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Community and Q&A

Roofing questions – Deck house

asantella | Posted in Energy Efficiency and Durability on

I have a Deck house located in the cold climate of New England. It is currently insulated with 1-1/2″ of polystyrene with a rubber roof. As the deck house is exposed beams with exposed 1-1/2″ tongue and groove fir. The rigid insulation is on top.

I am exposed on the water to high winds. The tongue and groove planks extend beyond the interior 4′-0″ in all directions. The winds get into the underside of the 4′-0″ eaves, under the insulation, and into the house through the planks. I am going to install a wind barrier under the eaves (a plastic called membrane), followed by a 3/8″ air gap with nailer strips, followed by tongue and groove 3/8″ fir to match under the eaves. On top as a new roof I am asking the roofer to apply 4″ of Polyisocyanurate followed by EPDM roof. Do you feel this is the right solution? Should I increase foam thickness?

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Replies

  1. Expert Member
    Peter Yost | | #1

    Hi asantella (be great to have a name for our GBA Q&A community to use) -

    In my experience, the ONLY way to eliminate air and water leaks associated with your "through" roof framing and deck is to do a chainsaw retrofit (there are several good GBA resources on this topic: https://www.greenbuildingadvisor.com/?s=chainsaw+retrofit). The through framing and decking moves too much over time to keep any seal between the overhang (outside the building) and your ceiling (inside the building).

    In terms of how much insulation you should have when you reroof: the minimum is R49 for climate zones 6- 8. And remember, that is a MINIMUM.

    Peter

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