Wayne, Pa. — Armed with the knowledge from building its first “green” elementary school, Radnor Township School District officials here decided to embark on an even more ambitious sustainable school project.
In some ways, the district was ahead of its time when it began the Radnor Elementary School's design process in 1998, prior to the release of the U.S. Green Building Council's Leadership in Energy and Environmental Design rating system.
Presently, district officials are seeking LEED-Gold certification after completing the district's new $48 million Radnor Middle School this year. Many of the elements that make the district's new school eligible for LEED certification are a residual effect of the community's forward thinking, according to Leo Bernabei, the school district's director of operations.
“The community and school district's interest is in supplying the best possible learning environment for the students and staff and to be environmentally responsive to the larger community more so than achieving any certification or getting any plaques,” Bernabei said.
Having energy efficient mechanical systems that save money in the long run also had an impact.
“One of the things that was offered by the construction manager as a big way to reduce the (middle school's) cost was to go to a more conventional system,” said Raymond Johnson, corporate principal of Concord Engineering Group. “The school district did not want to even entertain it because their operating costs (at the elementary school) were so low in comparison with their other buildings.”
Bernabei estimated the geothermal system at the four-story, 195,000-sq-ft. middle school has reduced operating costs from $1.50 per sq. ft. to $1.16 per sq. ft.
Like the district's elementary school, the new middle school's geothermal heating and cooling system circulates water in a closed-loop pipe system, using the earth's constant temperature of 55°F. Yet unlike the elementary school, which required a 60-well system, water at the middle school circulates through 144 wells that are 500 ft. underground.
The water then enters a system of 137 water source heat pumps that provide either heating or cooling depending on the time of year, according to Tim Moyer, project manager with Worth and Company.
A somewhat unique design feature used to facilitate maintenance is a closet for the heat pumps, according to Johnson. The closets, which open into the school's corridor, are next to the entrances of each classroom. Within the closet is the vertical heat pump on a stand, ducted into the ceiling of the room. The return air grille is in the back wall of the closet, communicating to the room.
Although the closet occupies approximately 16 sq. ft. of floor space, the maintenance benefits are significant, according to Johnson. The school's maintenance personnel can access components such as branch piping, condensate drain, disconnect switch, control box, volume dampers and filters through the closet door without disturbing the room's occupants.
But perhaps the most important feature of the school's geothermal system for the community is its ability to maintain high indoor air quality levels. The school district demanded high levels of indoor air quality after previously closing a school due to mold problems, according to Bernabei.
In order to improve indoor air quality and overall comfort, designers of the HVAC system decoupled the system's ventilation from heating and cooling, creating a separate system to provide fresh air throughout the building, Johnson said.
In addition to regulating space temperature, the middle school's HVAC system controls the building's humidity, according to Johnson. The system caps the humidity level at a set point of 60% relative humidity, he said.
Attention to detail also was necessary when installing the school's geothermal heating and cooling system, according to Moyer. While installing such a system may in some ways be simpler than a standard hot water/chilled water project, Moyer made sure not to overlook a step.
“One of the only negatives if you're a contractor who has not done a heat pump project before is you have to be very careful with the infiltration of dirt or dust in the piping,” Moyer said. “Water source heat pumps are very finicky with any particles in the water, so you have to do an extensive flushing and cleaning of the systems prior to startup.”