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Analysis Track
Understanding and Reporting
Degree Days, Greenhouse Gas,
Carbon Footprint
Presented by Steve Heinz, PE, CEM

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Degree Day Fundamentals

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“Degree Days” is a weather analytic
that is only useful in the context of
building energy consumption.

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Degree days measure how much the
temperature varies from a “balance
point temp” at which a building needs
no heating or cooling.

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Degree Days
Based on dry bulb temperature only
(does not account for humidity, wind,
sunshine, precipitation)
Concept developed in the 1930’s to
estimate residential gas demand

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Degree Days
Used widely today for fuel oil fill-ups.
BPT: NOAA’s selection of 65F as the
“balance point temperature” is a poor
choice for modern non-residential
buildings. 60F is better.

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The average annual temperature in San Diego is 65F.
The average annual temperature in Dallas is 65F.
In Dallas, annual A/C usage is 160% more and annual
heating use is 350% of San Diego. How can that be?
The average annual temperature in Orlando is 72F.
The average annual temperature in Phoenix is 72F.
In Phoenix, annual A/C usage is 63% more and annual
heating use is 100% more than Orlando. Huh?

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Warm days and cool days cancel each
other out when average temperature
is used

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These cities had the same 60F average
temp for two days. Was building energy
usage the same?
High Low Mean HDD CDD
San Diego
Day 1 65 55 60 0 0
Day 2 65 55 60 0 0
Average 60
Denver
Day 1 90 60 75 0 15
Day 2 60 30 45 15 0
Average 60

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Conclusion:
The use of Average Temperature fails
to be a good indicator of heating and
cooling needs.

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MDT (Mean Daily Temperature):
Middle value between daily high and
daily low
Typically it’s the outdoor temperature
at around 11:00 AM
CDD=MDT-BPT (when MDT>BPT)
HDD=BPT-MDT (when MDT<BPT)
DD=0 (when MDT=BPT)

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www.WeatherDataDepot.com

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www.WeatherDataDepot.com
Yearly comparison report
Charts
Excel and print
Monthly data
FAQs

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How is Weather Used in EnergyCAP?
Building ZIP Code
Weather link to WeatherDataDepot
Calendarization & Normalization
Cost Avoidance

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With weather adjustment, $78 savings

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Without weather adjustment (for
unusually mild winter), $352 savings

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Why not also adjust for humidity,
wind, sunshine, precipitation?
Data is expensive
Many fewer available stations
Huge increase in complexity
Marginal increase in accuracy

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Greenhouse Gas
Fundamentals

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Six gases that have global warming
potential:
Carbon dioxide
methane
nitrous oxide
Chlorofluorocarbons (sulfur
hexafluoride, hydrofluorocarbons,
perfluorocarbons)

©2013 EnergyCAP, Inc. @energycap www.EnergyCAP.com
Greenhouse Gas Fundamentals
Measured in equivalent metric tons of
CO2 (often shown as CO2e)
Metric ton=1,000 kg=2,205 lbs
U.S. national average is 20
mTon/person/yr

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EPA’s eGRID Database

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EPA’s eGRID Database

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EPA GHG Equivalencies
www.epa.gov/cleanenergy/energy-resources/calculator.htm

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EPA GHG Equivalencies
www.epa.gov/cleanenergy/energy-and-you/how-clean.html

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How is GHG Used in EnergyCAP?
Meter
Building and Organizational rollups
GHG Report

Questions
Visit the Ace Place to learn more!
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