Colleges and universities need to support their basic science research and education missions. At the same time, they must be vigilant about upgrading or replacing aging infrastructure, and finding ways to attract top faculty and students. To satisfy all these demands, higher-education institutions are constructing state-of-the art science facilities. Schools expect these new facilities to last for the next 50 years, so they want reliable mechanical/electrical/plumbing (MEP) systems that can support a flexible teaching and laboratory environment.
Achieving these goals requires an integrated planning and design approach. Design of an energy-efficient mechanical system depends, in particular, on the effective orientation of the building in relation to the sun; the design of the building envelope and roof for maximum efficiency; and space planning that segregates building uses, and allows for varying cooling and ventilation requirements. Extensive energy modeling at the planning stage of a project can help ensure that materials, systems and design decisions will deliver the desired results.
A typical benchmark used in designing an air-handling system for a modern science building is to provide 2.0 cfm per square foot for a facility that will house conventional laboratories and 2.5 cfm per square foot for those that include a vivarium, although these figures will vary according to the specific program requirements. Depending upon an institution's master plan, a school should consider increasing the capacity of the MEP systems or make provisions to allow for a future expansion. It is not unusual for air-handling units to be sized up by 10 to 20 percent to accommodate expansion.
Rather than relying on a single air-handling unit to provide total capacity, the system should be designed with multiple air-handling units using manifolds or interconnections to allow shared capacity. This design provides redundancy, ensuring reliable operation in the event that scheduled maintenance or equipment breakdown takes a unit out of service.
The MEP team also should analyze the viability of a variable-air-volume (VAV) control system for the project. In a VAV system, the amount of supply air delivered to the space is regulated based on thermal requirements and operating conditions. If a facility primarily will house classrooms and teaching laboratories, it will require maximum air volume when classes are in session and minimum air volume when they are not. Alternatively, two-position controls allow for occupied and unoccupied operational conditions only. The cost of a VAV control system may be justified based on life-cycle energy savings.
A heat-recovery system is a worthwhile investment for many institutions. These systems operate by capturing energy from exhaust streams, which is returned to supply streams. Heat exchangers and heat wheels, where appropriate, can be used for this purpose. Heat-recovery systems will reduce heating costs in the winter and cooling costs in the summer.
For indoor air quality, duct-mounted and wall-mounted sensors enable a building automation system to monitor levels of carbon dioxide and carbon monoxide, and make adjustments to meet ANSI/ASHRAE standards. These systems are effective in spaces with varying occupancies, such as classrooms and auditoriums, where they will adjust the amount of outside air supplied to the space depending upon air quality in the room.