Sonoma Sophisticate

Passive solar design with a microchip. That’s how Dietmar Lorenz describes the Sonoma Family Farm, one of the most recent and most imaginative residential project from Daniel Smith & Associates Architects (DSA Architects), where Lorenz is an associate.

The people at DSA Architects have been designing high-performing homes in California for 30 years and have always had an interest in passive strategies as a method to address energy use. The addition of active elements, mechanical systems, and how those two are integrated is what takes the Sonoma project to the next level. The project is registered under LEED for Homes and is aiming for a Platinum certification, but it turns out that there isn’t room in the rating system to account for all of the project’s innovations and its exemplary performance.

Sonoma Valley is known for the mild climate that facilitated the emergence of the California wine industry. While there are periods of severe temperatures, sunny winters make a natural environment for successful passive-solar homes, and summer heat can be mitigated with night venting. With this Sonoma site, Dan Smith, a principal at DSA Architects was interested in taking the performance of the project beyond what could be described as merely ‘efficient.’ “We are aiming to offset all the energy use, not just the heating and cooling but the entire plug load and domestic hot water as well,” Smith says. “Our goal is net-zero operating energy.”

In addition, DSA Architects always considers ‘embodied energy,’ the energy intensity of building materials and the construction itself. “These ideas have been around for a long time, but it takes dedication to do it right,” Smith says. “It takes idealistic and committed clients to go the whole way. The last push is tough, but we want to enable people to get to that level.” This required the integration of sophisticated technology with passive solar ideals all while maintaining a level of creative and aesthetic continuity. “A lot of effort went into making the buildings comfortable and beautiful but understated,” Lorenz says. “Everything rides simply on the land, but it also has very sophisticated solar engineering and technology.”

On the site are three main structures: the primary residence, a pool house, and a guesthouse. A barn and caretaker cottage are clustered nearby; the spaces are split so that each doesn’t have to be conditioned when not in use. All primary living spaces were laid out to take full advantage of the passive solar design; in addition to the 14-kilowatt photovoltaic array on the roof of the main house, the south-facing pool house roof is covered with 12 Heliodyne solar collectors that capture heat for domestic hot water, pool heating, and in-floor heating. The main residence also features automated natural ventilation; when the night temperature is cool enough, the transom windows automatically open and flush the building with cool air.

The building site is situated between a pond and a creek, two bodies of water that played into the theme of the design. “The design concept places the buildings along a green pathway that connects the creek and the pond [by] casually grouping buildings,” Lorenz explains, “each responding to their unique settings.” The placement of the residence leaves the bulk of the land available for the organic farm, which, just like the residential grounds, will implement the highest water conservation standards and sustainable practices.

To protect the extensive living room glazing from the low afternoon sun, the trellis extends beyond the southwest corner of the living roof.

Much of the project was designed with a California vernacular, utilizing open-air spaces, blending the indoors with the outdoors, and using a rural typology of simple gable roofs. A connective walkway is covered with a living roof, which “becomes the ligament connecting the buildings together and defining the circulation space,” Smith says.

For water conservation, an abandoned pool has been converted into a 20,000-gallon cistern, which is dedicated to living-roof irrigation and toilet flushing, while a greywater system directs shower water to supplement orchard irrigation. All interior trim and finishes were made from salvaged construction material, and the reconstituted doors come from salvaged Douglas fir.

“From the ground up there has been a comprehensive intention to mitigate environmental impact,” says Bruce Hammond, owner of Hammond & Company, the general contractor and homebuilder on the residence. Such an approach is in line with the company’s values; Hammond & Company was an early adopter of green building strategies—even by California standards—and claims among its credits a solar test home in 1982. “We’ve been very involved in green building both on the advocacy side and with the delivery of projects,” Hammond says. “It’s the language we live and breathe.” Sustainable material selection is also a trademark of interior designer Kathleen Navarra, principal at Navarra Design, who specified recycled content or salvaged components and kept an eye out for local production.

The project included various consultants and trades and frequently pushed the envelope. It was essential that all systems and materials be integrated within the style of the house. This, Smith says, is an exciting and ongoing challenge. “Architecture is the convergence of art and function,” he says. “Today there is a whole new set of things that a house is asked to do: ‘Be a net-zero . . . home. Fit into the landscape. What is a comfortable aesthetic for a net-zero house? How do you integrate it all?’ It’s a critical frontier for the design professions, and we find inspiration in this challenge.”