It’s Not Easy Being Net-Zero
Forward-thinking building owners, such as PNC Bank, are constructing new net-zero energy buildings, but a blog posting on HPAC Engineering questions whether some of these buildings really live up to their name.
PNC Bank has opened a new branch in Fort Lauderdale, Fla., that the company says is a net-zero building that will produce as much energy as it consumes. The Fort Lauderdale branch features 211 solar panels, high-efficiency LED lights and EnergyStar appliances. PNC expects this branch to use 50 percent less energy than a typical bank branch and exceed Leadership in Energy and Environmental Design (LEED) Platinum certification.
The 4,900-sq-foot building is PNC’s 119th newly constructed, LEED-certified building. Many of the money-saving features at the Fort Lauderdale building will become standard in the next generation of PNC’s buildings. To develop the net-zero energy branch, PNC Bank collaborated with Gensler, a global design firm, and the Department of Energy as part of the DOE’s Net-Zero Energy Commercial Building Initiative, which aims to improve the energy efficiency of new and existing commercial buildings.
But the term “net-zero” may have been inaccurate in the past. One of the most celebrated net-zero buildings – The Adam Joseph Lewis Center for Environmental Studies on the campus of Oberlin College in Oberlin, Ohio – did not produce enough energy to serve its needs for the first 11 years of its existence, according to HPAC Engineering.
Inaccurate and even misleading calculations by the design team are cited for the initial failure of the building to achieve net-zero energy. Even after adding a solar parking pavilion to contribute more energy, the building still had to get some of its electricity from the local utility for the years 2000 to 2011. Other problems included balancing heating and cooling loads from the building’s ground-source-heat-pump system; the complexity of the building’s HVAC system and controls; some defective PV modules; and lack of a specific person to monitor the building’s energy management system and oversee corrections.
In 2012, the Adam Joseph Lewis Center for Environmental Studies did finally cross the zero-energy threshold. That was the same year Oberlin College had a full-time energy manager for the building.
Despite the challenges at Oberlin College, others push forward with the net-zero concept. Global Real Estate firm Hines is constructing a 13-story, 415,000-sq-foot building at La Jolla Commons in San Diego that will achieve carbon neutrality on an annual basis through a combination of high-performance building design, directed biogas and on-site fuel cells.
As for the new PNC Bank, in addition to solar panels, the branch will include:
Daylight and occupancy sensors: The branch uses photo-sensors that control dimmable light fixtures as natural sunlight increases and occupancy sensors that prompt lights and computer monitors to shut off automatically in unoccupied spaces.
Direct Current (DC) power: Solar panels send energy from the sun to a DC ceiling grid system that powers LED interior lighting. This direct transfer of energy prevents the energy loss that would normally occur when converting DC to alternating current (AC).
Solar shading: A canopy covers the building’s southern exposure to reflect sun during the hottest part of the day without preventing natural daylight from entering the building, resulting in reduced cooling costs.