From the 1960s to the 1990s, HVAC systems in schools grew more sophisticated. Education institutions sought systems that conserved energy and helped improve indoor air quality.
When a building opens, systems usually operate as designed. As time goes by, they function less effectively. During the design of Red Wing High School, Red Wing, Minn., in the 1990s, life-cycle costing, value engineering and energy-conservation studies resulted in considerable cost savings:
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Rebates of $203,000 from the local utility company.
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Annual energy savings of $120,000.
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Preconditioning outside air during the heating season reduced the original boiler capacity requirements by 400 boiler horsepower and produced a first-cost savings of more than $500,000.
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Eliminating the need to install heating coils in the air-handling units resulted in an additional first-cost avoidance of $100,000.
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Reducing the size of chilled- and hot-water piping created more first-cost savings.
Mechanical equipment was situated close to acoustically critical spaces, such as the media center, classrooms, band, choir, orchestra hall and auditorium. Engineers worked with manufacturers and acoustical consultants to achieve the desired noise criterion (NC) levels. The HVAC system uses a mixed-flow-type fan design, which reduces airside noise by 20 decibels in the first two octave bands compared with conventional centrifugal fans. The system's round ductwork provides a 25-decibel reduction in duct breakout noise in the lower octave bands compared with regular ductwork. Integrating double-walled discharge plenums, the mixed-flow-type fans and the round ductwork allowed the school to eliminate almost all attenuators and achieve desired acoustic goals.
After several years of operation, the school adopted a new IAQ management plan to create a healthful environment. System maintenance became much more aggressive and frequent. All air filters in the district were changed from low- to medium-efficiency, or to high-efficiency HEPA filters (none of which use fiberglass). Pre-filters are used to extend the life of the HEPA filters.
As institutions upgrade HVAC systems with sophisticated equipment, the staff needs to be trained on proper operations and maintenance. Even after initial training, some staff members ignore proper procedures, which can lead to equipment problems. Training should include basic equipment operation, air-handling systems, energy recovery, heating systems, cooling systems, identifying problems, and operating computers for energy-management systems.
Building commissioning also can be an important step after a new facility is built. It ensures that building systems are designed, installed and tested to perform according to the design and a school's operational needs. A five-year cycle should be created for re-commissioning to make sure the systems still are operating correctly and providing energy savings as designed.
Rydeen, FAIA, is an architect/facility planning specialist and former president of Armstrong, Torseth, Skold & Rydeen, Inc. (ATS&R), Minneapolis. He can be reached at [email protected].
