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Originally Posted by kerry edwards
One issue you need to consider is whether the space between your rafters is filled with insulation or not. When I had a rental property reroofed, they wanted to vent the soffit and ridge but once they pulled off the old shingles, and sheathing I saw that it was useless because there was no pan to hold the insulation away from the sheathing so air could not flow from the soffit to the ridge. No need to spend the money if air wont flow.
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On an attic remodel I did (putting a small bedroom into an unused attic), we used the rigid foam board insulation, sometimes called polyiso board, 3 inches thick, 2 x 6 roof rafters with some backing blocks on the rafters to keep the foam board a couple inches away from the roof. We used the plastic corrugated ridge vent, I think it was only about 5" wide on each side, and though I was concerned about windblown rain, we've had no problem and we get some pretty serious storms here a few times each winter, though maybe not as severe as yours.
The foam board has great R value, I forget the number, but I think around 3 or 4 times the value per unit of thickness compared to fiberglass. You could make a good little reefer truck unit with this stuff.
I've not used the same corrugated plastic on soffits, but I bet it would work as well.
BTW, during the summer, if you get up by the ridge, you can feel the hot air poring out, and word is, it will increase your roof life dramatically.
Don't know if this is what you needed...