Weathered house wrap
I’m a DIY-er with a moderate amount of construction experience, and a bent for R & D…which is why I’m a big fan of GBA!
I am trying to finish a 28′ x 28′ shop that I built with PV solar in mind, and efficiency and durability as my primary goals. I’ve got 2×6 walls with t-profile strapping for wind shear. On that, I put 2″ of recycled polyiso (foaming the joints and broken corners, etc), and Kimberly-Clark Block-It house wrap, taping all seams. I plan to eventually dense-pack cellulose in the wall cavity. If my research is right, 2″ of polyiso in Zone 4a should be sufficient to avoid any condensation issues in the wall assembly.
Because I knew this could be in the weather a long time before I got the vertical steel siding put on, I used treated 5/4″ x 4″ decking for my perlins. If it matters, I can detail my window/doors assembly, which was inspired by info on GBA, but probably looks like a suspenders-and-belt approach. Again, durability generally trumps cost (especially labor) for this project.
Here is the question: this house wrap has been exposed to Kansas weather for over a year, and even though we got it on pretty tight, I can tell that the coating on the back side is flaking, and when it rains, the wrap is clearly soaking up some water. Am I stupid to go ahead and simply install my siding without replacing this? I was hoping that the 1″ rain screen gap would be insurance, but now I’m afraid it may be insufficient for protecting the wall assembly. Will the fiber-faced polyiso offer any significant resistance to moisture? I’m committed to doing it right, but removing all those perlins will look pretty daunting to my crew (ages 10-16 :-)), of whom only my oldest son and I are comfortable at the top of the gable ends (23′ to the peak).
Thanks for your help,