Humidifiers and Dehumidifiers - Moldy Floor Joist
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oneilldm
07-30-07, 05:57 PM
In the last few years I started to notice some dark, powdery mold developing on some of the floor joists under my house.
I have 2 questions:
1. Is there something I can spray on it to kill it!
2. I know the key is to keep my crawl space dry (it's only about 24" high). Besides using a dehumidifier, what else can I do? There is a vapor barrier but I noticed it doesn't cover everything and the perimeter is not covered. We live in Tennessee so it can get pretty humid. I've got one power vent and all my other vents are open. I read somewhere that having open vents lets humid air in only adding to the problem. Also, would a black vapor barrier be better?
Thanks
I have 2 questions:
1. Is there something I can spray on it to kill it!
2. I know the key is to keep my crawl space dry (it's only about 24" high). Besides using a dehumidifier, what else can I do? There is a vapor barrier but I noticed it doesn't cover everything and the perimeter is not covered. We live in Tennessee so it can get pretty humid. I've got one power vent and all my other vents are open. I read somewhere that having open vents lets humid air in only adding to the problem. Also, would a black vapor barrier be better?
Thanks
czizzi
08-01-07, 08:03 AM
You should add a 2nd power vent on the opposite side of the building. One blows air into the crawl the other blows air out.
Here is how I tackled my own problem. When I moved into my house in 2000, there was water dripping from the insulation in the crawl and puddles on the poly. We are in Southeast Virginia, so hot and humid are par for the course, we also are surrounded by Water.
We replaced the wet insulation and installed 2 commercial fans (not power vents) that we hooked up to a timer set next to the fuse box in the garage. Once per day, the fans come on for 1 hour and circulate the air. It is completely dry under my house and we have not had any moisture problems in the last 7 years.
Your power vent is attempting to do the same thing, but it is probably not moving enough air to do the trick (at best it is a 6" or 8" fan). It is attempting to push air out of the crawl so that fresh air can get in from the other side. But one vent only is pushing air out and expecting air to enter freely through the other 8 -10 vents. Not an efficient method to get air to move in an open system, air will seek to move through that which provides the least resistance. I don't think you will get an equal draw from all vents.
Circulating the air keeps the moisture from condensing on the floor joists by keeping things moving and gives time for the vents to dissipate the moist air. My fans are big enough that it probably causes some negative pressure that induces air movement throught the vents. These fans sit on the floor and blow towards the center of the space and are not near any vents. My crawl is L-shaped and one fan blows toward the center of each section of the L. The crawl is 30" and the fans are 24".
Keep us posted and good luck.
Here is how I tackled my own problem. When I moved into my house in 2000, there was water dripping from the insulation in the crawl and puddles on the poly. We are in Southeast Virginia, so hot and humid are par for the course, we also are surrounded by Water.
We replaced the wet insulation and installed 2 commercial fans (not power vents) that we hooked up to a timer set next to the fuse box in the garage. Once per day, the fans come on for 1 hour and circulate the air. It is completely dry under my house and we have not had any moisture problems in the last 7 years.
Your power vent is attempting to do the same thing, but it is probably not moving enough air to do the trick (at best it is a 6" or 8" fan). It is attempting to push air out of the crawl so that fresh air can get in from the other side. But one vent only is pushing air out and expecting air to enter freely through the other 8 -10 vents. Not an efficient method to get air to move in an open system, air will seek to move through that which provides the least resistance. I don't think you will get an equal draw from all vents.
Circulating the air keeps the moisture from condensing on the floor joists by keeping things moving and gives time for the vents to dissipate the moist air. My fans are big enough that it probably causes some negative pressure that induces air movement throught the vents. These fans sit on the floor and blow towards the center of the space and are not near any vents. My crawl is L-shaped and one fan blows toward the center of each section of the L. The crawl is 30" and the fans are 24".
Keep us posted and good luck.