A hundred million American homes need fixing. Could this be the ticket?
In a Twitter discussion about how we need to decarbonize a hundred million American homes, Professor Shelley L. Miller responded:
I have literally come to the conclusion that it will be cheaper in the end in so many ways to knock down all the leaky moldy badly built homes and rebuild than try to retrofit— Shelly L Miller (@ShellyMBoulder) September 21, 2018
But can these houses, in fact, be renovated instead of knocked down? Can they be insulated at a reasonable price? There have been a few attempts, with one of the most important being the first "chainsaw retrofit" in Saskatoon, Saskatchewan, in 1982. It was done by the late Rob Dumont and Harold Orr, the people behind the Saskatchewan Conservation House that was a Passivhaus pioneer.
As Martin Holladay of Green Building Advisor notes, there were two kinds of people working on energy conservation in the seventies and eighties: hippies and Canadians. While most of the American hippies were doing passive solar designs, the Canadians had a colder climate and not much sun, so they went for super insulation.
The first house Orr and Dumont renovated was a 1,200 square foot bungalow in Saskatoon. The first thing they did was cut off everything that hung out -- the soffits and eaves and overhangs. Dumont wrote:
In order to allow a continuous air-vapour barrier at the junction between the wall and roof, and to avoid having to wrap the existing eaves and overhangs, it was decided to remove the eaves and overhangs. To accomplish this, the plywood soffits were removed, and the shingles were removed from the eaves and overhangs. A power saw was then used to cut through the roof sheathing and part way through the roof truss eave projection and roof ladder in line with the outside of the existing wall of the house.
So how did it get to be called a 'chainsaw retrofit'? Martin Holladay writes:
As it turns out, the remodelers never used a chainsaw. “We used a circular saw to cut the framing — the cut was about 2 1/2 inches deep,” Orr told me recently. “We finished the cuts with a handsaw. When I started giving presentations about the house, numerous people said, ‘You should have used a chainsaw.’ So I started to call it the ‘chainsaw retrofit’ job.”
They then wrapped the house in 6 mil polyethylene sealed with acoustic sealant. The walls and roof were then framed out to allow for 8 inches of fiberglass insulation on the walls and roof, along with 4 inches inside the original studs.
The basement was also insulated and a heat recovery ventilator was added; you can get greater detail from Martin Holladay's article or the original report by Orr and Dumont to Canada's National Research Council.
They didn't have any of the high tech smart membranes or fancy foams, just basic old-school poly and fiberglass. But it worked:
This particular house, after retrofitting, proved to be the tightest house in Saskatchewan measured to date by the National Research Council. … The air leakage of the house as measured by pressure tests was reduced from 2.95 air changes per hour at 50 pascals to 0.29 at 50 pascals, a reduction of 90.1%. Before and after measurements were taken of the space heating requirements of the house. The design heat loss of the house was reduced from 13.1 kW at -34°C to 5.45 kW by the retrofit.
The retrofit cost US$ $18,230 in 1984 dollars, which the inflation calculator shows to be $44,240.82 today.
Reading Holladay's almost ten-year-old article, I am reminded again how little things have changed. Nate asks, "How are we going to decarbonize 100 million homes?" Holladay and Dumont discussed the same question.
The global climate crisis now compels our country to face a Herculean task — performing deep-energy retrofits on most existing buildings. “In construction, making decisions is not like solving a mathematical equation,” Dumont told me. “The economics are changing all the time: labor, materials, and energy costs always change. We have nine million existing dwellings in Canada, and over the next three decades I can see virtually all of them being retrofit.
As Holladay also noted, this works best for simple houses without a lot of bumps and jogs, but there are a lot of those. He concludes:
If you drive around your town with a “chainsaw retrofit” eye, as I do now, you’re likely to spot entire neighborhoods ripe for a skilled crew equipped with gas-powered Husqvarnas.
In Europe and more and more in North America, we beginning to see a modern high-tech version of the Chainsaw Retrofit, Energiesprong, where houses are wrapped in prefabricated insulation panels, complete with windows and doors.
It could be done, if anyone cared.