A new, third water-based cooling strategy—
particularly suited to high-heat equipment
corridors—is what we’ve dubbed “fan-assisted
chilled beams.” Borrowing from IT industry
existing technology, rear fan-doors, turned
horizontal, use the same 58 F entering water,
but can remove 20 k W/beam.
Finally, conventional fan coils offer a fourth
option for high-heat-gain space, though typically with wet coils, additional ductwork and
requiring floor space or a comparable maintenance access provision.
By engaging health and safety staff in a
demand-controlled ventilation strategy, lab
air changes per hour can often be reduced. For
labs dominated by ventilation requirements,
this strategy becomes the 600-lb gorilla of
energy conservation, sometimes offering simple payback in a few years.
Described as an integrated sensing and
control solution that cost-effectively reduces
building energy and operating expenses while
simultaneously improving IAQ, demand-controlled systems safely vary lab ventilation
rates, usually between 4 and 16 ACH, and may
drop them lower during unoccupied periods.
The system continuously monitors air quality
to optimize performance together with the
building management system. It senses indoor
environmental parameters such as total volatile organic compounds, particulates, air PH,
relative humidity, carbon dioxide and carbon
monoxide. Safety advantages include a more
informed staff and the ability to hyper-ventilate
a lab when an air quality incident is detected.
Another approach is to substitute or
replace energy-intensive fume hoods with
high-performance, low-flow systems. Putting
things into perspective, conventional fume
hoods blow through 25,000 k Wh/yr—the
equivalent of annual energy consumption for
three homes. By considering alternatives like
high-performance hoods, automatic sash clos-
ers, combination sashes and ductless hoods,
labs can reduce fume hood energy use by a
third or more (Figure 2, pg 2).
Sash-closing systems employ a passive infra-red motion detector to constantly monitor the
work area in front of a hood. When no motion
is detected, this triggers an automatic closing
process following an adjustable delay of 10 secs
to 30 mins. The electric drive unit and sash
bottom sensor are designed for safe operation.
Combination sash glazing employs horizontal sliding segments that allow access with less
open hood area, while also allowing a worker
to position a solid barrier in between them
and the research conducted in the hood.
As for ductless hoods, Green Fume Hood
technology is a stand-alone system that can
handle acids, solvents and bases with the same
filter. With its modular filtration column, it
can easily be relocated. However, this system
will only be effective if the lab operators work
consistently with a defined set of chemicals
that align with filter capabilities.
Another technology, point exhaust arms or
“snorkels”, can be an effective way to optimize
air change rates. These arms rotate 180 degrees
and can handle exhaust up to 400 F for
high-temperature extraction, thus increasing
by several times the average supply-air-to-ex-haust-temperature difference, with a reciprocal drop in airflow rate.
In addition, portable extractors—although
not meant to replace fume hoods—work to
re-circulate exhaust air to the room following
filtration via a pre-filter combined with HEPA
Can sustainable lab design go
continued from page 6
a baseline energy model, calculating initial and
ongoing operating costs and then determining
which building system options to target.
Looking at the overall project, reducing the
EUI or energy cost budget by 30% over ASHRAE
90.1 is more common—even as others aim higher with goals inspired by the net-zero-energy
Living Building Challenge or the 2030 Challenge
to design carbon-neutral buildings.
Getting down to the specifics, designers can
look at a number of technologies and strategies to improve efficiencies and drive down
DECOUPLED COOLING/HEATING SYSTEMS
One fundamental approach is de-coupling
building ventilation from lab heating and
cooling. This particularly suits labs where
power, as opposed to exhaust, dominates overall thermal needs, enabling a large reduction
in ventilation energy.
With this approach, lab-sensible heating and
cooling loads are handled by a local hydronic
system that typically engages a water-side economizer for refrigeration-free winter cooling.
With these systems in place, outside air ventilation airflows can be reduced to minimum
levels. Then, the reduced outside air ventilation
loads and lab dehumidification may be handled
by a dedicated outdoor air system (DOAS), typically involving heat recovery.
Of the four or more types of decoupled
hydronic systems, look for active chilled beams
to gain broad acceptance first (Figure 1, pg 1).
In this system, ducted, low-humidity, low-pressure supply air induces room air through
overhead coils and linear diffusers. Each coil
can cool with a nominal 58 F water circuit,
and some also heat with a nominal 120 F water
circuit. Although active beams involve induction, their quiet, dry-coil, low-energy, modular
design suits small and large labs alike, and may
go years with only face vacuuming as maintenance. This is a stark contrast to mid-century,
high-pressure perimeter induction units.
Similarly, passive or “non-ventilated”
chilled beams offer decoupled hydronic cooling, but solely by convection—fully separated from ventilation system energy. Passive
beams are virtually silent and, being ductless,
may provide more flexibility for relocation
to address lab turnover. Nevertheless, they
accommodate significantly lower heat densities and require a higher installation height
for comparable comfort levels—aspects that
preclude some lab applications.
Figure 3: Lighting at Univ. of California Berkeley’s Energy Biosciences Building is controlled by available daylight
or vacancy, and supplemented with task lighting when desired. Labs use under-shelf task lights for the benches
with occupancy sensors.