making the best use of energy modeling in designing high-performance green buildings by andy lau,...

Making the Best Use of Energy Making the Best Use of Energy Modeling in Designing Modeling in Designing

High-Performance Green BuildingsHigh-Performance Green Buildings

bybyAndy Lau, PE, LEED APAndy Lau, PE, LEED AP

July, 2007July, 2007

Engineers Are VitalEngineers Are Vital

USGBC’s Core PurposeUSGBC’s Core Purpose

To transform the way buildings are To transform the way buildings are designed, built and operated, enabling an designed, built and operated, enabling an environmentally and socially responsible, environmentally and socially responsible, healthy, and prosperous built environment healthy, and prosperous built environment that improves the quality of life in that improves the quality of life in communities.communities.

Reducing Energy UseReducing Energy Use

1.1. Reduce loadsReduce loads

2.2. Harmonize with climateHarmonize with climate

3.3. Optimize systemsOptimize systems

4.4. Use renewable energy Use renewable energy

The Heart of the Process – The Heart of the Process – Integrated DesignIntegrated Design

Team-basedTeam-based Stakeholders engaged throughoutStakeholders engaged throughout Early goals and team alignmentEarly goals and team alignment Expertise engaged early & throughoutExpertise engaged early & throughout Building as organismBuilding as organism Reduce redundanciesReduce redundancies Use analysisUse analysis

Integrated Design ProcessIntegrated Design Process

DiscoverySchematic Design Design

DevelopmentConstruction Documents/ Delivery

Front End Back End

Concept Design

(CoVO)- Continuous Value Optimization

CoVO CoVO

CoVO CoVO CoVO

Schematic Design Design Development Construction Documents/ DeliveryConcept Design

(VE)- Value Engineering

VE VE VE VE

Whole System Integrated Process (WSIP)Whole System Integrated Process (WSIP)

Traditional ProcessTraditional Process

What is an Energy Model?What is an Energy Model?

A tool for …A tool for … estimating energy estimating energy

use and savings as use and savings as a a guideguide in design, in design,

complyingcomplying with with standards, standards,

optimizingoptimizing economic economic and energy and energy performance.performance.

What an energy model is What an energy model is NOTNOT:: A substitute for A substitute for

experience & experience & collaborationcollaboration

A tool for load A tool for load calculations or calculations or HVAC system sizingHVAC system sizing but it can account for but it can account for

the effect of building the effect of building changes on HVAC changes on HVAC sizessizes

A predictor of A predictor of human behaviorhuman behavior

Why do we need an Energy Model?Why do we need an Energy Model?

To To informinform decisions decisions Only way to account Only way to account

for for synergistic synergistic interdependenciesinterdependencies Examples: Daylighting,Examples: Daylighting,

Heat RecoveryHeat Recovery LEED certificationLEED certification

Standardizes Standardizes measurement of measurement of energy savings energy savings

Reduces Reduces “gamesmanship”“gamesmanship”

Synergistic InterdependenciesSynergistic Interdependencies

Window selectionWindow selection

Heating & Cooling loads

HVAC Size

HVAC Energy Use

Daylighting

ElectricLighting

Energy Use

EliminatePerimeterHeating

NOTE:

= $

Using it effectivelyUsing it effectively

Pre-DesignPre-Design

Design CharretteDesign Charrette

Schematic DesignSchematic Design

• Identify strategiesIdentify strategies• Set goals Set goals

• Climatic analysisClimatic analysis• US EPA Target Finder analysisUS EPA Target Finder analysis

• Develop base caseDevelop base case• Develop high-performance visionDevelop high-performance vision

• Shape, massingShape, massing• Windows & Building envelopeWindows & Building envelope• DaylightingDaylighting• HVAC typeHVAC type

• Individual EEM’s and combosIndividual EEM’s and combos

Using it effectivelyUsing it effectively

Design DevelopmentDesign Development

Construction / BiddingConstruction / Bidding

CommissioningCommissioning

• Fine-tune detailsFine-tune details• Check progress, LEED points Check progress, LEED points

• ““Value” engineeringValue” engineering• Document for LEEDDocument for LEED

• Calibrate modelCalibrate model• Troubleshoot operation Troubleshoot operation

Start modeling ASAPStart modeling ASAP

When just 1% of a project’s When just 1% of a project’s

up front costs are spent…up front costs are spent…

up to 70% of its life-cycle costsup to 70% of its life-cycle costs

may already be committed.may already be committed.

Pre-design – climatic analysisPre-design – climatic analysis

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90 100

Tem

pera

ture

, °F

Relative Humidity, %

Typical Day Comfort Chart Williamsport, Pennsylvania

JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecemberApprox. Comfort Zone

Hot and/or humid – avoid sun and air

Mild – manage sun, use ventilation & air movement

Cold & dry – allow sun and humidify

Pre-design – EPA Target FinderPre-design – EPA Target Finder

Pre-design – EPA Target FinderPre-design – EPA Target Finder

In Schematic DesignIn Schematic Design

““Easy” via Easy” via “wizard’s”“wizard’s”

Define base Define base casecase

Define Define proposedproposed

Analyze EEM’sAnalyze EEM’s

Design DevelopmentDesign Development

Fine-tune the designFine-tune the design Optimization of specific componentsOptimization of specific components

Clearview Elementary

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

Windows only Skylight Clerestory

Lighting Energy Savings ($/sq.ft.)

0

20

40

60

80

100

120

140

Illuminance (fc)

Clearview, Windows/skylights, 3/21, 11 am, Clear Sky

120-140

100-120

80-100

60-80

40-60

20-40

0-20

0

20

40

60

80

100

120

140

Illuminance (fc)

Clearview, Windows/clerestories, 3/21, 11 am, Clear Sky

120-140

100-120

80-100

60-80

40-60

20-40

0-20

Measurement & VerificationMeasurement & Verification

Proposed energy model is calibrated to Proposed energy model is calibrated to actual post-occupancy operation actual post-occupancy operation conditions and weather data.conditions and weather data.

Verify that building systems and EEMs Verify that building systems and EEMs are operating as intended.are operating as intended.

Problems can be identified and Problems can be identified and solutions analyzed.solutions analyzed.

Model can be improved next time.Model can be improved next time.

Measurement & VerificationMeasurement & Verification

DEP Cambria, Ebensburg, PA: LEED SilverDEP Cambria, Ebensburg, PA: LEED Silver

Electric Use MeasurementsElectric Use Measurements

TABLE 1Comparison of Measured Power Levels with

PowerDOE Model (prior to calibration)

ItemMeasured

(kw)Modeled

(kw)Difference

(%)

Pumps-ground loop 4.06 2.60 -36.0

Fans-HVAC 8.60 9.23 7.3

Heat Recovery Ventilators 13.00 5.22 -59.8

Lights 21.90 18.64 -14.9

Equipment (plug) 17.80 17.80 0.0

Occupancy ComparisonOccupancy Comparison

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Fraction

Time of Day

DEP Ebensburg Occupancy Schedule - Weekday

WD Modeled

WD Measured

743 per-hr modeled vs. 706 per-hr reported (+5.1%)743 per-hr modeled vs. 706 per-hr reported (+5.1%)

Lighting ComparisonLighting Comparison

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Fraction

Time of Day

DEP Ebensburg Lighting Schedule - Weekdays

WD Modeled

WD Measured

226 kwh modeled vs. 310 kwh measured (-27%)226 kwh modeled vs. 310 kwh measured (-27%)

Plug Loads ComparisonPlug Loads Comparison

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Fraction

Time of Day

DEP Ebensburg Equipment Schedules - Weekday

WD Modeled

WD Measured

138 kwh modeled vs. 292 kwh measured (-53%)138 kwh modeled vs. 292 kwh measured (-53%)

  Model Actual Model/Actual

Month Energy Demand Energy1 Demand Energy Demand

(kwh) (kw) (kwh) (kw)    

Jan 33,095 82.7 35,111 82.9 0.943 0.998

Feb 29,147 83.3 34,777 78.6 0.838 1.060

Mar 32,260 83.5 35,247 75.4 0.915 1.107

Apr 29,894 86.1 34,761 74.3 0.860 1.159

May 30,688 84.5 34,531 77.0 0.889 1.097

        Avg 0.889 1.084

Comparison of Actual Energy Use in 2002 with Comparison of Actual Energy Use in 2002 with Calibrated Calibrated PowerDOE ModelPowerDOE Model

HVAC Energy use is underpredicted by about 16%HVAC Energy use is underpredicted by about 16%

Predicted SavingsPredicted Savings

 Case

Total(kwh)

Bill($)

Bill($/sq.ft.)

Savings(%)

ASHRAE Budget 624,302 64,556 1.87 Baseline

Proposed Original 253,814 26,561 0.77 -58.8

Proposed w/M&V Adj. 343,418 35,246 1.02 -45.5

Economics of Green Bldg’sEconomics of Green Bldg’s

Holistic approach needed Uses team knowledge Emphasis on reducing redundancies Comprehensive accounting

BIG SAVINGS can cost less than

Small Savings

Traditional Economic ApproachTraditional Economic Approach

Cumulative Savings

(+)

(-)

Cost Effectiveness LimitDiminishing

Returns

STOP

(payback, ROI, capital budget)Added Cost

Rocky Mountain Institute

Tunneling through the Tunneling through the Cost BarrierCost Barrier

Cumulative Savings

(+)

(-)

Cost Effectiveness LimitDiminishing

Returns

DETOUR

Rocky Mountain Institute

Reduced Costs

Neptune Township Community School

NJ Elementary School/Community Center ● 145,600 GSF ● SSP Architectural Group

EEM’sEEM’s

solar orientation R27 wall w/ blown

cellulose R30 roof insulation triple pane windows LPD 0.92 W/sf solar shading light shelves daylight dimming ground source heat

pumps underfloor air demand controlled

ventilation energy recovery units

Energy Modeling ResultsEnergy Modeling Results

EEM Cost Savings Payback

Lower Lighting Power Density

-$123,887 $12,549 NA

Daylighting $90,350 $16,584 5.45

Wood Triple Pane Windows

$69,896 $9,117 7.67

Extra Wall Insulation $46,302 $9,240 5.01

R30 Roof Insulation $41,789 $5,186 8.06

40% load reduction

Energy Modeling ResultsEnergy Modeling Results

EEM Cost Savings Payback

EEM Combination $124,450 $36,912 3.37

Cost Savings Payback

Holistic Effect -$275,550 $80,166 ??

HVAC System:Ground Source Heat Pumps40% load reduction = 10% cost reduction10% cost reduction = $400,000

Conclusions / RecommendationsConclusions / Recommendations

Start earlyStart early Allow adequate time for the analysisAllow adequate time for the analysis Communicate regularly and effectivelyCommunicate regularly and effectively Recognize design integration issuesRecognize design integration issues

Danger of line item “Value” engineeringDanger of line item “Value” engineering Use your head too!Use your head too!

Thank You