SU P P ORT
as possible in the masterplanning
or building design process to avoid
discovering potential performance
issues at a later stage when changes are
more difficult to make. There should be
consideration of siting and exhaust stack
and intake placement, followed by use of
dispersion modelling tools which show
the movement of fumes to optimise
exhaust design and achieve building
energy reduction goals.
How does planning for an existing
building or campus differ from
planning for new buildings?
When masterplanning a network of
buildings, site analysis for optimal layout
is critical. This involves considering the
aerodynamics of buildings, local wind
climate, phase of construction, and each
building’s intended use. For new or
existing laboratories, an evaluation of
exhaust dispersion levels is approached
in the same way – however, architecture,
structural or mechanical constraints that
exist for an existing building can limit
potential options. In such cases,
dispersion modelling can be used to
develop unique solutions, which may
include the use of smart, wind responsive
When masterpl anning a ne t work
o f b u i l d i n g s , s i t e a n a ly s i s f o r
o p t i m a l l ay o u t i s c r i t i c a l
exhaust fans, which automatically adjust
their output based on wind speed and
direction. When wind conditions don’t
create critical impacts on intakes or
pedestrian areas (as determined via wind
tunnel testing results), the exhaust fans
can be turned down while still ensuring
safe dispersion. It may also be possible to
consider other operational strategies for
an existing laboratory.
What methods are used
to evaluate dispersion?
The options for evaluating exhaust
dispersion levels range from simple
desk studies, through computational
modelling, to physical scale modelling in
a wind tunnel using tracer gases. Expert
selection of the appropriate modelling
tool depends on the building’s geometry
and location. Because exhausts typically
are located on building rooftops,
Evaluating aerodynamics
and wind flow at the
Francis Crick Institute
evaluating the aerodynamics and
windflow patterns created around the
buildings using tracer gas wind tunnel
modelling is the ideal method for
reducing energy usage and improving
health and comfort.
What if you don’t consider dispersion?
Exposure to hazardous emissions
or odours directly affects the health,
wellbeing and comfort of building
occupants, and can affect productivity
within the lab. Where local air quality
is being affected by an inadequately
designed system, use of certain chemicals
may need to be limited or eliminated,
which can profoundly affect research
outcomes. Unfortunately, this is often
the measure most used in response to
air-quality related complaints. Such poor
dispersion of laboratory fumes can both
negatively impact the neighbouring
community and potentially affect the
reputation and success of new science
facilities and science parks.
Are taller stacks the only option
for avoiding dispersion problems
while saving energy?
Definitely not. With appropriate
planning, both the design of the building
and the air intake/exhaust system can be
optimised to allow for short stacks. The
energy performance from short stacks
can be further optimized using smart,
wind-responsive exhaust fan operation.
Ultimately the objective should be to
achieve energy and aesthetic goals
through planning and design to avoid
the use of complex building control
systems, but this type of fan operation
can improve energy reduction for
existing facilities. ■
RWDI is renowned for expertise in
engineering modelling and analysis,
helping to create buildings that are more
efficient, sustainable, comfortable to
inhabit and resilient to natural disasters.
For further information visit rwdi.com
or contact [email protected]
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