Buildings move faster toward net zero
Buildings move faster toward net zero
A new generation of high performance buildings are demonstrating they can attain net zero energy use over the course of a year.
But there is great debate over how they do it. Can they buy renewable energy credits to achieve net zero? Must they generate 100 percent of their power from renewables onsite? What about combustion, and is that truly net zero?
"There was a lot of confusion in the marketplace about what net zero really means," Amanda Sturgeon, vice president of the International Living Future Institute (ILFI), said last week during a panel discussion on net zero certification during the Institute's annual Living Future conference.
The Institute is known for administering the Living Building Challenge, formed in 2006 with the aim of being a more stringent approach to green building certification than USGBC's LEED certification. To be certified as a Living Building, a building must not only be net zero energy, but also net zero water and waste.
In response to the varying definitions of net zero energy, ILFI also created a Net Zero Energy Building Certification for net zero buildings in 2011. The first building to achieve Net Zero Certification was IDeAs Z2, the San Jose headquarters of engineering firm Integral Group.
Net Zero criteria
Net Zero and LBC certification require performance monitoring for a full year after occupancy. This verifies the building is truly operating as claimed, and is a value added for the client, according to the panel of architects and engineers pursuing imminent certification on these net zero projects. They include the David & Lucile Packard Foundation (pictured above), zHome residential development, Jackson Sustainable Winery, UC Davis and DPR Construction's Phoenix Regional Office.
All Living Buildings are automatically certified as Net Zero buildings, but not all buildings going for Net Zero Certification need to pursue Living Building status.
However, Net Zero certified projects must meet some of the non-energy requirements of the Living Building Challenge, including site, beauty and equity.
"We require net zero buildings not be built on ecologically sensitive sites," Sturgeon said.
They must also follow the rights to nature imperative so, for example, the buildings are not allowed to block someone else's solar access.
Image courtesy of EHDD.
Net zero is not just about energy; site and beauty are always important, Sturgeon said: "These buildings should still be beautiful and bring delight and inspiration and should have an educational component."
And yes, they must be 100 percent powered by renewable energy.
"Part of the reason for requiring renewable energy is that we're really trying to move the renewables marketplace forward," Sturgeon explained.
A focus on occupants
The energy requirement, however, does not need to be about adding an enormous number of solar panels or energy technology. For example, to reach net zero the Packard Foundation incorporates many passive features, such as natural ventilation, that not only reduce energy use but also increase occupant comfort and happiness in the space.
"When you talk with the users, they talk about the courtyard," according to Integral Group's Eric Soladay who, along with Peter Rumsey and the Integral team, designed the building's mechanical systems.
The courtyard, banked by two 40-foot wide office spaces on each side, is great for ventilation, along with the building's operable windows.
"We can turn off the mechanical ventilation a lot of the year," Soladay said. "Occupants can spend four to six months a year with only passive heating and cooling."
In addition to reducing the building's need for energy, the passive systems have the best resiliency.
"Active controls fail," Soladay said. "We can overdesign these systems so easily."
Rather than installing sensors and automation for the windows, the design team decided a staff member should be notified when it's time to open the windows. As a result, occupants are engaged.
"We have a sophisticated window control system," Soladay said. "They're called staff."
Other tricks of the trade
Daylighting also helps bring the building closer to its net zero goal.
"Forty feet wide is a great width for designing zero energy buildings," said Scott Shell of EHDD, the building's architect. "It provides great daylight and views for the building occupants.
Daylight from the courtyard on one side, plus skylights and indirect lighting from hallway windows provide bright light while helping control the glare. In this case, a computer automatically controls the shades for optimal daylighting.
"When you visit this building, the lights are off and the daylight feels wonderful inside," Shell said.
Another low-tech system in Packard's net zero strategy is the use of chilled beams for heating and cooling.
"Don't let anyone tell you that chilled beams are really complicated or hard to understand," Soladay said. "They are just unusual in our market. It's a coil and some nozzles that have air and water pumped to them. It's very simple."
In this case, the beams are completely hidden because the owner wanted a homey feel rather than the industrial feel of most open offices that show ductwork.
"You can't see one duct or pipe in this building," Soladay said. "We went to great pains to coordinate all this and to tuck away the ducts. That was a trick."
Reducing plug loads
Finally, the design team worked with the building occupants, who play a significant role in helping the building achieve and maintain its net zero performance. Initially, occupant energy choices reduced the plug loads by 58 percent. After the design team completed a detailed study of building plug use, the occupants are now responsible for something more like an 80 percent plug load reduction, Soladay said.
"They've so owned the idea that they're responsible for plug loads," Soladay said. "When they buy office equipment, they really look at the energy use."
This occupant awareness may be partly why the Packard Foundation was able to reach net zero energy use within nine months of occupancy. Given how conscientiously the foundation operates the building, the project team believes the building actually will be a net producer, even in its first year of operation. The Packard Foundation will be the fifth building to achieve ILFI's official Net Zero Certification.