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