I think we're on the same page here. I looked into the vaious ridge vents a bit and saw that a lot of pros were recommending the Shingle Vent II. The leading contractor for the job is proposing OC Duration shingles. OC makes a similar ridge vent. It's rigid plastic, comes in 4ft sections, and allows 20 sq in of airflow per foot. So, I think I'm going to spec that.
On another subject, one roof section which is over the garage is low profile. It's right at the 2:12 min pitch for shingles. Two of the contractors want to put down ice barrier over the whole roof section.. The other one wants to use ice dam on the lower, two layers of felt on the upper part. His thinking is that applying a rubber like surface over the whole thing is not good, because it's better to let the sheathing breathe even a little from the top through the felt and shingles.
I looked into this a bit online and seems there are folks vigorously arguing both sides of that one two. The ice barrier the whole roof approach guys claim:
Done properly it's virtually impossible for water to even get behind the ice barrier material.
Even if it does, the roof can still dry out from the other side, ie attic side.
With felt and shingles the roof really can't breathe from the outside anyway.
Additional factors are that this section of roof has the least venting. It has continous soffit vents, but only a fraction of that near the top. I can increase that a bit but it's still not going to have the best venting. I also can't do a rolled roof, because it faces the street. The existing shingles have worked fine for 28 years and I'm assuming there is at most just 2 layers of felt, if that. Also they did lay the shingles closer together, I think
3" exposure vs 5". But can't do that with the new architectural shingle. Spec for that shingle say 2:12 is the min pitch, so I'm right at min there.Any thoughts?
And thanks for all the excellent advice...