Writing from just outside Des Moines, Iowa, “Green Geek” says he is thinking about upgrading exterior sheathing from 1/2-in. fiberboard to insulated ZIP sheathing and then adding new siding. What’s making this possible is an insurance check that covers hail damage to the existing siding.
“I want to choose an exterior insulation that will make my home more comfortable and reduce energy costs,” Geek says in this recent Q&A post.” As I understand it, ZIP R-12.6 uses polyiso foam, and polyiso doesn’t perform well when temps fall below 50°F.”
Geek can look forward to four months of winter weather with temperatures ranging from a low of -5°F to 32°F; in summer, there will be three or four months of high humidity and temperatures running all the way to 105°F.
Using the insulated sheathing would make it easy to install a rainscreen and siding, Geek says. (At the moment, the 2×4 walls are insulated with fiberglass batts, so the exterior wall R-value is well below what’s required in the most recent version of the International Residential Code or IRC. However, the addition of a continuous layer of insulation at R-10 or above would bring the house into compliance.)
Is there a down side to this plan? That’s the question for this Q&A Spotlight.
Is ZIP-R really an exterior insulation?
Jon R points out that Geek may want “exterior insulation,” but technically that’s not what he’s getting with ZIP-R. The insulation layer is bonded to the inside face of the OSB. “The OSB portion of the ZIP will be cold and so more subject…