ACH reductions and minimization of airflow
required for cooling. Energy-efficient lighting
and equipment are important tools for reducing
cooling-related airflow demand. In some cases,
it’s wise to consider decoupling the cooling load
from the airflow altogether via water-based
cooling (chilled beams, fan coil units). For animal labs, consider ventilated cage racks, which
allow room air change rates to be reduced since
general room air isn’t used to provide ventilation
to the animals. All of these strategies can have
important effects on both safety and comfort, so
input from the project’s EH&S team is a must.
VAV, DEMAND-BASED CONTROL, EXHAUST
The pyramid’s next-highest level encom-passes tactics that are still relatively low cost
and can deliver good energy savings. These
strategies allow airflow to be modulated
below the design maximum when labs are
unoccupied, or when conditions otherwise
make it suitable to deliver lower airflow.
• Selection of VAV fume hoods and lab
exhaust. VAV devices allow airflow to be
reduced when sashes aren’t fully open or
when hoods are idle. Occupancy sensors and
automatic sash closers can be helpful, as well
as “close the sash” campaigns encouraging
changes in user behavior. VAV can be used in
combination with high-performance (
low-flow) fume hoods.
• Selection of VAV makeup and supply
air. The VAV devices mentioned above work
hand-in-hand with VAV terminal units, such
as Venturi valves. These are required on fume
hoods, groups of snorkel exhaust devices, some
biosafety cabinets and the supply air from the
• Installation of demand-based control
technologies. This relatively new innovation
actively measures air quality using a sophisticated suite of sensors, which interact with the
lab’s control system to reduce air changes per
hour if no contaminants are detected. When
contaminants are detected, ACH is ramped up
to clear the air.
• Reducing exhaust energy. Older conventional exhaust designs discharge large quantities
of air at high velocities constantly, to avoid the
possibility that contaminated exhaust air will be
sucked back into the supply system (
re-en-trainment). Optimized exhaust system designs
may include air quality sensors (in the exhaust
airstreams), higher stacks, variable speed fans
(allowing reduced airflows), wind-responsive
controls and the reduction or elimination of
bypass air to reduce energy usage while maintaining safe operation.
Figure 2: Modeling of energy-recovery options for four climates (Singapore, Chicago, Atlanta, Houston) revealed
two highly recommended and two recommended designs. Dual-wheel and a single-wheel with heat-recovery
chiller outpaced other choices regardless of climate.
Figure 3: An enthalpy wheel energy-recovery system with a passive desiccant wheel and no reheat was
one of two highly recommended options in our analysis.
Figure 4: Enthalpy wheel energy recovery with a heat-recovery chiller for pre-cool and reheat was our
second highly recommended option for all studied areas.