Selected Highlights of the Labs21 2007 Annual Conference

Designing for Actual Not Theoretical HVAC Requirements in Laboratory Facilities

J. Patrick Carpenter, Vanderweil Engineers


Most of the "conventional wisdom" applied to the design of heating, ventilating, and air conditioning (HVAC) systems for laboratories has been around for quite some time. The approaches typically taken in laboratory designs for issues such as room ventilation (using dilution and distribution strategies), room pressurization (using continuous air volume differential strategies), fume hoods (using capture and dilution strategies), duct distribution (using transport velocity assumptions), cooling loads (using connected loads in conjunction with diversity and runtime considerations), and exhaust stacks (using dispersion strategies incorporating location, velocity, aspiration, etc.) are largely dictated by a series of generally accepted practices. However, few laboratory design professionals know or understand the assumptions and details that have historically driven these practices.

Most of these practices have strong precedent from an extensive base of largely successful laboratory installations—a success measured more by "does it work" than by "how well does it work." However, the real relevance and appropriateness of many of these practices or "rules of thumb" are rooted in a history of laboratory environments that bears little similarity to today's modern labs. The challenges of providing for safe, comfortable, and controlled environments in the uncertain realms of laboratory experimentation have traditionally and almost necessarily required conservative approaches that espouse more—more airflow, more velocity, more air changes, more outside air, more capacity, and ultimately more investment and more energy.

Historically, the "more is better" syndrome was often both necessary and appropriate. Because of the indeterminate nature of the work being done in laboratories—where varied chemicals in varied quantities were handled with varied procedures resulting in varied hazards—and because the monitoring and control  systems typically applied to laboratories were questionably relevant, accurate, and potentially unreliable, many standards and codes typically adopted conservative approaches.

This conservatism applied to essentially every aspect of laboratory design, including room ventilation rates, room pressurizations, hood face velocities and minimum hood exhaust airflows, duct velocities, equipment cooling loads, and exhaust fan stack velocities. It also was further compounded by extreme external design conditions, provisions for future unknowns, redundancy of systems—sometimes for worst case scenarios—as well as general safety factors. Collectively, this conservatism was found on some projects to result in two to three times the system sizes and energy uses that might otherwise have been achieved with more right-sized, performance-based control and efficiently operated systems.

But, energy and economic pressures together with enlightened consciousness of the needs for sustainability have put progressively more burden on owners and design professionals to challenge more of the traditional assumptions inherent in laboratory design. Everyone is driven to rationalize and better justify their decisions as the most appropriate and optimal rather than just being correct according to conventional practice. The professionally safe tactic traditionally encouraged that it was most important that the size must always be large enough, sometimes for every conceivable situation. This practice of effectively wrong-sizing rather than right-sizing is now being challenged on many fronts.

The diverse efforts of assorted constituencies are confronting each one of these conventional practices with alternative points of view and/or technologies. These efforts by a combination of user groups, safety personnel, government agencies, equipment manufacturers and professional societies are attempting to rationalize and justify what will likely be less conservative and more responsive approaches. The intent is to better define goals in more direct terms and to link them to more objective and more easily correlated performance criteria. Most of these efforts focus on integrating capacity, measurement, and control to achieve more customized and performance based approaches. With better defined and differentiated space and system needs for safety, comfort, and performance which considers dynamic as opposed to just static design load capabilities, the hope is to create a new paradigm of more appropriate, responsive, and economically viable objectives and approaches.

This paper defines and compares the historical context, current practices, and likely futures of design considerations in laboratories by fundamentally challenging every design assumption laboratory professionals make. By considering and comparing all aspects including comfort, safety, efficiency, effectiveness, flexibility, and reliability, this presentation identified the relevance and appropriateness of many design decisions for both architecture and engineering for their ultimate impact on engineering systems in laboratories. It focused on their impacts on performance, construction costs, and ultimately energy and sustainable costs and offered suggestions on a process that can meet all real requirements with less instead of more.

View this entire presentation in PDF format (1.7 MB, 59 pp)


J. Patrick Carpenter, P.E., a principal with Vanderweil Engineers in Princeton, New Jersey, is a nationally recognized leader in engineering systems for laboratory, animal, and other high-technology facilities. He graduated from the University of Pennsylvania with a Bachelor of Science degree in mechanical engineering and is a registered Professional Engineer in Pennsylvania and New Jersey.

Mr. Carpenter has over 35 years experience engineering systems for corporate, government, and institutional clients and has been responsible for the conception, development, commissioning, and troubleshooting of mechanical, electrical, and plumbing systems for numerous laboratory and vivaria projects. His holistic view of engineering emphasizes safety, reliability, operational effectiveness, energy conservation, flexibility, and sustainability of systems.

His experience includes projects for U.S. Department of Agriculture, University of Colorado Health Science Center, Rutgers University, Food and Drug Administration, University of Pennsylvania, University of Virginia, U.S. Environmental Protection Agency, National Institutes of Health, National Cancer Institute, U.S. Navy, Cornell University, Merck, DuPont, Johnson & Johnson, AstraZeneca, Wyeth-Ayerst, Aventis, Pfizer, Glaxo, Boehringer Ingelheim, Novartis, MedImmune, Exxon, ARAMCO, and Rohm & Haas.

He is active in professional organizations such as ASHRAE, AIHA, ISPE, and Building Commissioning Association. His ASHRAE activity includes 22 years involvement with technical committees involving laboratories, clean spaces, industrial ventilation, and energy calculations. He also served on the committee that rewrote ASHRAE Standard 100.5 for Energy Conservation in Existing Buildings and on committees for the 1995 and 2007 editions of ASHRAE Standard 110 for Performance Testing of Laboratory Fume Hoods. He has participated in all Labs21 Conferences over the last seven years, making nine presentations and moderating several sessions and roundtables.