Passive Progressive: A bamboo-clad passive house outside of Paris breaks free from local tradition.
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Architects Milena Karanesheva and Mischa Witzmann’s bamboo-clad passive house in Bessancourt, France, 20 miles northwest of Paris, has lured architectural tourists, locals, film crews, and friends of friends. They’ve come around to marvel at its presence in a town where 12th- and 13th-century structures along dense, narrow streets and courtyards trump modern design. As improbable as the house is, located between a historic district and small residences from the ’70s and ’80s, and as challenging as it was to build, it has helped promote the passive house ethos in a country that has been slower than others in Europe to adopt it.
When it was completed in 2009, the officially named Passive House was the second in France and the first in the Paris region. Since then, Karanesheva and Witzmann, wife and husband who founded their Paris-based firm Karawitz Architecture in 2005, have designed about seven passive houses. All except for two are in various stages of construction and completion. And in February, Karawitz was seeking a building permit for a coop apartment building in Paris that will use the passive house tenets.
The 1,900-square-foot, two-story bamboo Passive House is technically and programmatically straightforward, in large part because of strict local regulations and old civil codes, explains Karanesheva. They required a sloped roof and limited windows for intimacy and privacy. “We are modern architects—we are not from the 18th century. For us it was very important to make it contemporary,” says Karanesheva. She and Witzmann accomplished that by abstracting the traditional form.
A nearly 2-foot-wide “spine” splits the simple rectangle in two. The south-facing section of the house, where most of the openings are, is twice the size of the north-facing section. The kitchen and living room face the south on the ground floor; three bedrooms and a play area face the south on the second floor. Bathrooms and a laundry room face the north. The spine opens at two points, serves as load-bearing support, and hides mechanicals. A metal lattice walkway on the southern facade of the second floor doubles as a balcony and supports window shutters.
After contemplating dozens of types of wood cladding, Karanesheva and Witzmann chose bamboo for its airy quality and irregularity. “As the house was compact, it was important that the skin be very light, that you could look through it,” remarks Karanesheva. In Europe, there are few projects using bamboo, and cladding a home with the hollow stems gave it a more noble purpose. It was also less expensive than wood.
The relative simplicity of the house, however, belies the bureaucratic and technical struggles the architects endured to realize it. Karanesheva, who is Bulgarian, and Witzmann, who is Austrian and German, were familiar with the passive house concepts. The performance certification has roots in homes built across North America in the 1970s during the oil crisis, and was formalized in Germany in 1996, when Dr. Wolfgang Feist (see Feist’s Physics, p. 21 in the January/February 2011 issue) founded the PassivHaus Institut. But when the architects searched for a client to finance their prototype in France, they were met with doubts about its functionality and sometimes laughter.
“It was hopeless,” says Karanesheva. At the same time, their family needs were changing and they decided to build the house for themselves.
The site was an important factor—Karanesheva didn’t want to rely on a car, so the house had to be near the local rail station and amenities. A well-oriented spot just behind a church from the 12th century was perfect, but a local decision-making body in charge of protecting monuments initially resisted Karawitz’s design. Bamboo? Photovoltaics? Absolutely not. After many exchanges, the group’s skepticism turned into support, but not without some setbacks along the way. (Now even the local mayor is a fan.)
Simultaneously, Karanesheva and Witzmann had to find carpenters who could conform to the precise air tightness specifications necessary for passive houses—a rarity in France, where most builders are masons. With a carpenter from Brittany and a Paris-based firm specializing in sustainable construction in place, the project became a success.
“We thought, ‘Well, a house without heating could be a problem,’” says Karanesheva, but “I was surprised how comfortable it is.” When it’s sunny, the temperature in the house rises quickly, with only 0.48 air changes per hour and a heat recovery rate of 76 percent. The architects were in luck when it came to the triple-glazed windows as a local firm had just begun to supply them. While the ideal passive house should have less glazing, “our house has quite a lot of glazing proportional to the ground floor and envelope, but that’s because we like it,” comments Karanesheva.
The result is an elegant, modern take-off on the local barns of the Ile-de-France region, and a prototype against the odds. “It shows that it is possible, that costs are not higher than normal construction costs, and that it works,” says Karanesheva.
Laura Raskin is an editorial assistant at Architectural Record and a writer based in Brooklyn, New York.