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From Inside To Outside: Use Of Sophisticated Modeling Tools To Optimize Laboratory Ventilation

Duncan Phillips, Ph.D., P.E., and Aimée Smith, Rowan Williams Davies & Irwin, Inc.

A large component of the operating costs for a laboratory facility can be attributed to the HVAC systems. With rising fuel prices and resultant increases in energy costs, designing more efficient HVAC systems is becoming more important than ever for sustainable building design, because of the reduced energy usage, and ultimately the survival of the research industry. The presentation will focus on the specific issue of laboratory ventilation, both internally and externally, and will illustrate how considering both early in the design process can provide an optimized design that is "right-sized" for the intended use of the laboratory space.

Many laboratory designers are aware that ventilation systems tend to be over-designed. There is often a reluctance to reduce the ventilation rates due to the risk involved. Part of the risk is associated with the potential to compromise the indoor air quality and comfort within the laboratory space. This aspect of risk can be addressed at the design stage through the use of detailed modeling and optimization of the ventilation system. Internally, this would involve the use of computational fluid dynamics (CFD) modeling to determine the minimum number of air changes per hour (ACH) and optimal air distribution configuration that would lead to appropriate indoor air quality and comfort. This modeling has the ability to consider several internal variables as desired by the designer/owner; such as diffuser locations, heat from windows and equipment and chemical spills outside of fume hoods. Externally, dispersion modeling of the exhaust (using numerical or physical wind tunnel techniques) would be used to optimize the ventilation rate. Through evaluation of parameters such as exhaust and intake location, stack height and stack exit velocity, the minimum exhaust ventilation rates required to maintain acceptable air quality levels at the air intakes can be determined. Thus, any air entering the laboratory space would not compromise the indoor quality of air supplied by the internal ventilation system.

Specific examples will be used to demonstrate how these sophisticated modeling tools can be used to reduce the risk involved with "right-sizing" the laboratory ventilation system.

Labs21 Connection:

Aspects of the application that are unique/noteworthy and apply the Labs21 Approach include:

Minimize overall environmental impacts

  • Providing methodology/approach to achieve sustainable goals with respect to energy use while reducing the liability concerns.
  • Will contribute to reduction in energy use and consumption of fossil fuels, which would in turn reduce the emissions believed to be responsible for global warming.

Optimize whole building efficiency on a life-cycle basis

  • An optimized ventilation system can save owners a considerable amount in operating costs.
  • Combined approach that considers the "whole building" concept (e.g., how external and internal ventilation issues affect one another).

Establish goals, track performance, and share results for continuous improvement

  • Use of sophisticated modeling tools allows detailed evaluation of the building operations during the design stage (i.e., predictive).

The above discussion and points highlight that this presentation will focus on an approach that will achieve many, if not all of the Labs21 objectives. The main focus of the presentation is centered on increasing the efficiency of the laboratory's energy use, and providing designers with a method that will allow them to provide a more efficient design without concern for potential liability. Optimizing the system will result in less energy use and less fuel consumption, which will reduce the overall environmental impact. The consideration of both internal and external ventilation will protect occupant safety, and considers a whole building approach.

Biographies:

Duncan Phillips has a Ph.D. in Mechanical Engineering from the University of Waterloo in Ontario. During his graduate work he investigated the measurement and quantification of room air and contaminant mixing within occupied spaces. This work involved both the development of instrumentation for, and measurements of, contaminant transport. Duncan is a registered Professional Engineer in the Province of Ontario.

Duncan joined Rowan Williams Davies & Irwin Consulting Engineers in 2000. He is a Project Director/Senior Specialist for Ventilation and CFD. He is an Associate of the firm. His role at RWDI as the senior member of the CFD and ventilation team is to technically oversee the execution of client based projects. These projects include assisting in the design of buildings (e.g. laboratories, heathcare facilities, and stadia) to implement high performance ventilation systems (e.g. natural ventilation, displacement ventilation) for applications ranging from contaminant control and thermal comfort to thermal load management and sustainable building design.

Aimée Smith has a B.S. in environmental engineering from the University of Guelph and a Masters Degree in civil engineering from Carleton University. Her research work for her Masters Degree explored several aspects of decision making related to power generation including land use effects and toxicological effects of water, soil and air pollutants. As part of this work, Aimée used numerical dispersion modeling to quantify air pollutant levels.

Aimée is currently a project engineer in the environmental modeling division at Rowan Williams Davies & Irwin Inc. (RWDI) in Guelph, Ontario, Canada. Aimée focuses primarily on numerical and physical air quality modeling for different types of studies including exhaust re-entrainment and roadway emissions assessments. She specializes in exhaust re-entrainment studies for the design of building exhaust and air intake systems for laboratory, health care and other related facilities.

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