Using foam boards instead of standard vent chutes on rafters

Sep 26, 2007 4 Replies

Just like to get some thoughts on this product....(ignoring price)......using this in addition to the normal fiberglass batts.....so bascially this clip-vent system would just replace those standard vent chutes...using this with the standard 1" DOW Blue Styrofoam.,... (located in the Houston area)



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Thanks.



Well, ignoring cost, it seems like a superior solution. For one thing, it makes a channel that is essentially the full width of the rafter bay, which many of the chutes don't.

My only concern would be lack of fire resistance. I don't think unprotected foam board is allowed in many jurisdictions.

Paul F.

Well my opinion may not be worth much to you because my experience is in cold climates. Looks like a great setup for a cathedral ceiling. Might be a waste of money for the typical unheated attic in my area, where the chutes just go for a few feet along the wall plate area. I prefer to get cardboard chutes, since they install much easier and are also vapor permeable. Now maybe in a hot climate, using foil faced polyiso foam, they'd be the greatest thing since sliced bread.

Thanks for all the responses. I forgot to mention that it would strictly be for a cathedral type ceiling where there's no attic space and it would get the afternoon sun....

I am doing something VERY similar in my addition with a cathedral ceiling. I used 9 1/2" I-joists for the ceiling joists, and 3/4" polyiso board against the bottom of the top flange of each I-joist, forming a "chute" that is 1 1/2" deep. Below that, I used R-25 unfaced batts, giving the ceiling an R-value of just under 30. Great for a 10" thick cathedral ceiling in WI.

JK

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