HVAC CASE STUDY: THE WILLOW SCHOOL

Photos courtesy of Mitsubishi Electric Trane HVAC US (METUS)

Location: Gladwell, New Jersey
Architect: Farewell Architects
Engineer: Loring Consulting Engineers

The Project: The Willow School has a proud history of green building. In 2002, it built the first LEED Gold certified school building in the United States, and in 2007, the first LEED Platinum certified school building in New Jersey. Ever the pioneer, it wanted to up the ante for its new Health, Wellness, and Nutrition Center. This 20,000-square-foot building contains four classrooms, a faculty room, a movement area, a dining room, a commercial kitchen, health/wellness spaces, and a teaching kitchen—which further support the curriculum and mission of the school. Mark and Gretchen Biedron co-founded the Willow School. Mark Biedron commented on the thinking and process involved, stating, “With this project, we were focused on taking the Living Building Challenge (LBC). Being a ‘living building’ means, among other things, that everything in the building is 100 percent (solar-powered) electric.”

The Design: Michael Farewell, head designer at Farewell Architects, Princeton, New Jersey, was one of several professionals called in to meet this challenge. He designed the foundation of Willow’s energy efficiency: a high-performance envelope that he described as “a combination of effective machinery, where all of the energy is generated by solar panels on the roof. It is a whole package that saves energy without having to use any.”

Given the generated energy, it is no surprise that Biedron and his team compared an electric geothermal system and electric variable refrigerant flow (VRF) system to determine which would best meet Willow’s sustainability goals. Nitish Joy of Loring Consulting Engineers in Princeton was the lead mechanical engineer on the project. He said the selection process included “comparative data projections for each system [geothermal versus VRF] as paired with the super-insulated envelope. VRF was well ahead on net-zero efficiency.” Vin Farese, principal at Loring, noted that VRF solved an additional challenge: “As the LBC prohibited the use of fossil fuels in the building, the commercial kitchen had to be electric. That drove Willow toward selecting high-efficiency, electric heat pumps and using photovoltaic [panels] to offset the energy used.”

The inclusion of energy-recovery ventilation (ERV) units is another way that Willow has been able to further eliminate inefficiencies. When agreeable conditions make natural ventilation favorable—including having outdoor temperatures between 65 and 80 degrees Fahrenheit—a controls system prompts teachers and students to open classroom windows for outside air. Otherwise, the ERVs enable this new building to recover energy from exhaust air to simultaneously cool or heat outside ventilation air as it enters the building.

Learning from Design: Willow’s exceptional efficiency is easily illustrated inside the building’s Energy Gallery, where a touch-screen interface toggles between data from all energy systems inside the high-performance envelope. Biedron says, “We had to remain net zero or net positive. With solar panels and the electric systems, we were able to achieve this. A conventional facility built to code uses between 100–150 kBtu per square foot per year—but this building uses only 21 kBtu per square foot per year, including our commercial kitchen. If you remove the kitchen, it uses 15 kBtu per square foot per year. When people look at this building, they are looking at one of the most energy-efficient buildings in the country.”

Although the electric VRF systems can be conveniently stored in a space no bigger than a closet, Biedron wants their presence to be known. “Each of the classroom units is housed in a small closet at the back of the room. Indoor units for Think Spaces are in the Mezzanine, and condensers are on a concrete pad outside. We do not want to hide our units; in fact, we really try to open them up so anyone can come up and see them. We also have a whole page on our master touchscreen that shows the efficiency of our system so we can show people and inform them about VRF,” Biedron says.

The Results: In addition to this project earning LBC certification, Biedron is most enthusiastic about Willow being recognized as a Green Ribbon School. “We win so many awards for how green we are, but we also want to make sure that we are showcasing that same awareness for our academic rigor,” he says. The U.S. Department of Education introduced the Green Ribbon Program to recognize schools that provide strong academics and work to reduce environmental impact and improve the health of students and staff. Biedron says, “It is really the responsibility of the educational community to teach children how the planet works, why that is important, and how to use energy efficiently.