Since energy and natural resource consumption are huge components of a lab’s operating expenses, no lab design today ignores “green” issues.
Higher education is a robust market for lab design, but academic labs are challenging for designers because of their high energy usage. “On average, 40 percent of all energy consumed at a university goes to research laboratories,” says Chuck McKinney, marketing VP at Aircuity (Newton, MA). For example, at the University of California, Irvine, 17 lab facilities use two-thirds of campus energy, and the University of Pennsylvania’s lab buildings consume nearly twice as much energy as their footprints would indicate. “About 60 percent of energy usage goes to heating, cooling, and moving fresh air into and out of buildings. And it’s all once-use air—no recirculation.”
Why do labotories consume so much energy?
The short answer, according to Matt Gudorf, energy manager for the University of California, Irvine, is that laboratory buildings use 100 percent outside air ventilation, with no recirculation of return air. “The entire internal air volume of a typical lab building is exhausted to the atmosphere via high-velocity exhaust stacks every six to eight minutes,” he explains. “An enormous amount of energy is required to supply, heat, cool, humidify, dehumidify, filter, distribute, and exhaust this air, and this process takes place 24/7, whether laboratories are occupied or not.” This key parameter is known as air-changes per hour (ACH). Many labs in U.S. universities, colleges, and private-sector and governmental research facilities exhaust 10 or more ACH.
Lab air requirements arise from the need to exhaust dangerous fumes, as well as the need to maintain safety and comfort given general lab activity and heat-generating equipment like freezers, pumps, and spectrometers.
Fume hood exhaust requirements are legendary, as hoods pull through many building volume-equivalents of conditioned air. Engineers have been working to improve fume hoods and their utilization for years. Low-flow designs now rule for new installations and upgrades. Other strategies involve specifying only as many hoods as are absolutely necessary and educating workers to keep sashes closed whenever possible.
Labs, McKinney says, are typically overdesigned for huge heat loads “for the worst case. And once you’ve designed for those loads, you must install ventilation systems to handle them. One problem creates an even bigger problem, particularly for labs that don’t actually experience super-high loads.”
The biggest energy hog, however, is dilution air—the minimum amount of ventilation required to mitigate operations outside of hoods. Burners, smoke, equipment that generates heat, and many fumes, while not dangerous, can make the lab environment uncomfortable. ACHs—the air volumes exchanged per hour to maintain safety and comfort—vary widely. Clean rooms use up to 30 changes per hour, while semiconductor facility values are in the hundreds. A “typical” lab uses between six and ten changes per hour.
What is the “correct” number of air changes? “That’s a difficult question, even for environmental health and safety [EH&S] experts,” McKinney says. Rather than rely on calculations, projections, or usage estimates, Aircuity offers a system that monitors air for values of volatile organics, carbon dioxide, particulates, and humidity, and controls and varies air exchange rates accordingly. The system may specify rates as high as 12 during certain “events” or as low as two overnight, when labs are unoccupied.
Instead of installing sensors in every lab area, Aircuity samples air and returns it to a central bank of detectors capable of monitoring air in 20 different labs. The system also overcomes difficulties in sensor calibration by comparing lab levels of target analytes with those in outside air, providing relative measurements rather than absolute levels. The third advantage is the ability to collect data on “excursions,” which EH&S personnel can use to help labs maintain safe, comfortable environments.
Daniel L. Doyle, president, Grumman/Butkus Associates (Evanston, IL), has created a pyramid representation of steps a lab manager can take to make HVAC systems more energyefficient (see Figure 2).
At the bottom, Doyle explains, are lowest-cost, shortest-payback items that pay back the most in terms of energy savings—“things you can do right away, such as installing high-efficiency lighting to lower the cooling load.” Other steps include using low-flow fume hoods (down to 60 fpm face velocity) and lowering the air change rate. Any new lab or retrofit will automatically consider using low-flow hoods, reducing the number and/or size of hoods, or (if workflows dictate) replacing energy-gulping fume hoods with biosafety cabinets. “You can save a considerable amount of energy before installing any fancy controls,” says Doyle.
Next come variable air volume (VAV) systems that lower exhaust and air change requirements, depending on the circumstances. Occupancy and proximity sensors enable labs to lower fume hood exhaust from 100 fpm to 60 fpm, and they can lower air change rates significantly as well (see discussion with Aircuity’s Chuck McKinney).
Another midlevel strategy implemented at the design/build stage involves installing low-pressuredrop HVAC systems. This strategy uses slightly larger pipes and ducts, which add minimal cost to the build while providing extra capacity for the future.
The top two slices of the pyramid involve reducing or eliminating reheat energy and/or adding some heat recovery. “There are many ways to do this, depending on the climate,” says Doyle, such as connecting wraparound coils both upstream and downstream of the cooling coil. “Simultaneous heating and cooling is a big energy waster in labs,” he continues. “The idea here is to transfer waste heat from one area to another that requires heating. Related strategies include heat pipes, heat exchangers, runaround systems, enthalpy wheels, and desiccant wheels that eliminate reheat while dehumidifying the lab environment.
Image credit: Bill Timmerman, courtesy of SmithGroupAlthough air handling represents the single most significant energy consideration, other design strategies can save money as well. Doyle recommends using very high-efficiency lighting such as fluorescent or light-emitting diodes, which provide very long lamp life at low power consumption while eliminating the mercury disposal problems of fluorescents. The design for new constructions should also incorporate as much natural light as possible, keeping radiative heat loss in mind, and should consider task lighting for low-light areas. “Most lighting from ten a.m. to two p.m. can come from ambient lighting,” Doyle observes. Additional features include automatic occupancy sensor-based dimming controls, which have become standard for new labs and most renovations.
Water is becoming a scarce, expensive resource, so purified water should be used only when absolutely necessary. Using ultra-pure water is certainly required when making analytical standards or formulating cell culture. But tap water, which goes through treatment plants and may involve additional treatment at the lab facility, should never be used even for routine laboratory operations like cooling or vacuum. Designers should consider a means of recycling condensation from air handling systems, especially in humid climates, for operations like cleaning and rinsing. Doyle also suggests switching from film to digital photography, using low-water sterilizers and autoclaves, and harvesting rainwater where practical and legally feasible.