[andrewksu]

R-Values. Exponential going the wrong direction. After R-15 or so you slip into the long tail.

Good article here- http://www.energyvanguard.com/blog-building-science-HERS-BPI...

PH is performance based, but the religion is a bit excessive on R. I do greatly value the air tightness and the quantitative approach.

High R-Value walls are tough to build and get expensive quick. Double wall, exterior sheathing, more parts, more fasteners, etc. We use SIPS walls/roof that have very good R, very little thermal bridging and outstanding air tightness while being fast to build.