Michael Sterner is ready to build a new house in northern Wisconsin: a simple, two-story box of about 2,000 square feet. After studying many possible wall assemblies, he has settled on the double-stud wall as proposed by the Building Science Corporation.
The assembly consists of an inner 2×4 structural wall sheathed (on the outside) with 1/2-inch plywood and an outer 2×3 stud wall. Between the two there is a 4 1/2-inch space. Both stud cavities and the space between the two walls are insulated with cellulose.
“We chose this wall for its high R-value to cost ratio,” Sterner writes in a recent Q&A post. “It seems to be the least expensive option for a high R-value wall. It is easy to build, finish on the exterior and seems very durable.”
But that’s not quite the end of it.
“As I’ve been receiving insulation quotes, some challenges have been brought up with the execution of this wall system,” he continues, “mainly that in order to dense pack properly we’ll have to divide up the bays so they can be dense-packed two stud bays at a time.”
Further, with all that cellulose going into the wall, there will have to be some way for the air to escape. Sterner sees two options:
- Install netting on the outside of the wall, insulate the wall, then add the fiberboard and water-resistive barrier.
- Finish the wall and use a hole saw to bore holes for both the insulation and the escaping air. Later, patch the holes.
“Does anyone have thoughts or experience on executing this wall system and best practice?” Sterner asks. “Does anyone want to try to talk me out of this wall system toward a different high R-value wall assembly?”
That’s where we start this Q&A Spotlight.