Can I just use roxul to add extra r-value?


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Old 04-08-14, 05:24 PM
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Can I just use roxul to add extra r-value?

I have a foam core rim joists on my townhome. I'm wondering if I can just stick roxul r14 to add some extra insulation value before putting up drywall. Please see the attached pic to what they have used. I would use rigid foam but I have quite a few pipes/intakes/etc running to the exterior. Thanks for your help
 
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Old 04-08-14, 05:28 PM
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Roxul would be an excellent choice since it is water proof, fire resistant, mold resistant and easily cut to fit odd spaces as you describe. I don't see any draw back to using it in your situation.
 
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Old 04-08-14, 05:47 PM
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Would I have to try and put vapour barrier between each joist as well before installing drywall?
 
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Old 04-08-14, 05:50 PM
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Probably easier to stretch 6 mil plastic sheeting, stapling it to the joists,then hang the rock. You should have a vapor barrier toward the warm side, or living side.
 
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Old 04-08-14, 06:21 PM
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I've attached 4 photo's of the one area in my basement. I am an inside unit, with units are either side of me. The pink insulation & vapour barrier is what the builder installed and the other studs/roxul are what I installed.

How would you recommend I do the vapour barrier? Thanks again for your help
 
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Old 04-09-14, 03:51 AM
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What is the type of foam and how thick is it in the rim? If you have an r-value there of 14 or more you would probably be safe adding the roxul with no vapor retarder.

I did a commercial insulation job several years ago where roxul was used and it was specified that a vapor retarder be used. I purchased a product called "FSK" which is a fire rated foil laminated vapor retarder. It comes in rolls and I was able to cut it and made up a simple plywood template which fit the joist spacing and used the template to fold a simple flange on the foil so that it could look neat and be stapled to the sides of the joists.

Roxul (or a similar. Rock wool product) is also available with the same vapor retarder on the face but you have to get in contact with a commercial insulation supplier to get it and there may well be a minimum quantity order unless you are lucky enough to find a supplier that has a stock of it.
 
 

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