Chemistry labs: How the new math changes everything
We took the opportunity to look at a pair of lab projects for the Univ. Massachusetts Amherst (UMA)—the Life Science Laboratories (LSL) and the Physical Sciences Building (PSB)—and looked at how the approach to ventilation varies by lab type and how the changes in current standards impacted the design to give a sense of where we are headed in the design of chemistry labs and, in particular, fume hoods.
The rate of new construction at the UMA campus has increased significantly in the past 10 years. UMA has been evaluating lessons learned in the design and construction of lab projects as the institution continues to build and renovate science facilities. Mechanical systems, utilities, controls, security, energy, maintenance, lab size and lab design have been the major topics of these lessons learned. The institution has had ongoing discussions to review current policies for ventilation in labs in light of the new technologies and containment for fumes, vapors, particulates and other contaminants. The LSL has snorkel exhausts at 70 cfm in open lab areas above benches, as well as exhaust ports with blast gate dampers at 70, 100 and 220 cfm to capture heat and contaminated exhaust generated by analytical equipment and pumps. These ventilation devices are now utilized throughout UMA in all new facilities to capture heat and contaminated exhaust. LSL has also incorporated demand-controlled ventilation in the design, measuring and sensing of VOC and particulates in labs.
The PSB varied from the LSL in that there was one fume hood per 355 sf, while the LSL had only one fume hood per 1,280 sf. Other life science and engineering buildings on campus had only one fume hood per 860 sf. This significantly drove up the anticipated energy use for PSB, yet the newly adopted Massachusetts stretch energy code mandated that the PSB achieve a similar level of energy efficiency to the LSL. In addition, UMA Environmental Health and Safety (EH&S) doesn’t allow filtered fume hoods for any chemical use or process, and has a policy that the minimum face velocity for a fume hood will be no less than 80 fpm.
The challenge for the PSB is meeting the energy code requirements without compromising on EH&S requirements. This meant going back and revisiting the fundamental assumptions about fume hoods, not simply repeating the same strategies used on the last project. We identified seven key fume hood criteria that impact energy use:
- Room air change rate.
- Minimum fume hood flow rate.
- Worksurface area/hood volume.
- Face velocity.
- Sash opening.
- Open/closed %.
- Nighttime setback.
By surveying how the users planned on using the hoods, and carefully plugging each of these variables into a model that gave us an average cfm per hood, we were able to understand how even small changes to hood configuration impacted exhaust rates. Working together with the user group and EH&S, we developed a fume hood configuration and operating protocol with the potential to reduce overall cfm for the lab by almost 50%, or roughly $100,000 per year in energy costs.
So, what did we learn?
- In an ideal world minimum flow is much more important than face velocity.
- Height matters—if you don’t need the extra height, don’t put it in.
- There needs to be a standard developed for evaluating fume hoods in minimum flow conditions.
- Low-flow hoods don’t necessarily save energy in every application.
- Close the sash.
Chemistry labs are some of the biggest energy consumers on any campus, but by challenging the assumptions around fume hoods and understanding how the variables impact exhaust rates, it’s possible to see big reductions in overall energy use.
Greg Muth is a Senior Lab Planner and Project Manager at Wilson Architects with over 25 years of experience in labs and other high-tech spaces. He has been involved in the construction and renovation of over 15 million sf of S&T spaces around the world. Betsy Blunt is a Senior Lab Planner in Design and Construction Management at the Univ. of Masssachusetts Amherst, assessing research faculty needs.