High density styrofoam underlayment?

Thomas Petty
2/28/2018

I'm looking at replacing a 100 year old Victorian stamped tin shingle roof with a 26 gauge galvalume standing seam roof.

One contractor has a system by which they place a radiant barrier (silvered) fabric underlayment and then an inch or less thick high density Styrofoam board that has grooves for air transport from the eaves (adding eave vents if they don't exist) to the vented ridge. The system is called thermavent (http://www.thermaventilation.com/)

My question is - is this a good idea or are there potential problems ?

Todd Miller
Isaiah Industries, Inc.
3/1/2018

It seems like a reasonably well thought out system and I have worked some with something similar. The question would be whether your roofing manufacturer is okay with their product being installed directly over this system or if they'd require an additional layer of plywood or OSB decking.

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