Zoned comfort systems
Zoned comfort systems—such as unit ventilators, water source heat pumps, and fan coils—provide heating, cooling, and conditioning (e.g. humidity control by unit ventilators) to individual classrooms or zones. The advantage of a zoned comfort system is one unit can provide cooling to one space while another unit is providing heating to a different space. The units can be controlled so their space is not cooled or heated when not occupied—this helps reduce operating costs.
Central systems
Unlike zoned comfort systems, which control individual zones, a central system controls several zones (e.g. a block of classrooms, the administrative area, or the gymnasium). These systems condition air in a remote location, such as a mechanical room or on a roof, and distribute it through ductwork to the occupied spaces. Central systems can include air-handling units (AHUs) and chiller plants, rooftop systems, and vertical self-contained systems.
HVAC in action: Lakeshore Public School District
Located in Stevensville, along Lake Michigan in the southwestern region of the state, the Lakeshore Public School District consists of three K−5 elementary buildings, one middle school, and one high school. Nick White, director of operations for Lakeshore public schools, has orchestrated many changes at the five facilities, including broad HVAC upgrades improving both student and teacher comfort, as well as energy efficiency.
In 2013, White and the Lakeshore school board looked at options to enhance student achievement. It had been about 20 years since any of the schools had new heating equipment installed, and none of them had any form of air-conditioning.
“We would get daily complaints from teachers about the inconsistency of room heating. Students seated by old, under-the-window unit ventilators were either sweating or shivering,” said White. “In the mornings, the ventilators would be blasting heat and later, as the thermostat was satisfied, outside air was brought in to improve indoor air quality and student health.”
However, the fresh air entering the rooms became a textbook lesson in thermal shock. Cold air immediately conditioned students and teachers—the discomfort was so routine they knew to have their winter jackets nearby.
“Another issue that we would get regular complaints about was the noise of the units,” said White. “Teachers constantly had to yell to be heard over the incessant drone of the HVAC equipment.”
“Remember Charlie Brown’s teacher [with a voice like a muffled lullaby]? That’s how our teachers sounded to students before we got a new heating and cooling system; they couldn’t stay awake,” he said. “Our HVAC woes became a huge distraction.”
White contacted Scott Morgenstern, senior mechanical engineer for Kingscott Associates, an architectural and engineering firm based in Kalamazoo.
“Nick informed me the school district was looking to do a significant amount of renovating and remodeling in all of the schools,” explained Morgenstern. “The bulk of work to be funded was slated to improve classroom HVAC systems—replacing old unit ventilators with new, quiet, energy-efficient ones.”
“The old systems were not only noisy, but they weren’t providing sufficient air distribution,” he added. “They were basically oversized fan coil units that sat under classroom windows with the sole purpose of making life miserable for students and teachers alike.”
Overheating and underheating were sure to affect classroom conditions daily, and the discomfort was palpable. Outdoor conditions played an enormous role; another key variable was the location of a student’s chair. Teachers could move their desks, or walk about, but students were mostly unable to make improvements.
White and Morgenstern took a tour of nearby locations with unit ventilators already installed and running, as it always helps to demonstrate equipment operation. After further research into equipment capable of solving problems at the school district, they chose a system engineered specifically for classrooms.
“One of the first things that stuck out to me at the demo was the noise—or better, the lack of it,” said White. “We learned about the equipment’s impressive sound lab performance, but it was most impressive to see and hear the equipment during our tour. We were certain that we’d found the right technology for our schools.”
