hot roof vs vented attics
#1
05-14-12, 03:33 PM
Join Date: Apr 2009
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hot roof vs vented attics
I was just reading another post about sealing up foundation vents when Gunguy Supermoderator wrote the following sentence
He was speaking of venting issues. So I assume this is an issue and I would like some advice.
Read more: http://www.doityourself.com/forum/ba...#ixzz1usuk59sF
I'm racking my brain about an attic vent issue. The one I'm worried about is a flat roof about 12 x 14. It has 2 x 6 roof joists running North/South and for the last 93 years has not been insulated. This I found out while ripping off the ceiling sheet rock. I can certainly put a roof vent up near the top, my problem is that there is no easy way to draw the air from the bottom or the sides as this is a brick rowhouse.I'm looking at the neighbors house and I can't see any venting on any of them.So the big question is, do I rip out the bricks and install the vents for this small roof, or just put some R-19 with no vapor barrier in the joists and seal it up. Any comments would be helpful.
And lets not forget the hot roof vs vented attics.
Read more: http://www.doityourself.com/forum/ba...#ixzz1usuk59sF
I'm racking my brain about an attic vent issue. The one I'm worried about is a flat roof about 12 x 14. It has 2 x 6 roof joists running North/South and for the last 93 years has not been insulated. This I found out while ripping off the ceiling sheet rock. I can certainly put a roof vent up near the top, my problem is that there is no easy way to draw the air from the bottom or the sides as this is a brick rowhouse.I'm looking at the neighbors house and I can't see any venting on any of them.So the big question is, do I rip out the bricks and install the vents for this small roof, or just put some R-19 with no vapor barrier in the joists and seal it up. Any comments would be helpful.
#2
05-14-12, 05:12 PM
I don't think you will be able to get a complete circulation if the joists are all that is up there. Not sure how cross ventilation would work in your situation. If the joists are solid, no air can move sideways, EW to your vent. I wouldn't cut a hole in a good non leaking flat roof anyway 
It may be adding the non vb insulation, or better yet Roxul (fantastic stuff) would be a better bet.
It may be adding the non vb insulation, or better yet Roxul (fantastic stuff) would be a better bet.
#3
05-14-12, 08:35 PM
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I looked up that Roxul stuff, the R value is a little better. I guess you were suggesting it because(according to the web site) it doesn't matter if it gets wet. hmmmmm interesting stuff any idea how much more the stuff costs, I assume alot since I didn't see any prices.
Thanks again,
Scott
Thanks again,
Scott
#4
05-15-12, 03:00 AM
Not sure of the cost locally, but it is also fire retardant, and, as you say has a little better R value. Big orange has started selling it, so you may want to check there for pricing.
#5
05-15-12, 05:23 AM
I suggest spray 3 inches of closed cell spray foam against the roof deck. You need the ventilation to prevent moisture from condensing on the roof deck. The spray foam will completely seal the roof deck off from air flow. At 2 inches thickness it becomes a vapor retarder so you don't have to worry about water vapor passing through and condensing.
