Net Zero Cottage San Francisco, CA


On the rooftop of Zero Cottage you’ll find a garden flourishing in discarded motorcycle tires.

Image credit: Matthew Millman

In its first year alone, Zero Cottage has produced 22% more energy than it consumes.

Image credit: Matthew Millman

Architect David Baker says, “Net zero must fit into the overall framework and become integrated into the culture as a whole.”

Image credit: Matthew Millman

A heat-recovery ventilation system (HRV) uses heat generated from cooking, showering, and appliances to warm up the interior.

Image credit: Matthew Millman


Architect David Baker’s new hyper-sustainable San Francisco home pushes the boundaries of building green while providing a model for suburban and urban projects alike. Proving that good design can be smart, attractive, and perfectly suited to its site, the house has achieved the highest possible green building ratings: Passive House, Net Zero, and LEED Platinum. Says Baker of the home he shares with partner Yosh Asato. “Everything about this was an opportunity to try.”

Slotted into the bustling, dense Mission District neighborhood, the mixed-use site predates the 1906 earthquake. At the front of the lot sits a traditional Victorian that Baker turned into a two-level multipurpose space, with a community-oriented cultural event space called StoreFrontLab and a small rental studio below, and a two-bedroom rental apartment above. With permeable pavers diverting rain water from city sewers, solar hot water and electric fulfilling over half of the building’s needs, and thoughtful passive solar design overall, this building is carefully attuned to both the site and sustainability.

Yet the real centerpiece of the development is the home, named Zero Cottage, located at the other end of the lot on the site of a former stable. For Baker, whose firm David Baker Architects is known for its innovative, green projects, his home was his personal design lab. “You can only be so experimental with clients,” he said. “Here, I could inflict all my ideas on myself, it was really fun.”

Baker was guided by green certification standards. Passive House focuses on thermal energy, looking for tight, highly insulated buildings. Net Zero homes must generate at least as much energy as they are using and must demonstrate that after a year’s operation, and LEED Platinum requires that buildings meet a stringent series of checklist requirements.

A complex web of elements helps the house meet all three of these standards. Outside, the house is a simple rectangular form that is almost air tight, thanks to a layer of foam insulation that envelops the whole building, triple-glazed windows, and a heat-recovery ventilation system (HRV) that uses heat generated from cooking, showering, and appliances to warm up the interior. “The HRV means super-clean air, and the insulation keeps it quiet from traffic and outside noise,” says Baker. There is also a cantilevered solar canopy on the roof, a custom rain screen, a solar hot water heater, and salvaged metal tiles used as siding.

Inside the lofted top two floors of the 712-square-foot living space (the bottom floor is Baker’s 430-square-foot workshop), the details are similarly well considered. Salvaged wood floors are finished with flaxseed oil, low-energy appliances abound, and slender windows let in natural light while providing privacy from neighbors. There’s even a small door to the rooftop, where a garden of fava beans and black Czech hot peppers flourish in discarded motorcycle tires.

In its first year alone, the house has produced 22% more energy than it consumes. But can such an urban project be replicated in a suburban setting? “I wanted to show that I could make a net positive house in a super dense urban setting,” he explains. “Building net positive is easier in the suburbs, with more space to grow food, compost, have rain systems, solar systems, etc.”

Yet as Baker cautions, a net positive house where suburban sprawl necessitates use of a car “blows the carbon footprint out of the water.” So what’s the solution? As in so many other cases, we should look to smarter suburban planning where walkability and transit are part of the overall equation. “Net zero must fit into the overall framework and become integrated into the culture as a whole,” says Baker. “Looking back 50 years from now, the fact that this was even debated will seem amazing.”