High-Performance Lab Ventilation Systems Lower Costs, Protect Workers

This article originally appeared in Lab Manager.

Surging demand for new research laboratories is leading to record-setting investments in lab construction and renovation. At the same time, research universities and private labs are facing pressure to reduce energy use and related carbon emissions.

By upgrading to high-performance ventilation systems, labs can achieve reductions in both capital and operational costs — all while maintaining occupant safety.

Ventilation systems account for a particularly large share of construction costs as well as a significant source of energy demand. Rather than rely upon decades-old fume hoods, antiquated monitoring equipment, and legacy environmental health standards, high-performance lab equipment can potentially lower costs and improve sustainability.

Efficiency Without Sacrificing Safety

Mechanical, electrical and plumbing (M/E/P) systems are among the top contributors to lab construction costs, accounting for half of lab project budgets, on average. Ventilation systems are generally the largest consumer of building electricity throughout a lab’s lifetime. One recent National Institutes of Health (NIH) study found that ventilation systems were directly responsible for 44 percent of an NIH lab’s electricity use.

Source: naiop.org

Despite these high costs, the No. 1 design priority is to ensure that ventilation systems never sacrifice worker safety. Research labs contain a wide range of airborne hazards from chemical, biological or radioactive materials. Air-exchange systems are essential for preventing exposure to hazardous contaminants and establishing comfortable work conditions.

Lab managers and designers may not have to choose between occupant safety and energy efficiency. Smart labs can reduce energy consumption while maintaining occupant safety and — in labs with smaller footprints — potentially downsize the facility’s heating, ventilation and air conditioning (HVAC) infrastructure. Common high-performance measures include:

• Low-flow fume hoods
• Variable air volume (VAV) systems with active fume hood monitors and controls
• Dynamic sensing and air-exchange systems

Mechanical engineering researcher Nate Sunderlin evaluates the effects of freezing a Li-ion battery with liquid nitrogen. Photo by Werner Slocum / NREL

Low-Flow Fume Hoods

Fume hoods are critical enclosures for extracting airborne contaminants from research areas. Recent studies have shown that increasing the number of fume hood air changes does not, however, necessarily create a safer lab.

While conventional fume hoods have face velocities of 100 feet per minute (FPM), code requirements allow velocities as low as 60 FPM. Low-flow fume hoods meet American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) safety criteria, reducing trace gases below 0.1 parts per million (ppm).

Low-flow fume hoods feature a longer airfoil and articulating baffles to create a stabilized vortex. The hoods contain airborne contaminants, reducing air flow velocity by providing less turbulent airflow across the sash plane and a more stable vortex inside the fume hood.

A study commissioned by University of California in Irvine reported 60-FPM hoods have achieved 0.04 ppm, outperforming standard hoods operating at 80 or even 100 FPM. Equipment manufacturer Bedco claims their 60-FPM Vanguard fume hood reached containment measurements of .003 ppm with the full sash open.

That said, actual lab conditions are difficult to replicate within testing environments. Dynamic conditions affect fume hood performance, such as air disturbances created by diffusers, door swings, and occupant travel paths.

Low-flow hoods’ energy savings are hard to dispute. Labs can save thousands of dollars by transitioning from 100-FPM to low-flow alternatives. If a lab’s operating costs average $5 for each cubic feet per minute (CFM) of ventilation, UC-Irvine’s study found that a 70-FPM hood would consume an estimated 640 CFM, saving $1,350 per year for each upgraded hood.

Variable Air Volume Systems

VAV systems supply air at a variable airflow within consistent temperatures. Conventional air handling units, on the other hand, supply constant airflow at variable temperatures.

When attached to fume hoods, a VAV system can monitor face velocity, attenuating hood fans to adjust the make-up air supply. Monitoring systems react when a sash is raised or lowered, maintaining proper airflow velocity while conserving energy. VAV systems are standard practice in new lab designs, but many legacy facilities may need to be upgraded.

Source: sciencedirect.com

In the UC Irvine study, installing VAVs increased the low-flow hoods’ cost savings to $1,500-$3,000 per unit. Savings ranges will depend on whether a lab institutes additional zone pressure sensors or application-specific controls.

When evaluating energy savings, it is important to consider that VAV technology comes with higher implementation costs. Duct valve systems require additional preventative maintenance.

Monitoring Devices

Whenever a hood sash is lowered, VAV systems close a valve within the duct, reducing the amount of exhausted air. It is an important best practice to keep sashes closed whenever possible, dropping ventilation rates to the lowest possible levels.

Several universities have implemented “shut the sash” campaigns, placing stickers on the sliding glass sash to reinforce this best practice. Harvard University found the campaign reduced HVAC energy consumption by 70 percent, yielding savings of $200,000 per year. Yet other campuses have found the campaigns produce limited long-term benefits.

Rather than rely on voluntary behaviors, proactive labs can install motion sensors to detect when workers neglect to shut the sash while hoods are in use. Researchers at Massachusetts Institute of Technology (MIT) developed an alarm system, using a webcam combined with augmented reality to monitor the sash height and to detect if the hood is left unattended. MIT reported that each device costs $250-275, saving more than $350 in annual energy costs per hood.

Source: University of California – Irvine, Environmental Health & Safety

Dynamic Air Change Rate Variation

Lab ventilation systems are often overdesigned. Occupational Safety and Health Administration (OSHA) recommends an unoccupied lab’s air exchanges can drop to 4 air changes per hour (ACH) when no research activities are taking place. Yet standard lab designs circulate at steady rates between 6 and 12 ACH.

Labs can become “smart” if energy-efficient ventilation is combined with a dynamic sensing system. Recent advances in sensor devices enable regular collection of air samples at the exhaust fan inlet, accurately analyzing for volatile organic compounds (VOCs). The ventilation system adjusts fan speeds depending on the sampled air quality.

If the system detects an increase in contaminants, airflow is increased to a maximum level. During a spill, a rate as high as 16 ACH may be appropriate to ensure complete dilution. If no VOCs are detected, the airflow could be reduced — in some circumstances below OSHA guidelines to levels as low as 2 ACH.

Source: aircuity.com

Comprehensive Ventilation System Design

On average, labs consume five times more energy per square foot than an equivalent-sized office building. Unlike standard building HVAC systems, lab ventilation designs must not sacrifice occupational safety.

Toxic fume inhalation is one of the most common occupational hazards within lab settings. Risks vary between labs and change over time. To minimize exposure risks, ASHRAE recommends that lab air control systems be appropriate for whatever hazards are present.

Ventilation strategies should ideally be customized to each facility’s layout, equipment, operational requirements, and — with advanced diagnostics — a real assessment of the lab’s contamination threats.

A comprehensive HVAC design strategy can effectively achieve the lab’s safety, productivity, and energy efficiency goals. Ventilation design choices can lower overall airflow requirements and — depending on the number of fume hoods, type of controls and monitoring systems, and general lab operations — potentially allow for a downsizing of facility infrastructure.

By developing a customized ventilation design strategy, labs may find they can improve energy efficiency and even achieve a reduction in capital expenses. Few would disagree, lab investments are better spent on ground-breaking research than on circulating unnecessary air.