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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