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Old 02-02-2012, 06:45 PM   #1
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Roof soffit venting required?


Is venting required if I put 3 inch foam or fiberglass board directly under roof sheathing [inside of structure] and fill the rest with roxul insulation all between the 2 by 12 roof rafters? This is for my camp in VT. I was going to have it all spray foamed and was told no venting was needed. It's just a camp with vaulted ceilings. Need to know asap, thanks

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Old 02-02-2012, 07:03 PM   #2
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Roof soffit venting required?


go for it. That is known as a hot roof. Works fine according to the Building Science guys

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Old 02-02-2012, 07:42 PM   #3
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Roof soffit venting required?


Foam yes, fiberglass board...uhh...not too sure about that one, never heard of using that stuff in a situation like this.

Must be tight against the underside of the deck.

Andy.
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Old 02-03-2012, 05:24 AM   #4
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Roof soffit venting required?


I don't want to install soffit and ridge venting. With closed cell foam it is not required. I have access to double faced fiber board 3 and 1/4 in. thick and will install it tight and flush to underside roof, then use cans of spray foam to seal joints,then fill the rest with roxul. I just want to be sure this will be ok.
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Old 02-03-2012, 09:22 AM   #5
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Roof soffit venting required?


Here is one of the better sum-it-up articles out there.

http://www.buildingscience.com/docum...f-venting/view

Making your own SIP panel roof of sorts is quite easily doable and just requires a careful attention to the sealing of the layers and making sure that you have enough R-Value to the outside layer of the roof to prevent condensation on the structure of the roof.

3" of Iso should get you there and 11" of roxul should easily get you to the R-50+ level.

Make sure you air barrier details to the inside (i.e. drywall layer) are supremely tight. Air loss and the moisture it carries are the enemies of dry roof structure and condensation prevention.
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Old 02-03-2012, 02:07 PM   #6
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Roof soffit venting required?


All great info, thanks guy's.

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