When workers need to insulate the walls and roof of an existing building with exterior rigid foam, it often makes sense to cut off the roof overhangs first. With the eaves and rakes removed, wrapping the building in rigid foam is a snap. The missing roof overhangs can later be rebuilt by scabbing the necessary framing on the outside of the foam.
First described by Brian Marshall and Robert Argue in a 1981 book, The Superinsulated Retrofit Book, this method was dubbed the “chainsaw retrofit” technique by Rob Dumont and Harold Orr, the superinsulation pioneers who cut off the eaves and rakes of a ranch house at 31 Deborah Crescent in Saskatoon in the summer of 1982.
Although Orr refers to the Deborah Crescent project as a “chainsaw retrofit,” he admits that they never used a chainsaw on the job. “We used a circular saw to cut the framing — the cut was about 2 1/2 inches deep,” Orr told me. “We finished the cuts with a handsaw.”
In search of a real chainsaw retrofit
While attending the recent NESEA conference in Boston, I ran into Christian Corson, the builder responsible for a celebrated Passivhaus in Knox, Maine. Corson told me that he was now working on a chainsaw retrofit project.
“Have you finished cutting off the eaves yet?” I asked Christian.
“No, we’ve just started the job,” he told me.
“I’ve always wanted a photo of a builder tackling a chainsaw retrofit with an actual chainsaw,” I told Christian. “How about using a chainsaw and sending me the photos?”
Get out the Stihl
Like most Maine builders, Corson has a chainsaw, and he was happy to oblige. Corson recently sent me an e-mail that opened with two rhetorical quesitons: “Is it 1982, Saskatoon, Saskatchewan? Or 2012, Northport, Maine? Here are some pictures of…