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Old 10-30-2013, 08:08 AM   #1
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Open Web/Engineered Floor Joists & Insulation


I'm building a new home in Zone 4 (central VA). Per the information on Naima.org, I should have a vapor barrier. However, I have read on contractor talk and my insulation guy said the codes are changing and a vapor barrier is no longer necessary.

This is our retirement home and we don't want to have to redo anything later, so we are trying to get it right the first time.

My insulation guy wants to do all unfaced, but said he will do faced if we want - he just feels it's unnecessary. He also said that in the crawlspace and the garage, it's very hard to get the facing right up against the subfloor anyway since we have open-web joists. Per a few threads on contractortalk, there is disagreement about faced/unfaced in a crawlspace. Some say definitely unfaced, others say unfaced just acts as noise barrier if not faced.

We are used to using faced in prior home (Illinois), so are leary to go any other way. When I asked the insulation guy more questions, he said facing is no longer required because facing is supposed to face the "heated side of the house". We have hot humid summers and cold dry winters here, so sometimes the heated side will be outside, sometimes inside, so faced would be the wrong orientation for part of the year. I suppose that makes sense, but I'm particularly concerned about the crawlspace and the garage building up condensation from the temperature differences.

Our house has a brick veneer exterior (all sides). All joists are open-web and we wanted to use batting. Foam is out of the price range, plus in our area, neighbors have had major issues with carpenter ants and mold with foam applications (both open & closed cell). Blown in won't work easily due to settling issues in the crawlspace and we have a whole house fan in the attic. The quote included extra tiger teeth to hold the batting up in the crawlspace and garage overhead.

So....can a pro help me here?

Is unfaced ok for crawlspaces (10 mil poly on ground and up sides with dehumidifier system/vent fans).

How about the garage?

I've also read about Roxul insulation being stiffer - would that be better in an open-web joist system? Does that come faced/unfaced?

Thank you in advance for your help!
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Old 10-30-2013, 01:31 PM   #2
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Open Web/Engineered Floor Joists & Insulation


WHF should vent to exterior, not attic. Unfaced for your location; http://www.buildingscience.com/docum...commendations/

Full-depth fibrous with housewrap on joist bottoms against wind-washing or"super insulate"; http://www.buildingscience.com/docum...n-crawlspaces/


Roxul over fg; only comes in unfaced; http://www.roxul.com/products/reside...ul+comfortbatt Leave a few inches of block without poly for termite inspect; http://termites101.org/termite-basic...ites-by-region

Canned foam/XPS the rims after air sealing all wiring/plumbing holes/chases to stop stack effect; http://www.buildingscience.com/docum...l_seal_rev.pdf

http://www.wag-aic.org/1999/WAG_99_baker.pdf Add positive tie at beam/column if needed per code.

Gary
PS I even need to be selective when using a link because of wrong info in other parts of it....lol. Welcome to the forums!

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