Matching roofing SIP R-Value to wall R-Value.
Last Post 25 Dec 2022 02:42 PM by John S.. 0 Replies.
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25 Dec 2022 02:42 PM
Hi everyone, I hope to start a build of approx. 2000 sq. ft. Post and Beam kit in mid to late 2023. I will have a slab on grade for the flooring with hydronic heating/cooling embedded in the concrete, so I want the structure to be energy efficient.

In the area that I building, which will be on the Olympic Peninsula in Washington State overlooking the Straits of Juan de Fuca, the building regs call for at least R49 insulation in roof. I will upgrade the kit to 12" R51 SIP panels for the roof, on top of which I'll put a standing seam roof. I plan to go with 2" x 6" stick-built exterior walls vs SIP panels for a number of reasons. So I am looking at 2" insulated Zip panels over the 2" x 6" frame that yield an R12 insulating power. I plan to spray in closed cell foam in the frame, which at the maximum thickness of 5.5", yields an insulating value of R38.5 for a total of R50 in the walls. Is there a better solution then the spray-in closed celled foam for this?

Is it necessary to match R values for the roof and walls? Will the insulated Zip panels mitigate the thermal bridge of the studs effectively? By using closed cell foam, am I introducing some of the same issues I am trying to avoid with the SIP panels, i.e., remodeling exterior walls, pulling new wire (electric, speaker, cat5, etc.) or pipe in the wall, etc.?

Thanks for your insight and input. The high-efficiency home technology and application are new to me. So I'm trying to learn from you folks who have the bruises and scars healed from your learning curve. :)
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