Good morning, folks.
I’m remodeling a single-story home by removing the roof, building a new floor, kneewall, and steep roof (12/12 pitch). The new roof is a cruciform pattern with gable ends and big dormers front and back, right up to the ridge.
Here’s the kicker. The roofing manufacturers won’t warrantee their materials on an unvented roof, and while I have all the ridge and valley in the world, there is no eave to speak of for a soffit vent. How do I vent this? Anyone?
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Replies
When I get time later I'll try to find a link for vented drip edge. Check with your roofing supplier - they may carry it in stock or can order it.
Can I get that Little Debbie snack cracker out from under the heel of your pointy boot?..
http://grantlogan.net/
The roofing contractor agreed to vented drip edge, but again, there is very little eave, and the bulk of the roof is above the valleys. I've thought of drilling the rafters in a staggered pattern and power venting it, but that's too extreme. I'm afraid the unvented roof will bake the shingles, and I know they won't be warranteed. The insulation beneath the sheathing is cellulose blown in, and I can keep that away from the sheathing with Propa-vent or tyvek stapled between the rafters. There's just no path for air flow.
Find threads about venting. A recent report by a BuildingScience Corp. member found that in Jacksonville, FL (August 2001) the dark grey/black shingles on unvented roofs were on average only 0.2 degrees F hotter. If the shingles aren't baking now, they won't be baking with all the extra heat/temperature.
Gable end vents and ridge venting?-
seeyou,
What I did on mine is I used cedar breather under the shakes. That's aplastic mess material designed to hold the shake slightly iff the roof to allow it to vent and cool the shake.. You mentioned shingles, I don't know if it applies there as well. But you could always apply skip sheathing over your plywood deck. Your local sawmill should be able to sell you really cheap boards to be used as skip sheathing.. all the wood for my 15 sq. skipped sheathed east wing cost me well under $500.00
Yeah, I'm familiar with cedar breather. I've used it on occassion, but prefer to strap. The OP is installing asphalt shingles. Strapping and resheathing is an expensive, but possible solution.
Can I get that Little Debbie snack cracker out from under the heel of your pointy boot?..
http://grantlogan.net/
I understand your design, now. I'm guessing there will not be much attic space. What brand of shingle are you considering?
Can I get that Little Debbie snack cracker out from under the heel of your pointy boot?..
http://grantlogan.net/
See page six of the warranty. I don't exactly understand the specifics, but this might be worth pursuing.
Can I get that Little Debbie snack cracker out from under the heel of your pointy boot?..
http://grantlogan.net/
I guess they're right. I called CertainTeed and checked out the warrantee. Now all I have to do is convince the roofing sub. Thanks for the input, everyone.
Apparently, with Certainteed products (others may be similar), if you apply a radiant barrier below the sheathing, the attic may be unvented.
http://www.certainteed.com/NR/rdonlyres/3E07E5A5-DD97-4FDE-A108-C497E14B5AA7/0/2006GeneralAsphaltWarranty.pdf
Can I get that Little Debbie snack cracker out from under the heel of your pointy boot?..
http://grantlogan.net/
In addition to the Certainteed products that seeyou mentioned, look into Elk shingles. It's quite possible to find shingles that are waranted for use on an unvented roof. And roofs with big hips and valleys are nearly impossible to vent effectively, meaning that they're pretty much always effectively un-vented.
Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
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Andy, Valleys in and of themselves are not a problem. In many cases the valleys are open to attic space so with gable vents and ridge vents you should be ok.
NOW. If the valley is over a cathedral space, it seems to me that would be a problem. Jack rafters (if that is the term) run from teh ridge and but into teh valley rafter. NO VENTALATION POSSIBLE wiht teh exception of the ridge.
Is this a problem? Obviously less venting than with soffit vents. Obviously poor air flow even with a ridge vent. But can I guess you at least have a path in the rafter bays to the ridge and heat rises so it would flow out the top to some degree.
So is it better if possible to just forget the air space and go unvented and insulate from dry wall right up to the sheathing?
For venting to work, the soffit and gable vents must be balanced. That's not possible with either a hip or a valley.
That said, I don't think roof venting is worth a bucket of warm spit. So, insulate the rafters with closed cell foam and call it done.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom