By: Robert J. Tsal, Ph.D. and Geoffrey C. Bell, PE
Energy Efficiency and Air Distribution
Air distribution through a laboratory is critical to the facility's safety and energy efficiency; nonetheless, air distribution systems are typically treated as an afterthought in the design process. Small ductwork is often routed circuitously, resulting in significant energy waste. In addition, the system air velocity is usually selected by rule-of-thumb and its noise impact is addressed afterward. However, the design of an energy-efficient air distribution system should be an iterative process, facilitated with the "T-Method," which incorporates life-cycle cost. A key to saving energy is to reduce the friction loss of the air distribution system by using large-diameter, round ductwork, efficient fittings, lower coil and filter face velocities, and energy-efficient noise attenuators. [Houghton, et al, 1992]
Air distribution components typically used in the research laboratory include:
·Variable air volume (VAV) terminals or air balancing devices,
·Fire and smoke protection devices (supply side only), and
·Fume hoods, biological safety cabinets, or other exhaust devices. [Naughton, "HVAC Systems… Part 1," 1990]
Laboratory cleanrooms require special consideration because of the need to move large, laminar volumes of air for contaminant removal. For cleanrooms, energy efficiency is increased with efficient ductwork design and lower face velocities for coils, dampers, and filters. Naughton, in "HVAC Systems for Semiconductor Cleanrooms - Part 1" (1990) notes that,
When hundreds of thousands of cfm are involved, the reduction in fan static pressure of just 0.1 in. WC (24.9 Pa) can result in $7,200 per year of savings for a 10,000 ft2 (929m2) clean room. In addition to fan horsepower savings, each 0.1 in WC (24.9 Pa) will also produce 3.9 tons (13.7 kW) of air-conditioning savings due to the reduced fan heat load.
Duct Leakage and Laboratory Isolation
Ductwork Material and Construction
Ductwork Layout Recommendations
Computerized Ductwork Simulation
Economic Duct Optimization for California Laboratories
Cleanrooms—Pressurized Plenum vs. Ducted Designs
