Passive House Requires an Active Endeavor

By: Claire Trageser

Photos courtesy of Prospect Architecture

They might call the house “Passive,” but the effort required to insulate it is anything but

Early this fall, Martin Laskowski got a call from Jeremy Shannon, the lead architect at Brooklyn, New York-based Prospect Architecture, who had a challenging request. Shannon wanted Laskowski and his company, PolFoam, LLC, to boost the R-values of a renovated Brooklyn brownstone enough that it would qualify as a “Passive House.”

The “Passive” distinction is not easily earned. The concept, originally called Passivhaus when it began in Germany in the early 1990s, aims to use insulation so thick and airtight that the house will not need an internal heating source. To qualify, houses must have an air change per hour of less than 0.6 at a 50 Pascal pressure, an annual heat requirement of less than 4.75 kBtu per square foot per year (15 kWh/m2/year), and must use less than 38.1 kBtu per square foot per year (120 kWh/m2/year) in energy.

Although it takes a proactive effort to meet these strict standards, the name “Passive” is used because of the house’s minimal environmental impact.

As if those standards aren’t challenging enough, the fact that the brownstone is being renovated, not built from the ground up, adds even more obstacles.  The four-story landmark brownstone was built in Brooklyn’s Park Slope neighborhood in the 1890s and is protected by the Landmark Preservation District, which means that any visible alterations to the outside of the building must be approved by the Landmarks Preservation Commission. The building has a full cellar, 10-foot-9-inch (3.3 m) high ceilings, and original arched stained glass windows, all of which pose insulation issues. The renovation will be difficult, but it is also groundbreaking: This brownstone will be the very first Passive House townhouse retrofit happening in the United States.

Spray foam was a natural choice to help the building meet the Passive House standards, Shannon said.

“In New York City, space is a big issue, so getting as much R-value out of each inch is important,” he said. “The foam’s ability to act as an air barrier is also very important.”

Once the decision to use spray foam was made, Shannon needed to find the right SPF contractor. He had worked with unreliable contractors in the past, but then found Laskowski’s PolFoam on the Internet.

“I gave a price, they liked the price, so they said I got the job,” Laskowski said.

But soon after he landed the job, Laskowski encountered some problems. The first was a typical one for any resident of New York City: parking.

“It’s very hard to find a parking spot,” Laskowski said. “The only chance we get is on Mondays for street cleaning, when everyone has to move their cars from 9 to 10:30 a.m. We can park the truck and stay there the rest of the day.”

Using this schedule, Laskowski and his two-man crew only got a full day of work on Mondays, and also risked parking tickets.

“We take the spot before 9 a.m., even though we’re not supposed to park because of the street cleaning,” he said. “The meter maids and police don’t give us any problems since we’re there to do work. We haven’t gotten a ticket yet, but we should have. But this is my only chance for a spot, so I go for it.”

Once the crew had access to the building, they got to work. They began by spraying the front and back brick walls and 3 feet (0.9 m) of the party walls with 3.25 inches (8.3 cm) of Demilec’s HeatLok 217 closed-cell foam to produce an R-value of 21.5. They used a Graco E-30 proportioner, an Air Purge gun, 300 feet (91.4 m) of hose, a fusion gun and a 20-by-26-by-28-foot truck from Demilec.

Because the spray foam was closed-cell, it was trickier to work with, Laskowski said.

“It’s a lot denser than open-cell, so it’s more difficult to clean up overspray,” he said. “It’s a hard material to work with if you have to clean it and cut it off, since the material itself is somewhat hard.”

But overspray was sometimes necessary to be sure all the spaces were filled, especially in the building’s corners, Laskowski said.

“We had to shoot excessively to be sure all the gaps and holes were being filled,” he said. “We would spray a little too much, and when it expands, it comes out, so then we had to cut it off.”

To do this cutting, the crew used a 36-inch (0.9 m) Pneumatic Saw hooked up to an air compressor on top of the truck.

Because of the Passive House’s strict insulation requirements, filling all of those gaps and holes was especially important—so important, in fact, that Shannon called Laskowski back to the site after the first round of spraying was complete.

“It seems that SPF contractors don’t do quality analysis to the level required by the project, which is frustrating for us,” Shannon said. “This contractor is ultimately doing right by us, but we have to do a lot of following up.”
Shannon said all the rim joists were missed on the first pass, and the spray foam’s depth was not the uniform 3 inches (7.6 cm) he had specified.

To ensure that the foam was the right thickness, Shannon stuck 3-inch bamboo grilling skewers into the spray foam every few feet. If the bamboo stuck out past the foam, he knew it was too shallow.
“Because bamboo does not act as a thermal bridge, it can be left in place,” he said. “When the contractor comes back for the next spray, he can see where he’s low.”

Now that the walls satisfy Shannon’s standards, Laskowski will return for three more rounds of spraying. He’ll hit the window cavities, the basement walls, under the floor slab, and under the roof deck for the front and back cornices to complete the house’s airtight building envelope.

The job has been tricky, but so far Laskowski has been able to create the insulation that Shannon wanted and the Passive House community needed. And although the high-profile nature of the job adds additional stress for Laskowski, he said he is up to the challenge.

“Because this is the very first Passive House being done, they try to put a lot of pressure on our jobs,” he said. “We need to be nice and neat and clean, because a lot of pictures are being taken. I want my company to look extra clean and superb, basically.”

After the first round, Laskowski’s mission has been accomplished. But he will have to maintain an active effort to get the Passive House job done right.

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