Hello,

My family and I live in Anchorage, Alaska (climate zone 7) in a large modern home built in 1984. It features a flat roof, no overhangs, many windows, and sheetrock returns around the windows and doors. Shortly after moving in, we discovered that the uppermost roof plane was compromised and had it replaced (after an 18-month wait). Since then, we’ve updated some of the interior and uncovered several other “modern home” design flaws typical of the 1980s. We’re now building up the courage to tackle these issues head-on.

Our current wall assembly is standard for Alaska construction: sheetrock, poly vapor barrier, studs with fiberglass batt insulation, sheathing (no visible WRB or housewrap), and painted cedar shiplap siding. The wood-framed windows and doors likely performed well 40 years ago, but without overhangs, many have rotted due to constant moisture exposure.

Here’s where I need some advice: I plan to replace the windows and siding around the house, starting with a small test section. While everything is exposed, I’m considering upgrades to improve resilience, tighten the structure, and potentially enhance thermal performance. I’m planning to use locally manufactured fiberglass frame windows/doors that are better suited to our climate and moisture challenges. I’ve also considered adding eyebrow eaves above the windows for added protection. The windows could be inset into the 2×8 walls, or exterior foam insulation could be used to achieve a similar effect, though I’m unsure about the best way to detail this.

The Question: Given the current wall assembly, can I add 1-2 inches of exterior foam insulation, an external WRB like Benjamin Opdike UV Invisiwrap, furring strips, and Allura fiber cement board siding (cut into 2×4′ panels) without creating a “wet sandwich” that traps moisture? Would it be better to skip the additional insulation and focus on “tightening up” the existing sheathing with WRB, liquid flashing, and tape? There are a few areas, particularly near the foundation, where air leaks through the walls during storms. Some of our worst windows have also allowed rain to blow through in windstorms (possibly due to pressure differences). I imagine new windows, a proper WRB, and improved flashing could make a significant difference on their own, so should I just focus on that?

Thanks in advance!

Zak