Early American "superinsulated houses" (the term-of-art at the time) used 12+ inches of foam, but often forgot about humidity and ventilation. As a result, many

Early American "superinsulated houses" (the term-of-art at the time) used 12+ inches of foam, but often forgot about humidity and ventilation. As a result, many early examples became mushroom food. Modern passive houses use HRV/ERV technology, so they achieve high efficiency while avoiding moisture and mold. As usual, it's the early adopters that find the problems.