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Old 04-25-2012, 12:08 PM   #1
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Crawlspace Sprayfoam Recommendations


I live in Baltimore area, MD. I currently have an unconditioned crawlspace, with what is likely R13 FG falling out of the joists. HVAC is in the crawl. The ground is gravel and it can get moist; I have a sump pump down there. Short of the hurricane, it doesn't flood, but there is moisture.

Here's what I've come up with thus far:

DIY: install 10 mil vapor barrier according to recommendations here. Switch open vents to automatic opening vents (as HVAC is down there). Unless, because that system is down there, they should be left open.

CONTRACT: Sprayfoam insulation in rim joists and floor joists.

This is the part I'm looking for advice on: I have two quotes for sprayfoam. One for 2" closed cell + R19 FG in the floor joists and another for 3" closed cell, no FG. Price between them is negligible.

I've been to buildingscience.com and read up, so here's the questions:

Is it worth it to even consider the SP+FG combo?
With a good VB, is 2" closed cell enough?
3" seems like it's just going to pretty much fill the entire joist - is the extra inch worth the money? I'm gonna put down the VB anyway....

TIA for your advice - and I've learned a lot reading related posts on this forum....

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Old 04-26-2012, 11:34 AM   #2
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Crawlspace Sprayfoam Recommendations


2" of CC foam in the rim joist should be good.

Have you considered just making the crawl conditioned?

Flooding during the storms that we had would be expected but if you can change the drainage and get the water away from the home, I would convert it to conditioned.

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Old 04-26-2012, 11:40 PM   #3
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If you do condition it, supply intake air to HVAC. You're in Zone #4; http://publicecodes.citation.com/ico...001_par001.htm

R-19 is required---- -4" SPF or option "A"; http://publicecodes.citation.com/ico..._11_sec002.htm

Option "DIY": http://www.buildingscience.com/docum...n-crawlspaces/
Notice- no vinyl.

Check with local AHJ for radon; http://energy.cr.usgs.gov/radon/usrnpot.gif

Move your cursor over your area: http://termites101.org/termite-basic...ites-by-region

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Old 04-27-2012, 11:18 AM   #4
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Thanks so much, both of you'!

WindowsonWash - I can't condition the crawl. My house in the bottom of a bowl and I can't adequately run all the water away from the house. I've done the best I can, to reroute a lot of it, but at the end of the day, I can't change the overall location - which is the bottom of the bowl.

GBR in WA - thank you for the links - I hadn't come across those yet! I'm good on radon (passed before I bought the house), but just got treated for subterranean termites. Luckily, caught them early. But still.

So, I think I'm going to go with the contractor doing 3" of SP. Mostly because I dont want to deal with the moisture/mold potential with the open faced FG (as illustrated in the building science article), not to mention the potential for batts falling out the joists (which is inevitable.

Thank you so much!
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Old 04-27-2012, 11:46 AM   #5
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Water under the VB on the floor is not a big issue but leaving it vented and spray foaming the bands and floor is just fine too.

You still should have the VB across the floor and sealed to the stem walls regardless.
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Old 04-28-2012, 09:14 PM   #6
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"So, I think I'm going to go with the contractor doing 3" of SP. Mostly because I dont want to deal with the moisture/mold potential with the open faced FG (as illustrated in the building science article), not to mention the potential for batts falling out the joists (which is inevitable."--------------------- 3" of SPF is R-15, still short of your minimum code requirement.

"3" seems like it's just going to pretty much fill the entire joist - is the extra inch worth the money?"---------- Your floor joists are only 3-1/2"?

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Old 04-28-2012, 10:27 PM   #7
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Make sure you butter the entire exposed portion of the bottom of the joists.

This will protect them from sweating and any rot. Get their condensation resistant up.

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