The sign in the Whitmore Lake High School gymnasium says "The Home of the Trojans." Just like the Trojans of Homer's Iliad, these Trojans of Michigan have constructed an edifice to be envied. The new 150,000-square-foot high school, which opened in August 2006, is one of the first high schools in Michigan to achieve LEED® certification (Silver). Among its many sustainable features, a geoexchange system for heating, ventilating and air conditioning (HVAC) includes 67 McQuay water source heat pumps. The 430-ton HVAC system delivers conditioned air to classrooms and other spaces, helping to reduce energy costs by an estimated 35 percent compared to a conventional system.
A need to distinguish
Whitmore Lake High School, the only high school in the school district located near Ann Arbor, serves about 420 students in grades nine through 12. One of the project goals was to build an exceptional school that would stand out in the community. "There are several private schools in the area that local students could choose to attend," said Tom Dekeyser, principal of Whitmore Lake High School. "Plus, Ann Arbor public school students can choose to attend Whitmore Lake because we're so close. So we wanted to put our best foot forward and show that Whitmore Lake can make a difference. Achieving LEED certification was one way to distinguish ourselves, and we decided we wouldn't settle for anything less than LEED Silver. In fact, it was non-negotiable."
In addition to being a community icon, school officials wanted to minimize operating costs-especially as the cost of natural gas began to rise during the planning stages. The school board recognized that any additional first costs for the geoexchange system would be offset by the savings in energy costs. As a result of their foresight, the school anticipates saving about $80,000 per year. In the first year alone, that's more than double the added cost to construct the geoexchange system versus a conventional HVAC system.
Combination pond and horizontal loop system improve heat transfer
Although geoexchange systems reduce energy costs compared to traditional systems, Whitmore Lake's geoexchange system goes even farther by combining a horizontal loop and pond system. Approximately 47 miles of pipe are laid in a horizontal field and a 15-acre pond. The system has two horizontal layers of piping trenches dug eight feet deep. The top pipe is six feet below the surface and loops back with the second pipe two feet below that.
"We could have put the whole pipe system in one horizontal field, and still had an efficient system," said Bob Roop, mechanical engineer with Peter Basso & Associates. "We had plenty of real estate. But we had to create the pond to provide storm water retention and a fire protection water supply. The water in the ponds is a better heat transfer media than the soil, so we took advantage of what we had to construct anyway to further improve the efficiency of the geoexchange system."
Energy recovery systems are key to supplying heat on cold winter days
"When Whitmore Lake told us they wanted LEED certification, we did some comparative cost information and came back with some favorable numbers for a geoexchange system,"said Roop. "Our boiler tower systems consume about 28 percent less energy than traditional systems; we expect that Whitmore Lake, with its geoexchange system, to be about 33 percent less in energy consumption compared to a conventional building. Those numbers, combined with the ample real estate available, convinced school officials to go ahead with the system."
All of the McQuay geoexchange heat pumps, located throughout the school, are fed a pre-treated, measured amount of outside air from one of two pre-packaged energy recovery units. "All of the relief air from the building goes through the energy recovery unit," said Roop. "It has a plate-type heat exchanger and pretreats all the outside air. It maintains a discharge air temperature in winter of 60 degrees, so all of the outside air is pre-treated to 60 degrees.
"The 67 individual water source heat pumps are basically responsible for space tempering, and don't have to deal with the outside air load. We've found this to be very successful for supplying heat in a northern climate in the dead of winter. This is integral to all of our designs for the past 10 years; it's a keystone for making these systems more energy efficient."
McQuay water source heat pumps help meet LEED requirements
Working with Thermal-Netics, the McQuay representative firm, Roop and his team chose McQuay EnfinityTM water source heat pumps to help meet the requirements for efficient, reliable operation. Each McQuay unit responds only to the heating or cooling load of the individual zone it serves, whether it's a classroom or the natatorium. This provides excellent comfort levels for occupants, better control of energy use and lower seasonal operating costs. To help meet heating loads in the winter, a coaxial heat exchanger is designed for maximum heat transfer with minimum pressure drop. A high-efficiency motor and low-speed blower further reduce energy consumption. High energy-efficiency ratios (EER) and non-ozone-depleting R-410A refrigerant also helped to meet LEED requirements.
Creating a buzz in the community
With a specific goal in mind, the backing of the community, and an efficient HVAC system, Whitmore Lake has built its dream school. The school serves as a flagship for a growing community and a testament to their environmental mindset. Much like the Trojan's of Homer's Iliad, the Trojans of Whitmore Lake have an edifice worthy of an epic.
"Now that we've earned our LEED certification, the new school has created a buzz in the community; it has people excited," said Dekeyser. "Everyone from members of the community to prospective students and visiting sports teams are witnessing what Whitmore Lake has to offer. We're very pleased with the result."