131 - Two Q's: Isn't ZIP-R backwards? Shouldn't we rainscreen roofs as well as walls?

Two great questions on which the boys pontificate in fine form. Yes, ZIP-R is "backwards" (rigid insulation interior to structural sheathing) but that does not mean that it doesn't work; it does, just differently. So why don't we typically rain screen roof claddings? The short answer is it always costs more, regardless of the type of roof cladding. But you know the saying: vent until you
can't...

NOTE: - An Apology: Pete keeps saying "vinyl siding" when he means "vinyl wallpaper" in terms of what many older homes see as newly added covering over failed/failing plaster... Oh, and we can endlessly apologize for Steve's parting "jokes"...

PETE'S RESOURCES:
- "Calculating minimum thickness of rigid foam sheathing"

NOTE: Martin Holladay has more than one seminal GBA blog on the topic of adding continuous exterior rigid insulation to meet code--and even better--for greater energy efficiency and maintained moisture management.

- "Avoiding Wet Roofs:"
https://www.jlconline.com/how-to/insulation/avoiding-wet-roofs_o &
https://www.jlconline.com/how-to/insulation/avoiding-wet-roofs-part-ii_o