Off-the-Shelf Energy Efficiency Strategies Can Pay Big Dividends
The energy efficiency strategies employed in the retrofits on the nine office buildings were often off-the-shelf strategies. The "integrated design" strategy at the Beardmore included allowing the common spaces to be left without air conditioning to rely on natural convection technology. Barometric dampers were installed to exhaust rising warm air though the skylights in summer months and ceiling fans in the central stair atrium keep the building cool even as outdoor temperatures exceed 100 degrees. In the newer buildings profiled in the study, high-efficiency heating, ventilation and air-conditioning equipment was included in more than half.
Included in the retrofits for all of the buildings were high-efficiency lamps and ballasts. Seven out of nine incorporated daylight dimming controls within the lighting system. Of the most frequent measures applied, lighting-related measures, coupled with controls, ranked in three of the top five. "When looking at total energy consumed in commercial buildings, lighting is the largest individual use of power, accounting for 20 to 40 percent of the combined energy total," says Lyles. "As a result, lighting upgrades currently represent the most common and cost-effective improvements in existing buildings."
It's also one that tenants appreciate. Certainly, maintaining a high occupancy rate was a key motivation for improving energy efficiency at the 200 Market Building, a 19-story, 389,000-square-foot, high-rise built in 1973 in downtown Portland, Ore., that became the country's first LEED for Existing Buildings 2.0 Gold multi-tenant building. By utilizing a gross lease structure under which savings such as electrical and water usage go directly to net operating income, building owners have been able to pursue a number of major improvements, such as the reconfiguration of existing smoke evacuation shafts as fresh air intakes, which improved the ventilation rate by 70 percent, reduced fan and pump energy required to meet previous ventilation needs and provided free cooling.
In La Jolla, Calif., the Aventine Building, an 11-story, 253,000-square-foot, Class A office tower and adjacent six-story building constructed in 1990 also benefited by retrofits that addressed high-energy loads. A feasibility study had determined that upgrading a recently-installed chiller system to an all-variable-speed chiller plant with automated controls, while keeping two existing centrifugal chillers, would yield the greatest energy savings with the least capital investment. Upgrades included replacement of compressors with units that have VFDs and magnetic bearings and automated controls enabling chillers to communicate with each other, so that adjustments are made methodically, says building owner representative Carlos Santamaria.
Now certified at LEED Existing Building Platinum, the Aventine uses 23 kBtus/sf — 75 percent less than the national average for offices. "The transformation that occurred is a great story to demonstrate to others how they can turn an average building into an ultra-high efficient building," says Santamaria. "It just takes commitment, focused effort and, of course, making the right decisions with capital dollars."