I’m interested in building an unvented attic on an upcoming project, as proposed by Joseph Lstburek in his various publications. Basically, this involves sealing the eaves and ridge with foam, and installing insulation between the rafters (as opposed to blown insulation on top of the ceiling drywall). However, I can’t find anybody locally who has completed a project this way.

My question is, should I install foil-faced roof decking such as TechShield, or is there some reason the insulation just below the roof deck makes this a bad choice? Any insight would be appreciated.