sustitute for the correct fix which is proper ventilation.
I'm not sure of the layout but a fan to vigorously move the air around will do a faster and better job of drying things out. Also a way of then removing the moisture from the space. A dehumidifier would do it but openings to outside will do it better and faster.
The dehumidifier would be a nice touch after the problem were properly fixed.

I first thought of moving the air through the crawlspace with a fan or two after remembering how a solar fan on the sailboat eliminated a mildew problem. But, if the humidity is 90%, as it often is where I live, wouldn't it be better to recirculate the air and remove the moisture? As I mentioned, I have all the vents open and even a access opening in the garage with a screen over it. Pulling in humid air doesn't seem to make sense. Some of the units I looked at claim to remove up to 60 pints of water from the air in 24 hours. Why not try to treat the crawlspace like another room in the house and condition the air? While I was down there I thought I would add a light or two. I liked Lou's idea about shedding light. Bulbs are cheap.

You dont say where you are. take a look at www.ornlgov/roofs+wall/handbooks&factsheetfacts/index

We close up the crawl ways . No vents at all. if you have V/B down on the ground as you should and open the vents the warm air will come in on the cool groud and just sweat and sweat and you will never get the water out. Id go for it . Lou_2128

Also if you have your duct work in the crawl way we put small registers in them to let the AC and hot air out in it helps warm the floor in winter. Now this is in Missouri dont say it will work all over.;) ED

Newport News to be exact. I have heard of people cutting supplies in thier ducts to treat the crawlspace. I was just thinking of adding some lights (The would be nice even without a problem) and the dehumidifier. I'll close up the vents. The sill is tight and the VB is tight as well. I ad a problem with the link, but will try again. Thanks.

is this a dirt floor? If so you would be wise to tackle that first. You can do this... the max perm rate is 1.0 , common ones are 6 mil polyethylene or 45 mil EPDM, the joints dont have to be sealed but you should overlap the joints by about 6" min. Then you can put a layer of sand on top if desired but you won't be trying to ring out the ground moisture anyway. Your problem is another though, and more deadly, namely Radon gas. Unfortunately your in coal heaven, the build up of unventilated craw spaces is dangerous. Try the ground barrier first. An excellent book on this is," The Visual Handbook of Building and Remodeling", by Charlie Wing. It's available at local libraries. All the pro's use it.

We are completely around water. We're not in the coal mountains of Virginia but along the coast. I am familar with radon gas, but have never heard about that being a problem around here like it is in my home state (NJ, yes I am a yankee. Born there but out of there since 76!) ( I may be mistaken about this radon risk but....)We have a top notch home. VB is very well done with sealed seams. Up against the foundation is is just butted. I was thinking of securing it to the foundation wall while I was hanging out down there:) So, i am sticking with the plan of the dehumidifier and some lights unless somebody talks me out of it.

are the lights for you or to kill mold spores? If to kill mold spores use ultraviolet lights. I believe the UV may kill mold as well as bacteria. I can't swear to it, but it's worth checking out....