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Old 01-08-2014, 04:37 PM   #1
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Crawl Space Order between Foam Insulation and vapor Barrier


Only a small section of our house was built on a crawlspace, but it is cold and musty. I plan to install 2" Formular on the walls with a vapor barrier above the dirt floor.

Most sites say to continue the vapor barrier up the walls, but does the vapor barrier go between the wall and foam board or on top of the foam board?

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Old 01-09-2014, 09:09 PM   #2
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Crawl Space Order between Foam Insulation and vapor Barrier


Depends if the foamboard on wall goes below outside grade or not- it should, at least to "frost depth"; http://www.google.com/url?sa=t&rct=j...59026428,d.cGU

https://www.decks.com/deckbuilding/D...rost_Depth_Map

http://energy.cr.usgs.gov/radon/rnus.html

Leave top 2" of FB off for termite inspect; http://termites101.org/termite-basic...ites-by-region

Gary
PS. be sure to ventilate the space...per code.

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Old 01-10-2014, 07:46 AM   #3
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Crawl Space Order between Foam Insulation and vapor Barrier


Its easier to get a more complete seal if you seal the vapor barrier to the wall and not the foam.

Check code on the ability to leave exposed foams without ignition or thermal barriers.

Sounds like you are proposing to turn the crawl into a conditioned space so the venting suggestions might be moot.
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Old 01-10-2014, 04:24 PM   #4
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Crawl Space Order between Foam Insulation and vapor Barrier


"Sounds like you are proposing to turn the crawl into a conditioned space so the venting suggestions might be moot."------------------------------- you should really read the first link about ventilation I left..... lol.

Gary
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Old 01-10-2014, 05:25 PM   #5
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Crawl Space Order between Foam Insulation and vapor Barrier


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Originally Posted by Gary in WA View Post
"Sounds like you are proposing to turn the crawl into a conditioned space so the venting suggestions might be moot."------------------------------- you should really read the first link about ventilation I left..... lol.

Gary
I have read it from before. We have the same bookmarks Gary but you have them down to a fine science and cataloged for quick disbursement.

My point being about the language used is that most DIY readers will recognize the language and understand the idea of conditioning better and will likely commingle the ventilation term with how an ventilated crawl is used.

I also disagree with the idea of venting a seal crawlspace in order to introduce conditioned air via air loss. Seems to defeat the purpose of sealing up for a tighter envelope.

If the insulation and vapor barrier on the floor are right, it takes minute amounts of conditioned air to affect the necessary change via supply side or transfer.
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Old 01-10-2014, 07:58 PM   #6
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Crawl Space Order between Foam Insulation and vapor Barrier


I think it is prudent to supply some air, enough to remove moisture present. Rather too much than too little as the consequences can be disastrous with mold/mildew/rot and health problems too boot. And you will always have moisture in a crawlspace, IMO. They are not tested for air pressure leakage or intake with a blower door, until that happens, there will be small sources for moisture. Just as many think they air-sealed the framing well; at the blower door test- they wake up from the dream....lol. The best system I've seen is waste air from living areas (after an HRV) going through a dehumidifier, then supply the crawl, and exhaust it to exterior from there.

My statements are to meet code minimum, hence the link and this discussion. Though it sounded like you were saying one doesn't need ventilation (per code) in a conditioned crawl... as "mute" to me means "silent" or no contribution.

Gary
PS. be sure to ventilate the space... with house air- per code. Fixed it...lol.
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Last edited by Gary in WA; 01-10-2014 at 09:20 PM.
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Old 01-11-2014, 06:48 AM   #7
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Crawl Space Order between Foam Insulation and vapor Barrier


Agreed 100%.

Have to have some communication and circulation.
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Old 01-11-2014, 03:22 PM   #8
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Crawl Space Order between Foam Insulation and vapor Barrier


Thanks again for the links and information. I am going to take a few pictures tomorrow and confirm that I have understood everything correctly, before buying supplies.
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Old 01-14-2014, 10:20 PM   #9
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Crawl Space Order between Foam Insulation and vapor Barrier


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Originally Posted by KansasCity
Thanks again for the links and information. I am going to take a few pictures tomorrow and confirm that I have understood everything correctly, before buying supplies.
If you do this right (by following the links and suggestions provided) you will probably find a significant improvement in comfort and reduced energy usage right away. My crawl space used to get just above freezing during the winter months until I sealed the rim joists with 2" Foamular as well as closing off the two outside air vents. Now the crawl space stays around 63 degrees all year long.
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Old 01-16-2014, 10:23 PM   #10
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Crawl Space Order between Foam Insulation and vapor Barrier


It is only because excessive dampness in a crawlspace or basement can condense, you can install a vapor barrier to protect floor framing from becoming damp and covered with fungus, efflorescence, and rot. A vapor barrier consists of one or more layers of sheet plastic on top of the soil in the crawlspace or basement.Use extreme caution when working with wood preservatives that contain pesticides.
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Old 01-18-2014, 11:29 AM   #11
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Crawl Space Order between Foam Insulation and vapor Barrier


Sorry, this week was busier than expected. Finally snapped a few pictures today.

My guess for the crawl space addition was sometime in the 1930's, but I haven't been able to find a permit.

Door from basement to garage


Original Stone Foundation


The joist were insulated with fiberglass, which will be removed once the walls and insulated.


All the walls are concrete except this 4' brick section


Door to the outside


Exterior view of the crawlspace



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