Air/moisture sealing between ceiling and unconditioned attic – GreenBuildingAdvisor

Background: I am about to build a new, two-story house, with a full height basement in the Roanoke, VA area (Bedford County – Climate Zone 4A – Mixed Humid). It will have a vented, unconditioned attic space, R49/R50 blown cellulose insulation, raised heel trusses, asphalt shingles, and composite wood (LP) lap-siding over OSB sheathing using Benjamin Obdyke Hydrogap self-adhered WRB. Walls will be 2×6, 16″ O.C., advanced framing techniques, dense packed cellulose in the wall cavities.

My question: What is a good, cost effective (Pretty Good House approach) way to air and moisture seal the interface between the second floor ceiling and the unconditioned attic space? I do not plan to have any HVAC equipment or ducts in the unconditioned space.

Not a new problem, but I am looking for some recent examples of how folks have solved this issue without going to extremes of time and/or cost.