Structural Insulated Sheathing (SIS)

Once I learned that Dow Chemical (my old stomping ground for a few years) had last year reformulated Styrofoam to reduce the Global Warming Potential (GWP) of its blowing agent, my appreciation for the newer building products from Dow really came around. One other recent decision that was made easy has to do with the Sheathing we used.
Traditional construction around East TN uses OSB (Oriented Strand Boasd - basically, particle board) sheathing and an overlay vapor barrier of Tyvek house wrap. You've all seen these houses. They look like a house wrapped in white paper until the outside siding is later added. (One house being built near our rental still has only the Tyvek house wrap after over a year... I'm guessing they ran out of money when the wheels came of our economy). Tyvek makes a good vapor barrier and has been a staple of the building industry for years. Our specification for this house even calls for a conventional house wrap. Rick Hessick of BR2, our builder, suggested we look at SIS and with my new-found appreciation for styrofoam, we looked closely. It's a great idea! SIS replaces the OSB, and the tyvek. PLUS, it's got a better vapor barrier performance
because it can be sealed better AND it's got the insulating properties of 1/2" of styrofoam. Since we already planned to use foam for our insulation system, this product just adds to the R-value in our wall system. To top it off.... it's a real pretty blue :)