Since 2012, architect, David Baker, and design communications consultant, Yosh Asato, have made their home in Zero Cottage, a 712-square foot home in the Mission District designed by Baker with the goal of achieving Net Zero Energy certification. According to Living-Future.org, Net Zero certified buildings are rare, and must be designed to harness “energy from the sun, wind or earth to exceed net annual demand.”
“The basic concept is that you need hardly any energy for heating or cooling because the house is so well-insulated,” Baker recently told the San Francisco Chronicle. Baker explained that the cottage uses an innovative 92% efficient Heat Recovery Ventilation (HRV) system, that extracts heat from day-to-day use, “heat that you generate—taking a shower, cooking, using your computer.” The HRV system then uses that extracted heat to “warm fresh, incoming air.” Baker said that after using the HRV system, he never wants to build another house without one. “It’s an amazing system,” he said. “It’s so quiet, you can’t tell you are in the middle of the city.”
Zero Cottage also makes use of sustainable materials, like reclaimed metal tiles and wood flooring. “We… incorporated wood flooring salvaged from a pasta factory,” Baker explained. “We didn’t sand the wood at all; we just treated it with a natural flaxseed oil finish, which lets all of the history show through.”
LED light fixtures help to reduce electricity usage in Zero Cottage. “We found some great LED lighting by Pablo Designs,” said Asato. Most of the lights in the home are dimmable, which helps reduce the total wattage used.
The cottage’s “green roof” incorporates solar energy with an organic garden for what Baker calls “an intensive multiuse space.” Baker’s website, DBArchitect.com, explains that the roof contains “vegetable planters, composting, solar electric generation panels, a passive solar hot water collector and storage system, and a passive solar roof monitor,” all within 430 square feet.
Zero Cottage was also designed to meet the Passive House requirements set by the Passive House Institute in Germany, which regulate space heating and cooling energy demand, airtightness and thermal comfort. Zero Cottage is the first Passive House certified home in San Francisco, but meeting these requirements has put some restraints on the design. “The Passive House standard limits the amount of window area you can have,” explained Asato. “The windows [in Zero Cottage] are carefully placed so we have light and views—a sense of being in the city—as well as privacy.”
Asato said that living in Zero Cottage has made the couple even more “resource-conscious,” noting that they “rarely use the dryer,” and regularly “work the house—opening or closing windows—to keep the house comfortable year-round.”