Air Seal Rim Joist Cavity Thats Only 3" Deep?? - Insulation - DIY Chatroom Home Improvement Forum
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Old 03-25-2015, 05:11 PM   #1
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air seal rim joist cavity thats only 3" deep??


I was gonna seal with 2" rigid foam but that only leaves me with 1" for roxul r14?
Or should I do 1.5" xps and then the batting will sort of sit on top of the wall frame/ wall xps??

Also should I seal rim joist cavity with canned spray foam or is caulk ok? If caulk what type?

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Old 03-26-2015, 11:26 AM   #2
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air seal rim joist cavity thats only 3" deep??


is the roxul for fireproofing? if so, you can use drywall, cut to fit and keep the 2" of foam. foam or caulk are both fine, depending on the size of the gap. Any good quality latex would work.

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Old 03-26-2015, 02:29 PM   #3
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air seal rim joist cavity thats only 3" deep??


Roxul is to insulate as well as fireproof. What type of caulk fireproof? Or will spray foam seal better
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Old 03-27-2015, 09:11 AM   #4
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air seal rim joist cavity thats only 3" deep??


Could you add an inch of xps on top of the two inch? XPS is r5 per inch. An inch of Roxul is only between r3-r4 I think. You'll be drywalling over everything anyway or no?
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Old 03-27-2015, 09:24 AM   #5
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air seal rim joist cavity thats only 3" deep??


Just use the foam and cover with Drywall for your fireproofing.

Are you finishing the basement? Is the fireblocking done?
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Old 03-27-2015, 04:50 PM   #6
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air seal rim joist cavity thats only 3" deep??


It's a shallow basement ( 58")
Only. Used for storage.
I was gonna seal rim joist cavity with 2" rigid foam but that only leaves me with 1" for roxul r14?
Or should I do 1.5" xps and then the batting will sort of sit on top of the wall frame/ wall xps??
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Old 03-27-2015, 11:28 PM   #7
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air seal rim joist cavity thats only 3" deep??


I was gonna seal with 2" rigid foam but that only leaves me with 1" for roxul r14?
Or should I do 1.5" xps and then the batting will sort of sit on top of the wall frame/ wall xps??

Also should I seal rim joist cavity with canned spray foam pro foam or just reg foam and or fireproof foam?


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