At the David and Lucile Packard Foundation headquarters in Los Altos, California, more than 900 rooftop solar panels produce electricity. Inside the LEED Platinum-certified building, a chilled beam system supports energy-efficient heating and cooling.
Those features and more play a role in making the 49,000-square-foot facility one of roughly 500 documented zero net energy (ZNE) buildings in the United States. To qualify as ZNE, a building can use only as much energy as can be produced on-site via renewable sources, such as solar power and wind energy.
The ZNE approach is gaining momentum across the country as owners and developers face pressure from regulators and the market to supply new construction and retrofits that are more energy efficient. Contractors can play a major role in helping projects qualify for ZNE status by collaborating with clients to design more energy-efficient HVAC systems.
Energy efficiency is gaining momentum
The Packard building is running ahead of the curve in California, where energy code requirements now state that any new building built after 2030 must conform to net zero standards.
In the residential sector, the number of zero net energy homes in the U.S., is projected to climb from 750 in 2015 to roughly 27,000 in 2025, according to projections from market research firm Navigant Research. Mandates along the lines of the University of Hawaii’s pledge to achieve net zero energy consumption by 2035 are becoming increasingly common.
“Plus, [developers] are finding that tenants want to live or work in a sustainable building and, therefore, will pay a higher rent to do so because they can also attract better talent for their employees,” says Angela Simon, SMACNA’s secretary-treasurer and president of Western Allied Mechanical Inc., a SMACNA contractor based in California’s Bay Area.
Western Allied Mechanical served as the installing mechanical contractor for the Packard Foundation headquarters’ HVAC system, and was responsible for the HVAC system, chilled and hot water systems, radiant floor system, and chilled panel system. Western Allied Mechanical also carried the controls contractor under its contract.
Simon notes that the HVAC system installed at the Packard Foundation building differs from standard systems because it doesn’t use natural gas. Instead, the system uses a reverse-cycle heat pump and incorporates chilled beams, radiant panels, and in-floor radiant heating and cooling. Chillers in the mechanical room cool water at night and store it in a 25,000-gallon storage tank in the ground. During the day, the HVAC system uses the water from the tank, and the chillers bring the storage temperature in the tank back down at night.
Taking a seat at the table to influence systems design
According to sustainability consultant Jerry Yudelson, efforts to achieve ZNE should start with cutting energy use via more efficient mechanical systems, better insulation and similar design measures. That applies directly to mechanical contractors involved in designing and building air conditioning systems within the buildings.
For design-build projects in which subcontractors are collaborating with general contractors on the design of a building, sheet metal and air conditioning contractors have more opportunities to provide input on the design of the HVAC systems, according to Yudelson.
More importantly, he says, subcontractors can gain a better understanding of design-build projects’ cost structures and how HVAC systems fit within the larger context of achieving ZNE for the building. Naturally, the costs of the technologies involved in attaining ZNE status can spook some builders, so that kind of insight is necessary to determine the tradeoffs that may be required to implement more efficient—and pricier—HVAC systems.
“If you know this is a net zero project, make sure you have a seat at the table during the design process,” Yudelson advises. “Then you will have the most influence on something that you can actually build for the budget that you’re going to be given.”
Simon says her firm has fielded questions from builders and designers regarding occupants’ comfort in ZNE buildings. She admits that occupants will likely have to learn to live with higher temperatures, noting that the “high performance building standards” attached to one of Western Allied’s design projects for the U.S. Department of Energy called for room air temperature of 78 degrees.
Additionally, Simon says clients have expressed concerns about the longevity of energy efficient systems, many of which have detailed control systems and require diligent maintenance.
In terms of ensuring that ZNE projects are successful, Simon recommends educating field personnel on the rationale governing the design of specific HVAC systems. “Often, they are very different, and the duct design is critical,” she says. For field personnel, that means asking questions ahead of time to make sure any changes to a system are consistent with the purpose behind its design. Additionally, commissioning at the end of projects and recommissioning every year are both critical, according to Simon.