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Open Cell Foam In Crawl Space

Posted by LOTO (My Page) on
Sat, Dec 8, 12 at 8:49

I am getting ready to start my build on a new 2400 square foor home on a 4' crawl space and plan on using foam insulation in the home. I have spoken to 2 different foam companies and each is very reputable and been in the foam business a lng time but have 2 different recommendations.
Foam #1 recommends mainly closed cell application and #2 recommends all open cell. I have researched this forum and others and understand that some have concerns that insulating the roof "lid" wth closed cell might hide roof leakage and there are some concens with open cell insulation also but the above grade/roof structure isn't my biggest area of concern.

I am getting 2 very different opinions on the crawl space application. #1 recommends closed cell insulation on the exterior concrete wall/rim joist (no wall vents) and a floor liner and a conditioned crawl space and #2 recommends open cell on the floor joists/underside of plywood subfloor/rim only and a conventional crawl space with vents/no wall insulation but a poly liner on the crawl space (dirt) floor.
#2 has been in the spray foam only business for over 15 yeas and are quite large but this technique goes agains 99% of what I have read on the net. Opinions????

Follow-Up Postings:

RE: Open Cell Foam In Crawl Space

For an insulation and moisture control issues you should start with a description of your climate and HVAC system.

RE: Open Cell Foam In Crawl Space

I am in Zone 5 in Missouri with fairly mild short winters and long, hot, humid summers.
My HVAC will be Geo Thermal vertical closed loop.

RE: Open Cell Foam In Crawl Space

Our previous house had the vented crawl space with poly liner on the dirt floor and our new house has the sealed and conditioned crawl space and there is no comparison. The new house is much more comfortable, and we have practically no problems with the woodwork and hardwoods gapping and shrinking. We live in the SE, very hot humid summers, mild winters.

RE: Open Cell Foam In Crawl Space

The Building America series shows a conditioned crawl in mixed-humid climates and unconditioned crawls are advised against by the US Department of Energy. See here, for instance. OTOH, there is research( papers/174_Hales.pdf) showing vented crawls work well in cold and marine climates such as the Pacific Northwest.

Zone 5 is a cold climate.

You takes your choice!

Here is a link that might be useful: The SCARY Crawlspace

This post was edited by worthy on Sat, Dec 8, 12 at 14:55

RE: Open Cell Foam In Crawl Space

I appreciate the information. Most of the homes in my area are walk out basements built into the hillside and we own about 6,000 square feet on multiple levels and are downsizing and want a home all on one level. I have owned several homes with basements and they were great when the kids were younger and we needed more space but we just don't want a basement anymore. The problem I am seeing is that by the time I build a 4' crawl and condition/insulate the crawl to keep out moisture I might as well put a basement under it and not have any problems...but we don't want a basement.:(
btw...according to the map I am in Zone 4A

This post was edited by LOTO on Sat, Dec 8, 12 at 16:50

RE: Open Cell Foam In Crawl Space

My major concern would be moisture...closed cell does not absorb moisture, but open cell does...

RE: Open Cell Foam In Crawl Space

#2 contractor recently admitted he was incorrect in advising open cell foam in crawl...#2 is full of #2 and is out of consideration.

Another big decision is what to do about the floor of the crawl space(4 foot high). I do NOT want a basement (had several homes with basements and loved them but want a 1 level home now)but the dirt floor of a crawl space is not ideal either. I can get 4" of concrete poured in the crawl for around $6,000.00 and I haven't priced a crawl liner yet but even if it was 1/2 this price I still would rather have the concrete floor. My building site is not prone to water problems and I know concrete slabs don't cure all moisture problems but they go a long way if properly installed.

Anyone our there who went with a liner or dirt and opted for concrete later or wished the had?
btw...Merry Christmas !!

Here is a link that might be useful: Acreage Video

This post was edited by LOTO on Tue, Dec 25, 12 at 14:23

RE: Open Cell Foam In Crawl Space

put a vapor barrier on the ground before pouring
the slab, just like you do for building a house
on a slab.

persoanlly I'd do 3" (not average fill but 3" everywhere)
closed cell. don't really
think you'll need a vapor barrier at all.

best of luck

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