How to insulate a 2:12 skillion roof, vented vs unvented

We’re building a house and I’m trying to figure out the most cost efficient way to insulate the roof assembly.  My architect designed it as a vented assembly (see detail)… We’re building a house and I’m trying to figure out the most cost efficient way to insulate the roof assembly.  My architect designed it as a vented assembly (see detail)…Read MoreGreenBuildingAdvisor