ASHRAE Journal - July 2021 - 36

COLUMN ENGINEER'S NOTEBOOK
One might think occupancy schedules for academic
teaching labs would be easier to predict. However, many
student labs are now being done " on-demand, " which
means students can choose to do their labs anytime, day
or night. If laboratory airflows are reduced via occupancy
sensors, the likelihood of divergence between
modeled and actual results increases.
LEED Models and Investment-Grade Models
Many owners and some engineers don't understand
the difference between LEED models and investmentgrade
models. An energy model for LEED certification
compares the building performance against an ASHRAE
Standard 90.1 baseline. It is not intended to predict
actual performance. It is very important we educate
owners so they don't expect their building energy consumption
to match the LEED model.
Investment-grade models are used to predict energy
savings from energy conservation measures for a specific
building where past utility bills are available. It
can be calibrated using historic utility bills to better
HEAVY DUTY
CONSTRUCTION &
LARGE HEATING
SURFACE FOR LONG
LIFE (NOT LIGHT
WEIGHT)
EFFICIENCIES UP
TO 98%
SIMPLIFIED SYSTEM
DESIGN
Parker Boiler
205 TC Series
Condensing
Boilers
FULL FRONTAL
ACCESS TO TUBES &
COMBUSTION
MULTIPLE FUEL AND
NOx OPTIONS
FIGURE 4 Prototype vs. learned occupancy.
100
90
80
70
60
50
40
30
20
10
12 1 23 45 6789 10 11 12 123 45 678 9 10 11
a.m.
|
Learned Monday
Learned Thursday
Prototype Saturday
Learned Tuesday
Learned Friday
p.m.
Learned Wednesday
Prototype Weekday
Prototype Sunday, Holidays and Other
establish an accurate baseline. From there, different
energy conservation measures can be analyzed to
determine approximate savings and investment rate of
return. However, this analysis only applies to existing
buildings. New or fully renovated buildings have no utility
history that can be used to establish a baseline. This is
a valuable tool to compare options, but is not predictive
of consumption.
Conclusions
Many factors make predicting actual laboratory energy
performance difficult, if not impossible. Engineers
need to be prepared to educate and set expectations for
owners who ask for an accurate energy model to predict
energy costs. It cannot be used to accurately predict
future use or cost; however, it is an effective design tool
when used for comparative analysis. With few exceptions,
weather, occupancy and plug loads are held constant in
all modeling runs. Used in this way, their variance is less
of a factor on the outcomes and better highlights relative
performance differences between models.
References
1. National Weather Service. 2018. " National Weather Service
5930 Bandini Blvd.
Los Angeles, CA 90040
NEVER A COMPROMISE FOR
QUALITY OR SAFTEY
36
Tel: 323-727-9800
www.parkerboiler.com
Forecast Office: Kansas City/Pleasant Hill. " National Weather
Service. https://tinyurl.com/cv6adbsz
2. I2SL. " Labs 21 Best Practice Guides and Benchmarking. Louis
Stokes Laboratories Case Studies. " National Institutes of Health.
International Institute for Sustainable Laboratories.
ASHRAE JOURNAL ashrae.org J U LY 2 0 2 1
Occupancy (%)
https://www.tinyurl.com/cv6adbsz http://www.parkerboiler.com http://www.ashrae.org
ASHRAE Journal - July 2021

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