Joe Lstiburek called me last week to set the record straight. I had written an article about a study of moisture in double-stud walls in a Massachusetts home, and his company, Building Science Corporation (BSC), had done the research as part of the Building America program. They found elevated moisture content in the cold, exterior sheathing, and Joe wanted to make sure everyone knew, “I would never build that wall because I consider it too risky.”
The BSC study redux
The reason he called is I that I hadn’t done my job as a journalist. Of course, I’m not really a journalist; I just play one in this blog. But that doesn’t absolve me from the duty to dig deeper, especially when I ascribe a conclusion to a person when that conclusion came from third-party sources. In this case, the conclusion was that buildings are more robust than we give them credit for, a statement I had initially ended that article with.
Because of that conclusion and because I hadn’t made it clear that BSC only monitored the project, some readers had the mistaken impression that BSC had at least endorsed, if not designed, that double-stud wall. As mentioned above, Joe considers that wall too risky, and the excessive moisture content in the exterior sheathing confirms his misgivings. Although the sheathing wasn’t damaged when they deconstructed the wall sections after three years, the amount of moisture they saw during winter and spring was a concern.
As for the debate about where the moisture came from, Joe said it’s coming from inside. The perfect correlation between indoor relative humidity — low in winters 1 and 3, high in winter 2 — and sheathing moisture content — also low in winters 1 and 3, high in winter…