Cool Metal Roof Venting w/ Cor A Vent Question

Luke Sanford
So, the new roof materials are on the way, most of the old roof is ready to go, and now of course, is when I have questions. Last minute of course! We are planning a cool metal roof, which will be built up on battens over top of the existing asphalt shingles, and anticipating using Coravent products for the ridge vent. I was planing on using Coravent Purlin Vents for the eves, thinking that I could mount them vertically to the existing fascia, and run the eve trim or drip edge out over the vent. The Coravent purlin vents are 2" long, my roof will be 2 inches off the deck, and my eve trim is 3" tall. Is this going to work? I am worried that if the roof is up 2" and the eve trim is only 3", then my venting material only be 1" from the new roof (not adequate venting?) in which case I imagine I could rip the 2" vent down to 1". and have it flush with the eve trim's bottom. There are existing eve vents on one some of the roof, but not on very large 35ft mega dormer than spans for half of the roof's total square footage. I understand that I could very well open the old decking up and try to use the existing vents beneath it and direct the air flow underneath half the house, but what about the dormer with no venting? I really need a solution to this issue today. and after all of the venting questions, now I'm wondering, if the roof is up 2", and the eve trim is only 3", if that is a substantial drip edge? Geez, hope somone can give me a hand here! Thanks a million!
Todd Miller
Isaiah Industries, Inc.
Thanks for your question. Good to hear from you and thank you for choosing metal! Wow, that's the first I have seen those purlin vents. That's a neat product. You're not using it quite the way it's intended but, what do they say -- necessity is the mother of all invention?!? I have "lived there" Most of my life! Really I think 1" is adequate space. So, you're installing your battens vertically though?
Eric Novotny
An informed customer is the Best Customer!
What the design motivation behind the over deck vented roof? Are you turning the structure into an insulated roof deck or is it already and you are just looking to more so uncouple the roof from the structure? This is a great article on how to make an over roof deck vented design out of traditional building materials.

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