John writes from Moro, Illinois: "In constructing my next home (in a mixed-humid climate) I plan to use a wall design which will have the ability to dry to both the inside and the outside. It will consist of drywall, 2x4 wood framing, high density fiberglass batt insulation in the stud cavity, and fiberboard sheathing rated for wall bracing (high water vapor permeablilty) covered by vinyl siding. To reduce thermal bridging at the framing, I want to cover the sheathing with a material that can insulate and has a high water vapor permeance. All rigid foam boards seem to have low permeance. I am considering using your 703 board insulation. Is there any reason why this shouldn't be done? Do you have any suggestions for alternatives?"

Answer: Typically, FOAMULAR® insulation and housewrap are used to insulate under vinyl siding. We have no recommendations for using 703 board insulation in this fashion.