Despite tighter building codes and significant advances in building technology, buildings consume one-third of all energy in the United States at an annual cost of $200 billion, according to reports from the Lawrence Berkeley National Laboratory.
Commercial buildings alone consume about 15 percent of all energy at a cost of $85 billion each year, and half of this consumption is wasted in comparison to what is cost-effectively achievable.
“It’s a surprise to everybody, but, in order to have superior building performance, you need considerably less energy than standard practice,” says Volker Hartkopf, an architecture professor and director of The Center for Building Performance and Diagnostics (CBPD) at Carnegie Mellon University in Pittsburgh. “You can get away with one-fifth of energy required [for] best practices, currently 9 watts per square foot. We’re down to 0.20 (at the Robert L. Preger Intelligent Workplace, which houses the CBPD offices – see July 2002 Buildings, page 42). It’s not hard. We have daylight.”
Energy use can be streamlined in other areas to result in both efficiency and cost savings, too.
David Casavant of The Carlyle Consulting Group in Lake Worth, FL, notes the selection process of an HVAC system at the San Diego Department of General Services as a prime example.
The organization replaced the system, which was used to cool a 150,000-square-foot healthcare services complex in the city. The existing system was comprised of six 50-ton package units with 113 VAV boxes and controls. The selection team considered the following replacement options:
High-efficiency package units, similar to the existing system. Annual energy savings were projected at $149,970.
High-efficiency package units with variable frequency drive (VFD) upgrades. Annual energy savings were projected at $269,089.
Replace packaging units with chilled water system – water-cooled. Annual energy savings were projected at $340,098.
Replace package units with chilled water system – air-cooled. Annual energy savings were projected at $271,090.
Although options three and four provided the greatest energy savings, the installation of a cooling tower would be cost prohibitive, Casavant notes. “If the cooling tower were to be placed on the roof, costly structural enhancements would be required,” he explains. “Placing the tower at ground level would take away valuable parking spaces. That was determined not to be a good option as the parking situation was already ‘hostile.’”
As a result, according to Casavant, Option 2 – the air-conditioning units with the VFD upgrade – was selected. Additionally, the units selected offered both SA and RA fans as a standard feature.
Robin Suttell is contributing editor at Buildings magazine and based in Cleveland.