If you hang around GBA for even a few hours, you’re likely to see the editors and regular GBA contributors advising people in the forum that the only way to create a safe unvented roof is with a layer of air-impermeable insulation, either above or below the roof sheathing, before they consider using fibrous insulation in the assembly. Insulated roof assemblies are at the top of our list of FAQs and no doubt, this is good, conservative advice. But does it match research and real-world experience, is it true for all climates, and are vapor diffusion ports ever a legitimate solution?

This episode of The BS* + Beer Show begins with presentations from our panelists, Kohta Ueno of Building Science Corporation and Bill Hulstrunk of Yestermorrow Design/Build School and NatureTech. The presentations are followed by live participants’ questions and an illuminating discussion of unvented roof assemblies in general. Enjoy the show!

The next show is Thursday, May, 14 from 6 to 7:30 pm: Making concrete more sustainable. Our panelists are Bruce King, Bruce King PE and author of The New Carbon Architecture, Christie Gamble of CarbonCure, and Trevor Acorn, PE, engineer at Walter P. Moore. Use this link to register. 

Brian Pontolilo is a former editor at Fine Homebuilding magazine and Green Building Advisor.