We own an 1890s vintage balloon frame house in Buffalo, New York. We’re getting ready to have a tear-off roof replacement. The roofer will be using a 1/2″ plywood deck and top of the line Certainteed shingles on the job. We are not happy with the options available for adding soffit vents (there are currently none). A ridge vent will be installed and the attic is unfinished with no insulation and/or air seal on the gable ends. We generally open the windows on each gable end and put screens in them in the summer for ventilation. There is some insulation in the attic floor/second floor ceiling, and we plan to add more with vapor barrier to limit warm moist air getting into the attic. At the moment we have ice damn issue only in one small area over the bathroom.
My question is how bad it would be to not add soffit venting. Will we be sorry to have voided some portion of the warranty, or is the warranty very hard to make a claim against anyway?
One case against the soffit venting is that I read somewhere online that soffit venting should be placed at least 6″ way from the facia and this won’t be possible for us because our soffits are very narrow.
Thanks for your expert opinions.
Replies
There are others more expert than I on this forum who may have other suggestions, but I believe you can provide plenty of attic ventilation by means of gable vents (along with your ridge vents) that should remain open as a means of keeping the attic cold in the winter and cooler in the summer.
Regarding the vapor barrier you mentioned, be sure that it's not placed on top of the attic insulation--that would only trap moisture within the insulation and ceiling framing. In fact, you may not need to add a vapor barrier at all since the ceiling probably has a good many coats of paint that form an effective vapor barrier already. But it would be a good idea to dig down thru the insulation to expose the tops of wall partitions below and air-seal any leaks created by holes for wiring, pipes, etc.where warm, moist air could be finding its way into the attic.
You can always add vents down low on the roof to let air in.
This was posted recently in another post:
http://www.greenbuildingadvisor.com/blogs/dept/building-science/lstiburek-s-rules-venting-roofs
Dr. Lstiburek says, "That means the entire perimeter of the roof needs to have air inlets, meaning continuous soffit ventilation. It’s dumb to have baffles every third or fourth bay, the entire underside of the roof deck should be washed. Where the air leaves isn’t as important — whether it’s a ridge vent, or mushroom caps, or gables. What’s important is that you have continuous air entry at the perimeter of the roof down low. [emphasis added]"
He says it's really important.
>>>A ridge vent will be
>>>A ridge vent will be installed and the attic is unfinished with no insulation and/or air seal on the gable ends.
I don't believe there would normally be any insulation or vapor barrier in the gable walls of an unfinished attic. No?
A ridge vent will be
That's a good point. I didn't mean to imply that this was an unsual situation.
Be careful...
In Lstiburek's article on roof venting, one key point is that there should never be more ridge vent than there is soffit vent. I read that to mean that if you don't have soffit vents, don't add ridge vents. The reason is that due to convection and wind currents, the ridge vent will put the attic under a negative pressure that sucks in air. If you've got soffit vents, that's where the air will come from. If you don't, or if the soffit vents don't match the ridge vent, the air will be sucked out of the house. That's air you've already paid to heat or cool. It's also likely to be moisture laden, which could cause condensation. I think you'd be better off with matched gable vents than with an unbalanced ridge vent.
Also, check with the shingle manufacturer. Some (Elk, I think is one), still warrant shingles on unvented roofs.
Thanks, and update
I picked up on the need for balance from Lstiburek's article and it got me doing more research. I found a product called SmartVent that basically raises the shingles at the roof edge to allow air to get into the roof just above the soffit. Our roofer had used a similar product called Edge Vent - though only on houses with open soffits, where they install the Edge Vent several courses up from the edge, where it can channel the air into the attic - and he was happy to use that product (for twice the cost of retrofitting the continuous soffit vent he had first quoted - but we were happy to pay it).
They finished today and you really can't even tell the Edge Vent is there, it's the perfect solution for what we were trying to do - and what our soffits allowed.
Thanks to all who commented.