Bowdoin College
OP-5: Building Energy Efficiency

Part 1. Reduction in source energy use per unit of floor area

Institution has reduced its total source energy consumption per gross square metre or foot of floor area compared to a baseline.

Part 2. Site energy use per unit of floor area

Institution’s annual site energy consumption is less than the minimum performance threshold of 389 Btu per gross square metre per Celsius degree day (65 Btu per gross square foot per Fahrenheit degree day).

Performance for Part 2 of this credit is assessed using EUI-adjusted floor area, a figure that accounts for significant differences in energy use intensity (EUI) between types of building space.

This credit applies to all institutions.

Each part is scored independently. Points earned are calculated according to the formulas below. Please note that users do not have to calculate the number of points earned themselves; points will be calculated automatically when the data listed under Reporting Fields is entered in the online Reporting Tool.  

Part 1

An institution earns the maximum of 3 points available for Part 1 of this credit by reducing its total energy consumption per gross square metre/foot of floor area by 50 percent compared to a baseline. Partial points are awarded based on the reduction achieved. For example, an institution that reduced its total energy consumption per gross square metre/foot of floor area by 25 percent would earn 1.5 points (half of the points available for Part 1 of this credit).

Scoring for Part 1 is based on source energy, a figure that accounts for the energy used off-site to generate and transport imported electricity to the institution. For scoring purposes, imported electricity is converted to source energy through the use of an appropriate source-site ratio.

The STARS Reporting Tool calculates total energy consumption (source energy) according to the following formula:

Total energy consumption (source energy) =   { [ ( A × B ) + C ] × 0.003412 } + D + E

A = Imported electricity (kWh)

B = Source-site ratio for grid-purchased electricity

C = Electricity from on-site, non-combustion facilities/devices (e.g., renewable energy systems) (kWh)

D = Stationary fuels used on-site to generate electricity and/or thermal energy (MMBtu)

E = Imported steam, hot water, and/or chilled water (MMBtu)

Points earned for Part 1 of this credit are calculated according to the formula below. STARS awards only positive points; points will not be deducted if total energy consumption per gross square metre/foot of floor area increased rather than decreased during the time period.

Points earned for Part 1 = 6 × { [ ( A / B ) - ( C / D ) ] / ( A / B) }

A = Total energy consumption (source energy), baseline year (MMBtu)

B = Gross floor area of building space, baseline year (gross square metres or feet)

C = Total energy consumption (source energy), performance year (MMBtu)

D = Gross floor area of building space, performance year (gross square metres or feet)

Part 2

An institution earns the maximum of 3 points available for Part 2 when its total annual energy consumption is 90 percent or more below the minimum performance threshold of 389 Btu (0.000389 MMBtu) per gross square metre per Celsius degree day (0.000065 MMBtu per gross square foot per Fahrenheit degree day).

Incremental points are awarded based on the institution’s performance below the threshold. For example, an institution whose total annual energy consumption per gross square foot per Fahrenheit degree day is 35.75 Btu (i.e., 45 percent below the 65 Btu threshold) would earn 1.5 points (half of the points available for Part 2).

Scoring for Part 2 of this credit is based on site energy and EUI-adjusted floor area.The STARS Reporting Tool calculates EUI-adjusted floor area according to the following formula:

EUI-adjusted floor area = { A + [ 2 × ( B + C ) ] + D }

A = Gross floor area of building space (square metres or feet)

B = Floor area of laboratory space (square metres or feet)

C = Floor area of healthcare space (square metres or feet)

D = Floor area of other energy intensive space (square metres or feet)

The Reporting Tool calculates total energy consumption (site energy) according to the following formula:

Total energy consumption (site energy), performance year =  [ ( A + B ) × 0.003412] + C + D

A = Imported electricity, performance year (kWh)

B = Electricity from on-site, non-combustion facilities/devices (e.g., renewable energy systems), performance year (kWh)

C = Stationary fuels used on-site to generate electricity and/or thermal energy, performance year (MMBtu)

D = Imported steam, hot water, and/or chilled water, performance year (MMBtu)

Points earned for Part 2 of this credit are then calculated according to the following formula:

Points earned for Part 2 = 3⅓ × { [ A − ( B / C ) / D ] / A }

A = Minimum performance threshold (in MMBtu per square metre or foot per degree day)

B = Total energy consumption (site energy), performance year (MMBtu)

C = EUI-adjusted floor area, performance year (square metres or feet)

D = Total degree days, performance year (heating + cooling)

Timeframe

Performance Year

Report the most recent data available from the three years prior to the anticipated date of submission.  Institutions may use the most recent single year for which data is available or an average from throughout the period. Institutions may choose the annual start and end dates that work best with the data they have (e.g., fiscal or calendar year), as long as data are reported from a consecutive 12-month (or 3-year) period.

Report degree day and building space figures from the same time period as that from which energy consumption data are drawn (e.g., the consecutive 12-month or 3-year period that most closely overlaps with the building energy consumption performance period). Institutions may use average building space from throughout the period or a snapshot at a single representative point during the period.

Baseline Year

Report data from the baseline year, which may be:

• Any year from 2005 to the present

• A baseline year, 1990 to 2004, that the institution has adopted as part of its sustainability plans or policies or in the context of other reporting obligations

Recommended best practices for defining a baseline include:

• Using the average of three consecutive years to reduce the impact of outliers.

• Using the same baseline year for multiple credits to reduce reporting requirements. For example, institutions using 2005 for all STARS credits that are baseline-based would only have to calculate baseline weighted campus user data once.

• Ensuring that baseline and performance year data are valid and reliable (e.g., that the data were gathered in the same manner)

Institutions without valid and reliable historical data should use performance year data for both the baseline and performance year. Following this approach, an institution would not be able to claim points for reductions during its first STARS submission, but would be able to use its newly established baseline for subsequent submissions.

Institutions may choose the start and end dates that work best with the data they have (e.g., fiscal or calendar year), as long as data are reported from a consecutive 12-month (or 3-year) period.

Report degree day and building space data from the same period as that from which energy consumption data are drawn (e.g., the consecutive 12-month or 3-year period that most closely overlaps with the building energy consumption baseline period). Institutions may use average building space from throughout the period or a snapshot at a single representative point during the period.

Sampling and Data Standards

Include all building energy consumption, i.e., all electricity, stationary fuels, and other energy products used on-site by the institution (as the institution is defined in the overall STARS institutional boundary). Transportation fuels are excluded. Reporting on a sample or subset of buildings is not allowed for this credit.

Institutions that convert fuel on-site (e.g., on-campus cogeneration facilities and boilers) should report only the amount of fuel purchased/converted toward the total energy consumption figure, not the resulting heat, steam, hot/chilled water or electricity.

All reported energy consumption figures should be based on site energy (the amount of energy consumed by campus buildings) rather than source energy (the amount of energy consumed on campus plus the energy used off-site to generate and transport the energy to the institution). Source energy will be calculated automatically when the data listed under Reporting Fields is entered in the online Reporting Tool,

Consistent with U.S. EPA Portfolio Manager and published national and regional averages, the following default source-site ratios (i.e., primary energy factors) for imported electricity are used:

Institutions located outside the U.S. and Canada that have available national or regional primary energy factors (PEFs) for imported electricity may report those figures in lieu of the above and should document the source of the data in “Data source(s) and notes about the submission”. Please note that PEFs should be calculated on the basis that the PEF for on-site renewable energy equals 1 (as opposed to zero).

To simplify reporting, a single source-site ratio for imported electricity is used for both the performance year and the baseline year, and stationary fuels and imported thermal energy, which have lower and more locally variable distribution losses than electricity, are treated as site energy.

MMBtu (one million British thermal units - a standard measure of energy) is used to aggregate energy consumption data from multiple sources. An institution must report electricity data in kilowatt-hours, which are converted to MMBtu automatically in the Reporting Tool using a factor of 0.003412, All other figures (i.e., for stationary fuels and thermal energy) must be converted into MMBtu using the following equivalents prior to being entered into the Reporting Tool:

AASHE publishes a unit conversion tool that includes more detailed conversion factors (e.g., for liquid fuels). See also the International Energy Agency’s unit converter.

To simplify reporting, heating and cooling degree day data should use a single base temperature for the institution’s main campus location. Base temperature is the temperature below which the institution’s buildings require heating and above which the buildings require cooling. For U.S. and Canadian institutions, this is typically 65 °F (18 °C). Degree day data may be downloaded from DegreeDays.net (global data), ENERGY STAR Portfolio Manager (U.S. and Canada), or another source of national or international weather data.