24 Feb '12, 9pm

Green Building Q&A: Stacking Sips and nailbase for superinsulation

I have a passive house project in the colorado rockies and need heaps of insulation to make the numbers work (R-90 walls, R120 roof). A local supplier has polyurethane sips that come in at R 6.66 /inch, however only to a dimension of 8.25" thick for approx R50 for the 8" panel. I had thought about stacking nailbase SIP from the same manufacturer on top to achieve my R value, but my brain sounded alarm. There would be a layer of OSB that can't "breathe"-this seems bad. However, being a passive house it is going to very air tight, so the probability for moisture carried into the wall system seems low. However moisture could still enter by diffusion, and then has no place to go. I am now thinking of cantilevering TJI's ont he exterior of the SIP with cellulose to derive my desired R Value and allow that OSB skin to breathe, but I liked the simplicity of two systems (Load bear...

Full article: http://www.greenbuildingadvisor.com/community/forum/energ...

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