A school district’s biggest expense after payroll is its utility bill. Because the HVAC system is a major component of a school’s utility bill, careful evaluation of a school’s HVAC requirements and equipment options can help administrators save money while actually improving learning productivity.

Every school is different, so there is no one HVAC solution for all schools. Instead, there is a “best” solution for each individual school—chosen from careful evaluation—that maintains the highest possible indoor air quality at the lowest possible energy costs. A well-designed HVAC system maintains space temperature and humidity conditions, as well as minimum outdoor air amounts, economically and efficiently. ASHRAE standard 62.1-1999 recommends that each person in a classroom receive 15 cu. ft. per minute of fresh air, and a classroom with 30 people requires a ventilation rate of about 450 cfm. Factor in a school’s age, size, construction—such as walls, lights, doors and windows—zone requirements and the climate where the school is located, and it’s easy to see why schools present unique challenges for meeting HVAC requirements. The key is knowing how to balance all the elements of the equation.

Zone requirements are particularly important for schools. Each school has several different zones, each with specific needs for heating, cooling and ventilating. Classrooms generally have high ventilation requirements, three times that of an office, but only when occupied. Dedicated classrooms, such as science and computer areas, require extra cooling or ventilation. Administrative areas require lower heating and cooling, but are occupied over longer hours. Cafeterias need special ventilation for food preparation, and gymnasiums, occupied during the day and evening, have a range of load requirements and scheduling demands.

A variety of types of equipment and configurations are available to meet the requirements for schools.

Decentralized systems provide heating, cooling and conditioning, i.e., humidity control, to individual classrooms or zones. The advantage of a decentralized system is that it can provide cooling to one space and heating to another. Scheduling can be zone specific to allow for increased operating cost savings. Ideal for new or existing buildings, decentralized systems are easy to service and can rival the most advanced built-up systems for energy efficiency. A disadvantage is that the equipment resides in or near occupied spaces, so maintenance needs to be scheduled when the affected zone is not occupied.