Conditioned And Unconditioned Unvented Attics

Whether an attic is conditioned or not, the choice to vent or not to vent is a design and construction choice, not a requirement determined by the building code. In this recent Building Science Corporation article, Joe Lstiburek explains that attics can be designed and constructed to be either vented or unvented in any climate zone, and if the choice is to build an unvented conditioned attic, spray foam and rigid foam isn't necessarily required to insulate it as long as you follow a few design rules.