Fume Exhaust Systems, Hood Technologies and Controls:
Energy Conservation and Design Considerations for New and Retrofit
James J. Walker, PE,
Fred Hutchinson Cancer Research Center
Fume exhaust systems consume large amounts of energy and are expensive
to build or modify. It's important to understand all aspects of
the new one being proposed or one currently in place. Most centralized
exhaust systems are fairly typical in design, but there are many
options available to reduce energy consumption either in a new facility
or as retrofit projects. Centralized fume exhaust system conservation
projects implemented at Fred Hutchinson Cancer Center include Variable
Geometry Damper, System Static Pressure Reductions, and Bypass Air
Reductions. These will be discussed in addition to other options.
The application of constant volume, variable volume and low flow
hoods will be examined. Low flow hoods may or may not save energy
in your facility, but other considerations such as infrastructure
may be the deciding factor. Fume hood exhaust air valves are more
critical for some hood designs than others. Which system is right
for your application? Lab room pressurization control will be addressed
including supply air offset and actual room pressure sensing strategies.
When considering fume exhaust systems and related equipment or
changes to an existing system, the designer should first consider
whether the labs served are fume hood driven or air change driven
with respect to airflow. There may be no energy saving advantage
for low flow hoods in a lab that is driven by air change rates.
Does the owner have the training and staff available to keep more
sophisticated systems operating as designed?
In existing facilities, the owner's engineering staff needs to
be consulted to verify calculations and assumptions. Evaluate the
overall building energy impact of specific systems considered rather
than that from individual equipment options. Complicated systems
must be commissioned prior to turnover to owner and need to be recommissioned
over the life of the system to assure that they are still operating
safely and saving energy. Energy conserving systems are often installed
without clear means of savings verification by the owner. Instrumentation,
sensors and the ability to trend data will assure that the system
is successful. Flexibility needs to be considered in the design
since systems typically operate differently than the designer's
The unique approach of the Fred Hutchinson Cancer Research Center
is to seize the initiative for energy conservation for new and retrofit
design from the consulting world. Planning and Engineering functions
at the Center for over 12 years have far exceeded energy codes and
state of the art design when it comes to energy conservation. The
Center has been a proving ground for many new conservation concepts.
The drive for excellence in conservation comes from within.
Specifically, our fume exhaust systems and upgrades have been consistent
with the Labs 21 Approach in many ways. Fume exhaust systems and
modifications have always been pursued first with user safety in
mind. Our in house Environmental Health and Safety staff has always
been involved in each process and outside environmental consultants
are brought in when necessary. Consideration to the whole building
is given rather than just at the equipment or lab level. Retrofit
projects are always monitored both before and afterwards to compare
actual savings with calculations. In order to do this effectively,
measurables such as airflow, static pressure, amperage, motor speed
and fume concentrations must first be identified for tracking purposes.
Our pursuit of conservation extends beyond our internal organization
through educational programs such as innovative signage at fume
hoods, the use of building operations manuals for new building occupants
and articles on conservation in our company newspaper.
James Walker, PE, has a B.S. in Mechanical Engineering from
Seattle University. He has over 25 years of professional experience
as a mechanical engineer in manufacturing, consulting engineering
and facilities engineering. As a consulting engineer working for
a top 15 AE firm, he specialized in energy conservation starting
in 1982 and continuing over a 15 year period. His work involved
energy surveys of over 110 commercial and institutional facilities
to identify cost effective, energy saving measures and follow up
Mr. Walker is currently employed by the Fred Hutchinson Cancer
Research Center in Seattle as the Facilities Engineer where he has
served for 8 years. He is heavily involved with the implementation
of water, gas and electrical conservation projects and bringing
cutting edge conservation technology into practice.
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