The Hidden Life of Green

Sustainable Features In Buildings Don't Have To Be Front And Center To Have A Meaningful Impact On Performance

Through daylight harvesting strategies, electrical systems also play an important role in energy conservation: all offices and classrooms will be equipped with both occupancy and daylight photosensors. The office sensors will turn electric lights on and off as needed while the classroom sensors will be linked to dimming system controls to provide a more graduated response to available natural light. Another unobtrusive strategy in the building is displacement ventilation. Here, conditioned air is provided at relatively low velocity in the lower portion of a room, instead of the more conventional high-velocity airflow from registers located near the ceiling. Displacement ventilation requires less energy, is quiet, and easy to control. Wyatt reports that initial energy modeling of the design predicts that the building will use 47.5 percent less energy than the standard set by ASHRAE 90.1-1999, all with technology that is fairly tried. true, and inconspicuous. He doesn’t believe that people entering the building, which is expected to be completed by the end of this year, will immediately think “green.”

Meanwhile, Bruner/Cott & Associates was asked by Vanderbilt University in Nashville, Tennessee, to design a high-performance dining facility that would fit into the school’s Peabody campus, which was originally built in the Georgian style in 1914 and was designated a National Historic Landmark in 1966. Recalls Simmons, “Everyone felt that the LEED buildings didn’t have to look different to get certified. Just doing a smart building with sensible features could get you there.” The university set out hoping for a LEED-certified rating for the Commons Dining Center, but Simmons thinks they will achieve Silver. Group Six Consulting in Atlanta served as environmental consultants on the project, which will be completed this spring.

The elevations present classic visages: symmetric facades clad with red brick on a limestone base; limestone pilasters, sills, and headers; cornices of glass-fiber-reinforced concrete; traditional glazing proportions; and painted steel standing seam roofs on corner towers. Site conditions and program required the building to have a compact massing. To increase natural light penetration into the large floor plate, the architects created a central atrium, which may not be traditional Georgian but reads on the exterior like a clerestory base of a classical dome.

The building’s most sustainable feature is a special exhaust system in the kitchen. In a standard commercial kitchen, fresh air that has been heated up to 55 degrees and blasted out of the multiple ventilation hoods is subsequently exhausted in large quantities. “This wastes a huge amount of energy,” he continues. At Vanderbilt, the mechanical system uses 30 to 40 percent less make-up air than the standard, because part of the make-up air is ducted into special jets that induce currents within the hood that capture a much greater percentage of smoke and grease-laden vapors from the cooking equipment, reducing the necessary volume of exhaust air normally required by code. The jet hoods also remove the convection heat generated by the cooking equipment below. Simmons estimates that this technology alone will reduce the total HVAC energy load by as much as 5 percent.

Simmons explains that although the exhaust system is a little more expensive than conventional models, the reduction in air requirements allowed them to downsize the overall HVAC system, so the total cost for the mechanical system was less than if they had specified a less expensive exhaust system up front. Although the technology is clearly high-tech, it is not very visible. “The outside viewer would never notice it,” adds Simmons. “Even the chefs may not notice, except it’s more quiet.”

Contributing editor Nancy B. Solomon, AIA, writes about sustainability, computer technology, building science, and other topics of interest to the building design profession.