Crawl Space Insulation

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Old 09-27-07, 12:25 AM
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Crawl Space Insulation

I have a cabin in the mountains of Southern California - a low humidity climate with winter nighttime temperatures in the low 20s. The floor is uninsulated, the crawl space cripple walls are uninsulated, and the crawl space is vented. I want to add insulation, should I do so to the crawl space walls or to the floor? Doing the walls seems easier (and would protect the pipes from freezing) but then I would have to seal the vents and put a vapor barrier on the dirt. I don't have to do all that if I insulate the floor, but that is a tougher job. By the way, the addition to the house has an insulated floor, if that matters. Any suggestions?
 
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Old 09-27-07, 05:20 AM
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You have opened a can of worms, and you will be getting conflicting viewpoints, but friendly. Here, in the South, we are governed by the Southern Building Code, which mandates the vents be installed in the foundation, as you have them. However, they should be able to be closed in the wintertime. You can retrofit these vents very easily with automatic vents that cost about $15 each, which open in the summer and close in the winter (forgetting to close them causes alot of frozen pipes). Insulating the pipes individually will do more to help lessen the event of them freezing, but for creature comfort, insulating the floor joists with the vapor barrier up, and the batts supported by the appropriate wire bails will help tremendously. If the walls of the crawlspace are under grade level, they won't need insulation, as they are geothermally correct to begin with, but above grade, won't hurt.
 
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Old 09-27-07, 05:53 AM
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I would close the vents and do the walls since moisture is probably not a major issue for you. What is the soil like in your crawlspace, is it dry, does it ever appear damp, etc?

http://www.eere.energy.gov/buildings...pdfs/29238.pdf
 
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Old 09-27-07, 06:30 AM
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No moisture problems whatsoever, the soil under the house is bone dry. Crawl space walls are above grade and are wood (house was built in 1955, new construction in my area uses block walls).
 
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Old 09-27-07, 05:40 PM
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I sealed off the vents, put plastic on the ground and taped up all of the seams, treated the block walls with "Drylock", Insulated all of the walls that had wood in them and put plastic over that also. Installed a dehumidifer that runs 12 hours out of 24. The humidity stays about 45% most of the time in the basement. I live in the south and the humidity is so bad that that was a must to do. If not the floor joists were going to rot and there was an incrediable amount of water dripping off of the air condition ducts all summer, I had a major humidity in my crawl space. No problems so far and I have done this for about 2 years now.
 
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Old 09-28-07, 04:39 PM
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cm, I also live in the South with very high humidity. I have a few questions for you. Where did you buy your "Drylock"? Are you happy with it? What type of V.B. did you put down? Standard 6mm or something more substantial? Lastly, what type of dehumidifier did you buy?
I have sealed my vents and put in a cheap 40pt house dehumidifier that runs 24/7. My humidity dropped to 70%. My V.B. is in terrible shape and needs replacing. Looking for ideas. Thanks, Luke
 
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Old 09-28-07, 05:34 PM
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1) Bought the drylock at Home Depot, very happy with it applied it with a roller and brush about 15 gallons.
2) 6mm black I think which ever is the thickest
3) I have used a Kenmore 70 pint DH, I would not recommend those they have a fan problem, check on this site for other details on the Sears dehumidifiers and problems. I will go with a LG the next go around, you can get them at Home Depot.
I did tape the plastic to the block about 2 feet up from the dirt after I dry locked the block, and in some places I ran the plastic up to the sill plate and stapeled it there. My house is 2500 feet with the crawl space at one end 25 block high and on the other end 8 block high, plenty of room.
The 70 pint will pull out the humidity, when I first turned it on I was getting 5 gallons in 8 to 10 hours every day for about 2 weeks. After that I used the timer set for 6 hours on and 6 hours off. The wood in my crawl space had mold growing on it and this was a 2 year old house. If I had not done what I did the floor joists and wood would have been ruined. Ed here on this forum helped me years ago with his advise he gave me, it works. Hope I helped..thx gk
 
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Old 09-29-07, 12:20 PM
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Thanks cm. I too will DryLoc the walls. I had a crawlspace salesman come by yesterday. He recommended I pull out all my insulation as it was wet and contributing to the moisture problems. What do you think of that? He was also pushing for a large $2500 Honeywell Dehumidifier. Sure looks nice, but I don't have that kind of money. I might get something smaller. In pushing their V.B. system, he talked about the fiberglass 10mm V.B. as being so much superior to the standard 6mm plastic. If I can buy any of that myself, I wouldn't mind doing it myself. Of course, his crawlspace seal system was $2500. Anyone have any comments?
 
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Old 09-29-07, 10:02 PM
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$5000 to seal and dehum a crawlspace is just insane IMHO. He was right about pulling the insulation though. Once wet, fiberglass wont insulate anymore ever. Why not use your drylock and follow the tips i outlined in the other thread in sealing it yourself? Once done you could then monitor the humidity and see if you still need to get a small dehum.
 
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Old 09-30-07, 04:54 PM
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d00bs, I pulled all the insulation today. What a back breaker. $2500 is starting to sound better all the time! The humidity level is running 75% right now. It looks a lot better down there than a month ago. Lots drier. I did see a slight amount of white mold and more of the sandy dots of black mold when I pulled the insulation. All in all, though the mold wasn't as bad as I thought it would be. Once I get all the insulation out, I will start the V.B. replacement process. Does anyone know where I can buy a some reinforced poly? I know I can put down the 6mm stuff from Lowes/Home Depot, but I'd like to get something stronger if I can find it relatively cheap. I am also looking at a bigger dehumidifier. Any suggestions???
 
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Old 10-01-07, 10:33 PM
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Silly me, I wasn't thinking about the furnace under my house. So it's probably not a good idea to cover the crawl space vents. Therefore, I'll insulate the floors instead. I may just go with the kitchen and bathroom for now, because they are the coldest rooms in the house and they both have the easiest crawl space access.

The downside is that I believe my pipes would be more likely to freeze in the winter. So I'll be sure to insulate the pipes also. Any other considerations?
 
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Old 11-12-07, 12:25 AM
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I've been doing more homework and have come to the conclusion that I'd ideally prefer to insulate the crawl space walls and seal the vents. The only concern is that I have a floor furnace that takes combustion air from under the house. Anyone know if that can be ducted to take air from the outside?
 
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Old 11-12-07, 06:18 AM
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What about a "partially heated crawl space", where I insulate the crawl space walls, the floor above, and leave the vents? Then I can close the vents in the winter and open them in the spring.

http://www.oee.nrcan.gc.ca/residenti...?attr=4#inside
 
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