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.
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
Establish goals, track performance, and share results for continuous
- 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.
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
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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