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dmaceld
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Posts:494
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| 09/27/2008 10:46 PM |
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Using ICF makes it easy and logical to go with an unvented conditioned crawl space. Having indoor air instead of outdoor air circulating through the crawl space keeps it dryer and minimizes, or eliminates, mold problems. That is, after the house is complete and being lived in!
But, and it is a big but, the unvented part can bite you in the rear during construction. I just had a sickening revelation a couple of days ago.
After I put down the subfloor over the crawl space the only decent sized opening into it was the access hole. However, there are thousands of small holes, as in space between subfloor sheets, gaps between the ledger board and wall, nail holes, etc. Well, guess what? Rain water can easily move down into the crawl space but lots of air can't. We had several inches of rain in the weeks between the time the subfloor was put down and the roof sheating got put on. I sensed the crawl space was fairly humid, and in fact there was standing water for several weeks on the rat slab I have down there. I finally vacuumed the water out and installed a fan over the access hole to force ventilating air down there. Too late. Mold had already started to form on the underside of the subfloor and on the I joists. A couple of days ago a contractor I had come over to give me a bid to thoroughly clean the crawl space pointed out the mold.
So now I have, fortunately not very serious, mold to clean out in addition to all the sawdust, dirt, foam particles, etc. that has accumulated after the floor was installed.
Next time I build an ICF house, and I do plan to build another one, I will cut holes in the subfloor for the heating/cooling registers as soon as the floor is down. I will then place a blower over the access hole and make sure the crawl space gets ventilated periodically as needed, especially after a rain. I also won't leave standing water down there either.
I recommend you consider doing the same.
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Building house - what a way to spend retirement! |
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robinnc
Registered Users
Posts:115
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| 09/27/2008 11:31 PM |
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That sounds like 'very' good advice!!!
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Manfred
Registered Users
Posts:58
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| 09/28/2008 10:50 AM |
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| Another way to minimize construction water intrusion into the unvented crawl space is to install a 4" drainage pipe to daylight underneath the ratslab. This will take care of the gross amounts of water. It does not eliminate having to dry out the area with a blower or dehumidifier to get it below 65% humidity. 65% humidity is the magic number at what stage the mold spores proliferate. |
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dmaceld
Registered Users
Posts:494
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| 09/28/2008 11:51 AM |
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Posted By Manfred on 09/28/2008 10:50 AM
Another way to minimize construction water intrusion into the unvented crawl space is to install a 4" drainage pipe to daylight underneath the ratslab. This will take care of the gross amounts of water. It does not eliminate having to dry out the area with a blower or dehumidifier to get it below 65% humidity. 65% humidity is the magic number at what stage the mold spores proliferate.
I have that with an opening, with a strainer, at the surface of the rat slab. I'll put a plug in it when we move in. I got rid of the gross amount of water that way. The standing water stayed behind in a couple of low areas of the slab.
I've wondered about the humidity level at which mold proliferates. That's a good number to know. Thanks.
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Building house - what a way to spend retirement! |
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Jelly
Registered Users
Posts:274
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| 09/29/2008 10:34 AM |
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| Mac, I guess it wasn't possible to wait until the roof was on to put the subfloor in over the crawl space? |
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cmkavala
Registered Users
Posts:818
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| 09/29/2008 6:41 PM |
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| We have done insulated crawlspaces using a 2" "bull floated" slab over 6mil visqueen, and sump drain in middle -just in case |
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Chris Kavala
chris@southernsips.com
1-877-321-SIPS |
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dmaceld
Registered Users
Posts:494
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| 09/29/2008 11:15 PM |
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Posted By Jelly on 09/29/2008 10:34 AM
Mac, I guess it wasn't possible to wait until the roof was on to put the subfloor in over the crawl space?
Possible, maybe. Practical, no. We built the walls from off the subfloor and used it for bracing. The lot has a 4' slope from one corner of the house to the other. One part of the crawl space is 5' high!
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Building house - what a way to spend retirement! |
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Jelly
Registered Users
Posts:274
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| 09/30/2008 2:53 PM |
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| I see. I knew there must be a good reason why you did it in that order, because you seem very good at planning and problem solving. |
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