Closed cell spray foam/cellulose combination
Background: 1500 Sq Ft. single level home, Northern Minnesota Zone 7, almost 10,000 HDD.
I am getting ready to insulate my double studded walls. The wall cavity including 2 2×4 24″OC studs separated by a 1″ gap for a total cavity of 8″. The ceiling has 2′ energy heel trusses with 24+” of blown in cellulose
The original plan was to insulate the whole wall in cellulose, and at R3.9/inch the goal was 31 with no thermal bridging. Inside the cavity there was going to be a smart membrane (Intello Plus)
Recently my insulation contractor approached me with the idea of spraying the outside 2×4 wall with 3.5″ of closed cell spray foam. He would also encapsulate the exposed ends of the studs. Then he would then fill in the remaining 4″ cavity with cellulose. The positives are the Rvalue jumps to 40.1or a 23% increase. I would also save the costs of a very expensive air barrier I would have to meticulously detail. The downside is the added costs of the spray foam. I am getting a tremendous discount on the closed cell foam.
Please don’t overthink the costs of global warming etc…Just looking into the potential downside of this application as it relates to the wall.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part