ASHRAE Journal - January 2015 - 18

TECHNICAL FEATURE

PHOTO 1 Hood showing a standard ASHRAE 110 test with mannequin.

FIGURE 3 Fan selection for higher efficiency.

90
FEG 85
FEG 80
FEG 75
FEG 71
FEG 67
FEG 63
FEG 60
FEG 56
FEG 53
FEG 50

Peak Total Efficiency, pTE (%)

80
70
60
50
40
30
20

Impeller Diameter (in.)

should list the chemicals being used and those chemicals that may be used in the future. Exposure limits
are well documented.7 This can be a challenge in a
research-oriented endeavor but even a segregation
of most of the inventory can be a good step toward
containment.9
A health and safety consultant can be a big help with
housekeeping tasks when organizing chemical storage
and use.10
Using snorkels (point exhaust) as a substitute for
fume hoods can be an effective tool for energy conservation. Airflow requirements for snorkels are lower
than for fume hoods, and they are normally turned off
after use.

Architectural Considerations
To minimize cross drafts, hoods can be located in
alcoves (outdoor of walking traffic). Additionally, the
hoods can be in a secondary zone using air from other
parts of the building as supply air for the lab areas.
Added containment of the contaminants within the
fume hoods include various modifications including
airfoil sills and aerodynamic side posts. Low flow hoods
can be useful (reducing 100 fpm [0.5 m/s] face velocity
to about 60 fpm [0.3 m/s]) for very good reduction of
outdoor air. LBNL has designed and tested a low flow
hood using a different containment technology than a
standard hood using Standard 110 tests and reports good
containment.11
The low flow hood design is a good example of
innovative thinking for energy conservation in
laboratories.
18

ASHRAE JOURNAL

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JAN UARY 2015

Engineering Considerations
One simple way to design a laboratory is to start with
an ordinary space with the best available IAQ (see
Standard 62.1) and then add the ventilation requirements for fume hoods and containment devices.
Standard 62.1 suggests 1 to 2 ach rate (0.18 cfm/ft2 [0.9
L/s·m2]) for a standard space. As a contrast, most codes
for laboratories suggest between 4 and 8 ach. Example:
in a 200 ft2 (19 m2) lab with a 9 ft (3 m) ceiling, Standard
62.1 air change rates would call for about 30 to 60 cfm
(14 to 28 L/s). Compare these air change rates to those
for a research laboratory, which suggests 130 cfm to 260
cfm (61 L/s to 123 L/s). Exhaust for dedicated devices
must also be added to both calculations. Standard 62.1
can be a good standard for good IAQ and for energy conservation for the entire laboratory building. During the
design phase, the HVAC consultant and the health and
safety consultant can provide excellent combined design
recommendations.

Hardware Considerations
Preconditioning the Supply Air Using Room Exhaust
Preconditioning the supply air is a common method
of reducing the energy consumption of laboratories
(and most buildings). Current common energy transfer devices include plate exchangers, heat pipes and
enthalpy wheels. The plate exchangers and heat pipes
have a physical barrier between the supply and exhaust
airstreams, eliminating any concerns for cross contamination. But these heat transfer devices transfer only
sensible heat, not the total heat. Corrosion and condensation are normally considerations when selecting

ASHRAE Journal - January 2015

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