Selected Highlights of the Labs21 2007 Annual Conference

A Comprehensive Review of the Indoor Environmental Quality and Energy Impact of Dynamically Varying Air Change Rates at Multiple Laboratory Facilities

Gordon P. Sharp, Aircuity, Inc.


At the Labs21 2005 Annual Conference, a unique energy savings approach was presented that would dynamically vary the minimum air change rates, or air changes per hour (ACH) of a research laboratory based on the real time measurement of the laboratory's indoor environmental quality. Per this concept, the room's minimum ACH rate is reduced to a level such as two or four ACH when the laboratory air is determined to be clean from the real time measurement system. When air contaminants or odors are detected in the laboratory, the ACH rate is dynamically increased to a higher level such as 15 ACH to purge the space. When the measurement system senses the laboratory air has returned to a clean state, the air change rates are reduced to their lower levels. A design analysis for a Seattle laboratory showed that this approach could reduce building energy costs by 20 percent and cut the gross heating, ventilating, and air conditioning (HVAC) first cost by $1.05 million.

A year later, at the Labs21 2006 Annual Conference, a case study was presented on the implementation of this concept at the Harvard School of Public Health. Two laboratory areas were heavily instrumented and actual data was presented on the propagation time and spread of chemical vapors for different simulated release conditions. The results of this testing showed that chemical vapors spread uniformly through the laboratory with some expected variation due to distance.

This paper provides actual data and analysis of indoor environmental conditions at approximately 75 different laboratory areas at seven different laboratory facilities in the United States and Canada. Approximately 250,000 hours of environmental and control data were analyzed to draw many conclusions about the environmental conditions within these laboratories and the indoor environmental quality and energy impact of dynamically varying laboratory air change rates at six of these sites.

As an example, Figure 1 shows an averaged summary of the total volatile organic compounds (TVOC) data collected from all the laboratory and vivarium spaces. The graph indicates the percent of time that the TVOC levels in all the laboratories exceeded certain TVOC level thresholds, e.g. the percentage of time that the laboratory TVOC levels exceeded 0.25 parts per million was about 0.30 percent of the time, or on average about 30 minutes every week. Effectively, this means that there was on average about one event per week per laboratory area where the levels exceeded this threshold. This indicates that a significant amount of energy can be saved in the laboratory, and that it is important that the system respond to and achieve higher air change levels since events do happen periodically.

Percent of Time That Lab TVOC Levels were over Indicated Threshold Levels

 Figure 1: Percent of Time That Lab TVOC Levels were over Indicated Threshold Levels

Percent of Time That Lab Particle Levels were over Indicated Threshold Levels

Figure 2: Percent of Time That Lab Particle Levels were over Indicated Threshold Levels

Figure 2 shows similar averaged data for all the laboratory locations, except this graph depicts the percentage of time that the particle levels in the laboratory exceeded background (supply airflow) levels by some stated amount. Levels below 1 million particles per cubic foot should not require any increased laboratory airflow. Figure 2 indicates that this level is exceeded only on an average of 0.2 percent of the time. Thus, there is minimal impact on energy efficiency to provide proper safety by purging the laboratory at increased airflow during these potential smoke or aerosol events in the laboratory area.

In conclusion, with minimum air change rates, rather than hood makeup air or thermal load requirements often being the dominant factor determining today's laboratory air flow volumes, this concept for dynamically varying air change rates should significantly increase the energy efficiency of both new and existing facilities. Using this strategy, we can maintain occupant safety while furthering the goals of sustainable laboratory design.

View this entire presentation in PDF format (4.7 MB, 37 pp)


Gordon Sharp has over twenty five years of wide-ranging entrepreneurial experience and more than 20 U.S. patents to his name. From 1979 to 1985, he was vice president and co-founder of IMEC Corporation, a motor controls technology company from which he created a spin-off company called the Phoenix Controls Corporation. As president, CEO, and founder of Phoenix Controls, Mr. Sharp led the development of a $25 million venture capital backed world leader in laboratory airflow controls that was honored for three consecutive years by INC magazine as one of the 500 fastest growing private companies in America.

In early 1998 Phoenix Controls was acquired by Honeywell, Inc. Thereafter, in addition to participating in restructuring the Honeywell Home and Buildings Solutions business, Gordon led development of a Honeywell business unit, now known as Aircuity. In January of 2000, Aircuity became an independent, venture capital-backed company and today is the leading manufacturer of multiplexed sensing systems to optimize building ventilation for energy-efficient performance without sacrificing occupant comfort or health.

Mr. Sharp is the chairman and founder of Aircuity and a graduate of Massachusetts Institute of Technology with Bachelor's and Master's degrees in electrical engineering. He is a member of the American National Standards Institute (ANSI) Z9.5 Laboratory Ventilation Standard committee, and is a member of the board of directors of the International Institute for Sustainable Laboratories, a nonprofit foundation and official cosponsor of the Labs21 2007 Annual Conference.