Fume Hoods
Courtesy of Wilson HGA © Anton Grassl Photography
Energy efficiency measures for fume hoods can result in dramatic energy reductions. The Physical Sciences Building at UMass Amherst features intensive chemistry labs, where the fume hood air demands can exceed the lab air change rate, and the overall energy demands are high.
Net-Zero-Verified
Courtesy of BR+A Consulting Engineers
The John J. Sbrega Health and Science Building at Bristol Community College is a Net-Zero-verified building. It features instructional wet labs for dental hygiene, biology, and other disciplines, as well as dry labs for nursing and medical assisting.
Key questions asked during the planning process can drive the design of new and renovated research facilities, creating a high-performance, sustainable building with predictable operating costs. Questions from the building owner and stakeholders should focus on upfront costs, energy efficiency, long-term savings, safety, potential risks, construction materials, carbon reduction, zero waste, and performance vs. sustainability. For example: What energy efficiency measures should be explored? What safety strategies will have the most impact? What would it take to create a net zero lab?
“Active participation by an owner can have a significant impact on a project,” says Jacob Werner, director of sustainable design at Wilson HGA. “Answers to important questions should be evidence-based and consensus-based from a team of stakeholders, so the design process can be structured toward the best possible outcomes.”
Knowing which questions to ask will depend, in part, on which of the five sustainability standards an owner wants to achieve for a particular building:
- LEED – focuses on incremental improvement across a wide variety of sustainability criteria
- Zero Net Energy – focuses on achieving zero net energy consumption through highly energy-efficient building systems and reliance on renewable energy
- Living Building – achieves regenerative design in a broad range of sustainability categories, including energy positive, water positive, and carbon neutral construction
- WELL Building – focuses on the health and wellness of occupants
- Passive House – greatly reduces energy consumption and restricts energy demand to tight parameters
“When considering how to apply these standards to a laboratory project, decide how applicable they might be,” says Werner. “If the building’s use suggests that energy efficiency is the key factor, then it might be appropriate to pursue certain standards and not others.”
The Path to Net Zero
The John J. Sbrega Health and Science Building at Bristol Community College in Fall River, Mass., is a Net-Zero-verified lab building. The $31.5-million, 51,000-sf building, completed in 2016, features instructional wet labs for biology, microbiology, chemistry, dental hygiene, and clinical lab science; dry labs for nursing and medical assisting; a teaching clinic; offices; and study space.
Holistic strategies were used to achieve the college’s goal of being carbon neutral in the Sbrega building. A ground-source heat pump system avoids reliance on natural gas boilers, and renewable energy includes rooftop and site photovoltaic arrays, as well as solar thermal domestic hot water.
Thirteen filtered and four ducted fume hoods are used in the wet labs, and the air quality is actively monitored, allowing the air change rate in specific areas to be turned down as needed. When the spaces are occupied, there are four air changes per hour (ACH), but if contaminants are detected, the system ramps up to six ACH. Fan coil units cool the facility, and airflow passes through the fume hoods, with the filters returning cleaned air to the space.
“You are managing the air change rate to the exact tune that you actually need to keep the space clean and healthy,” says Jacob Knowles, director of sustainable design at BR+A Consulting Engineers.
People sometimes worry about the carbon footprint of the filters for the filtered fume hoods.
“Accounting for the embodied energy of the materials, filtered fume hoods have a lower carbon footprint than ducted ones, by about half,” says Kenneth Crooks, director of GreenFumeHood Technology at Erlab Inc. “This is due to the fact that the filtered fume hoods allow a reduction in the amount of HVAC infrastructure.”
Beyond the initial reduction in embodied energy, 216 watts are typically used in a 6-foot filtered fume hood, while the ducted hood uses dramatically more due to the need to condition the make-up air. Over the first 20 years, filtered fume hoods result in approximately one-tenth the carbon footprint, even accounting for filter replacement.
Beyond the energy savings of reduced exhaust and make-up rates, almost all of the air exhausted from the space is just “room air” that is no longer from ducted hoods. Therefore, enthalpy wheels are used to capture heat and cooling back out of the exhaust stream, which is much more efficient than a conventional glycol runaround heat recovery system.
The lighting power density was decreased by 50 percent with efficient LED fixtures, and a plug load study allowed systems to be right-sized. Other design features include an airtight envelope that exceeds the energy code, low-flow plumbing fixtures, and natural ventilation in the areas where chemicals are not used.
A $3 million savings was realized by not using large air handlers, chiller, mechanical penthouse, and big ductwork, and that money was reinvested in the geothermal heat pump system and fan coil units.
“There was a 1 percent cost premium of about $275,000 to do zero net energy,” explains Knowles. “That premium was more than covered by the utility incentives and the Massachusetts Department of Energy Resources Pathways to Zero grant. Without the grant, the simple payback timeline was two and a half years.”
Conserving Energy Without Compromising Safety
Design and construction of the $82 million Physical Sciences Building at the University of Massachusetts in Amherst required careful consideration of safety issues and energy consumption. The building, completed in March 2018 and certified as LEED Gold, includes the recreation of the 19th century research lab known as the West Experiment Station (WES). A new steel skeleton replaces the previous wood framing, increasing safety and stability for the station, and some bricks from the original facility were used in a cavity wall.
The Physical Sciences Building houses two floors of intensive synthetic chemistry labs, and because of the large amount of airflow, typical energy efficiency strategies—such as increased wall insulation and lighting occupancy sensors—had a minimal impact on the total energy usage.
In a chemistry lab, the fume hood air demands can exceed the lab air change rate, resulting in airflows three to six times more than those in a biology lab. This turns the lab into a wind tunnel, where a constant stream of outdoor air is sucked into the building; heated, cooled, humidified, and/or dehumidified; passed once through the lab; then exhausted back into the atmosphere. This constant airflow means the air in the building doesn’t stay long enough to lose or gain heat through the building’s exterior walls or windows. The most effective design strategies for a chemistry lab are those that reduce airflows.
“In this case, it wasn’t the air change rate driving energy use,” says Werner. “It was really the fume hoods, so we came up with an idea for a shut-the-sash fume hood campaign. Early modeling suggested that this simple program would boost energy savings by 20 percent, or about $90,000 per year.”
Shutting sashes on the fume hoods reduces energy consumption per fume hood by about 50 percent, increases safety, saves money, decreases fossil fuel consumption, and helps the university achieve its carbon reduction goals.
Financial Considerations for Energy Efficiency Measures
The 189,000-sf, four-story Jackson Laboratory for Genomic Medicine at the University of Connecticut is an example of a facility driven by the air change rate and not the fume hoods. The building, certified as LEED Gold, includes biological and computational lab space to accommodate microbiology, bioinformatics, and proteomics research.
A detailed analysis was conducted during the planning stage to determine the construction cost of each energy-conservation measure being considered, the expected operational savings, and the potential payback time. The results were used to determine which conservation strategies were the most cost effective relative to their positive impact.
The holistic approach at Jackson meant using chilled beams, return air from non-lab zones, reduced fan power, enhanced lighting controls, reduced lighting power, condensing boilers, a high-efficiency chiller plant, demand-based kitchen hood exhaust, and ceilings in labs to reduce the volume of space requiring air change rates. Using chilled beams and a reciprocating cogeneration system, which simultaneously produces electricity and thermal energy from a single fuel source, were among the most beneficial and cost-efficient strategies.
“Chilled beams rely primarily on water to provide supplemental cooling to that space,” says Knowles. “That way, the primary airflow to meet the lab air change rate can remain constant and not increase when the space requires more cooling. This saves energy by reducing the amount of air that has to be pushed at much higher static pressure by the air handling units. We downsized many of the air handling systems and reinvested that money into the chilled beams and other infrastructure.”
The Jackson project received nearly $1.2 million in energy incentives and is realizing an annual energy cost savings of $830,000.
Overarching Questions for Future Projects
Each project is unique and requires a customized approach that can be created by asking important questions to determine the best outcomes for operating efficiency. The best way to achieve both performance and sustainability is to ensure a building is flexible enough to meet changing needs.
“Systems must be designed to meet the demands placed on them, but they should also be responsive to reduced demand, capable of turning down to use dramatically less energy when appropriate,” says Werner. “An example of this is demand-based air change rates in cleanrooms—ramping up when the space is occupied and higher particle concentrations are detected, and ramping down when the space is unoccupied and low particle concentrations are detected.”
It is also essential to consider the potential risks that could impact a capital project. Ask questions and plan for various scenarios, such as dangerous weather conditions and site-specific issues. Disruptions could include a loss of power, lack of transportation, delayed response from emergency personnel, increased fire risk, loss of irreplaceable items, and property damage.
The potential impacts can be addressed by moving mechanical systems above the floor, using on-site power generation, using natural ventilation, training employees about emergency preparedness, using deployable barricades, and having strong exterior walls with increased thermal resistance.
By Tracy Carbasho
