Lina Petra
9/9/2017
Hello. I am building a summer house in Maine. This is a 20x40 house with a 12/17 roof (steep I know, it looks right with the tall thin design). I want to use metal because I do not ever want to have to re-do this roof. That said, this is a summer place, so heat may be more of a concern than cold. I want to use the upstairs for living so it can not get too hot. There will be no attic, and the roof rafters and 5/8 CDX plywood will be seen from the top floor, like a cathedral ceiling. Is there some kind of insulation I can put between the plywood and the metal roof that will not be too expensive and will cut out some heat? I will use ice and water shield. One of the things that happens in Maine is that summer homes get moldy over the winter if they are sealed up too tightly and insulated too much. I guess it is the difference in temperature from the outside and the inside causing condensation? I have looked at the Closed-cell polyethylene foam insulation called Prodex. While it can in no way meet it s claims of R-factor, might it work for this application? Is there something else I have not thought of? I am open to ideas. Thank you!
Todd Miller
Isaiah Industries, Inc.
9/9/2017
I feel like you will want and need insulation and ventilation, especially to help avoid ice dams in the winter if you heat the house. Have you looked at SIP panels? There are some that include ventilation as well.
Eric Novotny
An informed customer is the Best Customer!
9/10/2017
+1 Easiest thing to do here (especially considering the difficulty of the pitch) would be to use a SIP (Structurally Insulated Panel) to create a complete thermal brake from the interior. At that point, you would have both the thermal brake from the exterior as well as the air barrier (assuming you sealed the panels properly) to make the home as efficient and durable as possible.

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