NBI LEED Study - oberlin.edu IEPEC slides.pdf2009-August-14 Scofield 2009 IEPEC 1 A re-examination of the NBI LEED Building Energy Consumption Study John H. Scofield Department of

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2009-August-14 Scofield 2009 IEPEC 1

A re-examination of the NBI LEED Building Energy Consumption Study

John H. ScofieldDepartment of Physics & Astronomy

Oberlin College


NBI LEED Study• Long assumed that LEED buildings are energy-efficient

• Until 2007 little empirical data to support this

• USGBC engaged the New Buildings Institute to conduct a broad study of energy consumption by LEED commercial buildings

• NBI gathered energy consumption data volunteered by 121 of the 552 commercial buildings certified from 2000-6 under NCv2

• March 2008 NBI issued final report which concludesLEED buildings, on average, achieve 25-30% energy savings

• Study immediately drew criticism

• Cathy Turner (NBI) has made summary LEED data available for independent analysis

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Key PointsMain Deviations from NBI’s Analysis

Use gsf-weighting to calculate mean EUI for collection of buildings Construct comparable LEED and CBECS building subsetsFocus on source energy (not site energy) as metric for energy efficiency

Main ConclusionsComparing all LEED buildings to all US Commercial buildings (CBECS)

By any metric (site, source, median, mean) LEED buildings, on average, use more energy than conventional buildingsDue to differences in building types NOT indicative of energy efficiency

Comparing only “similar” building subsetsLEED buildings achieve no significant reduction in source energyconsumptionLEED buildings achieve 10-16% reduction in site energy consumption

LEED certification is not achieving any significant reduction in GHG from operation of commercial buildings


Site Energy Intensity for LEED

There’s a problemETot/ATot = 129 kBtu/sf

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How do you calculate the mean energy intensity for a collection of N buildings?


Example mean EUI calculation

1j

je e

N≡ ∑

Reed is 19% more energy efficient than Oberlin

1 Totj j

jTot Tot

Ee A eA A

≡ =∑

Oberlin is 7% more energy efficient than Reed

Oberlin College actually uses 7% less total energythan Reed College

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Site Energy Intensity for LEED

(129 kBtu/sf) x (13,500,000 sf) = 1,740 billion Btu


LEED SiteEI Histogram remaining gsffor whichEUI > 250

distribution of the mean

129 ± 12

gsf-weighted median, 80

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How much energy do conventional buildings use?


CBECSDOE/EIA Commercial Building Energy Consumption SurveyConducted every four years - latest data from 2003Data (including energy) gathered from M = 5,215 selected US buildingsEach sampled building represents itself and many (WJ-1) similar buildingsSummary Facts

Total number of Buildings: 4.86 million =

Total gsf: 71.7 billion sf =

Total Site Energy: 6.52 Quad =

Site Energy Intensity: 91.0 kBtu/sf =

1

M

JJ

N W=

= ∑

1

M

Tot J JJ

A W A=

= ∑

1

M

Tot J JJ

E W E=

= ∑Tot

TotTot

EeA

=

EIA uses gsf-weighting in calculating energy intensities.

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Compare LEED and CBECS SiteEI DistributionsComparing medians

LEED 14% > CBECSComparing means

LEED 41% > CBECS


But first …

Site energy is the wrong metric for measuring energy efficiency

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Site Energy

5.02 Q (electric) + 3 Q (ng) + …. = 8.37 Q Site Energy = ETot

ATot = 72 billion gsf

ETot/ATot = 116 kBtu/sf

(actually 22% lower)

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Primary Energy

Coal, natural gas, hydro, solar, nuclear, petroleum, etc.

This is the concern for energy security and GHG emission


Electric Energy

Secondary energy

Higher form of energy (work not heat)

3 units of primary energy used to produce 1 unit of electric energy

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Off-site energy losses

5 Q electric energy used on-site by commercial sector required 15 Q of primary energy in electric power sector.

Total on- and off-site energy used by commercial sector is 18.4 Q.


Source Energy

• Building source energy correlates with primary energy use, energy cost ($), and GHG emission

• EPA uses source energy for Building Energy Star scores

• NBI did not tabulate source energy for LEED buildingsbut … data included fuel type for 98 buildings

• Data for other 23 buildings were “lifted” from previous studies

• R. Diamond provided additional data for 11 of 23 buildings

• Have source energy data for 109 of the 121 LEED buildings

SourceEnergy = 3 (ElectricEnergy) + (nonElectricEnergy)

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Compare LEED and CBECS SourceEI Distributions


Constructing similar LEED and CBECS subsets

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LEED Building PBA’sBuilding Use # bldgs gsf gsf (%)

Labs 10 1,594,257 11.8%Data Centers 6 448,003 3.3%Supermarkets 2 99,060 0.7%Health care 1 12,177 0.1%Recreation 2 212,000 1.6%

high enegy 21 2,365,497 17.6%

Office 35 5,303,464 39.4%K-12 education 7 923,913 6.9%Public order 5 563,174 4.2%Interpretive Center 9 185,249 1.4%Library 4 400,760 3.0%Multi-use 18 1,589,739 11.8%Multi-unit residential 6 550,630 4.1%Remaining Types 16 1,573,129 11.7%

medium energy 100 11,090,058 82.4%Total 121 13,455,555 100.0%


CBECS by Principal Building Activity

CBECS medium energy subset-H

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Source EI for Medium Energy Buildings

LEED mean SourceEI is higher than CBECS - but the difference is not statistically significant


Source EI for Office Buildings

LEED mean SourceEI is slightly lower than CBECS - but difference is not statistically significant

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SiteEI for Office Buildings


Source EI for Newer Office Buildings

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Site EI for Newer Office Buildings


Summary Results• On the whole, LEED certification yields no significant reduction in

source energy used by medium energy or office buildings

Corollary: no significant reduction in GHG emission associated with commercial building operating energy

• On the whole, LEED certification is reducing site energy -- 10% for medium energy and 16% for office buildings

• There is no scientific basis for the Federal Govt. or other entities to require LEED certification for buildings as a measure to reduce GHG emission

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Green Is as Green DOESPerformance is more compelling than design awards

By Michael G. Ivanovich

The "Big & Green" exhibit was, for me, a disappointment because it "showed" design and "talked" quite a bit about performance; however, there was very little actual performance data to allow visitors to judge just how well these supposedly green buildings, or some of their more innovative features, are performing in real life.


LEED needs fixing• Need more building science and less marketing

• Vastly elevate the importance of energy consumption in rating

• Focus on source energy, not site energy

• Require mandatory energy monitoring and public disclosure

• Tie LEED certification to actual measured source energy performance (why not require LEED Pt to have EnergyStar score of >90, etc)

• Pay serious attention to plug loads

• Building energy use is about design, construction, and operation

Documents

NBI LEED Study - oberlin.edu IEPEC slides.pdf2009-August-14 Scofield 2009 IEPEC 1 A re-examination of the NBI LEED Building Energy Consumption Study John H. Scofield Department of