Opportunities for Achieving SignificantEnergy Reduction in Existing University Buildings:Developing efficient HVAC operations 

Michael Gevelber, Robert Choate, Kevin Sheehan, Thomas Vitolo,Elijah Ercolino, Leah Ricci, Liz Lacy, Matt McHale, et. al.

Acknowledgments:Aandy Ly, Energy Manager Dennis Carlberg, Sustainability Manager

Outline• Overview of BU energy use

• How is energy used in buildings?

• Major opportunities for energy savings: focus on HVAC- Unoccupied mode- Air changes

• Energy Benchmarks: When does gross EUI mislead- Implications for campus and buildingcomparisons

Michael Gevelber, Associate Professor Mechanical Engineering, Co-chair BU Energy Working Group, Member of BU Sustainability Comm, & Clean Energy and Environmental Sustainability Initiative (CEESI)

2008 2009

Summary of Findings from GE 520/MN 500: “Energy Audit/Conservation Analysis of BU’s Charles River Campus”

2010

Energy Intensity (Per Sq Foot)Total Energy Use

Cleveland, C. (2007, Oct 24). Energy and Emissions Footprint: Boston University Charles River Campus. Presentation to the BU Energy Club.

Results of 2007 Energy Audit

0.0E+00

2.0E+11

4.0E+11

6.0E+11

8.0E+11

1.0E+12

1.2E+12

1.4E+12

1.6E+12

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Btu

Heavy oil

Light oil

Electricity

Natural gas

68% Growth in Energy Use

100

110

120

130

140

150

160

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Btu

/sq.

foot

(100

0)

18% Increase in Energy Intensity

• What are the reasons for these trends?

• What can be done to reverse these trends?

Extended TeamMichael Field, Former Asst. Provost

Gary Nicksa, VP OperationsTom Daley, Assoc. VP FacilitiesBill Walter, Asst. VP FacilitiesDomenic D’Alleva, HVACTim O’Connor, ElectricalTom Parker, AutomationPaul Arsenault, HVAC

Mark Harney, Asst. VP FacilitiesAandy Ly, Asst. Dir., EnergyZhonghong Peng, Assoc. Dir.

Paul Rinaldi, Space ManagementKaren Zaharee, Analyst

Mike Penn, OEHS

Colleen McGinty, Director ConstructionShaun Finn, LEED Certified AP

Eric Gauthier, ITWilliam Steward, ITChuck Von Lichtenberg, IT

Building Managers:Carlos VazquezTyrone LawlessRoger SealeDennis BatistaFernando Sousa

Outside Experts:Domenic Armano, Manager, Johnson ControlsRay Thompson, Sales Manager, AndoverPeter Harris, Director Operations, B&V TestingStephen Drummey, Drummey Mechanical

Don DeRosa, Asst. Prof., SEDDoug Zook, Assoc. Prof., SEDSED Green Committee

Larry Valles, Lab Manager, Biology

Building Energy Use by FuelCharles River Campus 2005‐2007

Energy Supply106 kBtu

Energy Expenses/GHG

BU Energy Use Index: kbtu/ft2, by building type

72

106

72

109 11489

226

125141

361

248

92

0

50

100

150

200

250

300

350

400

Ret

ail

Activ

ity

Brow

nsto

ne R

esid

ence

s

Apa

rtmen

ts

Dor

ms

Brow

nsto

ne O

ffice

s

Labs

Cla

ssro

oms

Offi

ces

BU

MC

Res

earc

h

BU

MC

Edu

catio

n

BU

MC

Adm

in

CRC BUMC

kBTU

/Ft^

2

Average CRC Energy Density 117

Average BUMC Energy Density 335

SMG (220)

‐ Focus on high energy density buildings

Photonics (336)

LSEB (468)

140 BSR (140)

NOTES:(1)  BUMC Net Area does not include NEIDL and rental properties(2)  Data sources from BU energy audit class (M. Gevelber) & Facilities (P. Zhong & A. Ly)

FY2007 Net Area Energy CostCRC 9.3 M ft2 79%

BUMC(1) 1.2 M ft2 21%Total 10.5 M ft2 100%

Seven Building Analysis

‐Sargent  ‐SMG  ‐15 St Mary’s    

‐PRB  ‐44 Cummington  ‐LSEB  ‐Photonics

Energy Cost Density by Building

• What drives energy performance? • What are opportunities for improvement?

-

50

100

150

200

250

300

350

400

450

Sargent SMG 15 St. Marys PRB 44Cummington

Photonics LSEB

Kbt

u/sq

.ft.

$-

$2.00

$4.00

$6.00

$8.00

$10.00

$12.00

$14.00

$/sq

.ft.

Energy Cost Density

Energy Density

GasGas

Elec.Elec.

Building % Energy HVAC % Cost HVACSargent 71% 53%SMG 69% 57%15 St. Marys 60% 53%PRB 61% 50%44 Cummington 38% 18%Photonics 52% 28%LSEB 72% 64%

•HVAC accounts for 60‐70% ‐of energy use and 50‐65% of energy cost in a building.

HVAC Cost and Energy Implications

How does a Building HVAC system work?

Building:

70 Degrees

Outdoor Air Temp:

30 Degrees

Intake

Exh

aust

Air

How much energy can be saved in a building?

•Currently energy enriched air is being exhausted around the clock—not based on occupancy

•How can energy use be decreased without affecting comfort?

•Setback/Increase of temperature in winter/summer

•Dehumidify only when necessary

•Reduce exhaust of conditioned air during low occupancy

40,000 CF

Heating And/Or Cooling

Building Circulation

AHU

Return Air

Damper

Dampers

Building Energy Use 

Cooling season: May‐Late August

•Cool to 55, then heat to 70

Heating season: Sept – Mid April

Energy Use Determined By:Outdoor Conditions

• Temperature • Humidity

Indoor Air temp Settings

Percent of outside air needed foair quality

Heating Cooling

Average Daily Temp. 2007

Indoor Temperature

Outdoor Temperature

Average $/CFM Breakdown

Building CoolingReheatWinter Heating Fans

Average 14% 19% 43%

•$3-5/CFM=> Reduce CFM

$/CFM by Building

Summer Reheat

Winter Heating

Cooling

Fans

24%

Set Back Analysis

15 St Mary’s St.First Case Study

50,000 sq ft office/class building

Analysis of Summer Results (15 St Mary’s)

• Profound drop in demand (38%) during Unocc period• 11 hour unoccupied• Some implementation issues observed

WeekdayAverage Summer kWh 2009

020406080

100120140160180

1:00AM

4:00AM

7:00AM

10:00AM

1:00PM

4:00PM

7:00PM

10:00PM

TimekW

h

Should change start up to avoid spike User

Demand

Minimal Fan/AC Why so high?

Weekend

Average Summer kWh 2008

020406080

100120140160180

1:00AM

4:00AM

7:00AM

10:00AM

1:00PM

4:00PM

7:00PM

10:00PM

Time

kWh

2009 Unocc. modeUnocc. Mode Savings

User DemandWeekday

Weekend~40 kWh

Before Unocc. With Unocc.

Reduce Nighttime Exhaust (8 hrs)

•Find energy used to condition a unit volume of air

•Find volume of air exhausted

•Add energy used to condition air across all units of air exhausted

Estimated Savings

•11% of total oil ($7,400)•7% of total electric. ($10,900)

Estimated Implementation Cost

$17,500—about 1 year payback$17.5k to AndoverThe rest is Rebalance! Was it needed?

Estimate of Potential Setback Savings

Heating oil savings

Cooling electricity savings

Original Estimate Updated

13% ~$20k

$50k <2

21% $12,522

Implementation Lessons

• Need to spec out more thorough implementation– OA Damper Stuck open– Winter AHU heating level 100%– Spike when heat comes on

• Utility and AHU level analysis: check to see what’s really happening. Need to coordinate between HVAC staff, automation, and energy.

• What was really necessary– Rebalancing?

646668707274767880

12:00PM

6:00 PM 12:00AM

6:00 AM 12:00PM

Time of DayTe

mpe

ratu

re(F

)

02000400060008000

100001200014000160001800020000

12:00AM

6:00 AM 12:00PM

6:00 PM 12:00AM

Time of Day

Flow

(cfm

)

SAFlowRAFlow

Room Temp

Setpoint

Energy Savings: Solving for the Hidden Costs of HVAC

Our Focus: HVAC is 50‐70% of ALL energy used in mid/large size buildings

Achieving Energy Efficiency in Existing Commercial Buildings

Strategy: Reduce high air flow rates which were implemented when energy was cheap.

Our Solution • Develop new tool to re-optimize HVAC control • This is not addressed by current tools• Based on real buildings, experience and data

Funded by MA Clean Energy Center Professor Gevelber & Professor Wroblenski BU Mechanical Engineering

3.2

4.75

3.2

6.18

8.93

13.03

0

2

4

6

8

10

12

14

Sargent SMG 15 St. Marys PRB Photonics LSEB

Basis for Opportunity/Value• Many buildings designed when energy was cheap so used high air flow to assure ventilation, humidity, and 

thermal needs were met. • For existing buildings, hard to know “how low you can  go”• Should base design on minimum air flow for ventilation & lab safety• Our system provides easy basis to re‐optimize

Vent for 100%Lab

Target

Target

Req. for Ventilation

Office/Class

Lab

Overall Building ACH vs. Energy $/sq.ft.

Office/Class

Lab

ACH

Our Core ConceptRoom-by-room experiments

run through existing BASRoom-by-room experiments

run through existing BAS

Reset ACH through existing BAS software

Reset ACH through existing BAS software

Chiller

Air handling unit

VAV Box

Control

Determine actual ACH for each room (No plans needed)

Determine actual ACH for each room (No plans needed)

Establish minimum

ventilation needs

Establish minimum

ventilation needs

Aggregation enables

building-level optimization

Aggregation enables

building-level optimization

Enables monitoring/

diagnostics & commissioning

Enables monitoring/

diagnostics & commissioningBuilding HVAC Schematic

Which EUI should we use for analysis?

Energy Stars (based con CBECS data), and AASHE Stars program are based on gross square feet

• Does using gross area hide or distort both campus and building energy efficiencies?

• Key issues: - buildings with larger parking lots &- large interior spaces that are not conditioned

EUI Case Study: Medical Campus• 19 buildings including 2     

parking garages

Total Gross Area (sq. ft)

Total Net Area (sq. ft)

2,455,222 1,738,909

Gross Parking(sq. ft)

Net Parking(sq. ft)

969,998 620,491

Downtown Campus: Parking is 40% of Gross Area. Net is 71% of gross (but incl. parking since assignable) .

How does considering net & parking affect EUI Analysis (kbtu/sq ft)?

Analysis of Medical Campus EUI

Gross EUI* Inc. Parking

Net EUI Inc.Parking

136 190

•Using Gross EUI, including parking, hides major energy use!

•212% difference between net w/o Parking and Gross EUI

Why does this happen? parking uses 10-20 kbtu/ft^2, BUT need to consider net area includes parking since assignable!

Gross EUI w/o Parking

Net EUI w/o Parking

218 289

*EUI = Energy Use Intensity in kBtu/sq. ft

What are the effects of parking?

Analysis of BU Charles River Campus

• 280 Buildings

• Gross Area: 11,690,000 sq. ft.

• Net Area: 9,362,500 sq. ft.• (80% of gross)

• Building Parking: 701,400 ft2,

6% of area

Analysis of BU Charles River Campus

• While parking is only 6% area, its EUI is so low (10‐20 kBtu/sq. ft) that it distorts EUI calculation

Gross EUI

Net EUI

w/ Parking 124 155w/o Parking 132 167

• 25% difference in EUI net to gross, but35% difference in EUI for net and gross area w/o parking

Gross Area (sq.ft)

Net Area (sq.ft)

Parking (sq.ft)

Gross EUI

Net EUI

Net EUI w/o Parking

SMG classroom/offices 481,100 325,300 23,100 159 235 267

575 Comm: Dorm 87,600 79,000 33,000 82 90 160

808 Comm Art Space / Office

266,000 244,400 38,000 71 77 99

Analysis of Individual BuildingsGross & Net Areas w/ Parking

• For individual buildings, taking account of net area & parking yields significantly different results ( 68%-95%).

• Important for obtaining good building priority list

Summary

• What is the EUI of different buildings, org. by types:provides roadmap– Consider net area and w/o parking

• HVAC should be a major area of focus: 70% of energy– require better coordination amongst facility groups, some special

experts and manpower, , but offer substantial cost reduction and green benefits

• Implementing unoccupied modes– Low cost: <1 yr payback & 10-15% Energy savings

• Deeper savings: focus on ACH– Energy cost ACH….and we are over-ventilating our buildings– Mostly reprogramming, but rebalancing possibly required.

Average Electrical Use Breakdown

•Much of energy use is hidden both to occupants & building managers.

*HVAC elec is 58%

590 Comm Setback

• Unoccupied Hours:– Offices 6pm – 7am– Classrooms        11pm – 7am

• Affected area:– 55,000 ft2 (50’% area)– 222 terminal boxes

• Timeline:– Proposal  Dec‐2009– Implementation  Feb‐2010

• Project Managers:– Colleen Mcginty– Robbie Choate

Background/Overview

• Existing commercial buildings offer significant energy savings opportunity 36% of US electricity

• HVAC ~ 50‐70% of  building energy use, but use is hidden.  20‐35% of electricity used to push air!

• Key: reduce air flow.  

• Our solution: Re‐optimize building HVAC system based on software approach.

• Works with existing Building Automation System (BAS)

• Unique: Solves problem not addressed by current tools.

• Nega‐watt: cheapest energy “source” by 4‐10x

Building Floor Area ProfileCharles River Campus 2007

Building Energy Use Profile

Electricity HeatingOil & Gas