In San Francisco, where the city’s patchwork of microclimates deliver weather that is almost always moderate, upgrading the energy efficiency performance of a home to net-zero can include any number of strategies.
One NZE project in the city that attracted attention over the summer involves the renovation of a Queen Anne Victorian in Noe Valley, a relatively sunny residential neighborhood in the east-central part of town. Barbara Shands, a principal with LSarc, a San Francisco architecture firm working on the remodel, updated GBA with details about improvements that are expected to make the house one of the very first in the city to operate at net zero energy.
Plans call for retention of the front faÃ§ade, the building’s sidewalls (both of which abut the property line), the first 14 ft. 6 in. of original roof framing, and the floor framing. About 1,375 sq. ft. of the original floor space will be kept intact, although next year when the renovation is completed the interior space will total 2,424 sq. ft. Any dismantled framing lumber is expected to be reused where demolition occurs, Shands noted.
Leaning on solar energy
The house will be equipped with an 8-kW solar power installation on the roof (the owner has been in the solar power business for about 20 years, according to LSarc). The floors will feature inch-thick Gyp-Crete underlayment with radiant tubing heated by a 2/3-ton electric heat pump and through solar gain at the front of the house, which faces south. The floors at the north end will be finished with wood while those in the front section, where Marvin High-R Tripane wood-frame windows will help fill the faÃ§ade, will be finished with a thin layer of concrete to maximize the solar gain.
The R-19 walls and R-40 roof will be insulated with BioBased spray foam. The renovation also includes a three-story stairwell, topped with skylights that can be opened to create a ventilation stack for the interior. (Although the Bay Area’s inland regions may bake in 90°F heat during the summer, temperatures in San Francisco rarely exceed 80°F, which means very few houses in the city are equipped with air conditioners.)
A second heat pump will provide domestic hot water, LSarc says, and LED fixtures and high-efficiency appliances will be installed to lower the total electrical load. The property also will include a graywater reclamation system designed to provide irrigation for a vegetable garden and drought-tolerant landscape.