metal roof installation

john breska
5/8/2011
Hello, I'm having a new metal roof installed over shingles. I understand the strips or lats will be attached to the shingled roof then the metal attached to it. It's been suggesested that I put a styrofoam or insillation sheet in the spaces between the wood to add to stability as well as insulate. I think I've read on earlier posts that air flow between the existing roof and new metal roof works best. My question is which is the best way. Also: How much more expensive is 26 guage over 29 guage? Percentage wise?
Todd Miller
Isaiah Industries, Inc.
5/9/2011
Fist of all, some metal roofing products by design MUST be installed over battens, some CAN be installed over battens, and some MUST NEVER be installed over battens. So, if the product is to be installed this way, make sure it is approved by its manufacturer for this type of installation. An airspace creates a thermal break which is good from an energy efficiency standpoint. As little as a 1/2" is good. Insulation is also good. If your metal roof is okay for installation over battens then you should not need the insulation for support. Cross battens are also good -- vertical battens follow by horizontal ones, creating a chamber that can truly be vented with air brought in at the botton of the roof and exhausted out at the ride. I really cannot answer the cost question. There would be no set rule on that. It will not be a humoungous difference. But keep in mine that product gauge is only one factor to consider. Product design and proper installation are probably even more critical.

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