Net zero energy (NZE) projects represent a pinnacle of ambition for green building design, yet certified NZE buildings are still rare. With California leading the nation in renewable energy investments—and the State providing $3.2 billion in subsidies for residential and commercial near-zero energy buildings—what are the opportunities and challenges for implementing more projects that balance energy generation with consumption?
On the positive side, cost premiums for NZE projects appear to be leveling off. “When embarking on a new net zero energy construction, most people worry about cost,” says Tyler Bradshaw, Principal at Integral Group, an Oakland engineering firm specializing in energy efficiency strategies. “But thanks to the tax cuts implemented for net zero energy buildings in the last decade and the lower cost of solar and wind technology, the overall cost of construction is very close to a regular, grid-dependent building. Photovoltaics, of course, will probably always be a significant additional cost for projects pursuing NZE.”
NZE buildings rely on exceptional energy conservation and on-site renewables (generally solar, wind, or geothermal) to meet all needs for heating, cooling, and electricity. To qualify for Net Zero Energy Building Certification by the International Living Future Institute/Living Building Challenge, buildings must demonstrate net zero performance for at least one year. Recent California examples highlight the importance of integrated design, with coordination of architectural, engineering, and landscape strategies to meet these high standards.
The University of California at Davis West Village—the largest net zero energy development of its kind in the U.S.—employs integrated design in all levels of planning, design and implementation. The $280 million, 200-acre campus expansion meets energy demands through a combination of extensive on-site solar power generation and effective site planning, landscape design, and building energy efficiency measures. Energy efficient appliances and optimized solar orientation in site design have resulted in a reduced energy load that surpasses current building standards by more than 50 percent. The University of California at Davis and its development partner, West Village Community Partnership LLC, worked with SWA Group’s Sausalito office for site planning and landscape, and several architectural firms, to coordinate best energy practices for site infrastructure, buildings, and outdoor spaces. West Village Community Partnership reports seeing significant results and progress toward the overall project goals of energy self-sufficiency, thanks to coordinated efforts among Davis Energy Group, PG&E, SunPower, and in-house expertise at the University of California at Davis.
In Los Altos, the LEED Platinum David and Lucile Packard Foundation Headquarters highlights the importance of passive solar building design and passive cooling to reduce electrical demands. Designed by EHDD and Sherwood Design Engineers, the 49,000-square foot headquarters uses passive, bioclimatic design strategies to achieve high-energy performance for lighting, heating, and cooling. The design achieved a 65 percent energy use reduction through exceptional daylighting, enhanced envelope design, highly efficient HVAC systems, and an innovative effort to cut plug load energy in half. Sensors dim electric lighting automatically when daylight levels suffice and control under-counter LED task lights at each desk. These and similar measures, combined with a 285kw photovoltaic system, allow the building to satisfy its yearly energy demand on site. “At the time of this writing,” say Marc L’Italien, Principal at EHDD, “the Foundation has been operational for ten months. The data has been trending positive so, given the fact that we’re entering the warmer season, we have no reason to believe they won’t meet the net zero goal.”
Building retrofits, which currently account for approximately 61% of all construction each year nationwide, can be tougher than new construction. San Francisco’s newly opened Exploratorium, designed by EHDD and Integral Group, is on track to become the nation’s largest NZE building. “For the Exploratorium, we incorporated a large existing landmark building and had to retain its envelope,” says Integral Group’s Bradshaw. “This complicated our strategy tremendously. Historic materials, window frames and structures simply do not perform as efficiently as modern technology.” Marc L’Italien of EHDD points out the importance of ongoing monitoring for continued net zero performance. “You can no longer just hand over the keys at the end of a construction project. In the case of Exploratorium, we built an accurate energy model based on their current operation. In the final project, we established over 2000 monitoring points throughout the building to track progress.”
For the 6,560-square foot IDeAs Z2 Design Facility in San Jose, one of the first projects to be certified as Net Zero Energy by the International Living Future Institute, Integral Group worked with EHDD on customized features for renovation of a 1960s windowless concrete cube building, formerly used as a branch bank. A roof integrated PV membrane, consisting of highly efficient SunPower A-300 mono-crystalline solar cells, and a PV laminated glass entry canopy provide the necessary energy for the new facility. Customized features reduce energy load to less than one fourth the energy of a typical U.S. office; these including daylighting through oversized skylights that are sloped to reduce shading on the solar panels, radiant heating/cooling with a ground-source heat pump system, and high energy performance lighting and computing, with workstations equipped with occupancy-controlled power strips.
In San Leandro, California, a new Zero Net Energy Training Center also represents a retrofit of an existing building. The 46,000-square-foot tenant improvement project for the International Brotherhood of Electrical Workers Local Union 595 incorporates 45-foot tall windmills and a solar tracking “tree” to produce 139 kilowatts AC of power, or 10% higher than needed to serve the building at full capacity; this compares to 550 kilowatts for a similar commercial building without energy conservation measures. The design by FCGA Architecture and Environmental Building Strategies updates the building’s 1980s shell with automated lighting and ventilation systems, reducing the building’s estimated CO2 output by 175 tons per year.
In contrast to low scale buildings, higher density projects—especially multi-story buildings with multiple tenants—present more serious limitations for achieving net zero through onsite solar, wind, or geothermal energy sources. Taller building offer more limited surface for photovoltaic panels and wind turbines. Urban skylines reduce solar exposure, and city regulations often restrict the use of wind turbines. “Granted the right site conditions and amount of roof surface, it’s relatively easy to do a single-story net zero energy building,” says Bradshaw. “Two stories are much harder. Three become prohibitively difficult. Some buildings in tight urban spaces need to collect their energy off-site.”
As an example, Hines is currently building La Jolla Commons Tower II, a 415,000-square foot, 13-story Class A office tower in San Diego, designed by AECOM, that will become the nation’s largest carbon-neutral office building to date. The project utilizes a combination of high-performance building design, directed biogas (which may be captured from wastewater treatment or landfills), and onsite fuel cells to convert methane into electricity in a non-combustion process, generating approximately 5.0 million KWh of electricity annually. Bloom Energy designed and manufactured the fuel cells and WSP Flack + Kurtz provided engineering services for the project, which is seeking LEED Platinum certification. A five-year payback on the energy system is anticipated, and Hines hopes to extend fuel cell technology to additional properties in urban and less temperate locations.
While these technologies may be penciling out for commercial buildings or large-scale communities like West Village, California laws complicate prospects for smaller scale residential development. In order to facilitate use of renewable energy sources, the State’s 1996 Net Energy Metering bill allows customers with solar systems or wind turbines to sell electricity to utility providers at market rates. Commercial use buildings can connect the meters of several units to one single utility company meter, simplifying the calculation of electricity credits/debts significantly. This law does not apply to residential buildings, however; instead, each resident must have a separate meter connection to the utility company and to the solar panels/wind turbines, making multi-dwelling net zero projects more cumbersome to operate and less competitive on the market. Additionally, the performance of NZE buildings relies on the behavior of its users. While the staff of a commercial or business facility can be easily trained and monitored, the same is not true for multiple tenants of a residential or commercial building.
California’s ideal climate and forward-looking businesses promise a bright future for net zero energy projects. As technologies and policies evolve, NZE targets will continue to offer the tantalizing prize of renewable energy generation tied to sustainable, innovative design.