Technical Report

NREL/TP-550-47427

August 2010

Building Energy Simulation Test

for Existing Homes (BESTEST-EX) 

Phase 1 Test Procedure:

Building Thermal Fabric Cases

Ron Judkoff, Ben Polly, and Marcus Bianchi

National Renewable Energy Laboratory

Joel Neymark

J. Neymark & Associates

Link to Accompanying Zipped Data Files (2.9 MB)
National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401-3393

303-275-3000 • www.nrel.gov

NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency and Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

Contract No. DE-AC36-08-GO28308

Technical Report

NREL/TP-550-47427

August 2010

Building Energy Simulation Test

for Existing Homes (BESTEST-EX)

Phase 1 Test Procedure:

Building Thermal Fabric Cases

Ron Judkoff, Ben Polly, and Marcus Bianchi

National Renewable Energy Laboratory

Joel Neymark

J. Neymark & Associates

Prepared under Task No. ARRB.1000
NOTICE

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iii 

Acknowledgments 

For feedback and comments on the test procedure provided by BESTEST-EX Working Group 

participants during preliminary simulation trials, we wish to thank the following companies and 

individuals that ran simulations and responded to questionnaires: Apogee Interactive Inc.: Joel Gilbert, 

John Laun, Eric Shewbridge, Lei Wang; Architectural Energy Corporation: Brian Christensen, Rob 

Salcido; Conservation Services Group: Bruce Harley, Mick Rookwood, David Weitz, Michael Blasnik 

(consultant); Florida Solar Energy Center: Philip Fairey; ICF International: Brian Dean, Mike L’Ecuyer; 

Oak Ridge National Laboratory: Mark Ternes; Performance Systems Development LLC: Chris Balbach, 

Ethan MacCormick, John McCartney, Greg Thomas. 

Paul Norton of the National Renewable Energy Laboratory (NREL) provided initial organizational and 

management support during project startup. Ren Anderson of NREL also provided managerial support. 

Nick Long of NREL provided assistance with automating reference simulations.

We appreciate the support and guidance of Ed Pollock, Terry Logee, and Lew Pratsch, of the 

U.S. Department of Energy. 

 
iv 

Nomenclature 

A area 

Abs absorptance 

Abs In absorptance of inner pane 

Abs Out absorptance of outer pane 

ACH air changes per hour 

ACH50 air changes per hour at a pressure difference of 50 Pascals 

AIR approximate input range 

αext exterior solar absorptance 

ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers 

BA Building America 

BESTEST Building Energy Simulation Test 

BoC benefit of calibration 

“-C” calibrated energy savings test cases 

C3 fully random explicit input selection, near-nominal space heating/cooling 

consumption 

C4 fully random explicit input selection, high space heating/cooling consumption 

C5 fully random explicit input selection, low space heating/cooling consumption 

C6 fully random explicit input selection, mid-high space heating/cooling consumption 

C7 fully random explicit input selection, mid-low space heating/cooling consumption 

cfm cubic feet per minute 

CFM50 or 

CFM50

infiltration flow rate (in cfm) at a pressure difference of 50 Pascals 

CO or Col 

Springs 

Colorado Springs, Colorado 

Coef or Coeff coefficient 

COG center of glass 

COP coefficient of performance 

COPclg effective space cooling system coefficient of performance 

Corr. correction 

Cp specific heat, Btu/(lb·°F) [J/(kg·K)] 

D door 3' × 6'8" 

DHW domestic hot water 

Dir. nor. direct normal 

DOE U.S. Department of Energy 

DOE2.1E DOE-2.1E, Version JJHirsch PC 2.1 En136 

Ehtg effective space heating system efficiency 

E+ EnergyPlus, Version 3.1 

EIA Energy Information Administration 

ELA effective leakage area 

EOG edge of glass 

Ext. exterior 

F °F (used in units designators) 

hc convective surface heat transfer coefficient 

HEATCAP heat capacity 

Hemis hemispherical 

HERS Home Energy Rating System 

hi infrared radiative surface heat transfer coefficient 

ho combined convective and infrared radiative exterior surface heat transfer coefficient 

hs combined convective and infrared radiative interior surface heat transfer coefficient 
v 

HVAC heating, ventilating, and air-conditioning 

Ins insulation 

Int interior 

ISO International Standards Organization 

I-P inch-pound 

k thermal conductivity, Btu/(h·ft·°F) [W/(m·K)] 

LBL Lawrence Berkeley Laboratory, or Lawrence Berkeley National Laboratory 

Low-e low emissivity 

LV Las Vegas, Nevada 

Max maximum, also approximate input range maximum 

Min minimum, also approximate input range minimum 

NAHB National Association of Home Builders 

NCDC National Climatic Data Center 

NFRC National Fenestration Rating Council 

Nom nominal 

NREL National Renewable Energy Laboratory 

NSRDB National Solar Radiation Data Base 

N/A not applicable 

o.c. or O.C. on centers 

“-P” building physics test cases 

R unit thermal resistance, h·ft2·°F/Btu [m2

·K/W] 

REF average of reference program energy savings predictions using randomly selected 

explicit inputs (million Btu or kWh) 

Refl. reflectance 

Refl,f reflectance for radiation incident from the front (from the exterior surface) 

Refl,b reflectance for radiation incident from the back (from the interior surface) 

SC shading coefficient 

SHGC solar heat gain coefficient 

sol_abs solar absorptance 

SUNREL SUNREL, Version 1.14 

Surf surface 

TEMP temperature 

Tclg zone air temperature for cooling 

Thtg zone air temperature for heating 

TMY Typical Meteorological Year 

TMY2 or TM2 Typical Meteorological Year 2 

Trans. transmittance 

U unit thermal conductance or overall heat transfer coefficient, Btu/(h·ft2·°F) 

[W/(m2

·K)] 

UA thermal conductance 

UAinf or UAinfl equivalent thermal conductance due to infiltration 

UV ultraviolet 

Val value 

W Window, 3' × 5' 

WBAN Weather Bureau Army Navy 

WG CAL average working group calibrated energy savings prediction (million Btu or kWh) 

WG UNCAL average working group uncalibrated energy savings prediction (million Btu or kWh) 

 
vi 

Contents Page

Acknowledgments ................................................................................................ iii

Nomenclature ....................................................................................................... iv

Contents ............................................................................................................... vi

Accompanying Files (Electronic Media Contents) .......................................................... viii

Figures ................................................................................................................. ix

Tables .................................................................................................................. x

Introduction .......................................................................................................... xiii

 Overview of the BESTEST-EX Phase 1 Test Suite ................................................... xiii

 Methodology .............................................................................................. xiv

 Future Work ............................................................................................... xv

 Advice to Certifying Agency ........................................................................... xv

1.0 Test Procedures ........................................................................................... 1

 1.1 Modeling Approach ............................................................................ 1

 1.1.1 Time Convention ..................................................................... 1

 1.1.2 Geometry Convention ............................................................. 1

 1.1.3 Nonapplicable Inputs ............................................................... 1

 1.1.4 Consistent Modeling Methods .................................................... 1

 1.1.5 Equivalent Modeling Methods ................................................... 1

 1.1.6 Simulation Initialization and Preconditioning .................................. 1

 1.1.7 Simulation Duration ................................................................. 1

 1.1.8 Programs With Different Operational Modes Depending on Utility Data 

Availability ............................................................................ 1

 1.1.9 Order of Testing ...................................................................... 2

 1.2 Building Physics Test Input Specifications ................................................. 2

 1.2.1 The Pre-Retrofit Base-Case Building (Case L200EX-P) ........................ 3

 1.2.2 Building Physics Retrofit Test Cases .............................................. 29

 1.3 Calibrated Energy Savings Tests Input Specifications ..................................... 46

 1.3.1 Pre-Retrofit Base-Case Building (Case L200EX-C) ............................ 46

 1.3.2 Calibrated Energy Savings Retrofit Test Cases ................................. 58

References ............................................................................................................ 63

 
vii 

Appendix A Weather Data ...................................................................................... 67

Appendix B Selection of Internal Loads ...................................................................... 77

Appendix C Combined Surface Heat Transfer Coefficients ................................................ 81

Appendix D Infiltration Modeling .......................................................................... 93

Appendix E Window Modeling with WINDOW 5 ...................................................... 96

Appendix F Random Selection of Explicit Inputs for Case L200EX-C Reference Simulation 

Results .............................................................................................. 100

Appendix G Example Results ................................................................................... 104

Appendix H Definitions ...................................................................................... 118

Appendix I Recommendations for Future Work ......................................................... 120
viii 

Accompanying Files (Electronic Media Contents) 

The following files provided within BESTEST-EX-Phase-1-Proc-AccompanyingFiles.zip 

apply as they are called out in the test procedure: 

• README-BESTEST-EX-Files.doc: Electronic media contents. 

• Colorad.TM2: TMY2 weather data for Colorado Springs, Colorado, as described in Appendix A. 

• Lasvega.TM2: TMY2 weather data for Las Vegas, Nevada, as described in Appendix A. 

• BESTEST-EX-Phase-1-Output.xls: Spreadsheet standard output report for entering results. 

• B-EX-Phase-1-Ref-P-Results.xls: Spreadsheet that contains reference simulation results 

presented in Appendix G, Section G.1. Use BESTEST-EX-Phase-1-Output.xls to enter simulation 

results for the program being tested. 

The following reference simulation input files are provided for informative use. 

The subfolder B-EX-Ref-Simulation-Physics-Input-Files contains reference simulation input files 

developed by NREL for the building physics (“-P”) test cases of BESTEST-EX. The input files are 

organized in lower-tier subfolders as follows: 

Subfolder Reference simulation program

\DOE-2 DOE-2.1E Version JJHirsch PC 2.1En136 

\EnergyPlus EnergyPlus Version 3.1 

\SUNREL SUNREL Version 1.14 

\B-EX-Ref-Simulation-Weather-Files All programs 

Reference simulation input files are described further within README-BESTEST-EX-Files.doc.

 
ix 

Figures 

 Page

Figure 1-1. Base building axonometric .................................................................. 10

Figure 1-2. Floor plan – Case L200EX .................................................................. 11

Figure 1-3. East side elevation – Case L200EX .......................................................... 12

Figure 1-4 Exterior wall plan section – Case L200EX ................................................. 13

Figure 1-5. Raised floor exposed to air section – Case L200EX .................................... 13

Figure 1-6. Ceiling/attic/roof section – Case L200EX ................................................ 14

Figure 1-7. Interior wall plan section – Case L200EX .................................................. 15

Figure 1-8. Window detail, vertical slider (NFRC AA) with 23⁄4”-wide frame – Case L200EX . 16

Figure 1-9. Ceiling section – Case L200EX ............................................................ 31

Figure 1-10. Exterior wall plan section – Case L225EX ............................................... 34

Figure 1-11. South overhang – Case L270EX-P ......................................................... 44

Figure 1-12. Overhang for east and west windows – Case L270EX-P ............................... 45

Figure A-1. Sample file header and data in the TMY2 format for January 1 ........................ 70

Figure B-1. Normalized hourly profiles for internal loads due to occupants, gas, and 

electricity ....................................................................................... 80

Figure C1-1. Effect of window interior convective surface coefficient on average reference 

results for gas use and savings in cases with space heating ............................. 85

Figure C1-2. Effect of window interior convective surface coefficient on average reference 

results for electricity use and savings in cases with space cooling ..................... 86

Figure F-1. Triangular probability distribution assumed for random generation of explicit 

inputs ........................................................................................... 100

Figure G-1. Building physics heating tests: Reference simulation results........................... 105

Figure G-2. Building physics cooling tests: Reference simulation results........................... 105

Figure G-3. Field trial results for fully random, near nominal heating scenario (C3H) ........... 109

Figure G-4. Field trial results for fully random, high heating scenario (C4H) ...................... 110

Figure G-5. Field trial results for fully random, low heating scenario (C5H) ....................... 110

Figure G-6. Field trial results for fully random, mid-high heating scenario (C6H) ................ 111

Figure G-7. Field trial results for fully random, mid-low heating scenario (C7H) ................. 111

Figure G-8. Field trial results for fully random, near nominal cooling scenario (C3C) ........... 112

Figure G-9. Field trial results for fully random, high cooling scenario (C4C) ...................... 112

Figure G-10. Field trial results for fully random, low cooling scenario (C5C) ....................... 113

Figure G-11. Field trial results for fully random, mid-high cooling scenario (C6C) ................ 113

Figure G-12. Field trial results for fully random, mid-low cooling scenario (C7C) ................. 114

 
x 

Tables 

 Page

Table 1. BESTEST-EX Case Summary ................................................................. xvii

Table 1-1. Building Thermal Summary – Case L200EX ............................................... 17

Table 1-2. Other Building Details – Case L200EX ..................................................... 18

Table 1-3. Component Surface Areas and Solar Fractions – Case L200EX ......................... 19

Table 1-4. Material Descriptions Exterior Wall, Door, and Window – Case L200EX ............. 20

Table 1-5. Material Descriptions, Raised Floor Exposed to Air – Case L200EX ................... 21

Table 1-6a. Material Descriptions, Ceiling, Attic, and Roof – Case L200EX ......................... 22

Table 1-6b. Material Descriptions, Ceiling/Attic/Roof, Attic as Material Layer – 

Case L200EX ........................................................................................... 23

Table 1-7. Material Descriptions, Interior Wall – Case L200EX ......................................... 24

Table 1-8a. Conditioned Zone Equivalent Inputs for Weather-Driven Infiltration Models – 

Case L200EX ........................................................................................... 24

Table 1-8b. Equivalent Seasonal Constant Infiltration ACH and CFM – Case L200EX ............ 25

Table 1-9a. Daily Sensible Internal Loads – Case L200EX .............................................. 25

Table 1-9b. Normalized Hourly Profiles for Sensible Internal Loads – Case L200EX .............. 26

Table 1-10. Window Summary (Single-Pane Aluminum Frame With Thermal Breaks) – 

Case L200EX ........................................................................................... 27

Table 1-11. Glazing Summary, Single-Pane Center of Glass Values – Case L200EX ............... 28

Table 1-12. Optical Properties as a Function of Incidence Angle for Single-Pane Glazing – 

Case L200EX ............................................................................................ 29

Table 1-13. Conditioned Zone Equivalent Inputs for Weather-Driven Infiltration Models – 

Case L210EX-P ........................................................................................ 30

Table 1-14. Equivalent Seasonal Constant Infiltration ACH and CFM – Case L210EX-P ....... 30

Table 1-15. Building Thermal Summary – Case L220EX ............................................. 32

Table 1-16a. Material Descriptions, Ceiling – Case L220EX ............................................... 32

Table 1-16b. Material Descriptions for Attic as Material Layer – Case L220EX .................... 33

Table 1-17. Building Thermal Summary – Case L225EX ............................................. 35

Table 1-18. Material Descriptions, Exterior Wall – Case L225EX ..................................... 35

Table 1-19. Building Thermal Summary – Case L250EX ............................................. 38

Table 1-20. Window Summary (Double-Pane, Low-E, Argon Fill, Wood Frame, Insulated 

Spacer) – Case L250EX ......................................................................... 39

Table 1-21. Low-E Glazing With Argon Gas Fill Glazing Summary (Center of Glass Values) 

– Case L250EX ..................................................................................... 40

Table 1-22. Optical Properties as a Function of Incidence Angle for Low-Emissivity DoublePane Glazing – Case L250EX ............................................................... 41

Table 1-23. Component Solar Fractions – Case L250EX ................................................... 42

Table 1-24a. Case L200EX-C1H Reference Utility Energy Use Data....................................... 49
xi 

Table 1-24b. Case L200EX-C2H Reference Utility Energy Use Data....................................... 49

Table 1-24c. Case L200EX-C3H Reference Utility Energy Use Data....................................... 50

Table 1-24d. Case L200EX-C4H Reference Utility Energy Use Data....................................... 50

Table 1-24e. Case L200EX-C5H Reference Utility Energy Use Data....................................... 51

Table 1-24f. Case L200EX-C6H Reference Utility Energy Use Data....................................... 51

Table 1-24g. Case L200EX-C7H Reference Utility Energy Use Data....................................... 52

Table 1-25a. Case L200EX-C1C Reference Utility Energy Use Data....................................... 52

Table 1-25b. Case L200EX-C2C Reference Utility Energy Use Data....................................... 53

Table 1-25c. Case L200EX-C3C Reference Utility Energy Use Data....................................... 53

Table 1-25d. Case L200EX-C4C Reference Utility Energy Use Data....................................... 54

Table 1-25e. Case L200EX-C5C Reference Utility Energy Use Data....................................... 54

Table 1-25f. Case L200EX-C6C Reference Utility Energy Use Data....................................... 55

Table 1-25g. Case L200EX-C7C Reference Utility Energy Use Data....................................... 55

Table 1-26. Conditioned Zone Equivalent Input Decrease for Infiltration Models – 

Case L210EX-C .............................................................................. ................ 59

Table A-1. Site and Weather Data Summary for Colorad.TM2 Weather, Colorado Springs, 

Colorado ........................................................................................................ 67

Table A-2. Site and Weather Data Summary for Lasvega.TM2 Weather, Las Vegas, Nevada . 68

Table A-3. Header Elements in the TMY2 Format (for First Record of Each File) ............... 71

Table A-4. Data Elements in the TMY2 Format (for All Except the First Record) ................ 71

Table A-5. Solar Radiation and Illuminance Source Flags.................................................. 75

Table A-6. Solar Radiation and Illuminance Uncertainty Flags............................................ 75

Table A-7. Meteorological Source Flags ............................................................................. 76

Table A-8. Meteorological Uncertainty Flags ...................................................................... 76

Table B-1. Breakdown of B-EX Daily Internal Loads ........................................................... 77

Table B-2. Comparison of Proposed Internal Sensible Loads With Building America 

Prototype House Results ..................................................................................... 

79

Table B-3. Comparison of Proposed Internal Latent Loads With Building America Prototype 

House Results ..................................................................................................... 

79

Table C1-1. Disaggregated Interior Surface Film Coefficients .................................................... 82

Table C1-2. Interior Convective Surface Coefficients for Vertical Surfaces................................ 84

Table C1-3. Interior Convective Surface Coefficients for Roof and Gables ............................... 84

Table C1-4. Interior Convective Surface Coefficients for Horizontal Surfaces ........................... 84

Table C1-5. Interior Convective Surface Coefficients for Single-Pane Windows ....................... 84

Table C1-6. Effect of Window Interior Surface Convective Calculation for EnergyPlus 

Version 3.1 Versus Version 4.0 ............................................................................ 85

Table C2-1. Combined Exterior Heat Transfer Coefficients for Each Surface Type ................... 87

Table C2-2. Combined Exterior Heat Transfer Coefficients After Area Weighting .................... 88

Table C2-3. Disaggregated Exterior Film Coefficients for Opaque Surfaces .............................. 89
xii 

Table C2-4. Surface Roughness Multipliers ............................................................................. 90

Table C2-5. Exterior Convective Surface Coefficients for Vertical Surfaces .............................. 90

Table C2-6. Exterior Convective Surface Coefficients for Roof and Gables ............................... 90

Table C2-7. Exterior Convective Surface Coefficients for the Floor ........................................... 91

Table C2-8. Exterior Convective Surface Coefficients for Windows .......................................... 91

Table D-1. EnergyPlus Infiltration Sensitivity Test Results ...................................................... 94

Table F-1. Approximate Input Ranges (AIRs), Nominal Inputs, and Portions of AIRs Used 

for Generating Explicit Input Sets Corresponding to Low, Random, and High 

Space-Conditioning Energy Consumption .............................................................. 103

Table G-1. BESTEST-EX Building Physics Heating Tests Reference Results .......................... 106

Table G-2. BESTEST-EX Building Physics Cooling Tests Reference Results ......................... 106

Table G-3. Benefit of Calibration (BoC) for Working Group Field Trial .................................. 115

Table G-4. Benefit of Calibration for Combined Retrofit Cases (L300EX) in Working Group 

Field Trial ................................................................................................................. 116

 
xiii 

Introduction 

A number of computerized energy auditing systems use utility bill data and a variety of calibration 

methods with the objective of tuning their audit models to more accurately predict energy savings from 

retrofits. A potential increase in performance-based tax incentives for home energy retrofits is driving the 

need for establishing procedures to test the accuracy of building energy audit software used to predict 

retrofit energy savings. The National Renewable Energy Laboratory (NREL), in work spanning 30 years, 

has led development of numerous procedures for evaluating various aspects of building energy analysis 

computer programs used in both commercial and residential applications. Consequently, the U.S. 

Department of Energy (DOE) tasked NREL to develop a process for testing the reliability of models that 

predict retrofit energy savings, including their associated calibration methods. DOE asked NREL to 

conduct the work in phases so that a test procedure would be ready should DOE need it to meet legislative 

requirements related to residential retrofits in FY 2010. This report documents the initial “Phase 1” test 

procedure. NREL expects to continue to improve the test procedure as additional empirical residential 

energy retrofit data become available. This report has two purposes, a) to serve as a test procedure, and b) 

to describe the process of developing the procedure, and what was learned during the work. 

Overview of the BESTEST-EX Phase 1 Test Suite 

This test suite represents a set of cases applying the NREL BESTEST-EX Methodology. It includes two 

kinds of test cases: 

Building physics test cases with fully known inputs: A given audit model is tested using 

specified inputs; resulting outputs are compared with reference results from three detailed 

simulation programs (EnergyPlus version 3.1, DOE-2.1E version JJHirsch PC 2.1En136, and 

SUNREL version 1.14) presented in Appendix G. Tested program results may also be compared 

with example acceptance criteria (Judkoff et al. 2010), or other results generated using this test 

procedure. 

Calibrated energy savings test cases with specified base-case monthly utility bill data and 

uncertainty ranges for selected inputs: A given audit model (and associated calibration 

method) is tested by comparing utility-bill-calibrated energy savings predictions to results from 

the reference programs listed above. Reference results for the calibrated energy-savings tests are 

not published with the test procedure so that both automated and manual calibration methods are 

tested blind, without access to the reference results (answers). Practical application of this 

procedure requires that tested-program results are compared to reference results by a third-party. 

The calibrated energy savings tests represent a new methodological development, further 

described under “Methodology” below. 

The cases test the ability to model space heating loads in a representative heating climate and space 

cooling loads in a representative cooling climate. The building physics and calibrated energy savings 

cases include the following retrofit cases: infiltration air sealing, attic insulation, wall insulation, 

programmable thermostat, low-e windows, low exterior solar-absorptance roof (cool roof), and external 

solar shading. Combined retrofit cases are also included as appropriate to heating and cooling climates, 

respectively. The cases are summarized in Table 1. 

To help avoid user input errors, the input for the test cases is as simple as possible, and represents 

“typical” constructions and thermal and physical properties. The BESTEST-EX base building is based on 

HERS BESTEST (Judkoff and Neymark 1995a). Typical building descriptions and physical properties 

published by sources such as DOE, the National Association of Home Builders, the American Society of 

Heating Refrigerating and Air-Conditioning Engineers (ASHRAE), and the National Fenestration Rating 

Council (NFRC) are used for the test cases. The development team used empirical information from 

several large utility bill studies (Blasnik 2009), in consultation with industry participants (BESTEST-EX 
xiv 

Working Group 2009), to modify some of the thermal inputs to be more appropriate for poorly insulated 

older buildings. 

Methodology 

NREL has developed a number of building energy simulation test (BESTEST) suites for evaluating and 

diagnosing errors in software used for energy analysis of residential and commercial buildings. These test 

suites have been adopted and cited by many organizations such as the Internal Revenue Service (2008) 

(for certifying software used to determine tax deductions), ASHRAE (ANSI/ASHRAE/IESNA 2007), 

RESNET (2006, 2007), the International Energy Agency (Judkoff and Neymark 2009), and the European 

Community under their Energy Performance Directive (European Union 2002). These methods include 

software-to-software comparative testing, verification versus analytical solutions, and validation versus 

vetted empirical data. The theoretical basis for the BESTEST procedures is further described in the 

literature (ASHRAE 2009, Judkoff 1988, Judkoff et al. 2008, Judkoff and Neymark 2006). 

The building physics test cases described in the preceding section are a direct application of software-tosoftware comparative test methods. The calibrated energy savings tests required NREL to make a 

methodological advancement to existing comparative test methods, as follows. 

1. Introduce input uncertainty into the test specification (this represents uncertainty 

associated with developing inputs from audit survey data): 

a. Perform sensitivity tests on inputs with potentially high uncertainty to determine their 

relative effect on output; select the inputs that have the greatest effect on outputs as 

approximate inputs. 

b. Specify uncertainty ranges (approximate input ranges) for the approximate inputs. 

2. Develop reference simulation results: 

a. Generate base-case synthetic utility bill data using the same state-of-the-art reference 

simulation programs as used in the building physics test cases. 

i. For the reference simulations, inputs that are randomly selected from within the 

specified approximate input ranges are designated as explicit inputs; the reference 

simulation explicit inputs are not included in the test specification (kept secret) 

ii. All reference simulations use the same or equivalent explicit inputs for a given 

calibration scenario. 

b. Generate reference energy savings results by adjusting appropriate base case inputs 

(including explicit inputs) as specified for each retrofit case. 

3. Develop tested program results: 

a. Develop the preliminary non-calibrated base-case model for a given calibration scenario. 

b. Predict energy savings by either: 

i. Calibrating the base-case model inputs using the synthetic utility bills (described 

in 2a above) and then applying the specified retrofit cases to the calibrated 

model, or 

ii. Applying the specified retrofit to the non-calibrated base case model and then 

calibrating or correcting energy savings predictions using the synthetic utility 

bills (without adjustment to base-case model inputs), or 

iii. Other calibration methods. 
xv 

4. Compare results of tested programs (and their calibration techniques) versus reference 

simulation base-case usage and retrofit energy savings projections: 

a. Example acceptance criteria may be used to facilitate the comparison. 

The conceptual framework for this method was first proposed by Judkoff (2008) with important 

refinements contributed by others (Neymark and Norton 2009; Neymark et al. 2009). Development of the 

method was facilitated by convening a technical committee of software producers (the “BESTEST-EX 

Working Group”) to provide help with quantifying approximate input ranges and developing tested 

program results (see Step 1b and Step 3, respectively, above). The test procedure was developed in an 

iterative process that allowed improvement of the test specification during the simulation trials and helped 

simulation trial participants to improve their software. 

In its purest form, the calibration test would be implemented without using the reference simulation 

programs. Instead, synthetic utility billing data would be generated with the tested program itself. Such a 

pure calibration test requires a) automated calibration or b) that the modeler running the calibration test 

does not know the explicit inputs used to develop the synthetic utility bills, implying that an additional 

modeler is needed. 

Future Work 

For further development of BESTEST-EX, NREL intends to add features that may include retrofit 

measures such as HVAC equipment, duct sealing, domestic hot water, lighting, appliances, foundation 

insulation, and others. Future test cases may include selected cross-referenced cases from HERS 

BESTEST and other existing test procedures. NREL also plans to address using empirical data from 

existing audited homes to quantify accuracy of building energy simulation tools when used for modeling 

older poorly insulated buildings, and retrofits to those buildings. Based on this work, refinements to 

BESTEST-EX to better match empirical data may also be considered. Appendix I provides more detail 

about recommendations for future work. 

Advice to Certifying Agency 

This test procedure is written so that it may be referenced directly by a certifying agency. A tested 

program may be thought of as successfully completing the test procedure when its results compare 

favorably with reference program outputs on a case-by-case and a sensitivity (difference between selected 

cases) basis. Example acceptance criteria based on the reference results of Appendix G, Section G.1 of 

this report are included in Example Procedures for Developing Acceptance-Range Criteria for BESTESTEX (Judkoff et al. 2010). That document, which may also be referenced directly by a certifying agency, 

illustrates how a certifying agency may evaluate a software tool with BESTEST-EX. The procedure for 

developing example acceptance ranges is also provided there. A certifying agency using BESTEST-EX 

may adopt these acceptance criteria or develop their own criteria. Neither DOE, the National Renewable 

Energy Laboratory (NREL), nor the authors of this report can be held responsible for any misfortunes 

caused by the use of the BESTEST-EX test procedure or the BESTEST-EX example acceptance criteria 

in a certification program. 
xvi 

Table 1. BESTEST-EX Case Summary 

Abbreviations for Table 1: 

“-C” calibrated energy savings test cases 

CSprgs Colorado Springs, Colorado 

clg cooling 

DLEW double-pane, low-e window with wood frame and insulated spacer 

Ext exterior 

E/W east/west 

htg heating 

htg&clg heating and cooling 

Infl infiltration 

Ins insulation 

Low-e win low-emissivity window 

LV Las Vegas, Nevada 

OHANG overhang 

“-P” building physics test cases 

RoofAbs1 roof with high exterior solar absorptance 

RoofAbs2 roof with low exterior solar absorptance 

R-VAL (compos.) composite air-to-air R-value 

S south 

SATB single-pane window with aluminum frame and thermal break 

TSTAT thermostat 

68-62 68°F heating base set point with 62°F set point for specified times 

78-84 78°F cooling base set point with 84°F set point for specified times 

INFILTRATION R-VAL (compos.) WINDOW DATA Roof

Case (ACH, (h·ft2

·F/Btu) SHADE Solar TSTAT (°F,

(Notes 1,2,3) Test Type CSprgs / LV) CEILING WALLS TYPE (OHANG) Abs. CSprgs/LV) Context

L200EX Base 0.760 / 0.492 13.7 5.1 SATB NO 0.6 68 / 78 "-P", "-C"

L210EX Infl 0.382 / 0.246 13.7 5.1 SATB NO 0.6 68 / 78 "-P", "-C"

L220EX Attic Ins 0.760 / 0.492 42.7 5.1 SATB NO 0.6 68 / 78 "-P", "-C"

L225EX Wall Ins 0.760 / 0.492 13.7 13.0 SATB NO 0.6 68 / 78 "-P", "-C"

L240EX Tstat 0.760 / 0.492 13.7 5.1 SATB NO 0.6 68-62 / "-P", "-C"

78-84

L250EX Low-e win 0.760 / 0.492 13.7 5.1 DLEW NO 0.6 68 / 78 "-P", "-C"

L260EX-P RoofAbs1 0.760 / 0.492 13.7 5.1 SATB NO 0.8 68 / 78 "-P" only

L265EX RoofAbs2 0.760 / 0.492 13.7 5.1 SATB NO 0.2 68 / 78 "-P" htg&clg,

"-C" clg only

L270EX-P Ext. Shade 0.760 / 0.492 13.7 5.1 SATB S+E/W 0.6 68 / 78 "-P" only

L300EX-PH Combined 0.382 / 0.246 42.7 13.0 DLEW NO 0.6 68-62 "-P" htg only

L300EX-CnH "-C" htg only

L300EX-PC Combined 0.382 / 0.246 42.7 13.0 DLEW S+E/W 0.2 78-84 "-P" clg only

L300EX-CnC Combined 0.382 / 0.246 42.7 13.0 DLEW NO 0.2 78-84 "-C" clg only

Note 1: Changes to Case L200EX are highlighted with bold font.

Note 2: Nominal input values for "-P" cases are shown here. "-C" cases replace key nominal input values with 

 approximate input ranges. 

Note 3: "n" in case designator (e.g., "L300EX-CnH") indicates the calibrated energy savings case scenario number.

BESTEST-EX_CASES-020210.xls, B-EX(4)!a5:l28
1 

1.0 Test Procedures 

1.1 Modeling Approach 

This modeling approach shall apply to all test cases presented in Sections 1.2 and 1.3. 

1.1.1 Time Convention 

All references to time in this specification are to local standard time and assume that hour 1 = the interval 

from midnight to 1:00 a.m. Do not use daylight saving time or holidays for scheduling. Typical 

Meteorological Year 2 (TMY2) weather data are in hourly bins corresponding to local standard time. 

1.1.2 Geometry Convention 

If the program being tested includes the thickness of walls in a three-dimensional definition of the 

building geometry, then wall, roof, and floor thicknesses shall be defined such that the interior air volume 

of the building model remains as specified. Make the thicknesses extend exterior to the currently defined 

internal volume. 

1.1.3 Nonapplicable Inputs 

In some instances the specifications will include input values that do not apply to the input structure of 

the program being tested. When this occurs, disregard the nonapplicable inputs and continue. Such inputs 

are in the specifications for programs that may need them. 

1.1.4 Consistent Modeling Methods 

Where there are options in a simulation program for modeling a specific thermal behavior, consistent 

modeling methods shall be used for all cases. For example, if a software program provides a choice of 

methods for modeling windows, use the same window modeling method for all cases. 

1.1.5 Equivalent Modeling Methods 

Where a program or specific model in a program does not allow direct input of specified values, or where 

input of specified values causes instabilities in a program’s calculations, modelers should develop 

equivalent inputs that match the intent of the test specification as nearly as the software being tested 

allows. Such equivalent inputs are to be developed based on the data provided in the test specification, 

and such equivalent inputs shall have a mathematical, physical, or logical basis, and shall be applied 

consistently throughout the test cases. 

1.1.6 Simulation Initialization and Preconditioning 

If the program being tested allows, begin the simulation initialization process with zone air conditions that 

equal the outdoor air conditions. If the program being tested allows for preconditioning (iterative 

simulation of an initial time period until temperatures or fluxes, or both, stabilize at initial values), use 

that capability. 

1.1.7 Simulation Duration 

Results for the tests in Section 1 are to be taken from a full annual simulation. 

1.1.8 Programs With Different Operational Modes Depending on Utility Data Availability 

If the software being tested applies a different mode for running the building physics test cases (see 

Section 1.2) than for running the calibrated energy savings test cases (see Section 1.3)—i.e., when no 

utility billing data are available, versus when utility data are available—use the appropriate program 

mode corresponding to the specific test type; apply it consistently for the given test type. 
2 

1.1.9 Order of Testing 

The BESTEST-EX test suite has two main sections corresponding to two different types of test cases: 

• “Building Physics” test cases (Section 1.2) 

• “Utility Bill Calibration” test cases (Section 1.3). 

1.1.9.1 Building Physics Test Cases 

Start by running the building physics tests cases in Section 1.2. Building physics test case results may be 

compared to the reference simulation results provided in Appendix G (see Section G.1). Tested program 

results may also be compared with example acceptance criteria (Judkoff et al. 2010), or with other results 

generated using this test procedure. Diagnose disagreements and correct modeling errors before moving 

on to Section 1.3. Correction of modeling errors must have a mathematical, physical, or logical basis and 

must be applied consistently throughout the test cases. Some disagreements may have a logical basis (i.e., 

may be based on legitimate modeling differences). 

1.1.9.2 Calibrated Energy Savings Test Cases 

Next, run the calibrated energy savings test cases of Section 1.3. Section 1.3 is written such that a) a 

preliminary non-calibrated base-case model is developed as described in Section 1.3.1, b) inputs for the 

base-case simulation model (see Section 1.3.1) are calibrated using synthetic reference utility energy-use 

data given in Section 1.3.1.2, and c) inputs for retrofit cases (see Section 1.3.2) are developed using 

calibrated base-case inputs with modifications as specified for the given retrofit cases. Some modeling 

methods may calculate calibrated energy savings, without adjustment to model inputs, e.g., by comparing 

differences between base case utility billing data versus predicted non-calibrated base-case energy use, 

and then applying an appropriate adjustment to predicted non-calibrated energy savings. For programs 

that apply methods not requiring adjustment to base-case model inputs, use the utility bills called out in 

Section 1.3.1.2 for calibration; however, specific instructions of Section 1.3.1.2 (and elsewhere in Section 

1.3) regarding adjustment of inputs for calibration do not apply. 

Reference results for the calibrated energy-savings tests are not published with the test procedure, so that 

both automated and manual calibration methods may be tested blind, without access to the reference 

results. Practical application of this procedure requires that tested-program results are compared to 

reference results by a third-party. 

1.2 Building Physics Test Input Specifications 

The test cases are described in a manner that allows many different residential modeling tools, 

representing different degrees of modeling complexity, to be tested. Within this structure, figures and 

tables are grouped as summary data and supplemental data. The summary data, which are based on the 

supplemental data, are figures and tables that contain information that summarizes most of the input 

requirements for most users. The supplemental tables contain more detailed information that was required 

for generating a consistent set of inputs to the reference programs. Such data include material properties 

for modeling thermal mass and modeling the attic as a separate zone, interior solar distribution fractions, 

combined convective and radiative surface coefficients, hourly internal gains schedules, and detailed 

window optical properties. Use the supplemental data as needed, according to the inputs allowed by the 

tool being tested. 

Apply the modeling rules of Section 1.1 for all test cases. Abbreviations used in the tables, figures, and 

text are defined on the acronyms and abbreviations page included with the front matter. 

 
3 

1.2.1 The Pre-Retrofit Base-Case Building (Case L200EX-P) 

Begin with Case L200EX-P. Case L200EX-P shall be modeled as detailed in this section and its 

subsections. HERS BESTEST (Judkoff and Neymark 1995a) Case L200A is the basis for 

Case L200EX-P. 

A major part of the work for implementing the tests is assembling an accurate base building model. 

Double-check base building inputs before addressing the retrofit cases. 

1.2.1.1 Weather Data 

This case requires the use of both the Colorad.TM2 and Lasvega.TM2 weather data provided with 

accompanying files. These data are used for heating-only and cooling-only test cases, respectively, per 

Section 1.2.1.14. If the program being tested uses a different representation of weather, such as degree 

days, bin method, etc., then the above weather data shall be processed with the tested program’s weather 

data processor so its output will be based on the above data. A summary of the data and a description of 

TMY2 (.TM2) weather data format are provided in Appendix A. 

1.2.1.1.1 Ground Reflectance 

The solar reflectance of the site ground surface = 0.2. 

1.2.1.2 Output Requirements 

Output requirements are the same for all test cases. Use the output template BESTEST-EX-Phase-1-

Output.XLS, included with the accompanying electronic files, to enter monthly utility data (metered 

energy use) for a full-year simulation for the program being tested. Provide monthly natural gas 

consumption in million (106

) Btu, and electricity consumption in kWh. Monthly billing periods are 

assumed to run from the first day of the month to the last day of the month: e.g., January 1–31, February 

1–28. Results sets for heating and cooling building physics test cases are designated as LnnnEX-PH and 

LnnnEX-PC, respectively. Further instructions are included with the output template. 

If the software being tested does not include domestic hot water (DHW) in its analysis, develop gas DHW 

consumption using an external calculation (e.g., spreadsheet) and include the externally calculated DHW 

consumption with the tested program’s calculated space heating consumption in the total gas utility bill. 

1.2.1.3 Building Geometry and Material Properties 

The base building plan is a 1,539 ft2 floor area, single-story house with one conditioned zone (the main 

floor), an unconditioned attic, and a raised floor exposed to air. Note the following regarding information 

provided in figures and tables. 

• For the building physics tests use only “Nominal” Inputs provided in the tables; approximate 

input ranges (“Min” and “Max” values) are for use with Section 1.3. 

• Changes to HERS BESTEST Case L200A are highlighted with bold font in figures and 

tables. 

The following figures and tables contain information that is applicable to most users. Insulation R-values 

noted in the figures are nominal values; use the tables for finding appropriate inputs. 

Figure 1-1. Base building axonometric 

Figure 1-2. Floor plan – Case L200EX 

Figure 1-3. East side elevation – Case L200EX 

Figure 1-4. Exterior wall plan section – Case L200EX 

Figure 1-5. Raised floor exposed to air section – Case L200EX 

Figure 1-6. Ceiling/attic/roof section – Case L200EX 
4 

Figure 1-7. Interior wall plan section – Case L200EX 

Figure 1-8. Window detail, vertical slider (NFRC AA) with 23⁄4” wide frame – Case L200EX 

Table 1-1. Building Thermal Summary – Case L200EX 

Table 1-2. Other Building Details – Case L200EX. 

Relevant supplementary tables that include more detailed information are: 

Table 1-3. Component Surface Areas and Solar Fractions – Case L200EX 

Table 1-4. Material Descriptions, Exterior Wall, Door, and Window – Case L200EX 

Table 1-5. Material Descriptions, Raised Floor Exposed to Air – Case L200EX 

Table 1-6a. Material Descriptions, Ceiling, Attic, and Roof – Case L200EX 

Table 1-6b. Material Descriptions, Ceiling/Attic/Roof, Attic as Material Layer – 

Case L200EX (for calculating equivalent ceiling/attic/roof composite R-value) 

Table 1-7. Material Descriptions, Interior Wall – Case L200EX 

Table 1-8a. Conditioned Zone Equivalent Inputs for Weather-Driven Infiltration 

Table 1-8b. Equivalent Seasonal Constant Infiltration ACH and CFM – Case L200EX 

Table 1-9a. Daily Sensible Internal Loads – Case L200EX 

Table 1-9b. Normalized Hourly Profiles for Sensible Internal Loads – Case L200EX 

Table 1-10. Window Summary (Single-Pane Aluminum Frame With Thermal Break) – 

Case L200EX 

Table 1-11. Glazing Summary, Single-Pane Center of Glass Values – Case L200EX 

Table 1-12. Optical Properties as a Function of Incidence Angle for Single-Pane Glazing – 

 Case L200EX. 

Other details not described in these figures and tables are discussed topically in the following subsections. 

1.2.1.4 Attic 

Many residential energy analysis tools input an attic by specifying it within a menu of roof types, and 

then specifying the insulation-only R-value corresponding to the insulation installed on the attic floor. If 

this is the case for the software being tested, the information provided in Figure 1-6 will be sufficient. 

For programs such as those used for developing the reference results, more detailed information is 

required. The detailed information for modeling an attic as a separate zone is supplied in Table 1-6a. 

Table 1-6b gives similar information as Table 1-6a, except in Table 1-6b the attic space is modeled as a 

layer of thermal resistance between ceiling and roof materials. In the tables the modeled joist thickness is 

the same as that for the batt insulation (3.5 in.); the joists’ remaining height above the insulation is 

assumed to be at the attic air temperature and is not considered as thermal mass. 

Table 1-6b documents the calculation of ceiling/attic/roof composite air-air R-value noted in the building 

thermal summary of Table 1-1. In Table 1-6b, the equivalent resistance for the attic is based on values 

from the Cooling and Heating Load Calculation Manual (McQuiston and Spitler 1992, p. 4.12); typical 

ventilation by natural effects and roof solar absorptance of 0.6 were assumed. EnergyPlus preliminary 

sensitivity test results for the two-zone model versus the one-zone model indicate only a 0.2% difference 

in heating load results for Colorado Springs and 0.6% cooling load results for Las Vegas. 

As with other components—except where explicitly varied by the test specification—the attic must be 

modeled consistently for all test cases such that the modeling rules of Section 1.1 are applied. 
5 

1.2.1.5 Raised Floor Exposed to Air 

The raised floor exposed to air is provided as an idealization, because when HERS BESTEST was 

developed the state-of-the-art for modeling heat transfer between the house and the ground was not very 

advanced in whole-house simulation models. Such building-to-ground heat transfer occurs for slab-ongrade, basement, and crawl space constructions. To somewhat decouple the floor from the modeling 

problem, the raised floor is provided with R-19 batt insulation. To simulate a raised floor exposed to air, 

the test cases require the following assumptions: 

• Air temperature below the raised floor is assumed to equal outdoor air temperature. 

• The underside of the conditioned zone floor has an equivalent combined convective and radiative 

exterior film coefficient of 2.200 Btu/(h·ft2

·°F), consistent with a “rough” surface texture and zero 

wind speed (see Appendix C); if the program being tested cannot set the exterior surface 

coefficient to a fixed value, allow the exterior surface coefficient to vary with wind speed. If the 

tested program allows detailed designation of different surface heat transfer algorithms among 

specific surfaces, apply a surface convection algorithm that incorporates only surface-to-air 

temperature difference (excludes wind or sets wind speed = 0), and include infrared radiative 

exchange separately. 

• The conditioned zone floor exterior surface (surface facing downward) receives no solar 

radiation. 

The assumption of the air temperature below the raised floor being equal to ambient temperature may be 

approximated either by modeling a building that hovers above the ground (raised floor on stilts for 

example), or modeling a highly ventilated crawl space. The zero solar-radiation-to-exterior-floor 

assumption can be modeled by assigning the highest solar reflectance allowed by the software being 

tested to the underside of the floor and/or defining shading planes where walls would be if the raised floor 

were modeled as a crawl space. Infrared radiative exchange between the conditioned zone floor exterior 

surface (surface facing downward) and the ground surface (assumed at ambient air temperature) is 

modeled in the EnergyPlus and DOE-2.1E reference simulations; SUNREL applies the specified 

combined surface coefficient. 

1.2.1.6 Interior Walls 

The interior walls in the conditioned zone are included for modeling the effect of their mass. They are not 

intended to divide the conditioned zone into separately controlled zones. 

1.2.1.7 Infiltration 

1.2.1.7.1 Conditioned Zone 

Infiltration is modeled assuming blower door data are available for the pre-retrofit base case (L200EX-P). 

Detailed inputs for programs that apply Sherman-Grimsrud infiltration modeling are provided in 

Table 1-8a. Use only the inputs that apply to the software being tested. For programs that do not apply 

Sherman-Grimsrud modeling, values for equivalent seasonal constant air changes per hour (ACH) (or 

cubic feet per minute [CFM]) are included in Table 1-8b. These equivalent constant values are also 

included as part of the building overview description in summary Table 1-2; these are also used for 

developing building summary UA characteristics in Table 1-1. 

The equivalence of the inputs of Table 1-8a is based on the ASHRAE residential air leakage model 

(2005 ASHRAE Handbook of Fundamentals, pp. 27.12, 27.13, 27.21), which is based on the model 

developed by Sherman and Grimsrud (1980). Supporting information for ASHRAE residential air leakage 

model inputs used to generate reference simulation results is included in Appendix D. Appendix D also 

includes discussion of some other approaches to modeling infiltration given the results of fan 

pressurization (blower door) tests, along with development of the equivalent constant infiltration rates. 
6 

The Colorad.TM2 and Lasvega.TM2 climate sites are at 6,171 ft and 2,178 ft altitude, respectively, so the 

air is less dense than that at sea level for both locations. If the program being tested applies a constant 

infiltration rate only and does not use barometric pressure from the weather data, or otherwise does not 

automatically correct for the change in air density caused by altitude, adjust the constant specified 

infiltration rates (to yield mass flows equivalent to what would occur at the specified altitude), as shown 

in Table 1-8b. 

1.2.1.7.2 Attic 

Use the constant attic infiltration rate given in Table 1-8b only if the software being tested allows that 

input. Equivalent Sherman-Grimsrud model inputs were not developed for the attic. Attic infiltration is 

based on the Cooling and Heating Load Calculation Manual (McQuiston and Spitler 1992) for typical 

ventilation by natural effects. The calculation technique used for developing altitude effects on infiltration 

is included in HERS BESTEST Appendix B. 

1.2.1.8 Internal Loads 

All internal loads data are new for this test specification; i.e., changed from HERS-BESTEST. These 

are non-HVAC related internally generated loads in the conditioned zone from equipment, lights, people, 

etc. The internal loads schedules disaggregate sensible and latent loads. Internal loads are further 

disaggregated by associated fuel type, where internal loads related to DHW are associated with gas use 

and all other non-HVAC related internal loads are associated with electricity use. There are no internal 

loads in the attic. The selection of sensible and latent internal loads and the development of schedules are 

described in Appendix B. Details about internal loads are provided below; summary data are given in 

Table 1-2. 

If the software being tested does not include DHW in its analysis, develop gas DHW consumption using 

an external calculation (e.g., spreadsheet) and include the externally calculated DHW consumption with 

the tested program’s calculated space heating consumption in the total gas utility bill. 

1.2.1.8.1 Sensible Loads 

Nominal values for daily total sensible internal loads disaggregated for occupants, electricity, and gas are 

specified in Table 1-9a. Normalized sensible load hourly profile fractions for the conditioned zone are 

specified in Table 1-9b; the hourly fractions apply for all days of the year as given. 

1.2.1.8.1.1 Radiative and Convective Fractions 

Sensible loads are 70% radiative and 30% convective. 

1.2.1.8.2 Latent Loads 

Modeling latent loads for space cooling requires assumptions about the moisture removal by a mechanical 

space cooling condensing unit. For the Phase 1 Test Procedure latent loads are not applied. This is 

because the currently specified idealized equipment for sensible cooling (see Sections 1.2.1.13 – 1.2.1.15) 

does not give guidance about latent load removal. For developing reference simulation results, latent 

loads were not included, as they have no effect on the results.

1.2.1.8.3 Fractions of Base Load Usages to Internal Gains 

Only a fraction of the non-HVAC energy from electricity and gas used in a home is converted to sensible 

internal gains. To generate synthetic utility bills, percentages of non-HVAC gas energy and electric 

energy converted to sensible loads must be assumed. The following nominal values are used for 

conversion of non-HVAC energy use to sensible internal gains: 

• 75% of the non-HVAC energy for electric appliances and lights 

• 27.5% of the non-HVAC energy for gas DHW. 
7 

These values were developed in consultation with the BESTEST-EX Working Group (2009). Further 

background discussion is included in Appendix B. Resulting nominal non-HVAC energy usage based on 

these fractions is included in Table 1-9a. 

Reference simulations integrate internal gains by applying internal gains fractions for electricity (X%) 

and gas (Y%) using the following steps: 

1. Convert the sensible internal gains due to non-HVAC electric appliances and lights (divide by

X%/100) to obtain base load electricity consumption. 

2. Convert the sensible internal gains due to non-HVAC gas appliances (DHW) (divide by Y%/100) 

to obtain base load (DHW) gas consumption. 

3. Each month: 

a. Add the non-HVAC electricity consumption to the monthly HVAC electricity 

consumption and 

b. Add the non-HVAC gas consumption to the monthly HVAC gas consumption. 

4. Use kWh for metered electricity consumption and million (106

) Btu for metered natural gas 

consumption. 

1.2.1.9 Combined Radiative and Convective Surface Heat Transfer Coefficients 

If the program being tested does not allow variation of combined surface coefficients, or if it 

automatically calculates interior and exterior surface convection and radiation, this section may be 

disregarded. 

Combined surface coefficients are denoted in various section drawings throughout Section 1 as “Interior 

Film” and “Exterior Film” (e.g., see Figures 1-4 through 1-7). If the program being tested uses combined 

surface coefficients, use the information given in Table 1-2; this information is also included with the 

detailed material descriptions (e.g., see Tables 1-4 through 1-7). 

ASHRAE Terrain Class 2 (suburban/urban terrain per ASHRAE [2005, p. 16.3]) is assumed. See 

Appendix C for more information about surface coefficients. 

1.2.1.10 Opaque Surface Radiative Properties 

These properties apply to all opaque exterior and interior building surfaces; they are roughly equivalent to 

medium color paint or a light color roof. 

The nominal value for exterior surface solar absorptance is 0.6. All other opaque surface radiative 

properties have explicit inputs, as shown in Table 1-2. 

1.2.1.11 Windows 

A great deal of information about the window properties has been provided so equivalent input for 

windows is possible for many programs. Use only the information (nominal values) relevant to the 

program being tested. The basic properties of the single-pane window, including shading coefficient (SC), 

solar heat gain coefficient (SHGC), and thermal resistance, are provided in Table 1-1. Additional 

information is included in Figure 1-8, Table 1-4, and Tables 1-10 through 1-12. This information was 

drawn primarily from the WINDOW 5.2 (2005) software for developing detailed glazing properties (see 

Appendix E). For programs that need transmittance or reflectance at other angles of incidence, interpolate 

between the values of Table 1-12 using the cosine of the incidence angle as the basis of interpolation. 

Where other unspecified data are needed, values that are consistent with those quoted must be calculated. 

For the base case, total glass and frame areas for each wall may be combined into a single large area for 

that wall. For more detailed models, exterior surface convective coefficients may vary with the height of 

the surface centroid. 

 
8 

1.2.1.12 Interior Solar Distribution 

If the program being tested does not allow for variations of interior solar distribution, this section may be 

disregarded. Interior solar distribution is the fraction of transmitted solar radiation incident on specific 

surfaces in a room. If the program being tested does not calculate this effect internally, use the interior 

solar fractions from Table 1-3. The calculation of transmitted solar radiation reflected back out through 

windows (cavity albedo) is presented in HERS BESTEST Appendix E. 

1.2.1.13 Mechanical System 

This mechanical system applies to the conditioned zone only; it does not apply to the unconditioned attic. 

The mechanical system shall be modeled with the following features as noted below and in Sections 

1.2.1.14 and 1.2.1.15: 

• 100% convective air system 

• The thermostat senses only the air temperature 

• Nonproportional type thermostat (see Section 1.2.1.14) 

• No latent heat extraction. 

1.2.1.14 Thermostat Control Strategies 

Seasonal thermostat control settings are shown for heating and cooling climates in Sections 1.2.1.14.1 and 

1.2.1.14.2, respectively. 

1.2.1.14.1 Colorad.TM2 

For Colorad.TM2 weather data (heating only) 

 During heating season (October 7–May 16): 

 HEAT = ON IF TEMP < 68°F; COOL = OFF 

 During non-heating season (May 17–October 6): 

 HEAT = OFF; COOL = OFF. 

Where: “TEMP” refers to conditioned zone-air temperature. 

The designated heating season is the time period during which approximately 95% of the total heating 

load occurs as indicated by an EnergyPlus simulation of Case L200EX-P. 

1.2.1.14.2 Lasvega.TM2 

For Lasvega.TM2 weather data (cooling only) 

 During cooling season (March 28–October 28): 

 COOL = ON IF TEMP > 78°F; HEAT = OFF 

 During non-cooling season (October 29–March 27): 

 COOL = OFF; HEAT = OFF. 

Where: “TEMP” refers to conditioned zone-air temperature. 

The designated cooling season is the time period during which approximately 95% of the total cooling 

load occurs as indicated by an EnergyPlus simulation of Case L200EX-P. 

 
9 

1.2.1.14.3 Nonproportional Thermostat 

The thermostat is nonproportional in the sense that when the conditioned zone-air temperature exceeds 

the thermostat cooling set point, the heat extraction rate is assumed to equal the maximum capacity of the 

cooling equipment. Likewise, when the conditioned zone-air temperature drops below the thermostat 

heating set point, the heat addition rate equals the maximum capacity of the heating equipment. A 

proportional thermostat throttles the heat addition rate (or extraction rate) in proportion to the difference 

between the zone set point temperature and the actual zone temperature. If the program being tested 

requires use of a proportional thermostat, a proportional thermostat model can be made to approximate a 

nonproportional thermostat model by setting a very small throttling range (the minimum allowed by the 

program being tested). 

1.2.1.15 Equipment Characteristics 

HEATING CAPACITY = 3.413 million Btu/h (effectively infinite) 

EFFECTIVE HEATING EFFICIENCY = 70% 

COOLING CAPACITY = 3.413 million Btu/h (effectively infinite) 

EFFECTIVE COOLING COEFFICIENT OF PERFORMANCE = 3.0 

FAN POWER = 0 W (no fan electricity use) 

WASTE HEAT FROM FAN = 0 W. 

Equipment efficiency is constant: independent of part loading, indoor dry-bulb temperature and humidity 

ratio, outdoor dry-bulb temperature and humidity ratio, and/or other conditions. The heating efficiency 

may be thought of as the ratio of heat provided to the space by the furnace divided by the furnace gas use 

measured at the meter, and includes all losses associated with furnace efficiency, air distribution, etc. 

Similarly, the cooling coefficient of performance (COP) may be thought of as the ratio of sensible heat 

extraction from the space by the space cooling equipment divided by the electricity use measured at the 

meter, and includes all losses associated with system efficiency, air distribution, etc.; latent load is not 

considered. 

The 3.413 million Btu/h requirement comes from the IP units equivalent of 1 MW. If the software being 

tested does not allow this much capacity, use the largest system it allows. 

The intent of the very high equipment heating and cooling capacities is to produce only pure heating load 

and sensible cooling load outputs by assuring that the zone load is always met, and that the zone air 

temperature is always maintained at the appropriate thermostat set point (or within the minimum 

throttling range allowed by the program being tested) when either heating or cooling is required. If 3.413 

million Btu/h of capacity causes the simulation program being tested to become unstable, then use a 

smaller value for over-sizing equipment, but not less than the capacity required to maintain the set point 

temperature for each case. 
10 

Figure 1-1. Base building axonometric
11 

 

Note: To match the interior wall length and corresponding interior wall area of Table 1-3, a 9’ length of interior wall was removed from the original HERS BESTEST floor plan. 

Legend:  W = Window (3’ wide × 5’ high), see Figure 1-8  D = Solid-core wood door (3’ wide x 6’-8” high) 

Figure 1-2. Floor plan – Case L200EX 
12 

 

Note: All windows located vertically as shown; see Figure 1-8 for window detail

Figure 1-3. East side elevation – Case L200EX
13 

 

Figure 1-4. Exterior wall plan section – Case L200EX 

Figure 1-5. Raised floor exposed to air section – Case L200EX 

 

Air Gap (R-1.01) 

Notes for raised floor exposed to air:

• Exposed to outdoor dry-bulb temperature 

• 0 wind speed (low exterior surface convection coefficient) 

• Exterior floor receives no solar 

Fiberglass Batt (R-19) 

(Insulation thickness not to scale) 
14 

 

Figure 1-6. Ceiling/attic/roof section – Case L200EX 

 (R-11)

(Insulation thickness not to scale) 
15 

Figure 1-7. Interior wall plan section – Case L200EX 

 
16 

Figure 1-8. Window detail, vertical slider (NFRC AA) with 23⁄4”-wide frame – Case L200EX
17 

Table 1-1. Building Thermal Summary – Case L200EX 

 R-Value (Note 2a) U-Value (Note 2a) 

Min Nominal Max Min Nominal Max UA 

ELEMENT AREA h·ft2·F/ h·ft2·F/ h·ft2·F/ Btu/ Btu/ Btu/ Min Nominal Max 

(Notes 1a, 1b) ft2 Btu Btu Btu (h·ft2·F) (h·ft2·F) (h·ft2·F) Btu/(h·F) Btu/(h·F) Btu/(h

Exterior Walls (Note 3) 1034 4.50 5.09 6.20 0.161 0.196 0.222 166.8 203.1 229

North Windows (Note 4) 90 1.29 0.774 69.6East Windows (Note 4) 45 1.29 0.774 34.8West Windows (Note 4) 45 1.29 0.774 34.8South Windows (Note 4) 90 1.29 0.774 69.6Doors 40 3.28 0.305 12.2 

Ceiling/Attic/Roof (Notes 5a, 5b ) 1539 7.10 13.67 19.30 0.052 0.073 0.141 79.7 112.6 216

Floor (Note 5a) 1539 20.05 0.050 76.8 

Infiltration (Note 6) Colorado Springs, CO 94.1 133.9 147 Las Vegas, NV 70.5 100.6 110Interior Walls 1024 

TOTAL BUILDING  Excluding Infiltration 544.4 613.5 744

 Including Infiltration (Colorado Springs, CO) 638.5 747.4 891

 Including Infiltration (Las Vegas, NV) 614.9 714.1 854

WINDOW SUMMARY: SINGLE PANE, ALUMINUM FRAME WITH THERMAL BREAK (Note 7) Area U (Note 2a) SHGC (Note 8) Trans. (Note 9) 

ft2 Btu/(h·ft2·F) (dir. nor.) (dir. nor.) 

Glass pane 10.96 0.770 0.862 0.837 

Aluminum sash w/ thermal break 4.04 0.785Window, composite 15.00 0.774 0.679 0.612 

Note 1a: Changes to HERS BESTEST Case L200A are highlighted with bold font. R- and U- values include surface coefficients.Note 1b: "Min" = approximate input range minimum; "Max" = approximate input range maximum; "Nominal" = based on values from HERS BESTEST Case L200A, reNote 2a: Includes interior and exterior surface coefficients.Note 2b: Heat capacity includes building mass within the thermal envelope (e.g., insulation and insulation thickness of structural framing are included, exterior siding and roof/attic m

Variation in modeled attic insulation and joist thickness results in small thermal mass variation; EnergyPlus simulations show minimal sensitivity to such mass variations

Note 3: Excludes area of windows and doors. ASHRAE framed area fraction of 0.25 is assumed for 2x4 16" O.C. construction.Note 4: Window area and other properties are for glass and frame combined. The accompanying window summary disaggregates glass and frame properties for a single window unit

 North and south walls contain six window units each; east and west walls contain three window units each.Note 5a: ASHRAE roof/ceiling framing area fraction of 0.1 applied to both ceiling and floor. Note 5b: Bold italic font indicates correction of Case L200A ceiling/attic/roof summary R- and U-values and related summary UA values originally published in HERS BESTES

 (Previous R- and U-values were listed as 11.75 and 0.085, respectively). This error occurred for the Case L200A summary compilation only; related supplemental (more 

 detailed) data used to calculate ceiling/attic/roof summary data were correct for this test case. Revision here also addresses minor scaled h,ext correction noted in Table 1-6b.

Note 6: Infiltration UA = (infiltration mass flow) x (specific heat). Assumes air properties: specific heat = 0.240 Btu/(lb·F); density = 0.075 lb/ft3 at sea level, adjusted for altitude per 

 The following values were used to obtain infiltration UA Location ACH Min ACH nominal ACH Max Volume (ft3) Altitude (ft) Min UAinf (B

 (see Tables 1-8a and 1-8b for supporting details): Colo Sprgs 0.534 0.760 0.835 12312 6171 94.1 13

Las Vegas 0.345 0.492 0.540 12312 2178 70.5 10

Note 7: These data summarize one complete window unit per detailed description of Figure 1-8 and Tables 1-10 through 1-12.Note 8: SHGC is the Solar Heat Gain Coefficient that includes inward flowing fraction of absorbed direct normal solar radiation added to direct normal transmittance; see ASHRAE 2

Note 9: "Trans." is the direct normal transmittance. Shading coefficient (SC) is the direct normal SHGC for a specific glazing unit divided by 0.87 per ASHRAE 2005 Fundamentals , 

B-EX-Spec.xls, r:a275..p321 
18 

Table 1-2. Other Building Details – Case L200EX 

 Conditioned Zone (Notes1a, 1b)

AIR VOLUME (ft3

) 12312 3463

INFILTRATION ACH CFM

(See Table 1-8a for Sherman-Grimsrud inputs) Min Nominal Max Min Nominal Max ACH CFM

Colorado Springs

 Programs with auto-altitude adjustment (Note 2b) 0.534 0.760 0.835 109.6 156.0 171.3 2.400 138.5

 Programs with site fixed at sea level (Notes 2b,2c ) 0.425 0.604 0.664 87.1 124.0 136.2 1.908 110.1

Las Vegas

 Programs with auto-altitude adjustment (Note 2b) 0.345 0.492 0.540 70.8 101.0 110.8 2.400 138.5

 Programs with site fixed at sea level (Notes 2b,2c) 0.318 0.454 0.498 65.3 93.1 102.2 2.213 127.7

SENSIBLE INTERNAL GAINS (Note 3) Attic

(see Table 1-9b for hourly profiles) Min Nominal Max Internal Gains

Electric appliance daily internal gains (Btu/day) 18234 36468 80000 0

Fraction non-HVAC electricity to sensible gains 60% 75% 90%

Resulting annual non-HVAC electric usage (kWh/y) 2167 5202 14264

Gas appliance daily internal gains (Btu/day) 7464 14928 22392 0

Fraction non-HVAC gas to sensible gains 20% 27.5% 35%

Resulting annual non-HVAC gas usage (MBtu/y) 7.78 19.81 40.87

Occupant daily internal gains (Btu/day) 4347 8694 13041 0

COMBINED RADIATIVE AND CONVECTIVE Exterior film U-val Interior film U-val

 SURFACE (FILM) COEFFICIENTS (Note 4) Btu/(h·ft2

·F) Btu/(h·ft2·F)

Walls and doors 3.628 1.213

Ceiling n/a 1.163

Roof and Gables 3.962 1.148

Raised floor exposed to air 2.200 1.163

Windows 2.609 1.115

Window frames 2.609 1.280

SURFACE RADIATIVE PROPERTIES Exterior Interior

Min Nominal Max

Shortwave (visible and UV) absorptance 0.500 0.600 0.800 0.600

Longwave (infrared) emittance n/a 0.900 n/a 0.900

TRANSMITTED SOLAR, INTERIOR DISTRIBUTION SUMMARY INSIDE SOLAR

AREA FRACTION

ft2 (Note 5)

Total Opaque Interior Surface Area (Note 6) 6272.7 0.8025

Solar to Air (or low mass furnishings) 0.1750 (Note 7)

Solar Lost (back out through windows) 0.0225 (Note 8)

Note 1a: Changes to HERS BESTEST Case L200A are highlighted with bold font. 

Note 1b: "Min" = approximate input range minimum; "Max" = approximate input range maximum; "Nominal" = original value 

 from HERS BESTEST Case L200A; nominal values in bold are changed from HERS BESTEST.

Note 2a: Attic infiltration is assumed as a constant, same as in HERS BESTEST; Sherman-Grimsrud modeling is not applied for the attic. 

Note 2b: For unconditioned zone this input is for programs that do not use more detailed methods. Given values are based on 

 application of ASHRAE Residential Air-Leakage model in EnergyPlus for heating season based on given nominal inputs of 

 effective leakage area at 4Pa, stack coefficient and wind coefficient (see Tables 1-8a and 1-8b).

Note 2c: HERS BESTEST Appendix B describes the algorithm used for adjusting infiltration rates if the software 

 being tested does not account for variation of air density with altitude (i.e., site fixed at sea level).

Note 3: See Table 1-9a for equivalent usage input calculations. Latent internal gains are not applied; see Section 1.2.1.8.2.

Note 4: Use listed values for programs that do not automatically calculate surface heat transfer; see Appendix C for combined surface coefficient details.

Note 5: Solar energy transmitted through windows is assumed as distributed to interior opaque surfaces in proportion 

 to their areas. Only the radiation not directly absorbed by lightweight furnishings (assumed to exist only for the pur-

 pose of calculating inside solar fraction) or lost back out through windows is distributed to interior opaque surfaces.

Note 6: Total area of just those surfaces to which an inside solar fraction is applied (see Table 1-3).

Note 7: Based on the midpoint of the range given by SUNCODE-PC User's Manual (Kennedy et al. 1992), p. 2-16.

Note 8: Calculated using the algorithm described in HERS BESTEST Appendix E; value varies slightly as a function of film coefficients.

B-EX-Spec, s:a2..f57 12-Aug-10

 Attic 

(unconditioned) 

(Note 2a)
19 

Table 1-3. Component Surface Areas and Solar Fractions – Case L200EX

(Note 1) HEIGHT or INSIDE

LENGTH WIDTH MULTIPLIER AREA SOLAR

ELEMENT ft ft ft2 FRACTION

EXT. NORTH/SOUTH WALLS (Note 2)

Gross Wall 8.0 57.0 1.0 456.0

 Gross Window 5.0 3.0 6.0 90.0

 Window Frame Only 24.2 0.0031

 Door 6.67 3.0 1.0 20.0 0.0026

 Net Wall (Note 3) 346.0

 Insulated Wall (Note 3) 259.5 0.0332

 Framed Wall (Note 3) 86.5 0.0111

EXTERIOR EAST/WEST WALLS

Gross Wall 8.0 27.0 1.0 216.0

 Gross Window 5.0 3.0 3.0 45.0

 Window Frame Only 12.1 0.0016

 Net Wall (Note 3) 171.0

 Insulated Wall (Note 3) 128.3 0.0164

 Framed Wall (Note 3) 42.8 0.0055

INTERIOR WALLS 

Gross Wall (Note 4) 8.0 128.0 1024.0

 Unframed Wall (Note 4) 921.6 0.1179

 Framed Wall (Note 4) 102.4 0.0131

FLOOR/CEILING

Gross Floor/Ceiling 57.0 27.0 1.0 1539.0

 Insulated Floor/Ceiling (Note 5) 1385.1 0.1772

 Framed Floor/Ceiling (Note 5) 153.9 0.0197

ROOF

Roof Deck (Note 6) 57.0 14.2 2.0 1622.2

Attic E/W Gable (Note 7) 4.5 27.0 2.0 121.5

TRANSMITTED SOLAR, INTERIOR DISTRIBUTION SUMMARY

Total Opaque Interior Surface Area (Note 8) 6272.7 0.8025

Solar to Air (or low mass furnishings) 0.1750 (Note 9)

Solar Lost (back out through windows) 0.0225 (Note 10)

Note 1: Changes to HERS BESTEST L200A highlighted with bold font. 

Note 2: Solar energy transmitted through windows is assumed as distributed to interior opaque surfaces in proportion to their

 areas. Only the radiation not directly absorbed by lightweight furnishings (assumed to exist only for the purpose of 

 calculating inside solar fraction) or not lost back out through windows is distributed to interior opaque surfaces.

Note 3: Net wall area is gross wall area less the rough opening areas of the windows and door. Insulated and framed exterior 

 wall sections are defined in Figure 1-4. ASHRAE framed area fraction of 0.25 is assumed for 2x4 16" O.C. construction.

Note 4: Width is the total length of all interior walls. Framed wall area is assumed to be 10% of gross wall area for 2x4 16" O.C.

 framing. Only one side of the wall is considered for listed area. This area is multiplied by 2 for determining solar fractions.

 Solar fractions shown are for just one side of the interior wall. 

Note 5: Insulated and framed floor and ceiling sections are defined in Figures 1-5 and 1-6, respectively. ASHRAE 

 roof/ceiling framing area fraction of 0.1 applied to both ceiling and floor.

Note 6: The multiplier accounts for the northward and southward sloped portions of the roof deck.

Note 7: Gable area is calculated as a triangle. Multiplier accounts for east- and west-facing gable ends.

Note 8: Total area of just those surfaces to which an inside solar fraction is applied.

Note 9: Based on the midpoint of the range given by SUNCODE-PC User's Manual (Kennedy et al. 1992), p. 2-16.

Note 10: Calculated using the algorithm described in HERS BESTEST Appendix E; value varies slightly with film coefficients.

B-EX-Spec.xls, c!:a2..i52 02-Feb-10
20 

Table 1-4. Material Descriptions Exterior Wall, Door, and Window – Case L200EX 

EXTERIOR WALL (inside to outside) R-Value U-Value(Note 1) Thickness Min Nominal Max Min Nominal Max k DEN

Min Nominal Max h·ft2·F/ h·ft2·F/ h·ft2·F/ Btu/ Btu/ Btu/ Btu/

ELEMENT (Source) in. in. in. Btu Btu Btu (h·ft2·F) (h·ft2·F) (h·ft2·F) (h·ft·F) lb

Int Surf Coef (Note 2) 0.824 1.213

Plasterboard 0.5 0.450 2.222 0.0926 Air gap (Note 3) 3.5 1.010 0.990Frame 2x4 16" O.C. (Note 3) 3.5 4.373 0.229 0.0667 Fiberboard sheathing 0.5 1.320 0.758 0.0316 Hardboard Siding, 7/16" 0.0685 0.44 1.1355 0.105 0.670 1.739 0.575 1.492 9.530 0.0544 

Ext Surf Coef (Note 2) 0.276 3.628Total air - air, non-frame section 3.985 4.550 5.619 0.178 0.220 0.251Total air - air, frame section 7.348 7.913 8.982 0.111 0.126 0.136Total air - air, composite section (Note 4) 4.500 5.091 6.200 0.161 0.196 0.222Total surf - surf, non-frame sect. 2.885 3.450 4.519 0.221 0.290 0.347

Total surf - surf, frame section 6.248 6.813 7.882 0.147Total surf - surf, composite sect. (Note 5) 3.400 3.991 5.100 0.196 0.251 0.294DOORSolid core door 1.75 2.179 0.459 0.0669 Total air - air, door only (Note 6) 3.279 0.305WINDOW: 1-PANE, AL FRAME WITH THERMAL BREAK R-Value U-Value SHGC Tr(Note 7) Thickness Area h·ft2·F/ Btu/ (dir. nor.) (dir

ELEMENT (Source) in. ft2 Btu (h·ft2·F) (Note 8) (No

Int surf coef, glass (Note 2) 0.897 1.115Int surf coef, frame (Note 2) 0.781 1.280Glass pane (Note 9a) 0.118 10.96 0.019 52.881 0.862 

Aluminum sash w/ thermal break 4.04 0.110 9.096

Ext surf coef (Note 10) 0.383 2.609Window composite air-air 15.00 1.292 0.774 0.679 

Note 1: Changes to HERS BESTEST Case L200A are highlighted with bold font.  "Min" = approximate input range minimum; "Max" = approximate input range maximum;"Nominal" or "Nom" = original value from HERS BESTEST Case L200A. 

 designated approximate inputs only: for the exterior wall this is variation of modeled hardboard siding thickness to obtain the total air-air composite section R-value ra

Note 2: Use listed values for programs that do not automatically calculate surface heat transfer. See Appendix C for more information about combined surface heat transfer coNote 3: R- and U-values shown in the row are for "air gap" and framed section only as appropriate. See Figure 1-4 for section view of exterior wall.Note 4: Total composite R-values based on 25% frame area section per ASHRAE. Note 5: Total surf-surf composite R-value is the total air-air composite R-value less the resistances due to the film coefficients.

Note 6: Door has same film coefficients as exterior wall.Note 7: This section summarizes the detailed window description of Tables 1-10 through 1-12. Areas pertain to one complete window unit only (see Figure 1-8).  If the software being tested is capable of modeling windows in greater detail than shown here, use Tables 1-10 through 1-12.Note 8: SHGC is the Solar Heat Gain Coefficient that includes inward flowing fraction of absorbed direct normal solar radiation added to direct normal transmittance; see ASHRAE Note 9: "Trans." is the direct normal transmittance. Shading Coefficient (SC) is the direct normal SHGC for a specific glazing unit divided by 0.87, per ASHRAE 2005 Funda

Note 9a: Minor correction to original HERS BESTEST; exclusion of prior Window 4.1 surface coefficient assumptions gives precise agreement with Table 1-11 conductance.

Note 10: Use for programs that do not automatically calculate surface heat transfer. Exterior surface coefficient is same for both frame and glass. See Appendix C for more about 

B-EX-Spec.xls i:a2..p50 
21 

Table 1-5. Material Descriptions, Raised Floor Exposed to Air – Case L200EX 

RAISED FLOOR EXPOSED TO AIR (inside to outside)(Note 1) Thickness R-Value U-Value k DENSITY Cp

h·ft2·F/ Btu/ Btu/

ELEMENT in. Btu (h·ft2·F) (h·ft·F) lb/ft3 Btu/(lb

Int Surf Coef (Note 2) 0.860 1.163Carpet w/ fibrous pad (Note 3) 2.080 0.481 0.Plywood 3/4" 0.75 0.937 1.067 0.0667 34.0 0.Fiberglass batt (Note 4) 6.25 19.000 0.053 0.0274 0.6 0.Joists 2x8 16" O.C. (Note 4) 6.25 7.809 0.128 0.0667 32.0 0.Ext Surf Coef (Note 2) 0.455 2.200Total air-air, insulated section 23.331 0.043Total air-air, framed section 12.140 0.082Total air-air, composite section (Note 5) 21.362 0.047Total surf-surf, composite section (Note 6) 20.048 0.050

Note 1: Changes to HERS BESTEST Case L200A are highlighted with bold font. Note 2: Use listed values for programs that do not automatically calculate surface heat transfer.  See Appendix C for more about combined surface heat transfer coefficients.Note 3: There is not enough information available for modeling thermal mass of carpet. Note 4: The fiberglass batt is modeled for the insulated section only, and the joists are modeled for the frame section only. See Figure 

 view of floor. Modeled joist thickness is same as for insulation; joists' remaining thickness below insulation is assumed to be at outdo

 temperature with no insulating value and is not considered as thermal mass.Note 5: HERS BESTEST framed area fraction of 0.1 applied.Note 6: Total air-air composite R-value less the film resistances.

B-EX-Spec.xls i:a56..i82 25-M
22 

Table 1-6a. Material Descriptions, Ceiling, Attic, and Roof – Case L200EX 

CASE L200EX: CEILING/ATTIC/ROOF (inside to outside), R-Value U-Value attic as unconditioned zone Thickness Min Nominal Max Min Nominal Max k 

(Notes 1a, 1b) Min Nominal Max h·ft2·F/ h·ft2·F/ h·ft2·F/ Btu/ Btu/ Btu/ Btu/

ELEMENT in. in. in. Btu Btu Btu (h·ft2·F) (h·ft2·F) (h·ft2·F) (h·ft·F

CEILING (1539 ft2 total area)

Int Surf Coef (Note 2) 0.860 1.163

Plasterboard 0.5 0.450 2.222 0.092Fiberglass batt (Note 3) 1.149 3.5 5.545 3.612 11.000 17.428 0.057 0.091 0.277 0.026

Joists 2x6 24" O.C. (Notes 3, 3a) 1.149 3.5 5.500 1.436 4.373 6.872 0.146 0.229 0.696 0.066

Int Surf Coef (Note 2) 0.860 1.163

Total air-air, insulated section 5.781 13.170 19.597 0.051 0.076 0.173Total air-air, framed section 3.605 6.543 9.041 0.111 0.153 0.277Total air-air, composite section (Note 4a) 5.452 11.958 17.549 0.057 0.084 0.183Total surf-surf, composite section (Note 4b) 3.733 10.239 15.829 0.063 0.098 0.268END GABLES (121.5 ft2 total area)

Int Surf Coef (Note 2) 0.871 1.148

Plywood 1/2" 0.5 0.625 1.601 0.066Hardboard siding, 7/16" 0.44 0.670 1.492 0.0544 Ext Surf Coef (Note 5) 0.252 3.962

Total air-air 2.418 0.414ROOF (1622 ft2 total area)

Int Surf Coef (Note 2) 0.871 1.148

Plywood 1/2" 0.5 0.625 1.601 0.066Asphalt shingle 1/4" 0.25 0.440 2.273 0.047Ext Surf Coef (Note 5) 0.252 3.962

Total air-air 2.188 0.457Total Roof/Gable UA,surf-surf (Notes 6, 7 ) 1617 Btu/(h·F)

Note 1a: Changes to HERS BESTEST Case L200A are highlighted with bold font. Use this table if attic modeled as separate zone.Note 1b: "Min" = approximate input range minimum; "Max" = approximate input range maximum; "Nominal" = original value from HERS BESTEST Case L2 Max and Min are provided for designated approximate inputs only: for the ceiling/attic/roof assembly this is variation of modeled insulation and joist  thickness to obtain the total air-air composite section R-value range, as shown in Table 1-6b.Note 2: Use listed values for programs that do not automatically calculate surface heat transfer. See Appendix C, Section C.1 for more on combined interior surface he

Note 3: The fiberglass batt is modeled for the insulated section only, and the joists are modeled for the frame section only. See Figure 1-6 for section view of ceiling/attic/r thickness is same as for insulation; joists' remaining height above insulation is assumed to be at attic air temperature and is not considered as thermal mass.Note 3a: For Case L200EX-C reference simulations (see Sec. 1.3.1.2), maximum modeled joist thickness is 5.5" while modeled batt insulation thickness may be sli

Note 4a: Based on 90% insulated section and 10% frame section per ASHRAE; applies to temperature difference between room air and attic air.Note 4b: The "Composite surf-surf" R-value is the composite air-air R-value less the two interior film coefficient R-values.Note 5: Use listed values for programs that do not automatically calculate surface heat transfer. See Appendix C, Section C.2 for more on combined exterior surface he

Note 6: Area weighted sum of plywood and asphalt shingle or wood siding material layers, does not include film coefficients. This value used for developing Table 1-6b.Note 7: This value corrected from original HERS BESTEST; gable area was previously double counted.

B-EX-Spec-Pilot i:a90..i136 
23 

Table 1-6b. Material Descriptions, Ceiling/Attic/Roof, Attic as Material Layer – Case L200EX 

CASE L200EX: CEILING/ATTIC/ROOF (inside to outside) R-Value U-Value(Notes 1a, 1b) Thickness Min Nominal Max Min Nominal Max k DENS

Min Nominal Max h·ft2·F/ h·ft2·F/ h·ft2·F/ Btu/ Btu/ Btu/ Btu/

ELEMENT in. in. in. Btu Btu Btu (h·ft2·F) (h·ft2·F) (h·ft2·F) (h·ft·F) lb/ft

CEILING/ATTIC AIR (1539 ft2 total area)Int Surf Coef (Note 2) 0.860 1.163

Plasterboard 0.5 0.450 2.222 0.0926 50Fiberglass batt (Note 3) 1.149 3.5 5.545 3.612 11.000 17.428 0.057 0.091 0.277 0.0265 0Joists 2x6 24" O.C. (Notes 3, 3a) 1.149 3.5 5.500 1.436 4.373 6.872 0.146 0.229 0.696 0.0667 32

Attic air (Note 4) 1.300 0.769ROOF DECK AND GABLE PROPERTIES SCALED TO CEILING AREA, 1539 ft2 (Note 5a)

Plywood 1/2" (Note 6) 0.5 0.551 1.814 0.0756 38

Hybrid shingle/siding (Notes 5b, 6 ) 0.25 0.400 2.499 0.0521 79

Total roof deck/gable, surf-surf (Notes 5c, 6 ) 0.951 1.051

Ext Surf Coef (Note 2) 0.223 4.489

SUMMARY CEILING/ATTIC/ROOFTotal air-air, insulated section (Note 7a) 7.396 14.784 21.212 0.047 0.068 0.135Total air-air, framed section (Note 7a) 5.220 8.157 10.656 0.094 0.123 0.192Total air-air, composite section (Note 7b) 7.100 13.673 19.300 0.052 0.073 0.141Total surf-surf, composite section (Note 8) 6.017 12.591 18.217 0.055 0.079 0.166

Note 1a: Changes to HERS BESTEST Case L200A are highlighted with bold font. Use this table if attic modeled as material layer.Note 1b: "Min" = approximate input range minimum; "Max" = approximate input range maximum; "Nominal" = original value from HERS BESTEST Case L200A. Max and Min are only provided for designated approximate inputs: for the ceiling/attic/roof assembly this is variation of modeled insulation and joist  thickness to obtain the total air-air composite section R-value range, as shown.Note 2: Use listed values for programs that do not automatically calculate surface heat transfer. See Appendix C for more on combined surface heat transfer coefficients.

Note 3: The fiberglass batt is modeled for the insulated section only, and the joists are modeled for the frame section only. See Figure 1-6 for section view of ceiling/attic/roof. Modele is same as for insulation; joists' remaining height above insulation is assumed to be at attic air temperature and is not considered for thermal mass.Note 3a: For Case L200EX-C reference simulations (see Sec. 1.3.1.2), maximum modeled joist thickness is 5.5" while modeled batt insulation thickness may be slightly greateNote 4: Average winter/summer values for natural ventilation (2.4 ACH), R-11 ceiling insulation, ext abs = 0.6., includes interior films. Based on ASHRAE Load Calculation Manual, 1992, Tables 4.5 and 4.5a, "Effective Resistances of Ceiling or Attic Air Spaces."Note 5a: Scaled properties are presented for use with ASHRAE equivalent attic air space R-value. U, R, and k are scaled on area; density and Cp are scaled on volume (area and thicknNote 5b: This "material" combines roofing and end gable materials into one hybrid layer of material. Note 5c: Based on total roof/gable "UA,surf-surf" calculated in Table 1-6a.Note 6: Minor errata note: Values corrected from original HERS BESTEST; gable area was previously double counted in scaling. Previous R-value for  "Total roof deck/gable, surf-surf" = 0.899 hft 2F/Btu would have resulted in 0.3% overall R-value effect versus original value. This correction is propagated through to summary 

Note 7a: (ceiling interior film coefficient) + (ceiling materials) + (attic as material layer) + (scaled roof deck/gable materials) + (scaled exterior film coefficient), for a given section.Note 7b: Based on 10% frame area fraction per ASHRAE; applies to temperature difference between room air and ambient air. Note 8: Based on total air-air composite R-value less R-values of interior film coefficient and scaled exterior film coefficient.

B-EX-Spec.xls i:a140..o181 
24 

Table 1-7. Material Descriptions, Interior Wall – Case L200EX 

Table 1-8a. Conditioned Zone Equivalent Inputs for Weather-Driven Infiltration Models – 

Case L200EX 

 

INTERIOR WALL 

 (Note 1) Thickness R U k DENSITY Cp

h·ft2

·F/ Btu/ Btu/

ELEMENT (Source) in. Btu (h·ft2

·F) (h·ft·F) lb/ft3 Btu/(lb·F)

Int Surf Coef (Note 2) 0.824 1.213

Plasterboard 0.500 0.450 2.222 0.0926 50.0 0.260

Frame 2x4, 16" O.C. (Note 3) 3.500 4.373 0.229 0.0667 32.0 0.330

Plasterboard 0.500 0.450 2.222 0.0926 50.0 0.260

Int Surf Coef (Note 2) 0.824 1.213

Note 1: Changes to HERS BESTEST Case L200A are highlighted with bold font. 

Note 2: Use listed values for programs that do not automatically calculate surface heat transfer.

 See Appendix C, Section C.1, for more on combined interior surface heat transfer coefficients. 

Note 3: Frame 2x4 only applies to 10% of the interior wall area. 

B_EX-Spec.xls g!:a2..g17 24-Mar-10

Input (Note 1) Min Nominal Max

CFM at 50 Pa (Colorado Springs) (Notes 2, 3) 2800 4000 4400

CFM at 50 Pa (Las Vegas) (Notes 2, 3) 2600 3714 4085

Air Volume (ft3

) 12312

ACH at 50 Pa (Colorado Springs) (Notes 2, 3) 13.65 19.49 21.44

ACH at 50 Pa (Las Vegas) (Notes 2, 3) 12.67 18.10 19.91

Altitude (Colorado Springs), ft 6171

Altitude (Las Vegas), ft 2178

Air density (Colorado Springs), lb/ft3 (Note 4) 0.060

Air density (Las Vegas), lb/ft3 (Note 4) 0.069

Equivalent Leakage Area at 50 Pa, in2 (Note 5) 200.7 286.7 315.3

Effective Leakage Area at 4 Pa, in2

 (Note 5) 137.4 196.3 215.9

Number of Building Stories 1.0

ASHRAE Stack coefficient cfm2/(in4 °F) (Note 5) 0.0150

ASHRAE Wind coefficient cfm2/(in4mph2) (Note 5) 0.0012

Note 1: This table is new (relative to HERS BESTEST) for the BESTEST-EX test specification.

Note 2: Volumetric flow rates are different for each climate.

Note 3: To simplify the test specification, uncertainties not directly related to CFM50 measurements are included with the CFM50 approximate input 

 range. Resulting approximate input range as percent of variation from nominal value for effective leakage area at 4 Pa is the same as for CFM50.

Note 4: Calculation of air density as a function of altitude is described in HERS BESTEST, Appendix B. 

Note 5: Used for ASHRAE Residential Air Leakage model (2005 ASHRAE Handbook of Fundamentals , pp. 27.12–27.13, 27.21); model is based on 

 Sherman-Grimsrud (1980), assuming highly sheltered building (Shelter Class 5) in rural terrain. See Appendix D for supporting details. Leakage area 

 approximate input range is the same for both Colorado Springs and Las Vegas. 

B-EX-Spec, t:a2..f29 04-May-10
25 

Table 1-8b. Equivalent Seasonal Constant Infiltration ACH and CFM – Case L200EX 

Table 1-9a. Daily Sensible Internal Loads – Case L200EX 

(Notes 1, 2, 3, 4, 5, 6) Occupants 

Sensible 

Electricity 

Sensible 

Gas 

Sensible 

Daily Sensible Load 

 Min (Btu/day) 4,347 18,234 7,464 

 Nominal (Btu/day) 8,694 36,468 14,928 

 Max (Btu/day) 13,041 80,000 22,392 

Internal Gains Fractions (Note 7) 

 Min − Max 

 Nominal 

n/a 

n/a 

60%–90% 

75% 

20%–35% 

27.5% 

Resulting Metered Annual non-HVAC 

Energy Usage 

Electricity 

(kWh) 

Gas

(million Btu/yr) 

 Min (Note 8) n/a 2,617 7.78 

 Nominal (Note 9) n/a 5,202 19.81 

 Max (Note 10) n/a 14,264 40.87 

Note 1: All internal gains data are new (relative to HERS BESTEST) for this test specification. 

Note 2: “Min” = approximate input range minimum; “Max” = approximate input range maximum; “Nominal” is the basis value for 

range determination developed in Appendix B. 

Note 3: For reference simulations hourly loads are found by multiplying the randomly selected daily totals for each category by

their respective normalized hourly profiles in Table 1-9b. 

Note 4: Sensible gains are 70% radiative and 30% convective. 

Note 5: The MAX value for “Electricity Sensible” was adjusted to 80 kBtu according to consultation with the BESTEST-EX 

Working Group (2009). 

Note 6: Gas sensible loads are from DHW only; electric sensible loads are from all other non-HVAC appliances. 

Note 7: Percentage of metered energy use that becomes sensible internal gains 

Note 8: = (Minimum Load/day) / (Maximum Internal Gains Fraction) * (365 day/yr) / (1000000 (/M)) [million Btu] 

Note 9: = (Nominal Load/day) / (Nominal Internal Gains Fraction) * (365 day/yr) / (1000000 (/M)) [million Btu] 

Note 10: = (Maximum Load/day) / (Minimum Internal Gains Fraction) * (365 day/yr) / (1000000 (/M)) [million Btu]

 Conditioned Zone (Notes1a, 1b)

AIR VOLUME (ft3

) 12312 3463

INFILTRATION ACH CFM

Min Nominal Max Min Nominal Max ACH CFM

Colorado Springs

 Programs with auto-altitude adjustment (Note 3) 0.534 0.760 0.835 109.6 156.0 171.3 2.400 138.5

 Programs with site fixed at sea level (Notes 3,4 ) 0.425 0.604 0.664 87.1 124.0 136.2 1.908 110.1

Las Vegas

 Programs with auto-altitude adjustment (Note 3) 0.345 0.492 0.540 70.8 101.0 110.8 2.400 138.5

 Programs with site fixed at sea level (Notes 3, 4) 0.318 0.454 0.498 65.3 93.1 102.2 2.213 127.7

Note 1a: Changes to HERS BESTEST Case L200A are highlighted with bold font. 

Note 1b: "Min" = approximate input range minimum; "Max" = approximate input range maximum; "Nominal" = original value 

 from HERS BESTEST Case L200A; nominal values in bold are changed from HERS BESTEST.

Note 2: Attic infiltration is assumed as a constant, same as in HERS BESTEST; Sherman-Grimsrud modeling is not applied for the attic. 

Note 3: For conditioned zone this input is for programs that do not use more detailed methods. Given values are averages based on 

 application of ASHRAE Residential Air-Leakage model in EnergyPlus for the heating or cooling season rounded to the nearest month 

 (e.g. October - April for heating) as appropriate, based on given nominal inputs of effective leakage area at 4Pa, stack coefficient, 

 and wind coefficient (see Table 1-8a). See Appendix D for supporting detail.

Note 4: HERS BESTEST Appendix B describes the algorithm used for adjusting infiltration rates if the software 

 being tested does not account for variation of air density with altitude (i.e., site fixed at sea level).

B-EX-Spec, u:a3..f24 12-Aug-10

 Attic 

(unconditioned) 

(Note 2)
26 

Table 1-9b. Normalized Hourly Profiles for Sensible Internal Loads – Case L200EX 

Hour (Note 1) Occupants 

Sensible 

Electricity 

Sensible Gas Sensible 

1 0.061 0.022 0.036 

2 0.061 0.020 0.035 

3 0.061 0.019 0.035 

4 0.061 0.020 0.035 

5 0.061 0.025 0.036 

6 0.061 0.038 0.039 

7 0.061 0.048 0.046 

8 0.052 0.050 0.048 

9 0.024 0.038 0.048 

10 0.015 0.034 0.047 

11 0.015 0.032 0.045 

12 0.015 0.031 0.044 

13 0.015 0.030 0.043 

14 0.015 0.029 0.042 

15 0.015 0.029 0.041 

16 0.015 0.034 0.041 

17 0.018 0.051 0.042 

18 0.032 0.065 0.043 

19 0.053 0.077 0.044 

20 0.053 0.083 0.044 

21 0.053 0.082 0.044 

22 0.061 0.066 0.043 

23 0.061 0.046 0.041 

24 0.061 0.031 0.038 

Note 1: All internal gains data are new (relative to HERS BESTEST) for 

this test specification. 

 
27 

Table 1-10. Window Summary (Single-Pane Aluminum Frame With 

Thermal Breaks) – Case L200EX 

Property (Note 1) Value Units Notes

GENERAL PROPERTIES

Area, gross window 15.00 ft2 (Note 2)

Width, frame 2.75 in.

Area, frame 4.04 ft2

Area, edge of glass (EOG) 3.57 ft2

Area, center of glass (COG) 7.39 ft2

Area, net glass 10.96 ft2 (Area,EOG + Area,COG)

OPTICAL PROPERTIES

Absorptance, frame 0.60

Transmittance, frame 0.00

COG/EOG optical properties (see Table 1-11) (Note 3)

Solar Heat Gain Coefficient (Note 4)

 (SHGC), glass 0.862

 (SHGC), frame 0.180

 (SHGC), gross window 0.679

Shading Coefficient (SC), 0.780 (Note 4)

 gross window 

Dividers, curtains, blinds, and None

 other obstructions in window

THERMAL PROPERTIES (conductances/resistances include film coefficients)

Conductance, frame 0.785 Btu/(h·ft2

·F) Aluminum frame with thermal 

(R-Value) 1.274 h·ft2

·F/Btu break (Note 5)

Conductance, edge of glass 0.770 Btu/(h·ft2

·F) (Note 3)

(R-Value) 1.299 h·ft2

·F/Btu

Conductance, center of glass 0.770 Btu/(h·ft2

·F)

(R-Value) 1.299 h·ft2

·F/Btu

Conductance, net glass 0.770 Btu/(h·ft2

·F) (Note 6)

(R-Value) 1.299 h·ft2

·F/Btu

Conductance, gross window 0.774 Btu/(h·ft2

·F) (Note 7)

(R-Value) 1.292 h·ft2

·F/Btu

COMBINED SURFACE COEFFICIENT CONDUCTANCES

Exterior Surf Coef, glass and frame 2.609 Btu/(h·ft2

·F) see Table 1-2

Interior Surface Coefficient, glass 1.115 Btu/(h·ft2

·F) see Table 1-2

Interior Surface Coefficient, frame 1.280 Btu/(h·ft2

·F) see Table 1-2

Note 1: Changes to HERS BESTEST Case L200A highlighted with bold font.

Note 2: Area for one representative window unit. See Figure 1-8 for a schematic representation of frame, center-of-

 glass (COG) and edge-of-glass (EOG) areas; dimensions are based on an NFRC size AA vertical slider. Gross window

 area is the sum of frame, COG and EOG areas. 

Note 3: Edge-of-glass optical properties and conductance are the same as the center-of-glass properties. Table 1-12 gives 

 optical properties as a function of incidence angle.

Note 4: These are the overall window (including COG, EOG, and frame) properties for direct normal solar radiation. 

Note 5: The frame conductance presented here is the thermal resistance of the aluminum sash with thermal break

 listed in Table 1-4 (as calculated in HERS BESTEST) adjusted with resistances of updated BESTEST-EX film

 coefficients. Material properties for dynamic modeling of window frames (density, specific heat, etc.) are not given.

Note 6: Net glass conductance includes only the COG and EOG portions of the window.

Note 7: Gross window conductance includes the frame, EOG, and COG portions of the window. 

B-EX-Spec.xls, b!a48:j97 02-Feb-10
28 

Table 1-11. Glazing Summary, Single-Pane Center of Glass Values – Case L200EX 

Property Value Units Notes

GENERAL PROPERTIES (Note 1)

Number of Panes 1

Pane Thickness 0.118 in.

SINGLE PANE OPTICAL PROP. (Note 2)

Transmittance 0.837

Reflectance 0.075

Absorptance 0.089

Index of Refraction 1.5223

Extinction Coefficient 0.7806 /in.

Solar Heat Gain Coefficient (SHGC) 0.862

Shading Coefficient (SC) 0.991 (Note 3)

Optical Properties as Function of Incident Angle (See Table 1-12)

THERMAL PROPERTIES

Conductivity of Glass 0.520 Btu/(h·ft·F)

Conductance of Glass Pane 52.881 Btu/(h·ft2

·F)

(R-Value) 0.019 h·ft2

·F/Btu

Exterior Combined Surface Coefficient 2.609 Btu/(h·ft2

·F) (Note 4)

(R-Value) 0.383 h·ft2

·F/Btu

Interior Combined Surface Coefficient 1.115 Btu/(h·ft2

·F) (Note 4)

(R-Value) 0.897 h·ft2

·F/Btu

U-Value from Interior Air to Ambient Air 0.770 Btu/(h·ft2

·F)

(R-Value) 1.299 h·ft2

·F/Btu

Hemispherical Infrared Emittance 0.84

Infrared Transmittance 0

Density of Glass 154 lb/ft3

Specific Heat of Glass 0.18 Btu/(lb·F)

Note 1: Changes to HERS BESTEST Case L200A highlighted with bold font.

Note 2: Optical properties listed in this table are for direct normal radiation.

Note 3: SC = SHGC/0.87 per Equation 91 (p. 31.39) of ASHRAE 2005 Fundamentals.

Note 4: See Table 1-2.

 B-EX-Spec.xls, b!a3..f35; 24-Mar-10
29 

Table 1-12. Optical Properties as a Function of Incidence Angle for 

Single-Pane Glazing – Case L200EX 

1.2.2 Building Physics Retrofit Test Cases 

This section describes revisions to the base building required to model the retrofit test cases. For 

convenience, relevant portions of the appropriate base building tables and figures have been reprinted, 

with changes to the base-case model to be applied in the retrofit cases highlighted in bold font. 

Where applicable, summary figures and tables are listed first, with supplementary tables listed afterward. 

1.2.2.1 Case L210EX-P: Air-Seal Retrofit 

Case L210EX-P is exactly as Case L200EX-P, except for the following changes. 

1.2.2.1.1 Conditioned Zone 

Changes to detailed inputs for programs that apply Sherman-Grimsrud infiltration modeling are provided 

in Table 1-13. Use only the inputs that apply to the software being tested. For programs that do not apply 

Sherman-Grimsrud modeling, values for “equivalent seasonal constant ACH” (or CFM) are included in 

Table 1-14. The equivalence of the inputs is discussed in Section 1.2.1.7 and Appendix D. 

If the program being tested applies a constant infiltration rate only and does not use barometric pressure 

from the weather data, or otherwise does not automatically correct for the change in air density caused by 

altitude, adjust the constant specified infiltration rates (to yield mass flows equivalent to what would 

occur at the specified altitude), as shown in Table 1-14. 

 Properties (Notes 1a, 1b, 2, 3)

Angle Trans Refl Abs SHGC 

0 0.836 0.075 0.089 0.862

10 0.836 0.075 0.089 0.862

20 0.834 0.075 0.090 0.861

30 0.830 0.077 0.093 0.857

40 0.820 0.082 0.097 0.849

50 0.799 0.099 0.101 0.829

60 0.751 0.143 0.105 0.782

70 0.639 0.252 0.108 0.671

80 0.389 0.505 0.106 0.420

90 0.000 1.000 0.000 0.000

Hemis 0.756 0.136 0.098 0.785

Note 1a: Changes to HERS BESTEST Case L200A are highlighted with bold font.

Note 1b: Updates to incident-angle dependent transmittance, reflectance, and absorptance are for

 WINDOW 5 (WINDOW 4.1 was used for HERS BESTEST). Direct normal transmittance = 0.837

 (per Table 1-11) used as input for WINDOW 5 glass pane resulted in transmittance = 0.836 for

 0-incidence angle shown here.

Note 2: Trans = Transmittance, Refl = Reflectance, Abs = Absorptance, SHGC = Solar Heat Gain

 Coefficient, Hemis = Hemispherically integrated property.

Note 3: SHGC is from Equations 74 and 81 (pp. 31.36-37) of 2005 ASHRAE Handbook of Fundamentals.

 These apply updated window surface coefficients of Table 1-2. 

B-EX-Spec, b!:a118..g142 12-Aug-10
30 

1.2.2.1.2 Attic 

Attic infiltration is the same as in the base case (L200EX-P). 

Table 1-13. Conditioned Zone Equivalent Inputs for Weather-Driven Infiltration Models – 

Case L210EX-P

Table 1-14. Equivalent Seasonal Constant Infiltration ACH and CFM – Case L210EX-P 

Input (Note 1) Value

CFM at 50 Pa (Colorado Springs) (Note 2) 2000

CFM at 50 Pa (Las Vegas) (Note 2) 1857

Air Volume (ft3

) 12312

ACH at 50 Pa (Colorado Springs) (Note 2) 9.75

ACH at 50 Pa (Las Vegas) (Note 2) 9.05

Altitude (Colorado Springs), ft 6171

Altitude (Las Vegas), ft 2178

Air density (Colorado Springs), lb/ft3

 (Note 3) 0.060

Air density (Las Vegas), lb/ft3

 (Note 3) 0.069

Equivalent Leakage Area at 50 Pa, in2 (Note 4) 143.3

Effective Leakage Area at 4 Pa, in2

 (Note 4) 98.1

Number of Building Stories 1.0

ASHRAE Stack coefficient cfm2

/(in4 °F) (Note 4) 0.0150

ASHRAE Wind coefficient cfm2

/(in4mph2) (Note 4) 0.0012

Note 1: Changes to Case L200EX are highlighted with bold font.

Note 2: Volumetric flow rates are different for each climate.

Note 3: Calculation of air density as a function of altitude is described in HERS BESTEST, Appendix B. 

Note 4: Used for ASHRAE Residential Air Leakage model (2005 ASHRAE Handbook of Fundamentals, pp. 27.12 – 27.13, 27.21); model is based on 

 Sherman-Grimsrud (1980), assuming highly sheltered building (Shelter Class 5) in rural terrain. See Appendix D for supporting details. 

B-EX-Spec, t:a100..f124 01-Mar-10

 Conditioned Zone (Note 1)

AIR VOLUME (ft3

) 12312 3463

INFILTRATION UAinfl (Note 2)

ACH CFM Btu/(h·F) ACH CFM

Colorado Springs

 Programs with auto-altitude adjustment (Note 3) 0.382 78.4 67.3 (Note 4) 2.400 138.5

 Programs with site fixed at sea level (Notes 3, 5) 0.304 62.3 1.908 110.1

Las Vegas

 Programs with auto-altitude adjustment (Note 3) 0.246 50.5 50.3 (Note 4) 2.400 138.5

 Programs with site fixed at sea level (Notes 3, 5) 0.227 46.6 2.213 127.7

Note 1: Changes to Case L200EX are highlighted with bold font. 

Note 2: Attic infiltration is same as Case L200EX; Sherman-Grimsrud modeling is not applied for the attic. 

Note 3: For conditioned zone this input is for programs that do not use more detailed methods. Given values are averages based on 

 application of ASHRAE Residential Air-Leakage model in EnergyPlus for appropriate space conditioning season based on 

 given inputs of effective leakage area at 4Pa, stack coefficient, and wind coefficient (see Table 1-13).

Note 4: Infiltration UA = (infiltration mass flow) x (specific heat). Assumes air properties: specific heat = 0.240 Btu/(lb·F); density = 0.075 lb/ft3

 at 

 sea level, adjusted for altitude per HERS BESTEST Appendix B. 

Note 5: HERS BESTEST Appendix B describes the algorithm used for adjusting infiltration rates if the software being tested does not account for

 variation of air density with altitude (i.e., site fixed at sea level).

B-EX-Spec, u:a30..f50 12-Aug-10

 Attic (uncond.)
31 

1.2.2.2 Case L220EX-P: Attic Insulation Retrofit 

Case L220EX-P is exactly as Case L200EX-P, except that 2.0 in. of cellulose is blown between the 

joists on top of the existing fiberglass batt with a further 6.0 in. of blown cellulose covering the joists and 

cellulose (see Figure 1-9). The full joist thickness (5.5 in.) is modeled in this case. Use inputs from Case 

L200EX-P, except for changes called out by the retrofit (highlighted with bold font in figures and tables 

cited below). The following figure and tables highlight the retrofit. 

Figure 1-9 Ceiling section – Case L220EX 

Table 1-15 Building Thermal Summary – Case L220EX 

Table 1-16a Material Descriptions, Ceiling – Case L220EX 

Table 1-16b Material Descriptions for Attic as Material Layer – Case L220EX (for calculation 

of equivalent ceiling/attic/roof composite R-value see discussion of the base 

building attic in Section 1.2.1.4). 

Note: Changes to Case L200EX are highlighted with bold font. 

Figure 1-9. Ceiling section – Case L220EX 

Fiberglass Batt (R-11) 

2.0” Blown Cellulose, between joists (R-7.2) 

6.0” Blown Cellulose, over joists and 

cellulose (R-21.7) 

Attic Air 

2 × 6, 24” o.c. 
32 

Table 1-15. Building Thermal Summary – Case L220EX 

Table 1-16a. Material Descriptions, Ceiling – Case L220EX

AREA R U UA HEATCAP

ELEMENT ft2 h·ft2

·F/Btu Btu/(h·ft2·F) Btu/(h·F) Btu/F

(Notes 1a, 1b) (Note 2) (Note 2) (Note 2) (Note 3)

Exterior Walls 1034 5.09 0.196 203.1 1356

North Windows 90 1.29 0.774 69.6

East Windows 45 1.29 0.774 34.8

West Windows 45 1.29 0.774 34.8

South Windows 90 1.29 0.774 69.6

Doors 40 3.28 0.305 12.2 62

Ceiling/Attic/Roof (Note 4) 1539 42.67 0.023 36.1 2122

Floor (Note 4) 1539 20.05 0.050 76.8 1881

Infiltration 

 Colorado Springs, CO 133.9

 Las Vegas, NV 100.6

Interior Walls 1024 1425

TOTAL BUILDING 6846

 Excluding Infiltration 537.1

 Including Infiltration, Colorado Springs, CO 671.0

 Including Infiltration, Las Vegas, NV 637.6

Note 1a: Changes to Case L200EX are highlighted by bold font. Supplementary data are included in Table 1-16a 

 for attic modeled as a separate zone and Table 1-16b for attic modeled as material layer (single-zone model).

Note 1b: Nominal values are carried over from Case L200EX-P, and are included for background only, except where

 highlighted by bold font.

Note 2: Includes interior and exterior surface coefficients.

Note 3: Heat capacity includes building mass within the thermal envelope (e.g., insulation and insulation thickness of 

 structural framing are included, exterior siding and roof/attic mass are excluded). 

Note 4: ASHRAE roof/ceiling framing area fraction of 0.1 used for both ceiling and floor. 

B-EX-Spec.xls, r:a326..g354 02-Feb-10

CEILING (inside to outside) 

(Notes 1a, 1b) Thickness R U k DENSITY Cp

h·ft2

·F/ Btu/ Btu/

ELEMENT in. Btu (h·ft2

·F) (h·ft·F) lb/ft3 Btu/(lb·F)

CEILING (1539 ft2

 total area)

Int Surf Coef 0.860 1.163

Plasterboard 0.5 0.450 2.222 0.0926 50.0 0.26

Fiberglass batt (Note 2) 3.5 11.000 0.091 0.0265 0.6 0.20

Blown Cellulose, 2.0" (Note 2) 2.0 7.229 0.138 0.0231 1.5 0.33

Joists 2x6 24" O.C. (Note 3) 5.5 6.872 0.146 0.0667 32.0 0.33

Blown Cellulose, 6.0" (Note 4) 6.0 21.687 0.046 0.0231 1.5 0.33

Int Surf Coef 0.860 1.163

Total air-air, insulated section 42.085 0.024

Total air-air, framed section 30.728 0.033

Total air-air, composite section (Note 5) 40.585 0.025

Total surf-surf, composite sec. (Note 6) 38.866 0.026

Note 1a: Changes to Case L200EX are highlighted with bold font. Use this table if attic modeled as separate zone.

Note 1b: Only nominal values are carried over from Case L200EX, and are included for background only except where highlighted by bold font.

Note 2: Insulated section only, see Figure 1-9 for section view of ceiling. 

Note 3: Framed section only, see Figure 1-9 for section view of ceiling. 

Note 4: This layer of cellulose covers both the framed and insulated sections; see Figure 1-9.

Note 5: Based on 90% insulated section and 10% frame section per ASHRAE; applies to temperature difference between room air and attic air.

Note 6: The "Total surf-surf, composite sec." R-value is the composite air-air R-value less the two interior film coefficient R-values.

B-EX-Spec.xls, h:a70..i96 12-Aug-10
33 

Table 1-16b. Material Descriptions for Attic as Material Layer – Case L220EX 

1.2.2.3 Case L225EX-P: Wall Insulation Retrofit 

Case L225EX-P is exactly as Case L200EX-P, except that the exterior walls have R-13 blown cellulose 

insulation as shown in the following figure and tables. 

Figure 1-10 Exterior wall plan section – Case L225EX 

Table 1-17 Building Thermal Summary – Case L225EX 

Table 1-18 Material Descriptions, Exterior Wall – Case L225EX. 

 

COMPOSITE CEILING/ATTIC/ROOF (inside to outside) 

(Notes 1a, 1b) Thickness R U k DENSITY Cp

h·ft2

·F/ Btu/ Btu/

ELEMENT in. Btu (h·ft2

·F) (h·ft·F) lb/ft3 Btu/(lb·F)

CEILING/ATTIC (1539 ft2

 total area)

Int Surf Coef 0.860 1.163

Plasterboard 0.5 0.450 2.222 0.0926 50.0 0.26

Fiberglass batt (Note 2) 3.5 11.000 0.091 0.0265 0.6 0.20

Blown Cellulose, 2.0" (Note 2) 2.0 7.229 0.138 0.0231 1.5 0.33

Joists 2x6 24" O.C. (Note 3) 5.5 6.872 0.146 0.0667 32.0 0.33

Blown Cellulose, 6.0" (Note 4) 6.0 21.687 0.046 0.0231 1.5 0.33

Attic air space (Note 5) 1.750 0.571

Total roof deck/gable, surf-surf (Note 6) 0.951 1.051

Ext Surf Coef (Note 7) 0.223 4.489

SUMMARY CEILING/ATTIC/ROOF

Total air-air, insulated section 44.150 0.023

Total air-air, framed section 32.792 0.030

Total air-air, composite section (Note 8) 42.672 0.023

Total surf-surf, composite sec. (Note 9) 41.589 0.024

Note 1a: Changes to Case L200EX are highlighted with bold font. Use this table if attic modeled as a material layer.

Note 1b: Only nominal values are carried over from Case L200EX, and are included for background only, except where highlighted by bold font.

Note 2: Insulated section only, see Figure 1-9 for section view of ceiling.

Note 3: Framed section only, see Figure 1-9 for section view of ceiling.

Note 4: This layer of cellulose covers both the framed and insulated sections; see Figure 1-9.

Note 5: Average winter/summer values for natural vent (2.4 ACH), R-30 ceiling ins, ext abs = 0.6, includes interior films.

 Based on McQuiston and Spitler (1992), Tables 4.5 and 4.5a, "Effective Resistances of Ceiling or Attic Air Spaces".

Note 6: From Table 1-6b (Case L200EX).

Note 7: Scaled to 1539 ft2

.

Note 8: Based on 10% frame area fraction per ASHRAE; applies to temperature difference between room air and ambient air.

Note 9: Based on total air-air R-value less R-values of interior film coefficient and scaled exterior film coefficient.

B-EX-Spec.xls, h:a99..i132 16-Apr-10
34 

Note: Changes to Case L200EX are highlighted with bold font. 

Figure 1-10. Exterior wall plan section – Case L225EX 

Cellulose (R-13) 
35 

Table 1-17. Building Thermal Summary – Case L225EX 

Table 1-18. Material Descriptions, Exterior Wall – Case L225EX 

AREA R U UA HEATCAP

ELEMENT ft2 h·ft2

·F/Btu Btu/(h·ft2·F) Btu/(h·F) Btu/F

(Notes 1a, 1b) (Note 2) (Note 2) (Note 2) (Note 3)

Exterior Walls (Note 4) 1034 13.00 0.077 79.6 1618

North Windows 90 1.29 0.774 69.6

East Windows 45 1.29 0.774 34.8

West Windows 45 1.29 0.774 34.8

South Windows 90 1.29 0.774 69.6

Doors 40 3.28 0.305 12.2 62

Ceiling/Attic/Roof (Note 5) 1539 13.67 0.073 112.6 1356

Floor (Note 5) 1539 20.05 0.050 76.8 1881

Infiltration 

 Colorado Springs, CO 133.9

 Las Vegas, NV 100.6

Interior Walls 1024 1425

TOTAL BUILDING 6341

 Excluding Infiltration 490.0

 Including Infiltration, Colorado Springs, CO 623.9

 Including Infiltration, Las Vegas, NV 590.6

Note 1a: Changes to Case L200EX are highlighted by bold font. 

Note 1b: Only nominal values are carried over from Case L200EX, and are included for background only, except where

 highlighted by bold font.

Note 2: Includes interior and exterior surface coefficients.

Note 3: Heat capacity includes building mass within the thermal envelope (e.g., insulation and insulation thickness of 

 structural framing are included, exterior siding and roof/attic mass are excluded). 

Note 4: Excludes window and door areas. ASHRAE framed area fraction of 0.25 used for 2x4 16" O.C. construction.

Note 5: ASHRAE roof/ceiling framing area fraction of 0.1 used for both ceiling and floor. 

B-EX-Spec.xls, r:a362..g391 02-Feb-10

EXTERIOR WALL (inside to outside) R U k DENSITY Cp

 (Note 1) Thickness h·ft2

·F/ Btu/ Btu/

ELEMENT in Btu (h·ft2

·F) (h·ft·F) lb/ft3 Btu/(lb·F)

Int Surf Coef 0.824 1.213

Plasterboard 0.5 0.450 2.222 0.0926 50.0 0.26

Blown Cellulose (Note 2) 3.5 13.000 0.077 0.0224 3.5 0.33

Frame 2x4 16" O.C. (Note 3) 3.5 4.373 0.229 0.0667 32.0 0.33

Fiberboard sheathing 0.5 1.320 0.758 0.0316 18.0 0.31

Hardboard siding, 7/16" 0.44 0.670 1.492 0.0544 40.0 0.28

Ext Surf Coef 0.276 3.628

Total air - air, insulated section 16.540 0.060

Total air - air, frame section 7.913 0.126

Total air - air, composite section (Note 4) 12.998 0.077

Total surf - surf, insulated section 15.440 0.065

Total surf - surf, frame section 6.813 0.147

Total surf - surf, composite section (Note 5) 11.898 0.084

Note 1: Changes to Case L200EX are highlighted with bold font. 

Note 2: Insulated section only, see Figure 1-10 for wall section view. Cellulose properties per manufacturer literature.

Note 3: Framed section only, see Figure 1-10 for section view of wall. 

Note 4: Total composite R-values from 75% insulated section, 25% framed section per ASHRAE.

 Thermal properties of windows and doors are not included in this composite calculation.

Note 5: Total surf-surf composite R-value is the total air-air composite R-value less the resistances due to the surface coefficients. 

B-EX-Spec.xls h:a2..g27 02-Feb-10
36 

1.2.2.4 Case L240EX-P: Programmable Thermostat Retrofit 

Case L240EX-P is exactly as Case L200EX-P, except for changes described in Sections 1.2.2.4.1 and 

1.2.2.4.2. 

1.2.2.4.1 Colorad.TM2 

For Colorad.TM2 weather data (heating only), thermostat setback is applied on all nights during the 

heating season from 10:00 p.m. to 6:00 a.m. as shown below. 

 During heating season (October 7 – May 16): 

 10:00 p.m.–6:00 a.m.: HEAT = ON IF TEMP < 62°F; COOL = OFF 

 6:00 a.m.–10:00 p.m.: HEAT = ON IF TEMP < 68°F; COOL = OFF 

 During non-heating season (May 17 – October 6): 

 HEAT = OFF; COOL = OFF. 

 Where: 

• “TEMP” refers to conditioned zone-air temperature. 

• The heating season start/stop dates are the same as for Case L200EX-P. 

1.2.2.4.2 Lasvega.TM2 

For Lasvega.TM2 weather data (cooling only) thermostat setup is applied on all days from 8:00 a.m. to 

5:00 p.m. as shown below. 

 During cooling season (March 28 – October 28): 

 8:00 a.m.–5:00 p.m.: COOL = ON IF TEMP > 84°F; HEAT = OFF 

 5:00 p.m.–8:00 a.m.: COOL = ON IF TEMP > 78°F; HEAT = OFF 

 During non-cooling season (October 29 – March 27): 

 COOL = OFF; HEAT = OFF. 

 Where: 

• “TEMP” refers to conditioned zone-air temperature. 

• The cooling season start/stop dates are the same as for Case L200EX-P. 

1.2.2.5 Case L250EX-P: Double-Pane Low-Emissivity Window With Wood Frame Retrofit 

Case L250EX-P is exactly as Case L200EX-P, except that all single-pane windows are replaced with 

double-pane low-emissivity (low-e) windows with wood frames and insulated spacers. Window and 

frame geometry remain as for Case L200EX-P. The following tables specify basic properties of the 

window, including shading coefficient (SC), solar heat gain coefficient (SHGC), and thermal resistance: 

Table 1-19 Building Thermal Summary – Case L250EX 

Table 1-20 Window Summary (Double-Pane, Low-E, Argon Fill, Wood Frame, Insulated 

 Spacer) – Case L250EX 

Table 1-21 Low-E Glazing System With Argon Gas Fill Glazing Summary (Center of Glass 

 Values) – Case L250EX 

Table 1-22 Optical Properties as a Function of Incidence Angle for Low-Emissivity Double- 

 Pane Glazing – Case L250EX 

Table 1-23 Component Solar Fractions – Case L250EX. 
37 

Use only the information that is relevant to the program being tested. Window properties are drawn from 

WINDOW 5.2 (2005) software for window thermal analysis (see Appendix E). For programs that need 

transmittance or reflectance at other angles of incidence, interpolate between the values of Table 1-22 

using the cosine of the incidence angle as the basis of interpolation. Where other unspecified data are 

needed, values that are consistent with those quoted must be calculated. 

There is a slight change in interior surface solar distribution caused by reduced solar lost (cavity albedo); 

for tools that can vary this input, values are included in Table 1-23. 

Note for highlighting of changes in Tables 1-19 through 1-23. 

• Because of the large number of changes to the window for this case, changes to Case 

L200EX are not highlighted; rather, bold font in Tables 1-20, 1-21, and 1-22 highlights 

changes to HERS BESTEST Case L130A window inputs only (as a convenience for those 

who have previously run HERS BESTEST). 

• Bold font in Tables 1-19 and 1-23 highlights changes to Case L200EX (usual convention). 

 
38 

Table 1-19. Building Thermal Summary – Case L250EX 

 

AREA R U UA HEATCAP

ELEMENT ft2 h·ft2

·F/Btu Btu/(h·ft2·F) Btu/(h·F) Btu/F

(Notes 1a, 1b) (Note 2) (Note 2) (Note 2) (Note 3)

Exterior Walls (Note 4) 1034 5.09 0.196 203.1 1356

North Windows (Note 5) 90 3.58 0.279 25.1

East Windows (Note 5) 45 3.58 0.279 12.6

West Windows (Note 5) 45 3.58 0.279 12.6

South Windows (Note 5) 90 3.58 0.279 25.1

Doors 40 3.28 0.305 12.2 62

Ceiling/Attic/Roof (Note 6) 1539 13.67 0.073 112.6 1356

Floor (Note 6) 1539 20.05 0.050 76.8 1881

Infiltration 

 Colorado Springs, CO 133.9

 Las Vegas, NV 100.6

Interior Walls 1024 1425

TOTAL BUILDING 6080

 Excluding Infiltration 479.9

 Including Infiltration (Colorado Springs, CO) 613.8

 Including Infiltration (Las Vegas, NV) 580.5

WINDOW SUMMARY: DOUBLE-PANE, LOW-E, WOOD FRAME, INSULATED SPACER 

(Note 7) Area U SHGC Trans. SC

Btu/(h·ft2·F) (dir. nor.) (dir. nor.)

ft2 (Note 2) (Note 8) (Note 9) (Note 10)

Double-pane, low-e, argon 10.96 0.236 0.440 0.389 0.506

Wood frame, insulated spacer 4.04 0.396

Window, composite 15.00 0.279 0.346 0.284 0.398

Note 1a: Changes to Case L200EX are highlighted by bold font. 

Note 1b: Only nominal values are carried over from Case L200EX, and are included for background only, except where

 highlighted by bold font.

Note 2: Includes interior and exterior surface coefficients.

Note 3: Heat capacity includes building mass within the thermal envelope (e.g., insulation and insulation thickness of

 structural framing are included, exterior siding and roof/attic mass are excluded).

Note 4: Excludes areas of windows and doors. ASHRAE framed area fraction of 0.25 is assumed for 2x4 16" O.C. 

Note 5: Window area and other properties are for glass and frame combined. The accompanying window summary 

 disaggregates glass and frame properties for a single window unit. North and south walls contain six window units each;

 east and west walls contain three window units each.

Note 6: ASHRAE roof/ceiling framing area fraction of 0.1 applied to both ceiling and floor. 

Note 7: These data summarize one complete detailed window unit per Figure 1-8 and Tables 1-20 through 1-22. 

Note 8: SHGC is the Solar Heat Gain Coefficient, which includes the inward flowing fraction of absorbed direct normal 

 solar radiation in addition to direct normal transmittance (see 2009 ASHRAE Fundamentals , pp. 15.17-15.18).

Note 9: "Trans." is the direct normal transmittance.

Note 10: Shading coefficient (SC) is the direct normal SHGC for a specific glazing unit divided by 0.87, per 2005 ASHRAE

 Fundamentals, p. 31.39

B-EX-Spec.xls, r:a103..g147 25-Mar-10
39 

Table 1-20. Window Summary (Double-Pane, Low-E, Argon Fill, Wood Frame, 

Insulated Spacer) – Case L250EX 

Property (Note 1) Value Units Notes

GENERAL PROPERTIES

Area, gross window 15.00 ft2 (Note 2)

Width, frame 2.75 in.

Area, frame 4.04 ft2

Area, edge of glass (EOG) 3.57 ft2

Area, center of glass (COG) 7.39 ft2

Area, net glass 10.96 ft2 (Area,EOG + Area,COG)

OPTICAL PROPERTIES

Absorptance, frame 0.60

Transmittance, frame 0.00

COG/EOG optical properties (see Table 1-21) (Note 3)

Solar Heat Gain Coefficient (Note 4)

 (SHGC), glass 0.440

 (SHGC), frame 0.091

 (SHGC), gross window 0.346

Shading Coefficient (SC), 0.398 (Note 4) 

gross window 

Dividers, curtains, blinds, and None

other obstructions in window

THERMAL PROPERTIES (conductances/resistances include film coefficients)

Conductance, frame 0.396 Btu/(h·ft2

·F) Wood frame with insulated spacer

(R-Value) 2.528 h·ft2

·F/Btu (Note 5) 

Conductance, edge of glass 0.264 Btu/(h·ft2

·F) from WINDOW 5

(R-Value) 3.782 h·ft2

·F/Btu

Conductance, center of glass 0.222 Btu/(h·ft2

·F)

(R-Value) 4.500 h·ft2

·F/Btu

Conductance, net glass 0.236 Btu/(h·ft2

·F) (Note 6)

(R-Value) 4.238 h·ft2

·F/Btu

Conductance, gross window 0.279 Btu/(h·ft2

·F) (Note 7)

(R-Value) 3.585 h·ft2

·F/Btu

COMBINED SURFACE COEFFICIENT CONDUCTANCES

Exterior Surf Coef, glass and frame 2.609 Btu/(h·ft2

·F) See Table 1-21

Interior Surface Coefficient, glass 1.070 Btu/(h·ft2

·F) See Table 1-21

Interior Surface Coefficient, frame 1.216 Btu/(h·ft2

·F)

Note 1: Changes to the low-e window of HERS BESTEST Case L130A are highlighted with bold font.

Note 2: Area for one representative window unit. See Figure 1-8 for a schematic representation of frame, center-of-

 glass (COG) and edge-of-glass (EOG) areas; dimensions are based on an NFRC size AA vertical slider. Gross window

 area is the sum of frame, COG, and EOG areas. 

Note 3: Edge-of-glass optical properties are the same as the center-of-glass optical properties. Table 1-22 gives

 optical properties as a function of incidence angle.

Note 4: These are overall window (including COG, EOG, and frame) properties for direct normal solar radiation. 

Note 5: The frame conductance presented here is based on HERS BESTEST, Table 2-22, adjusted for the exterior and interior

 surface coefficients shown in this table. Material properties for dynamic modeling of window frames (density, specific heat, 

 etc.) are not given.

Note 6: Net glass conductance includes only the COG and EOG portions of the window.

Note 7: Gross window conductance includes the frame, EOG, and COG portions of the window. 

B-EX-Spec, L:a68..h118; 02-Feb-10
40 

Table 1-21. Low-E Glazing System With Argon Gas Fill Glazing Summary 

(Center of Glass Values) – Case L250EX 

Property Value Units Notes

GENERAL PROPERTIES (Note 1)

Number of Panes 2.000

Pane Thickness 0.118 in

Argon Gap Thickness 0.500 in

OUTER PANE OPTICAL PROP. (Note 2)

Transmittance 0.450

Reflectance (outside facing surf.) 0.340

Reflectance (inside facing surf.) 0.370

Absorptance 0.210

Index of Refraction (Note 3)

Extinction Coefficient (Note 3)

INNER PANE OPTICAL PROP.

Transmittance 0.837

Reflectance 0.075

Absorptance 0.089

Index of Refraction 1.5223

Extinction Coefficient 0.7806 /in

DOUBLE PANE OPTICAL PROP.

Transmittance 0.389

Reflectance,f 0.350 (Note 4)

Reflectance,b 0.337 (Note 4)

Absorptance (outer pane) 0.219

Absorptance (inner pane) 0.041

Solar Heat Gain Coefficient (SHGC) 0.440

Shading Coefficient (SC) 0.506 (Note 5)

Optical Properties as a Function (See Table 1-22)

of Incident Angle

THERMAL PROPERTIES

Conductivity of Glass 0.520 Btu/(h·ft·F)

Combined Radiative and Convec- 0.318 Btu/(h·ft2

·F) (Note 6)

tive Coefficient of Argon Gap

(R-Value) 3.144 h·ft2

·F/Btu

Conductance of Glass Pane 52.881 Btu/(h·ft2

·F)

(R-Value) 0.019 h·ft2

·F/Btu

Exterior Combined Surface Coef. 2.609 Btu/(h·ft2

·F)

(R-Value) 0.383 h·ft2

·F/Btu

Interior Combined Surface Coef. 1.070 Btu/(h·ft2

·F)

(R-Value) 0.935 h·ft2

·F/Btu

U-Value, Air-Air 0.222 Btu/(h·ft2

·F)

(R-Value) 4.500 h·ft2

·F/Btu

Hemispherical Infrared Emittance 0.84 (Note 2)

Infrared Transmittance 0

Density of Glass 154 lb/ft3

Specific Heat of Glass 0.18 Btu/(lb·F)

Note 1: Changes to low-e window of HERS BESTEST Case L130A highlighted with bold font. 

Note 2: Optical properties listed in this table are for direct normal radiation. The inside facing

 surface of the outer pane has emissivity = 0.04.

Note 3: Single values of index of refraction and extinction coefficient do not adequately 

 describe the optical properties of coated glass.

Note 4: Reflectance,f and Reflectance,b are overall solar reflectances for radiation incident

 from the front (from the outside) and back (from the inside), respectively.

Note 5: SC = SHGC/0.87 per Eqn. 91 (p. 31.39) of ASHRAE 2005 Fundamentals.

Note 6: Calculated from WINDOW 5 output; Ugap = (Utot)(dTtot)/(dTgap),

 for center of glass values at winter design conditions.

B-EX-Spec, L:a3..h59; 25-Mar-10
41 

Table 1-22. Optical Properties as a Function of Incidence Angle for Low-Emissivity 

Double-Pane Glazing – Case L250EX 

 Properties (Notes 1a, 1b, 2, 3)

Angle Trans Refl,f Refl,b Abs Out Abs In SHGC 

0 0.389 0.350 0.337 0.219 0.041 0.440

10 0.389 0.350 0.337 0.219 0.041 0.440

20 0.384 0.349 0.335 0.226 0.042 0.437

30 0.376 0.351 0.336 0.231 0.042 0.429

40 0.366 0.359 0.341 0.232 0.043 0.420

50 0.346 0.373 0.355 0.236 0.044 0.401

60 0.305 0.402 0.388 0.250 0.043 0.360

70 0.226 0.471 0.470 0.264 0.038 0.279

80 0.107 0.639 0.645 0.224 0.029 0.149

90 0.000 0.999 1.000 0.001 0.000 0.000

Hemis 0.323 0.391 0.378 0.235 0.041 0.376

Note 1a: Changes to low-e window of HERS BESTEST Case L130A are highlighted with bold font.

Note 1b: Updates to incident-angle dependent transmittance, reflectances, and absorptances are

 for WINDOW 5 (WINDOW 4.1 was used for HERS BESTEST).

Note 2: Trans = Transmittance; 

 Refl,f = Overall solar reflectance for radiation incident from the front (i.e., from the outside);

 Refl,b = Overall solar reflectance for radiation incident from the back (i.e., from inside the zone);

 Abs Out = absorptance of outer pane; Abs In = absorptance of inner pane; SHGC = solar heat gain coefficient;

 Hemis = hemispherically integrated property. Transmittance, reflectance, and SHGC are overall 

 properties for the glazing system (inside pane, argon fill, and outer pane), excluding the frame.

Note 3: SHGC is from Equations 18, 19, and 21 (pp. 15.17-18) of ASHRAE 2009 Fundamentals. 

 These apply updated window surface coefficients of Table 1-21. 

B-EX-Spec, b!:a148..h175 02-Feb-10
42 

Table 1-23. Component Solar Fractions – Case L250EX 

HEIGHT or INSIDE

ELEMENT LENGTH WIDTH MULTIPLIER AREA SOLAR

(Note 1) ft ft ft2 FRACTION

EXTERIOR NORTH/SOUTH WALLS (Note 2)

Gross Wall 8.0 57.0 1.0 456.0

 Gross Window 5.0 3.0 6.0 90.0

 Window Frame Only 24.2 0.0031

 Door 6.7 3.0 1.0 20.0 0.0026

 Net Wall (Note 3) 346.0

 Insulated Wall (Note 3) 259.5 0.0335

 Framed Wall (Note 3) 86.5 0.0112

EXTERIOR EAST/WEST WALLS

Gross Wall 8.0 27.0 1.0 216.0

 Gross Window 5.0 3.0 3.0 45.0

 Window Frame Only 12.1 0.0016

 Net Wall (Note 3) 171.0

 Insulated Wall (Note 3) 128.3 0.0166

 Framed Wall (Note 3) 42.8 0.0055

INTERIOR WALLS 

Gross Wall (Note 4) 8.0 128.0 1024.0

 Unframed Wall (Note 4) 921.6 0.1190

 Framed Wall (Note 4) 102.4 0.0132

FLOOR/CEILING

Gross Floor/Ceiling 57.0 27.0 1.0 1539.0

 Insulated Floor/Ceiling (Note 5) 1385.1 0.1788

 Framed Floor/Ceiling (Note 5) 153.9 0.0199

TRANSMITTED SOLAR, INTERIOR DISTRIBUTION SUMMARY

Total Opaque Interior Surface Area (Note 6) 6272.7 0.8097

Solar to Air (or low mass furnishings) 0.1750 (Note 7)

Solar Lost (back out through windows) 0.0153 (Note 8)

Note 1: Changes to Case L200EX are highlighted with bold font.

Note 2: Solar energy transmitted through windows is assumed as distributed to interior opaque surfaces in proportion to their

 areas. Only the radiation not directly absorbed by lightweight furnishings (assumed to exist only for the purpose of 

 calculating inside solar fraction) or lost back out through windows is distributed to interior opaque surfaces.

Note 3: Net wall area is gross wall area less the rough opening areas of the windows and door. Insulated and framed exterior 

 wall sections are defined in Figure 1-4. ASHRAE framed area fraction of 0.25 is assumed for 2x4 16" O.C. construction.

Note 4: Width is the total length of all interior walls. Framed wall area is assumed to be 10% of gross wall area for 2x4 16" O.C.

 framing. Only one side of the wall is considered for listed area. This area is multiplied by 2 for determining solar fractions.

 Solar fractions shown are for just one side of the interior wall. 

Note 5: Insulated and framed floor and ceiling sections are defined in Figures 1-5 and 1-6, respectively. ASHRAE 

 roof/ceiling framing area fraction of 0.1 applied to both ceiling and floor.

Note 6: Total area of just those surfaces to which an inside solar fraction is applied.

Note 7: Based on the midpoint of the range given by SUNCODE-PC User's Manual (Kennedy et al. 1992), p. 2-16.

Note 8: Calculated using the algorithm described in HERS BESTEST, Appendix E; value varies slightly with film coefficients.

B-EX-Spec.xls, c!a62..g107 02-Feb-10
43 

1.2.2.6 Case L260EX-P: High Solar Absorptance Roof (Cool Roof Base Case) 

Case L260EX-P is exactly as Case L200EX-P, except that exterior shortwave (visible and UV) 

absorptance (αext) is 0.8 for the roof only. 

1.2.2.7 Case L265EX-P: Low Solar Absorptance Roof (Cool Roof) 

Case L265EX-P is exactly as Case L200EX-P, except that exterior shortwave (visible and UV) 

absorptance (αext) is 0.2 for the roof only. 

1.2.2.8 Case L270EX-P: External Shading 

Case L270EX-P is exactly as Case L200EX-P, except for the following changes: 

• An opaque overhang is included at the top of the south, east, and west exterior walls. The 

overhang extends outward from this wall 6.0 ft (see Figures 1-11 and 1-12). Window horizontal 

spacing along the walls is shown previously in Figure 1-2. The overhang traverses the entire 

length of the south, east, and west walls. 

• External shading device (overhang) optical properties: 

o Solar absorptance = 1 (reflectance = 0, transmittance = 0) independent of incidence angle. 

o Infrared emittance = 0. 

o Apply these values as nearly as the program being tested allows. 

o All heat from solar radiation absorbed by the shading devices is dissipated to the ambient 

environment via convection. 

o The properties listed above apply to both sides of the shading devices. 

o If the program being tested does not allow variation of these properties, use its default 

values. 

o Thickness: If the program requires an input for thickness of shading devices, use the 

smallest allowable value (e.g., 0.001 m). 

Recall from Section 1.1 that this test requires use of consistent modeling methods for the test cases. 
44 

Figure 1-11. South overhang – Case L270EX-P 

W

6’-0”

2’-0”

W

W

W

W

W

D

6’-

Legend:  W = Window module (3’ wide x 5’ high), see Figure 1-8  D = Door (3’ wide x 6’-8” high) 

Overhang (opaque) 

Overhang (opaque) Window module 

(see Figure 1-8) 

Axonometric 

South Wall Only 
45 

Figure 1-12. Overhang for east and west windows – Case L270EX-P 

8’-0”

6

W

2’-0”

27’-0”

W

W

Axonometric – Shaded East/West Wall 

Legend: 

• W = Typical window module (3’ wide × 5’ high), see Figure 1-8. 

Ov
46 

1.2.2.9 Case L300EX-P: Combined Retrofits 

Case L300EX-P is exactly as Case L200EX-P, except for the following changes. 

1.2.2.9.1 Case L300EX-PH 

For the heating climate (Colorad.TM2 weather) include: 

• Air-seal retrofit as described in Section 1.2.2.1 

• Attic insulation retrofit as described in Section 1.2.2.2 

• Wall insulation retrofit as described in Section 1.2.2.3 

• Programmable thermostat retrofit as described in Section 1.2.2.4 

• Low-e window retrofit as described in Section 1.2.2.5. 

1.2.2.9.2 Case L300EX-PC 

For the cooling climate (Lasvega.TM2 weather) include: 

• All the retrofits listed in Section 1.2.2.9.1 

• The low solar absorptance roof retrofit as described in Section 1.2.2.7 

• The external shading retrofit as described in Section 1.2.2.8. 

1.3 Calibrated Energy Savings Tests Input Specifications 

Run the calibrated energy savings test cases after the building physics test cases of Section 1.2 are 

complete, with all Section 1.2 results disagreements diagnosed and all found modeling errors corrected. 

Correction of modeling errors must have a mathematical, physical, or logical basis and must be applied 

consistently throughout the test cases. Some disagreements may have a logical basis (i.e., may be based 

on legitimate modeling differences). 

The Section 1.3 test cases are based on the Section 1.2 test cases with changes noted in the following 

sections. Except where noted, figures and tables for the building physics base case (L200EX-P) are 

applied for developing the calibrated base case (L200EX-C). 

Section 1.3 is written such that: a) a preliminary non-calibrated base-case model is developed as described 

in Section 1.3.1, b) inputs for the base-case simulation model (see Section 1.3.1) are calibrated using 

reference utility energy-use data given in Section 1.3.1.2, and c) inputs for retrofit cases (see Section 

1.3.2) are developed using calibrated base-case inputs with modifications as specified for the given 

retrofit cases. Some modeling methods may calculate calibrated energy savings, without adjustment to 

model inputs, e.g., by comparing differences between base-case utility billing data versus predicted noncalibrated base-case energy use, and then applying an appropriate adjustment to predicted non-calibrated 

energy savings. For programs that apply methods not requiring adjustment to base-case model inputs, use 

the utility bills called out in Section 1.3.1.2 for calibration, however, specific instructions of Section 

1.3.1.2 (and elsewhere in Section 1.3) regarding adjustment of inputs for calibration do not apply. 

1.3.1 Pre-Retrofit Base-Case Building (Case L200EX-C) 

Case L200EX-C is exactly as Case L200EX-P, except for changes described in the following 

subsections. 

1.3.1.1 Approximate Inputs 

Approximate input ranges are provided for selected base-case model input parameters listed in Section 

1.3.1.2. The selected parameters strongly affect energy use predictions and are commonly known to have 

pre-retrofit audit uncertainty. For calibrating the pre-retrofit base case to reference utility energy-use data, 

variation of approximate inputs is allowed during the model calibration phase, as described in Section 

1.3.1.2. The following nomenclature is used to denote approximate input ranges in the data tables: 
47 

• “Min”: approximate input range minimum value 

• “Max”: approximate input range maximum value. 

For parameters with approximate input ranges, the nominal values provided in data tables are for use with 

the Section 1.2 building physics test cases, and as described in Section 1.3.1.2. 

Where approximate input ranges are provided, explicit inputs for reference programs are selected from 

within the approximate input range as described in Appendix F. Symmetric or asymmetric triangular 

probability distribution is assumed as appropriate within the given approximate input ranges for randomly 

selecting explicit inputs used for developing reference utility energy use data. 

1.3.1.2 Calibration of Pre-Retrofit Base-Case Inputs 

• For programs (or program modes) not requiring use of utility billing data to run a simulation, use 

the nominal inputs and results for Case L200EX-P (see Section 1.2.1) as the uncalibrated 

simulation. For programs (or program modes) requiring use of utility billing data, use the nominal 

inputs (see Section 1.2.1) as applicable for uncalibrated inputs. 

• For the Colorad.TM2 heating only climate, calibrate the base-case approximate inputs using the 

reference utility energy-use data given in Tables 1-24a through 1-24g for the following base-case 

calibration scenarios. 

o Table 1-24a, Case L200EX-C1H, targeted high space heating use 

o Table 1-24b, Case L200EX-C2H, targeted low space heating use 

o Table 1-24c, Case L200EX-C3H, fully random selection, near-nominal space heating use 

o Table 1-24d, Case L200EX-C4H, fully random selection, high space heating use 

o Table 1-24e, Case L200EX-C5H, fully random selection, low space heating use 

o Table 1-24f, Case L200EX-C6H, fully random selection, mid-high space heating use 

o Table 1-24g, Case L200EX-C7H, fully random selection, mid-low space heating use. 

• For the Lasvega.TM2 cooling only climate, calibrate the base-case approximate inputs using the 

reference utility energy-use data given in Tables 1-25a through 1-25g for the following base-case 

calibration scenarios. 

o Table 1-25a, Case L200EX-C1C, targeted high space cooling use 

o Table 1-25b, Case L200EX-C2C, targeted low space cooling use 

o Table 1-25c, Case L200EX-C3C, fully random selection, near-nominal space cooling use 

o Table 1-25d, Case L200EX-C4C, fully random selection, high space cooling use 

o Table 1-25e, Case L200EX-C5C, fully random selection, low space cooling use 

o Table 1-25f, Case L200EX-C6C, fully random selection, mid-high space cooling use 

o Table 1-25g, Case L200EX-C7C, fully random selection, mid-low space cooling use. 

• Use the calibration method typically applied by your software; this test procedure does not 

provide guidance for calibration methodologies. Only approximate inputs related to the model 

parameters listed below are allowed to be varied for calibration. 

o Exterior wall R-value (see Tables 1-1 and 1-4) 

 For calibrating the exterior wall inputs, assume the empty cavity (air gap) Rvalue and wood-framing material properties are explicitly known; vary material 

properties of exterior siding/sheathing and/or interior wall materials only. This 

allows development of a clearer relative retrofit effect in Case L225EX-C. To 

develop reference simulation program base-case explicit inputs, only the exterior 

hardboard siding thickness was randomly varied as shown in Table 1-4. 

o Composite ceiling/attic/roof R-value (see Tables 1-1, 1-6a, and 1-6b) 
48 

 To develop reference simulation program base-case explicit inputs, the batt 

insulation (and modeled joist) thicknesses were randomly varied (see Tables 1-6a 

and 1-6b). Attic joist thickness varies with insulation thickness. However, the 

maximum modeled attic joist thickness is 5.5 in.; modeled batt insulation 

thickness may be slightly greater than 5.5 in. 

o Infiltration rate or leakage area, etc. (see Tables 1-2, 1-8a, 1-8b, and Section 1.3.1.3.1) 

o Internal gains and related fractions of base load energy use corresponding to sensible 

internal gains (see Tables 1-2, 1-9a, 1-9b, and Section 1.3.1.3.2) 

o Exterior solar absorptance (see Table 1-2 and Section 1.3.1.3.3) 

o Thermostat heating and cooling set points (see Section 1.3.1.3.4) 

o Thermostat heating and cooling season start/stop dates (see Section 1.3.1.3.4) 

o Furnace efficiency (see Section 1.3.1.3.5) 

o Mechanical cooling COP (see Section 1.3.1.3.5). 

• Develop calibrated approximate inputs independently for each space heating and space cooling 

base-case scenario. Model parameters listed above are applicable to both space heating and space 

cooling scenarios, except heating set point, heating season start/stop dates, and furnace efficiency 

apply to space-heating cases only; cooling set point, cooling season start/stop dates, and cooling 

COP apply to space-cooling cases only. 

• It may be reasonable for calibrated inputs to vary slightly outside of specified approximate input

ranges because randomly selected explicit inputs for the reference simulations can occur near the 

extremes of a given approximate input range. 

• Use the new base-case models with the calibrated approximate inputs to develop the input files 

for the retrofit cases of Section 1.3.2. 

Reference energy use data provided in Tables 1-24a through 1-24g and Tables 1-25a through 1-25g are 

the average of the results for the reference simulation models using EnergyPlus, SUNREL, and 

DOE-2.1E. The reference simulations apply explicit inputs randomly selected from within the given 

approximate input ranges (see Appendix F). All reference simulation explicit inputs are selected 

independently for each space-heating and space-cooling base-case scenario, except heating thermostat 

settings/schedule and furnace efficiency are only selected for space heating cases, and cooling thermostat 

settings/schedule and cooling COP are only selected for space cooling cases. The reference simulation 

explicit inputs are intended to be unknown for the software being tested and are not given in the test 

specification. Thirteen months of base-case energy use data are provided as recommended by the 

BESTEST-EX Working Group (2009). In Tables 1-24a through 1-24g and Tables 1-25a through 1-25g, 

gas use is for the furnace and DHW only; electricity use is for space cooling equipment and all other 

appliances (except DHW); and HVAC fan electricity is zero, as specified in Section 1.2.1.15. 
49 

Table 1-24a. Case L200EX-C1H Reference Utility Energy Use Data 

(Approximate input selection targeted for increased base-case space heating energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 29.60 569.6 

February 22.14 514.5 

March 21.76 569.6 

April 14.12 551.3 

May 5.88 569.6 

June 1.38 551.3 

July 1.43 569.6 

August 1.43 569.6 

September 2.44 551.3 

October 9.75 569.6 

November 19.23 551.3 

December 26.34 569.6 

January 29.60 569.6 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for the furnace and DHW only. 

Note 3: Electricity use is for all non-space-heating system appliances except DHW. HVAC 

fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 

Table 1-24b. Case L200EX-C2H Reference Utility Energy Use Data 

(Approximate input selection targeted for decreased base-case space heating energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 18.93 745.8 

February 13.86 673.7 

March 13.50 745.8 

April 7.55 721.8 

May 2.03 745.8 

June 1.97 721.8 

July 2.03 745.8 

August 2.03 745.8 

September 1.97 721.8 

October 2.98 745.8 

November 11.65 721.8 

December 16.55 745.8 

January 18.93 745.8 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for the furnace and DHW only. 

Note 3: Electricity use is for all non-space-heating system appliances except DHW. 

HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 
50 

Table 1-24c. Case L200EX-C3H Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for near-nominal base-case space heating 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 24.24 381.0 

February 18.18 344.1 

March 17.92 381.0 

April 11.76 368.7 

May 3.61 381.0 

June 1.88 368.7 

July 1.94 381.0 

August 1.94 381.0 

September 1.88 368.7 

October 6.88 381.0 

November 15.87 368.7 

December 21.66 381.0 

January 24.24 381.0 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for the furnace and DHW only. 

Note 3: Electricity use is for all non-space-heating system appliances except DHW. 

HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 

Table 1-24d. Case L200EX-C4H Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for high base-case space heating 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 28.87 318.8 

February 21.77 288.0 

March 21.51 318.8 

April 14.30 308.6 

May 6.97 318.8 

June 2.19 308.6 

July 2.26 318.8 

August 2.26 318.8 

September 3.56 308.6 

October 10.23 318.8 

November 19.13 308.6 

December 25.84 318.8 

January 28.87 318.8 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for the furnace and DHW only. 

Note 3: Electricity use is for all non-space-heating system appliances except DHW. 

HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 
51 

Table 1-24e. Case L200EX-C5H Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for low base-case space heating 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 18.01 749.5 

February 13.04 676.9 

March 12.58 749.5 

April 7.73 725.3 

May 2.25 749.5 

June 1.99 725.3 

July 2.06 749.5 

August 2.06 749.5 

September 1.99 725.3 

October 3.60 749.5 

November 10.78 725.3 

December 15.61 749.5 

January 18.01 749.5 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for the furnace and DHW only. 

Note 3: Electricity use is for all non-space-heating system appliances except DHW. 

HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 

Table 1-24f. Case L200EX-C6H Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for mid-high base-case space heating 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 25.68 605.6 

February 19.20 547.0 

March 18.98 605.6 

April 12.33 586.1 

May 4.72 605.6 

June 1.70 586.1 

July 1.75 605.6 

August 1.75 605.6 

September 1.70 586.1 

October 8.08 605.6 

November 16.66 586.1 

December 22.85 605.6 

January 25.68 605.6 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for the furnace and DHW only. 

Note 3: Electricity use is for all non-space-heating system appliances except DHW. 

HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 
52 

Table 1-24g. Case L200EX-C7H Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for mid-low base-case space heating 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 20.24 780.3 

February 14.83 704.8 

March 14.49 780.3 

April 9.02 755.1 

May 3.49 780.3 

June 1.52 755.1 

July 1.57 780.3 

August 1.57 780.3 

September 1.52 755.1 

October 5.38 780.3 

November 12.49 755.1 

December 17.70 780.3 

January 20.24 780.3 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for the furnace and DHW only. 

Note 3: Electricity use is for all non-space-heating system appliances except DHW. 

HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 

Table 1-25a. Case L200EX-C1C Reference Utility Energy Use Data 

(Approximate input selection targeted for increased base-case space cooling energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 1.98 687.4 

February 1.79 620.9 

March 1.98 787.3 

April 1.92 1167.9 

May 1.98 1449.0 

June 1.92 2006.2 

July 1.98 2284.2 

August 1.98 2190.2 

September 1.92 1781.2 

October 1.98 1203.0 

November 1.92 665.3 

December 1.98 687.4 

January 1.98 687.4 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for DHW only. 

Note 3: Electricity use is for space conditioning equipment and all appliances except 

DHW. HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 

 
53 

Table 1-25b. Case L200EX-C2C Reference Utility Energy Use Data 

(Approximate input selection targeted for decreased base-case space cooling energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 2.67 322.7 

February 2.41 291.5 

March 2.67 372.0 

April 2.58 703.3 

May 2.67 920.4 

June 2.58 1368.4 

July 2.67 1584.4 

August 2.67 1505.5 

September 2.58 1191.6 

October 2.67 701.5 

November 2.58 312.3 

December 2.67 322.7 

January 2.67 322.7 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for DHW only. 

Note 3: Electricity use is for space conditioning equipment and all appliances except 

DHW. HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 

Table 1-25c. Case L200EX-C3C Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for near-nominal base-case space cooling 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 1.53 558.8 

February 1.39 504.7 

March 1.53 558.8 

April 1.49 928.4 

May 1.53 1177.1 

June 1.49 1616.5 

July 1.53 1839.4 

August 1.53 1760.6 

September 1.49 1434.0 

October 1.53 870.3 

November 1.49 540.8 

December 1.53 558.8 

January 1.53 558.8 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for DHW only. 

Note 3: Electricity use is for space conditioning equipment and all appliances except 

DHW. HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 
54 

Table 1-25d. Case L200EX-C4C Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for high base-case space cooling 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 2.15 654.8 

February 1.94 591.5 

March 2.15 777.2 

April 2.08 1118.8 

May 2.15 1393.3 

June 2.08 1938.2 

July 2.15 2211.2 

August 2.15 2115.6 

September 2.08 1712.4 

October 2.15 1165.9 

November 2.08 645.2 

December 2.15 654.8 

January 2.15 654.8 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for DHW only. 

Note 3: Electricity use is for space conditioning equipment and all appliances except 

DHW. HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 

Table 1-25e. Case L200EX-C5C Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for low base-case space cooling 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 1.34 419.6 

February 1.21 379.0 

March 1.34 436.6 

April 1.30 639.5 

May 1.34 814.5 

June 1.30 1193.0 

July 1.34 1379.0 

August 1.34 1315.1 

September 1.30 1049.4 

October 1.34 674.3 

November 1.30 406.0 

December 1.34 419.6 

January 1.34 419.6 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for DHW only. 

Note 3: Electricity use is for space conditioning equipment and all appliances except 

DHW. HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 
55 

Table 1-25f. Case L200EX-C6C Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for mid-high base-case space cooling 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 1.98 764.0 

February 1.79 690.1 

March 1.98 764.0 

April 1.92 1144.2 

May 1.98 1427.7 

June 1.92 1944.3 

July 1.98 2208.7 

August 1.98 2118.4 

September 1.92 1737.4 

October 1.98 1154.5 

November 1.92 739.4 

December 1.98 764.0 

January 1.98 764.0 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for DHW only. 

Note 3: Electricity use is for space conditioning equipment and all appliances except 

DHW. HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 

Table 1-25g. Case L200EX-C7C Reference Utility Energy Use Data 

(Fully random approximate input selection, selected for mid-low base-case space cooling 

energy consumption) 

Month 

(Note 1) 

Total Gas Use 

(million Btu) (Note 2)

Total Electricity Use 

(kWh) (Notes 3, 4)

January 1.71 851.3 

February 1.54 768.9 

March 1.71 851.3 

April 1.65 1106.9 

May 1.71 1368.9 

June 1.65 1783.5 

July 1.71 2008.0 

August 1.71 1935.5 

September 1.65 1624.0 

October 1.71 1117.6 

November 1.65 823.9 

December 1.71 851.3 

January 1.71 851.3 

Note 1: For first day of month to last day of month; 28 days in February. 

Note 2: Gas use is for DHW only. 

Note 3: Electricity use is for space conditioning equipment and all appliances except 

DHW. HVAC fan electricity is not included (= 0 as specified in Section 1.2.1.15). 

Note 4: 0.2930711 Wh = 1 Btu (ASHRAE 2005). 
56 

1.3.1.3 Topical Details 

1.3.1.3.1 Infiltration 

The approximate input ranges shown in Tables 1-2, 1-8a, 1-8b (containing infiltration input data) are 

meant to include all factors that would account for uncertainty in the resulting energy load, including the 

uncertainties associated with blower door measurements caused by user error, instrument calibration 

error, measurement repeatability, outdoor wind speed, etc., along with other modeling uncertainties such 

as crack type, leak location, etc. Although, it may be more realistic to exclude uncertainties not related 

directly to one-point CFM50 (cubic feet per minute at 50 Pascals) measurements from the CFM50

approximate input range, it is simpler to specify consistent approximate input ranges for all inputs, as 

different tested programs may require different inputs. Therefore, resulting approximate input range as 

percent variation from nominal value for effective leakage area at 4 Pa is the same as for CFM50 (see 

Table 1-8a). 

1.3.1.3.2 Internal Loads 

1.3.1.3.2.1 Sensible Loads 

Approximate input ranges for daily total sensible internal loads are specified in Table 1-9a. Normalized 

sensible load hourly profile fractions for the conditioned zone are specified in Table 1-9b; the hourly 

fractions apply for all days of the year as given. Approximate input ranges are given for the daily sensible 

internal loads disaggregated for occupants, electricity, and gas. For developing reference utility billing 

data and other reference simulation results (see Section 1.3.1.2), a different randomly selected explicit 

input for daily total value is chosen for each of the three categories within the minimum and maximum 

values listed in Table 1-9a. The hourly internal sensible gains are then calculated by multiplying the 

randomly selected daily totals by the schedules listed in Table 1-9b. 

1.3.1.3.2.2 Latent Loads 

As with the building physics tests of Section 1.2, latent loads are ignored (see Section 1.2.1.8.2). For 

developing reference simulation results, latent loads were not included, as they have no effect on the 

results. 

1.3.1.3.2.3 Fractions of Base Load Usages to Internal Gains 

Only a fraction of the non-HVAC energy from electricity and gas used in a home is converted to sensible 

internal gains. To generate synthetic utility bills, percentages of non-HVAC gas energy and electric 

energy converted to sensible loads must be assumed. The following approximate input ranges are used 

for conversion of non-HVAC energy use to sensible internal gains: 

• 60%–90% of the non-HVAC energy for electric appliances and lights 

• 20%–35% of the non-HVAC energy for gas DHW. 

These values were developed in consultation with the BESTEST-EX Working Group (2009). Further 

background discussion is included in Appendix B. Resulting ranges of non-HVAC energy usage based on 

these fractions are included in Table 1-9a. 

Synthetic reference utility energy use data (provided in Section 1.3.1.2) integrate internal gains using the 

following steps: 

1. Randomly select explicit conversion factors for electricity (X%) and gas (Y%) from within the 

approximate input ranges described above. 

 
57 

2. Perform the conversions: 

a. Convert the sensible internal gains due to non-HVAC electric appliances and lights 

(divide by X%/100) to obtain base load electricity consumption. 

b. Convert the sensible internal gains due to non-HVAC gas appliances (DHW) (divide by

Y%/100) to obtain base load (DHW) gas consumption. 

3. Each month: 

a. Add the non-HVAC electricity consumption to the monthly HVAC electricity 

consumption. 

b. Add the non-HVAC gas consumption to the monthly HVAC gas consumption. 

4. Use units of kWh for metered electricity consumption and million (106) Btu for metered natural 

gas consumption. 

1.3.1.3.3 Opaque Exterior Surface Radiative Properties 

The approximate input range for exterior surface solar absorptance is 0.5–0.8 for all opaque 

exterior surfaces except window frames. Window frames remain at 0.6. All other opaque surface 

radiative properties have explicit inputs as shown in Table 1-2. 

For the reference simulations, the same randomly selected exterior solar absorptance value applies to all 

wall and roof exterior surfaces for a given base-case scenario. 

1.3.1.3.4 Thermostat Control Strategies 

Seasonal thermostat control settings are shown for heating and cooling climates in Sections 1.3.1.3.4.1 

and 1.3.1.3.4.2, respectively. The heating and cooling season start/stop dates are intentionally not given to 

the user. For developing the reference utility data (see Section 1.3.1.2), the start/stop dates are randomly 

selected from within an approximate input range based on the period when a given fraction of full-year 

space conditioning load (heating or cooling load, as appropriate) would occur for the randomly selected 

base-case explicit inputs (including the randomly selected thermostat set point), as follows: 

• L200EX-C1 (targeted high space conditioning): 95%–99% of full-year load 

• L200EX-C2 (targeted low space conditioning): 90%–95% of full-year load 

• L200EX-C3 through C7 (fully random selection): 90%–99% of full-year load. 

1.3.1.3.4.1 Colorad.TM2 

For Colorad.TM2 weather data (heating only) 

 During heating season (season start/stop dates intentionally not given): 

 HEAT = ON IF TEMP < Thtg; COOL = OFF 

 During non-heating season (season start/stop dates intentionally not given): 

 HEAT = OFF; COOL = OFF. 

Where: 

• “TEMP” refers to conditioned zone-air temperature 

• The approximate input range for Thtg is 60°–75°F. 

1.3.1.3.4.2 Lasvega.TM2 

For Lasvega.TM2 weather data (cooling only) 

 During cooling season (season start/stop dates intentionally not given): 

 COOL = ON IF TEMP > Tclg; HEAT = OFF 

 
58 

During non-cooling season (season start/stop dates intentionally not given): 

 COOL = OFF; HEAT = OFF. 

Where: 

• “TEMP” refers to conditioned zone-air temperature. 

• The approximate input range for Tclg is 71°–86°F. 

1.3.1.3.5 Equipment Characteristics 

EFFECTIVE HEATING EFFICIENCY = Ehtg 

EFFECTIVE COOLING COEFFICIENT OF PERFORMANCE = COPclg

Where: 

• The approximate input range for Ehtg is 60%–80%. 

• The approximate input range for COPclg is 2.5–3.5. 

For generating reference utility energy use data, randomly selected heating efficiencies and cooling COPs 

are modeled as constant: independent of part loading, indoor dry-bulb temperature and humidity ratio, 

outdoor dry-bulb temperature and humidity ratio, and other conditions. 

1.3.2 Calibrated Energy Savings Retrofit Test Cases 

This section describes revisions to Case L200EX-C required to model the calibrated energy savings 

retrofit test cases. 

In these test cases, the modeling physics of the retrofit technology as applied to the calibrated base-case 

model are precisely known. Use the calibrated inputs developed for each Case L200EX-C base-case 

scenario as the basis for the retrofit cases. There are seven base-case scenarios for each climate (14 total 

for heating and cooling) with six energy-savings cases in the heating climate and seven energy-savings 

cases in the cooling climate within each scenario. This results in a total of (7 × 7) + (7 × 8) = 105 total 

calibrated energy-savings case results sets, including the base case results sets. These are labeled as 

LnnnEX-C1H through LnnnEX-C7H for cases with space heating, and LnnnEX-C1C through LnnnEXC7C for cases with space cooling. 

For convenience, except where noted, figures and tables used for the building physics (EX-P suffixed) 

retrofit cases of Section 1.2.2 are applied for developing the calibrated retrofit cases. Nominal inputs

included (in non-bold font) in Section 1.2.2 tables called out in Section 1.3.2 are for reference only. Do 

not apply the nominal (non-bold font) values given in those tables if they were varied as part of the 

calibration process for Case L200EX-C. Changes to the calibrated base-case model to be applied as 

explicit inputs, or as explicit changes to calibrated inputs, in the calibrated energy savings (“-C”) 

retrofit cases are highlighted with bold font in the tables. 

Where applicable, summary figures and tables are listed first; supplementary tables are listed afterward. 

The retrofits are done as relative changes to the calibrated base-case inputs, except for low-e windows 

(Case L250EX-C) and cool roof (Case L265EX-C). For example, if in Case L200EX-C calibration 

yielded a pre-retrofit “air-air composite” ceiling/attic/roof R-value = 9 (versus nominal R-13.7), apply the 

blown cellulose retrofit explicitly as indicated to the calibrated (R-9) ceiling/attic/roof model. In this case, 

resulting composite R-values given in the material description table for the building physics retrofit case 

(L220EX-P) do not apply for the calibrated energy savings retrofit case (L220EX-C). 
59 

1.3.2.1 Case L210EX-C: Air-Seal Retrofit 

Case L210EX-C is exactly as Case L200EX-C, except apply a decrease to the effective leakage area at 4 

Pa (ELA4) of 100 in.2

 to the calibrated base-case input files for the base-case scenarios (L200EX-C1 

through L200EX-C7); i.e., for each scenario (“-Cn”): 

ELA4L210EX-Cn = ELA4L200EX-Cn − 100 (in.2

) 

Where: 

ELA4L210EX-Cn = resulting effective leakage area for Case L210EX-Cn 

ELA4L200EX-Cn = calibrated base-case effective leakage area for Case L200EX-Cn, where 

this value may vary for each base-case scenario “n”, if infiltration was 

adjusted as part of the calibration. 

Equivalent decreases to other relevant equivalent inputs that may be used by various programs are 

given in Table 1-26. 

This retrofit will yield results labeled L210EX-C1H through L210EX-C7H and L210EX-C1C through 

L210EX-C7C, corresponding to each calibrated base-case scenario. 

Table 1-26. Conditioned Zone Equivalent Input Decrease for Infiltration Models – Case L210EX-C 

Input (Note 1) Value Decrease

CFM at 50 Pa (Colorado Springs) (Note 2) 2038

CFM at 50 Pa (Las Vegas) (Note 2) 1892

ACH at 50 Pa (Colorado Springs) (Note 2) 9.93

ACH at 50 Pa (Las Vegas) (Note 2) 9.22

Equivalent Leakage Area at 50 Pa, in2 (Note 3) 146.1

Effective Leakage Area at 4 Pa, in2

 (Note 3) 100.0

UAinfl

Equivalent Constant Seasonal Decrease: ACH, CFM, UAinfl ACH CFM Btu/(h·F)

Colorado Springs (Note 5)

 Programs with auto-altitude adjustment (Note 4) 0.389 79.8 68.5

 Programs with site fixed at sea level (Notes 4, 6) 0.309 63.4

Las Vegas

 Programs with auto-altitude adjustment (Note 4) 0.251 51.4 51.2

 Programs with site fixed at sea level (Notes 4, 6) 0.231 47.4

Note 1: Decrease the calibrated base-case value(s) appropriate for your program by the amount shown.

Note 2: Volumetric flow rates are different for each climate.

Note 3: Used for ASHRAE Residential Air Leakage model (2005 ASHRAE Handbook of Fundamentals, pp. 27.12 – 27.13, 27.21); model is based on 

 Sherman-Grimsrud (1980), assuming highly sheltered building (Shelter Class 5) in rural terrain. See Appendix D for supporting details. 

Note 4: This input is for programs that do not use more detailed methods. Given value decreases are based on 

 application of ASHRAE Residential Air-Leakage model in EnergyPlus for appropriate space conditioning season based on 

 given input decrease of effective leakage area at 4Pa, using stack coefficient and wind coefficient given previously (see Table 1-8a).

Note 5: Infiltration UA = (infiltration mass flow) x (specific heat). Assumes air properties: specific heat = 0.240 Btu/(lb·F); density = 0.075 lb/ft3

 at 

 sea level, adjusted for altitude per HERS BESTEST Appendix B. 

Note 6: HERS BESTEST Appendix B describes the algorithm used for adjusting infiltration rates if the software 

 being tested does not account for variation of air density with altitude (i.e., site fixed at sea level).

B-EX-Spec, t:a193..f224 16-Apr-10
60 

1.3.2.2 Case L220EX-C: Attic Insulation Retrofit 

Case L220EX-C is exactly as Case L200EX-C, except apply the blown cellulose prescribed for Case 

L220EX-P (see Tables 1-16a and 1-16b, Section 1.2.2.2) to the calibrated base-case input files for each of 

the base-case scenarios. Apply only the material properties for ‘blown cellulose’ and for the ‘Joists 2×6 

24” O.C.’ using 5.5 in. thickness; do NOT change any other inputs to match those indicated in Tables 1-

16a, 1-16b, or 1-15, that may have been varied during the base-case calibrations. This will yield results 

labeled L220EX-C1H through L220EX-C7H and L220EX-C1C through L220EX-C7C, corresponding to 

each calibrated base-case scenario. 

This retrofit is a relative change to the base case; for example (hypothetically) if in Case L200EX-C, 

calibration yielded a pre-retrofit “air-air composite” ceiling/attic/roof R-value = 11 (versus nominal R13.7), apply the blown cellulose explicitly as indicated (2.0 in. over fiberglass batt and an additional 6.0 

in. over both insulated and framed sections) to the calibrated (hypothetical R-11) model. Model the full 

5.5 in. joist thickness in this retrofit. Depending on how the model was calibrated, total cumulative 

material thicknesses for the framed and insulated sections may be different. This also implies that the 

composite R-values for the building physics retrofit case given for the ceiling in Table 1-16a and for the 

ceiling/attic/roof assemblies in Tables 1-16b and 1-15 do not apply. 

1.3.2.3 Case L225EX-C: Wall Insulation Retrofit 

Case L225EX-C is exactly as Case L200EX-C, except replace the R-1.01 air gap of Table 1-4 with R-13 

(optimally installed) blown cellulose (see Figure 1-10). Apply only the material properties for “blown 

cellulose” given in Table 1-18 (see Case L225EX-P, Section 1.2.2.3) to the calibrated base-case input 

files for each base-case scenario (L200EX-C1 through L200EX-C7). Do NOT change any other inputs to 

match those indicated in Table 1-18 or Table 1-4 that may have been varied during the base-case 

calibrations. This will yield results labeled L225EX-C1H through L225EX-C7H and L225EX-C1C 

through L225EX-C7C, corresponding to each calibrated base-case scenario. 

1.3.2.4 Case L240EX-C: Programmable Thermostat Retrofit 

Case L240EX-C is exactly as Case L200EX-C, except for changes described in Sections 1.3.2.4.1 and 

1.3.2.4.2. Apply the changes to the calibrated base-case input files for each base-case scenario. This will 

yield results labeled L240EX-C1H through L240EX-C7H and L240EX-C1C through L240EX-C7C, 

corresponding to each calibrated base-case scenario. 

1.3.2.4.1 Colorad.TM2 

For Colorad.TM2 weather data (heating only) thermostat setback is applied on all nights during the 

heating season from 10:00 p.m. to 6:00 a.m. as shown below. 

 During heating season: 

 10:00 p.m.–6:00 a.m.: HEAT = ON IF TEMP < Thtg − 6°F; COOL = OFF 

 6:00 a.m.–10:00 p.m.: HEAT = ON IF TEMP < Thtg; COOL = OFF 

 During non-heating season: 

 HEAT = OFF; COOL = OFF. 

Where: 

• “TEMP” refers to conditioned zone-air temperature. 

• Thtg is as determined during the calibration phase of Case L200EX-C (see Section 1.3.1.2). 

• The heating season start/stop dates are as determined during the calibration phase of Case 

L200EX-C (see Section 1.3.1.2). 

 
61 

1.3.2.4.2 Lasvega.TM2 

For Lasvega.TM2 weather data (cooling only) thermostat setup is applied on all days from 8:00 a.m. to 

5:00 p.m. as shown below. 

 During cooling season: 

 8:00 a.m.–5:00 p.m.: COOL = ON IF TEMP > Tclg + 6°F; HEAT = OFF 

 5:00 p.m.–8:00 a.m.: COOL = ON IF TEMP > Tclg; HEAT = OFF 

 During non-cooling season: 

 COOL = OFF; HEAT = OFF. 

Where: 

• “TEMP” refers to conditioned zone-air temperature. 

• Tclg is as determined during the calibration phase of Case L200EX-C (see Section 1.3.1.2). 

• The cooling season start/stop dates are as determined during the calibration phase of Case 

L200EX-C (see Section 1.3.1.2). 

1.3.2.5 Case L250EX-C: Low-Emissivity Window Retrofit 

Case L250EX-C is exactly as Case L200EX-C, except that all single-pane windows are replaced with 

double-pane low-emissivity (low-e) windows with wood frames and insulated spacers, as specified for 

Case L250EX-P (see Section 1.2.2.5). This will yield results labeled L250EX-C1H through L250EX-C7H 

and L250EX-C1C through L250EX-C7C, corresponding to each calibrated base-case scenario. 

As there are no approximate input ranges for the base-case single-pane window, the same single-pane 

window inputs are applied in the reference simulations for Case L200EX-C as were applied in Case 

L200EX-P. This test case may then be thought of as a “very absolute” retrofit, where retrofit of the singlepane window system with the low-e window system is applied exactly as in Case L250EX-P, except that 

other conditions (thermostat settings, thermal conduction through other envelope surfaces, equipment 

efficiency, etc.) may vary in the Case L200EX-C calibration. 

1.3.2.6 Case L265EX-C: Low Solar Absorptance Roof (Cool Roof) 

Case L265EX-C is exactly as Case L200EX-C, except that exterior shortwave (visible and UV) 

absorptance (αext) is 0.2 for the roof only. This case is to be done by applying only space-cooling-only 

thermostat settings (see Section 1.3.1.3.4.2) using the Lasvega.TM2 weather data. This will yield results 

labeled L265EX-C1C through L265EX-C7C, corresponding to each calibrated base-case scenario. 

This test case may be thought of as an “absolute” retrofit, where energy savings for the fixed value 

(αext = 0.2) cool roof retrofit are calculated based on the calibrated opaque surface solar absorptance 

selected from 0.5 ≤ αext ≤ 0.8 during the calibration phase of Case L200EX-C (see Section 1.3.1.3.3). 

1.3.2.7 Case L300EX-C: Combined Retrofits 

Apply the changes specified for Case L300EX-C (see Sections 1.3.2.7.1 and 1.3.2.7.2) to the calibrated 

base-case input files for each base-case scenario. This will yield results labeled L300EX-C1H through 

L300EX-C7H and L300EX-C1C through L300EX-C7C, corresponding to each calibrated base-case 

scenario. 

Case L300EX-C is exactly as Case L200EX-C, except for the following changes. 

 
62 

1.3.2.7.1 Case L300EX-CH 

For the heating climate (Colorad.TM2 weather) include the: 

• Air-seal retrofit as described in Section 1.3.2.1 

• Attic insulation retrofit as described in Section 1.3.2.2 

• Wall insulation retrofit as described in Section 1.3.2.3 

• Programmable thermostat retrofit as described in Section 1.3.2.4 

• Low-e window retrofit as described in Section 1.3.2.5. 

1.3.2.7.2 Case L300EX-CC 

For the cooling climate (Lasvega.TM2 weather) include: 

• All the retrofits listed in Section 1.3.2.7.1 

• The low solar-absorptance roof retrofit as described in Section 1.3.2.6. 
63 

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67 

Appendix A Weather Data 

A.1 Weather Data Summary 

Site and weather characteristics corresponding to Colorad.TM2 and Lasvega.TM2 weather data are 

summarized in Tables A-1 and A-2, respectively. Details about TMY2 (.TM2) weather data file format 

are included in Section A.2. 

Table A-1. Site and Weather Data Summary for Colorad.TM2 Weather, Colorado Springs, Colorado 

(Note 1)

Weather Type Cold Clear Winters 

Weather Format Typical Meteorological Year 2 (TM2) 

Latitude 38.8° North 

Longitude 104.7° West 

Altitude 1881 m = 6171 ft 

Time Zone −7 

Site ASHRAE Terrain Class 2 (suburban/urban) 

(Notes 2, 3) 

Mean Annual Wind Speed 4.36 m/s = 9.75 mph 

Mean Annual Ambient Dry-Bulb Temperature 9.0°C = 48.2°F (Note 4) 

Mean Annual Daily Temperature Range 13.2°C = 23.8°F (Note 5) 

Minimum Annual Dry-Bulb Temperature −21.1°C = −6.0°F 

Maximum Annual Dry-Bulb Temperature 34.4°C = 93.9°F 

Maximum Annual Wind Speed 17.5 m/s = 39.1 mph 

Heating Degree Days (Base 18°C = 64.4°F) 3568°C·days = 6422°F·days 

Cooling Degree Days (Base 18°C = 64.4°F ) 272°C·days = 490°F·days 

Mean Annual Dew Point Temperature −2.3°C = 27.9°F 

Mean Annual Relative Humidity 50.8% 

Global Horizontal Solar Radiation Annual Total 547.3 kBtu/(ft2·yr) (Note 4) 

Direct Normal Solar Radiation Annual Total 670.1 kBtu/(ft2·yr) (Note 4) 

Diffuse Horizontal Solar Radiation Annual Total 172.7 kBtu/(ft2·yr) (Note 4) 

Note 1: Unless otherwise noted, values are from EnergyPlus weather pre-processor statistics report. 

Note 2: See ASHRAE 2005, p. 16.3. This assumption was applied for developing equivalent constant seasonal 

exterior surface coefficient inputs; see Appendix C, Section C.3. 

Note 3: Infiltration modeling is based on Sherman-Grimsrud (1980), assuming a highly sheltered building (Shelter 

Class 5) in rural terrain; see Appendix D. 

Note 4: Calculated value based on EnergyPlus weather pre-processor statistics report. 

Note 5: Calculated value based on DOE-2.1E weather pre-processor statistics report. 
68 

Table A-2. Site and Weather Data Summary for Lasvega.TM2 Weather, Las Vegas, Nevada (Note 1) 

Weather Type Hot Dry Summers 

Weather Format Typical Meteorological Year 2 (TM2) 

Latitude 36.1° North 

Longitude 115.2° West 

Altitude 664 m = 2178 ft 

Time Zone −8 

Site ASHRAE Terrain Class 2 (suburban/urban) 

(Notes 2, 3) 

Mean Annual Wind Speed 4.06 m/s = 9.08 mph 

Mean Annual Ambient Dry-Bulb Temperature 19.5°C = 67.1°F (Note 4) 

Mean Annual Daily Temperature Range 13.0°C = 23.4°F (Note 5) 

Minimum Annual Dry-Bulb Temperature −4.4°C = 24.1°F 

Maximum Annual Dry-Bulb Temperature 44.4°C = 111.9°F 

Maximum Annual Wind Speed 20.6 m/s = 46.1 mph 

Heating Degree Days (Base 18°C = 64.4°F) 1248°C·days = 2246°F·days 

Cooling Degree Days (Base 18°C = 64.4°F ) 1806°C·days = 3251°F·days 

Mean Annual Dew Point Temperature −1.2°C = 29.8°F 

Mean Annual Relative Humidity 29.4% 

Global Horizontal Solar Radiation Annual Total 658.7 kBtu/(ft2·yr) (Note 4) 

Direct Normal Solar Radiation Annual Total 826.3 kBtu/(ft2·yr) (Note 4) 

Diffuse Horizontal Solar Radiation Annual Total 174.4 kBtu/(ft2·yr) (Note 4) 

Note 1: Unless otherwise noted, values are from EnergyPlus weather pre-processor statistics report. 

Note 2: See ASHRAE 2005, p. 16.3. This assumption was applied for developing equivalent constant seasonal 

exterior surface coefficient inputs; see Appendix C, Section C.3. 

Note 3: Infiltration modeling is based on Sherman-Grimsrud (1980), assuming a highly sheltered building (Shelter 

Class 5) in rural terrain; see Appendix D. 

Note 4: Calculated value based on EnergyPlus weather pre-processor statistics report. 

Note 5: Calculated value based on DOE-2.1E weather pre-processor statistics report. 
69 

A.2 TMY2 Weather Data Format Description 

The following TMY2 format description is extracted from Section 3 of the TMY2 user manual (Marion 

and Urban 1995) with minor edits. 

For each station, a TMY2 file contains 1 year of hourly solar radiation, illuminance, and meteorological 

data. The files consist of data for the typical calendar months during 1961–1990 that are concatenated to 

form the typical meteorological year for each station. 

Each hourly record in the file contains values for solar radiation, illuminance, and meteorological 

elements. A two-character source and uncertainty flag is attached to each data value to indicate whether 

the data value was measured, modeled, or missing, and to provide an estimate of the uncertainty of the 

data value. 

Users should be aware that the format of the TMY2 data files is different from the format used for the 

NSRDB and the original TMY data files. 

File Convention 

File naming convention uses the Weather Bureau Army Navy (WBAN) number as the file prefix, with the 

characters TM2 as the file extension. For example, 13876.TM2 is the TMY2 file name for Birmingham, 

Alabama. The TMY2 files contain computer readable ASCII characters and have a file size of 1.26 MB. 

File Header 

The first record of each file is the file header that describes the station. The file header contains the 

WBAN number, city, state, time zone, latitude, longitude, and elevation. The field positions and 

definitions of these header elements are given in Table A-3, along with sample FORTRAN and C formats 

for reading the header. A sample of a file header and data for January 1 is shown in Figure A-1. 

Hourly Records 

Following the file header, 8,760 hourly data records provide 1 year of solar radiation, illuminance, and 

meteorological data, along with their source and uncertainty flags. Table A-4 provides field positions, 

element definitions, and sample FORTRAN and C formats for reading the hourly records. 

Each hourly record begins with the year (field positions 2-3) from which the typical month was chosen, 

followed by the month, day, and hour information in field positions 4-9. The times are in local standard 

time (previous TMYs based on SOLMET/ERSATZ data are in solar time).
70 

 14944 SIOUX_FALLS SD -6 N 43 34 W 96 44 435  85010101000000000000?00000?00000?00000?00000?00000?00000?010A710A7-150A7-211A7060A70975A7360A7052A70161A700945A70999099 85010102000000000000?00000?00000?00000?00000?00000?00000?010A710A7-144A7-206A7060A70975A7350A7077A70161A700914A70999099 85010103000000000000?00000?00000?00000?00000?00000?00000?010A710A7-144A7-200A7063A70975A7340A7062A70161A700732A70999099 85010104000000000000?00000?00000?00000?00000?00000?00000?010A710A7-150A7-206A7063A70976A7330A7072A70161A700640A70999099 85010105000000000000?00000?00000?00000?00000?00000?00000?010A710A7-156A7-217A7060A70976A7330A7067A70161A700640A70999099 85010106000000000000?00000?00000?00000?00000?00000?00000?010A710A7-167A7-222A7062A70976A7340A7067A70161A700640A70999099 85010107000000000000?00000?00000?00000?00000?00000?00000?004A704A7-183A7-233A7065A70977A7300A7052A70193A777777A70999999 85010108000000000000?00000?00000?00000?00000?00000?00000?002A702A7-194A7-244A7065A70978A7310A7036A70193A777777A70999999 85010109010212970037G50173G40024G50038I50071I40033I50043I604A700A7-200A7-256A7062A70978A7330A7046A70193A777777A70999999 85010110028714150157G50560G40043G50159I50444I40069I50079I600A700A7-189A7-256A7056A70979A7310A7067A70193A777777A70999999 85010111043614150276G40714G40056G50286I40642I40088I50111I500A700A7-172A7-250A7051A70979A7310A7062A70161A777777A70999999 85010112053014150357G40782G40064G50374I40735I40098I50131I500A700A7-167A7-244A7051A70978A7300A7062A70161A777777A70999999 85010113056214150387G40806G40067G50407I40767I40101I50139I500A700A7-156A7-244A7047A70978A7320A7067A70193A777777A70999999 85010114053014150359G40788G40064G50377I40742I40098I50131I500A700A7-144A7-239A7045A70978A7310A7062A70193A777777A70999999 85010115043614150277G40716G40056G50289I40645I40088I50111I500A700A7-139A7-239A7043A70978A7330A7052A70193A777777A70999999 85010116028614150157G50564G40043G50162I50450I40069I50080I600A700A7-139A7-233A7045A70978A7300A7052A70161A777777A70999999 85010117010412730038G50209G40021G50038I50104I40030I50038I600A700A7-150A7-233A7049A70978A7290A7041A70241A777777A70999999 85010118000000000000?00000?00000?00000?00000?00000?00000?000A700A7-167A7-233A7057A70978A7000A7000A70241A777777A70999999 85010119000000000000?00000?00000?00000?00000?00000?00000?000A700A7-172A7-233A7059A70978A7000A7000A70241A777777A70999999 85010120000000000000?00000?00000?00000?00000?00000?00000?000A700A7-178A7-233A7062A70978A7000A7000A70241A777777A70999999 85010121000000000000?00000?00000?00000?00000?00000?00000?000A700A7-183A7-239A7062A70978A7260A7015A70241A777777A70999999 85010122000000000000?00000?00000?00000?00000?00000?00000?000A700A7-183A7-239A7062A70977A7220A7021A70241A777777A70999999 85010123000000000000?00000?00000?00000?00000?00000?00000?000A700A7-178A7-239A7059A70977A7220A7015A70241A777777A70999999 85010124000000000000?00000?00000?00000?00000?00000?00000?000A700A7-178A7-239A7059A70977A7240A7010A70241A777777A70999999 1 1 1  1 2 3 4 5 6 7 8 9 0 1 2 123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890

(for field position identification only)

Figure A-1. Sample file header and data in the TMY2 format for January 1 
71 

Table A-3. Header Elements in the TMY2 Format 

(For First Record of Each File) 

Field Position Element Definition 

002 - 006 WBAN Number Station’s WBAN number (see Table 2-1 of Marion and Urban [1995]) 

008 - 029 City City where the station is located (maximum of 22 characters) 

031 - 032 State State where the station is located (abbreviated to two letters) 

034 - 036 Time Zone 

Time zone is the number of hours by which the local standard time is 

ahead of or behind Universal Time. For example, Mountain Standard Time 

is designated -7 because it is 7 hours behind Universal Time. 

038 - 044

038 

040 - 041 

043 - 044 

Latitude 

Latitude of the station 

N = North of equator 

Degrees 

Minutes 

046 - 053

046 

048 - 050 

052 - 053 

Longitude 

Longitude of the station 

W = West, E = East 

Degrees 

Minutes 

056 - 059 Elevation Elevation of station in meters above sea level 

FORTRAN Sample Format: 

( 1X,A5,1X,A22,1X,A2,1X,I3,1X,A1,1X,I2,1X,I2,1X,A1,1X,I3,1X,I2,2X,I4 ) 

C Sample Format: 

( %s %s %s %d %s %d %d %s %d %d %d )

Table A-4. Data Elements in the TMY2 Format 

(For All Except the First Record) 

Field Position Element Values Definition 

002 - 009

002 - 003 

004 - 005 

006 - 007 

008 - 009 

Local Standard Time 

Year 

Month 

Day 

Hour 

61 - 90 

1 - 12 

1 - 31 

1 - 24 

Year, 1961-1990 

Month 

Day of month 

Hour of day in local standard time 

010 - 013 Extraterrestrial Horizontal 

Radiation 

0 - 1415 Amount of solar radiation in Wh/m2 received 

on a horizontal surface at the top of the 

atmosphere during the 60 minutes preceding 

the hour indicated 

014 - 017 Extraterrestrial Direct Normal 

Radiation 

0 - 1415 Amount of solar radiation in Wh/m2 received 

on a surface normal to the sun at the top of the 

atmosphere during the 60 minutes preceding 

the hour indicated 

018 - 023

018 - 021 

022 

023 

Global Horizontal Radiation 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 1200 

A - H, ? 

0 - 9 

Total amount of direct and diffuse solar 

radiation in Wh/m2 received on a horizontal 

surface during the 60 minutes preceding the 

hour indicated 

024 - 029

024 - 027 

028 

029 

Direct Normal Radiation 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 1100 

A - H, ? 

0 - 9 

Amount of solar radiation in Wh/m2 received 

within a 5.7° field of view centered on the sun, 

during the 60 minutes preceding the hour 

indicated 
72 

Table A-4. Data Elements in the TMY2 Format (Continued) 

Field Position Element Values Definition 

030 - 035

030 - 033 

034 

035 

Diffuse Horizontal Radiation 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 700 

A - H, ? 

0 - 9 

Amount of solar radiation in Wh/m2

received from the sky (excluding the 

solar disk) on a horizontal surface 

during the 60 minutes preceding the 

hour indicated 

036 - 041

036 - 039 

040 

041 

Global Horiz. Illuminance 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 1,300 

I, ? 

0 - 9 

Average total amount of direct and 

diffuse illuminance in hundreds of lux 

received on a horizontal surface 

during the 60 minutes preceding the 

hour indicated. 

0 to 1,300 = 0 to 130,000 lux 

042 - 047

042 - 045 

046 

047 

Direct Normal Illuminance 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 1,100 

I, ? 

0 - 9 

Average amount of direct normal 

illuminance in hundreds of lux 

received within a 5.7 degree field of 

view centered on the sun during the 

60 minutes preceding the hour 

indicated. 

0 to 1,100 = 0 to 110,000 lux 

048 - 053

048 - 051 

052 

053 

Diffuse Horiz. Illuminance 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 800 

I, ? 

0 - 9 

Average amount of illuminance in 

hundreds of lux received from the sky 

(excluding the solar disk) on a 

horizontal surface during the 60 

minutes preceding the hour indicated. 

0 to 800 = 0 to 80,000 lux 

054 - 059

054 - 057 

058 

059 

Zenith Luminance 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 7,000 

I, ? 

0 - 9 

Average amount of luminance at the 

sky’s zenith in tens of Cd/m2 during 

the 60 minutes preceding the hour 

indicated. 

0 to 7,000 = 0 to 70,000 Cd/m2

060 - 063

060 - 061 

062 

063 

Total Sky Cover 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 10 

A - F, ? 

0 - 9 

Amount of sky dome in tenths covered 

by clouds or obscuring phenomena at 

the hour indicated 

064 - 067

064 - 065 

066 

067 

Opaque Sky Cover 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 10 

A - F 

0 - 9 

Amount of sky dome in tenths covered 

by clouds or obscuring phenomena 

that prevent observing the sky or 

higher cloud layers at the hour 

indicated 

068 - 073 

068 - 071 

072 

073 

Dry-Bulb Temperature 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

-500 to 500 

A - F 

0 - 9 

Dry-bulb temperature in tenths of °C 

at the hour indicated. 

-500 to 500 = -50.0 to 50.0 °C 

074 - 079 

074 - 077 

078 

079 

Dew Point Temperature 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

-600 to 300 

A - F 

0 - 9 

Dew point temperature in tenths of °C 

at the hour indicated. 

-600 to 300 = -60.0 to 30.0 °C 

080 - 084

080 - 082 

083 

084 

Relative Humidity 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 100 

A - F 

0 - 9 

Relative humidity in percent at the 

hour indicated 
73 

Table A-4. Data Elements in the TMY2 Format (Continued) 

Field Position Element Values Definition 

085 - 090 

085 - 088 

089 

090 

Atmospheric Pressure 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

700 - 1100 

A - F 

0 - 9 

Atmospheric pressure at station in millibars at 

the hour indicated 

091 - 095 

091 - 093 

094 

095 

Wind Direction 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 360 

A - F 

0 - 9 

Wind direction in degrees at the hour 

indicated. (N = 0 or 360, E = 90, S = 180, W = 

270). For calm winds, wind direction equals 

zero. 

096 - 100 

096 - 98 

99 

100 

Wind Speed 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 400 

A - F 

0 - 9 

Wind speed in tenths of meters per second at 

the hour indicated. 

0 to 400 = 0 to 40.0 m/s 

101 - 106 

101 - 104 

105 

106 

Visibility 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 1609 

A - F, ? 

0 - 9 

Horizontal visibility in tenths of kilometers at 

the hour indicated. 

7777 = unlimited visibility 

0 to 1609 = 0.0 to 160.9 km 

9999 = missing data 

107 - 113 

107 - 111 

112 

113 

Ceiling Height 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 30450 

A - F, ? 

0 - 9 

Ceiling height in meters at the hour indicated. 

77777 = unlimited ceiling height 

88888 = cirroform 

99999 = missing data 

114 - 123 Present Weather See 

Appendix B of 

Marion and 

Urban (1995) 

Present weather conditions denoted by a 10-

digit number. See Appendix B of Marion and 

Urban (1995) for key to present weather 

elements. 

124 - 128 

124 - 126 

127 

128 

Precipitable Water 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 100 

A - F 

0 - 9 

Precipitable water in millimeters at the hour 

indicated 

129 - 133 

129 - 131 

132 

133 

Aerosol Optical Depth 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 240 

A - F 

0 - 9 

Broadband aerosol optical depth (broad-band 

turbidity) in thousandths on the day indicated. 

0 to 240 = 0.0 to 0.240 

134 - 138 

134 - 136 

137 

138 

Snow Depth 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 150 

A - F, ? 

0 - 9 

Snow depth in centimeters on the day 

indicated. 

999 = missing data 

139 - 142 

139 - 140 

141 

142 

Days Since Last Snowfall 

Data Value 

Flag for Data Source 

Flag for Data Uncertainty 

0 - 88 

A - F, ? 

0 - 9 

Number of days since last snowfall 

88 = 88 or greater days 

99 = missing data 

FORTRAN Sample Format: 

(1X,4I2,2I4,7(I4,A1,I1),2(I2,A1,I1),2(I4,A1,I1),1(I3,A1,I1), 

 1(I4,A1,I1),2(I3,A1,I1),1(I4,A1,I1),1(I5,A1,I1),10I1,3(I3,A1,I1), 

 1(I2,A1,I1)) 

C Sample Format: 

(%2d%2d%2d%2d%4d%4d%4d%1s%1d%4d%1s%1d%4d%1s%1d%4d%1s%1d%4d%1s%1d%4d%1s 

 %1d%4d%1s%1d%2d%1s%1d%2d%1s%1d%4d%1s%1d%4d%1s%1d%3d%1s%1d%4d%1s%1d%3d 

 %1s%1d%3d%1s%1d%4d%1s%1d%5ld%1s%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%1d%3d%1s 

 %1d%3d%1s%1d%3d%1s%1d%2d%1s%1d)

Note: For ceiling height data, integer variable should accept data values as large as 99999.
74 

For solar radiation and illuminance elements, the data values represent the energy received during the 60 

minutes preceding the hour indicated. For meteorological elements (with a few exceptions), observations 

or measurements were made at the hour indicated. A few of the meteorological elements had 

observations, measurements, or estimates made at daily, instead of hourly, intervals. Consequently, the 

data values for broadband aerosol optical depth, snow depth, and days since last snowfall represent the 

values available for the day indicated. 

Missing Data 

Data for some stations, times, and elements are missing. The causes for missing data include such things 

as equipment problems, some stations not operating at night, and a National Oceanic and Atmospheric 

Administration (NOAA) cost-saving effort from 1965 to 1981 that digitized data for only every third 

hour. 

Although both the National Solar Radiation Database (NSRDB) and the TMY2 data sets used methods to 

fill data where possible, some elements, because of their discontinuous nature, did not lend themselves to 

interpolation or other data-filling methods. Consequently, data in the TMY2 data files may be missing for 

horizontal visibility, ceiling height, and present weather for up to 2 consecutive hours for Class A stations 

and for up to 47 hours for Class B stations. For Colorado Springs, Colorado, snow depth and days since 

last snowfall may also be missing. No data are missing for more than 47 hours, except for snow depth and 

days since last snowfall for Colorado Springs, Colorado. As indicated in Table A-4, missing data values 

are represented by 9’s and the appropriate source and uncertainty flags. 

Source and Uncertainty Flags 

With the exception of extraterrestrial horizontal and extraterrestrial direct radiation, the two field 

positions immediately following the data value provide source and uncertainty flags both to indicate 

whether the data were measured, modeled, or missing, and to provide an estimate of the uncertainty of the 

data. Source and uncertainty flags for extraterrestrial horizontal and extraterrestrial direct radiation are not 

provided because these elements were calculated using equations considered to give exact values. 

For the most part, the source and uncertainty flags in the TMY2 data files are the same as the ones in 

NSRDB, from which the TMY2 files were derived. However, differences do exist for data that were 

missing in the NSRDB, but then filled while developing the TMY2 data sets. Uncertainty values apply to 

the data with respect to when the data were measured, and not as to how “typical” a particular hour is for 

a future month and day. More information on data filling and the assignment of source and uncertainty 

flags is found in Appendix A of Marion and Urban (1995). 

Tables A-5 through A-8 define the source and uncertainty flags for the solar radiation, illuminance, and 

meteorological elements. 
75 

Table A-5. Solar Radiation and Illuminance Source Flags 

Flag Definition 

A Post-1976 measured solar radiation data as received from NCDC 

or other sources 

B Same as “A” except the global horizontal data underwent a 

calibration correction 

C Pre-1976 measured global horizontal data (direct and diffuse were 

not measured before 1976), adjusted from solar to local time, 

usually with a calibration correction 

D Data derived from the other two elements of solar radiation using 

the relationship, global = diffuse + direct × cosine (zenith) 

E Modeled solar radiation data using inputs of observed sky cover 

(cloud amount) and aerosol optical depths derived from direct 

normal data collected at the same location 

F Modeled solar radiation data using interpolated sky cover and 

aerosol optical depths derived from direct normal data collected at 

the same location 

G Modeled solar radiation data using observed sky cover and aerosol 

optical depths estimated from geographical relationships 

H Modeled solar radiation data using interpolated sky cover and 

estimated aerosol optical depths 

I Modeled illuminance or luminance data derived from measured or 

modeled solar radiation data 

? Source does not fit any of the above categories. Used for nighttime 

values, calculated extraterrestrial values, and missing data 

Table A-6. Solar Radiation and Illuminance Uncertainty Flags 

Flag Uncertainty Range (%) 

1 Not used 

2 2 - 4 

3 4 - 6 

4 6 - 9 

5 9 - 13 

6 13 - 18 

7 18 - 25 

8 25 - 35 

9 35 - 50 

0 Not applicable 
76 

Table A-7. Meteorological Source Flags 

Flag Definition 

A Data as received from NCDC, converted to SI units 

B Linearly interpolated 

C Non-linearly interpolated to fill data gaps from 6 to 47 hours in 

length 

D Not used 

E Modeled or estimated, except: precipitable water, calculated 

from radiosonde data; dew point temperature calculated from 

dry-bulb temperature and relative humidity; and relative 

humidity calculated from dry-bulb temperature and dew point 

temperature 

F Precipitable water, calculated from surface vapor pressure; 

aerosol optical depth, estimated from geographic correlation 

? Source does not fit any of the above. Used mostly for missing 

data 

Table A-8. Meteorological Uncertainty Flags 

Flag Definition 

1 - 6 Not used 

7 Uncertainty consistent with National Weather Service 

practices and the instrument or observation used to obtain the 

data 

8 Greater uncertainty than 7 because values were interpolated 

or estimated 

9 Greater uncertainty than 8 or unknown 

0 Not definable 
77 

Appendix B Selection of Internal Loads 

The internal loads described in the test specification result from equipment, lights, people, etc. Values and 

schedules are based on information available in the literature (DOE 1989, BA 2009). Specifically, the 

daily total internal loads were calculated from information in Appendix D of the report, Affordable 

Housing Through Energy Conservation (DOE 1989). Details of these calculations are described below. 

An adjustment was made to the approximate input range for the sensible internal gains from electricity 

based on consultation with the BESTEST-EX Working Group (2009). Normalized hourly profiles were 

adapted from the Building America Analysis Spreadsheet (BA 2009) for internal loads caused by 

occupants, electricity, and gas. A discussion of these profiles is included in this appendix. 

Although latent loads are developed and discussed in this appendix, they are not applied in the test 

specification (see Section 1.2.1.8.2). Future versions of BESTEST-EX may use the latent loads and 

profiles developed in this appendix. 

B.1 Calculation of Daily Internal Gains 

Table D.a in Appendix D of DOE (1989) was modified to calculate the daily internal gains for BESTESTEX. These results are referred to as “B-EX” internal loads. The following items are considered, and their 

contributions to the daily internal loads are shown in Table B-1: 

• One refrigerator 

• One electric range 

• One gas domestic hot water system 

• One electric dryer 

• One television 

• Miscellaneous (assumed to be electric) 

• Lighting 

• People.

Table B-1. Breakdown of B-EX Daily Internal Loads 

Source 

Daily Sensible 

Load (Btu/day) 

Daily Latent Load 

(Btu/day) 

New Refrigerator 10,517 0 

Range (electric) 7,479 3,739 

DHW (gas) 14,928 1,301 

Dryer (electric) 841 0 

Television 1,870 0 

Miscellaneous 2,804 0 

Lighting 12,957 0 

People 8,694 6,871 

 

Total 60,090 11,911 

The total B-EX internal sensible load of 60 kBtu/day is greater than the DOE (1989) value of 56 kBtu/day 

calculated for the average family home. This difference appears because specific systems were chosen in 

the B-EX analysis. Thus, the number of refrigerators, ranges, etc. per household is no longer fractional, as 

it was in the DOE calculation for the average family home. Decisions were made about the location of the 

equipment for BESTEST-EX: all equipment except for 10% of the lighting is located inside the 

conditioned zone. Key differences for each item affecting the sensible internal gains are listed below. 
78 

Freezer and Old Refrigerator 

Unlike the DOE (1989) report, no old refrigerator or freezer is modeled. This represents an approximate 

2.3 kBtu/day decrease when B-EX is compared to DOE (1989). 

Range 

Modeling one electric range for B-EX leads to a negligible difference when compared to DOE (1989). 

Water Heater 

DOE (1989) assumes sensible gains come from standby losses and the heating of incoming cold water. 

22.5 therms/yr/system is the assumed sensible load caused by standby losses from water heaters (50% of 

the gas units are assumed to be outside the conditioned space). The other portion of the sensible gains 

comes from the energy used to heat the incoming cold water. Most of this energy leaves the zone when 

water goes down the drain, but 9.5 therms/yr/system is assumed to be sensible gains in the conditioned 

space. This leads to 32 therms/yr/system. 

For one gas water heating system located in the conditioned space, the sensible gains caused by standby 

losses would be 45 therms/yr (twice that of DOE [1989]), for a total of 54.5 therms/yr. This corresponds 

to an approximate 6.1 kBtu/day increase when B-EX is compared to DOE (1989). 

Dryer 

One electric dryer is assumed in the conditioned space, which represents a 0.3 kBtu increase between BEX and DOE (1989) report. 

Television, Miscellaneous, Lighting, and People 

For these categories the values used in B-EX are identical to those in the DOE (1989) report. 

Summary 

The differences in sensible internal loads described above account for the 4 kBtu net increase in sensible 

internal gains when B-EX is compared to DOE (1989). 

B.2 Building America Internal Gains 

DOE (1989) was used because it offers a straightforward method to calculate the internal gains without 

requiring many more additional assumptions about the building. However, because internal gains may 

change with the introduction of new and improved technology, it was important to compare these results 

to a newer reference. The Building America Analysis Spreadsheet (BA 2009) was used to perform a 

rough check on the internal gains caused by occupants, electricity, and gas. Engineering judgment was 

used for the numerous additional inputs required by the spreadsheet. The effect of sensible tank standby 

losses was also added to the spreadsheet using the relationship 

tank Δ≅ TUAQ (Btu/h)

where a ΔT of 52°F was assumed based on a tank water temperature of 120°F and a zone temperature of 

68°F. Tables B-2 and B-3 show the results of the DOE calculation versus the results of the Building 

America (BA) calculation for sensible and latent internal gains, respectively. In general the BA analysis 

predicts higher internal sensible and latent loads than those calculated by DOE (1989), but the percent 

distribution between occupants, electricity, and gas show good agreement. 
79 

Table B-2. Comparison of Proposed Internal Sensible Loads With 

Building America Prototype House Results

 Occupants Electricity Gas Total 

BESTEST-EX 

(Btu/day) 8,694 36,468 14,928 60,090 

% of Total 14.5 60.7 24.8 

BA Analysis 

(Btu/day) 10,805 45,661 18,308 74,775 

% of Total 14.4 61.1 24.5 

Table B-3. Comparison of Proposed Internal Latent Loads With 

Building America Prototype House Results

 

Occupants 

Latent 

Electricity 

Latent 

Gas 

Latent Total 

BESTEST-EX 

(Btu/day) 6,871 3,739 1,301 11,911 

% of Total 57.7 31.4 10.9 

BA Analysis 

(Btu/day) 8,075 3,783 1,689 13,547 

% of Total 59.6 27.9 12.5 

B.3 Normalized Hourly Profiles 

The normalized hourly profiles for internal loads caused by occupants, electricity, and gas in the test 

specification are adapted from the BA Benchmark Analysis. For BESTEST-EX, the only non-HVAC 

equipment using gas is the DHW system. The hourly schedule for the sensible loads caused by gas is a 

load-weighted combination of the BA schedule “Combined DHW,” which accounts for hot water use, and 

an assumed uniform schedule for standby losses. Because latent internal gains from gas (DHW) are 

closely related to gas usage, the BA schedule “Combined DHW” is used for the gas latent internal gains. 

The hourly schedule for the sensible loads from electricity is a load-weighted combination of the BA 

schedules for “Lights” and “Equipment Sensible Load (no lights, water heater, or occupancy).” The 

hourly schedule for latent loads from electricity is the BA schedule “Equipment Latent Load (no lights, 

water heater, or occupancy).” The BA schedule “Occ” is used for sensible and latent loads caused by 

occupants. Finally, a few normalized hourly load fraction values were varied slightly in Table 1-9b to 

obtain a daily sum of 1.000 for each load type. These schedules are plotted in Figure B-1. Occupant loads 

are highest in the late evening/early morning hours; electric and gas loads peak near breakfast and dinner. 
80 

Figure B-1. Normalized hourly profiles for internal loads due to occupants, gas, and electricity 

B.4 Conversion Metered Gas and Electricity Use to Internal Gains 

Only a fraction of the metered gas and electricity use is converted to internal sensible gains. The 

percentage of energy converted depends largely on the performance, use, and location of the equipment 

(inside or outside the conditioned zone). For example, a house with a gas water heater in the garage could 

have a significantly lower percentage of non-HVAC gas energy converted to sensible internal gains than 

an identical house with the same water heater in the conditioned zone. Analysis of B-EX internal loads 

indicates that 74% of the metered non-HVAC electric energy and 20% of the metered non-HVAC gas 

energy is converted to sensible internal gains. A rough comparison using the BA Analysis Spreadsheet 

yields the same electric conversion factor of 74%. The BA conversion factor for gas is not readily 

available, because the BA Analysis Spreadsheet does not calculate the total DHW energy consumption. 

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0 4 8 12 16 20 24

Hour

Occupants (Sensible + Latent) Electricity (Sensible) Electricity (Latent) Gas (Sensible) Gas (Latent)

Hourly Fractions 
81 

Appendix C Combined Surface Heat Transfer Coefficients 

This appendix documents the development of equivalent constant combined interior and exterior surface 

coefficients for programs that do not automatically calculate surface heat transfer. Using combined 

coefficients is an idealized simplification of the convective and radiative heat transfer at the surfaces. 

Assumptions about convective and radiative components of the combined coefficients are provided. If the 

program being tested requires disaggregated (separate convective and radiative) surface coefficients, 

values provided in the tables included in this appendix may be used. Other disaggregated coefficients may 

also be used if there is a physically logical basis for selecting them. 

This appendix also documents modeling of surface heat transfer with EnergyPlus that supports 

development of the equivalent constant combined coefficients. For programs that use detailed inputs for 

automated calculation algorithms, Section C.3 includes relevant terrain assumptions that may be used for 

correcting wind speed given in the weather data. Appendix C and Appendix D (related to infiltration 

modeling) were developed based on initial simulations with EnergyPlus; EnergyPlus has different 

assumptions and definitions for parameters used for correcting wind speed for infiltration and exterior 

surface coefficient modeling. This resulted in different wind speed adjustments for modeling infiltration 

and exterior coefficients in the EnergyPlus reference model. 

C.1 Interior Surface Coefficients 

Table C1-1 gives combined convective and radiative interior surface heat transfer coefficients (hs), along 

with disaggregated convective (hc) and radiative (hi) coefficients. These coefficients are calculated by 

adding the constant equivalent convective portions (derived from EnergyPlus simulations, see Section 

C.1.1) with the calculated radiative portions (based on HERS BESTEST Appendix D, see Section C.1.2 

below). The BESTEST-EX coefficients are displayed under the heading “B-EX.” For historical reference, 

the original HERS BESTEST coefficients are also shown in italics under the heading “HERS.” Table C1-

1 indicates a substantial difference between interior surface coefficients of HERS BESTEST—which are 

based on ASHRAE coefficients used for developing design loads—versus the interior surface coefficients 

calculated for BESTEST-EX. Additional research is needed to understand these differences. 

A simplifying assumption for direct addition of convective and radiative surface coefficients to develop 

combined interior surface coefficients for BESTEST-EX is that for the radiative portion for a given 

surface, the mean radiant surface temperature of all other surfaces (for internal surfaces and the insidefacing portion of exterior surfaces) equals the zone air temperature. As the actual mean radiant surface 

temperature may be less than the zone air temperature in heating mode, and greater than the zone air 

temperature in cooling mode, this simplifying assumption may tend to overestimate radiative exchange. 

Additional research is needed to refine calculation of equivalent combined surface coefficients that 

integrate radiative exchange with convective heat transfer of more advanced algorithms. The current 

simplified calculation results in the following: 

• Resulting BESTEST-EX combined coefficients are 9%–24% lower than the ASHRAE combined 

coefficients 

• A more realistic algorithm for surface convection is applied 

• Reference simulation modeling is improved. 

EnergyPlus simulations were performed to assess the equivalence of the “B-EX” constant inputs. Because 

of the nature of the inside heat balance formulation in EnergyPlus, constant combined coefficients could 

not be implemented. Therefore, the constant convective terms were used in simulations that automatically 

calculate interior radiative exchange, and compared to the full “detailed” interior convection algorithm 

simulations. The constant convective coefficients led to annual ideal sensible heating (Colorado Springs) 

and cooling (Las Vegas) loads 4.1% and 4.8% less, respectively, versus the “detailed” interior convection 
82 

algorithm simulations (using Case L200EX nominal inputs, except with full-year heating/cooling 

seasons). 

Table C1-1. Disaggregated Interior Surface Film Coefficients 

(Btu/(h·ft2

·°F))

Vertical Surfaces (T = 68oF) (528oR) (ε = 0.9) B-EX HERS

hi 0.908 0.908 

hc 0.305 0.552 

hs = hi + hc 1.213 1.460 

Gables/Roof Surfaces (T = 68°F) (528°R) (ε = 0.9) (Note 1) 

hi 0.908 0.908 

hc 0.240 0.422 

hs = hi +hc 1.148 1.330 

Horizontal Surfaces (T = 68oF) (528oR) (ε = 0.9) 

hi 0.908 0.908 

hc 0.255 0.399 

hs = hi + hc 1.163 1.307 

Single-Pane Glass Surfaces (T = 68oF) (528oR) (ε = 0.84) 

hi 0.848 0.848 

hc 0.267 0.612 

hs = hi + hc 1.115 1.460 

Single-Pane Window Aluminum Frame Surfaces (T = 68oF) (528oR) (ε = 0.84) (Note 2)

hi 0.848 0.848 

hc 0.432 0.612 

hs = hi + hc 1.280 1.460 

Low-e Glass Surfaces (T = 68oF) (528oR) (ε = 0.84) 

hi 0.848 0.848 

hc 0.222 0.485 

hs = hi + hc 1.070 1.333 

Low-e Window Wood Frame Surfaces (T = 68oF) (528oR) (ε = 0.84) (Note 2)

hi 0.848 0.848 

hc 0.368 0.485 

hs = hi + hc 1.216 1.333 

Note 1: The values for HERS BESTEST sloped surface are shown here, though different coefficients would be used 

for the gable and roof surfaces types in HERS BESTEST. 

Note 2: Window glass and frames are disaggregated here because overall air-air U-value for these components is 

greater than that for other envelope components. 
83 

C.1.1 Convective Portion 

The EnergyPlus “detailed” interior convection algorithm was used in the reference simulations. Unlike 

HERS BESTEST, which assigns constant convection coefficients for interior surfaces based on their 

orientation only, the EnergyPlus detailed algorithm used in the EnergyPlus reference simulations 

calculates the interior convection coefficients based on the temperature difference between the surface 

and zone air, as well as the orientation of the surface (interior convection coefficients for the window 

panes are calculated in EnergyPlus V3.1 following ISO 15099 Section 8.3.2.2, which is summarized in 

EnergyPlus Engineering Reference [2009]). According to the EnergyPlus Engineering Reference, the 

“detailed” algorithm is taken from Walton (1983), which is derived from Table 5 on p. 3.12 in the 

ASHRAE Handbook of Fundamentals (2001). 

For vertical surfaces, the convection coefficient is calculated according to the equation 

3

1

c 31.1 Δ= Th (C-1) 

where ΔΤ = {(Air Temperature) − (Surface Temperature)} (K) and hc is the interior convection coefficient 

having units of W/(m2

·K). 

For (ΔΤ < 0.0 AND an upward facing surface) OR (ΔΤ > 0.0 AND a downward facing surface) the 

following relationship for enhanced convection is used: 

Σ−

Δ = cos283.7482.9 3

1

T

hc

 (C-2) 

where Σ is the surface tilt angle. 

For (ΔΤ > 0.0 AND an upward facing surface) OR (ΔΤ < 0.0 AND a downward facing surface) the 

following relationship for reduced convection is used: 

Σ+

Δ = cos382.1810.1 3

1

T

hc

 (C-3) 

EnergyPlus evaluates the interior convection coefficients on a time step basis. Therefore, because of the 

transient nature of the interior surface and zone air (when floating) temperatures, the interior convection 

coefficients change with time. To provide equivalent inputs for programs that require constant interior 

surface heat transfer coefficients, EnergyPlus simulations were performed and the time-varying interior 

convection coefficients were analyzed (using Case L200EX nominal inputs). For each surface type 

(exterior wall framed, exterior wall unframed, interior wall, door, floor framed, floor batting, ceiling 

framed, ceiling batting, attic floor framed, attic floor batting, gable, roof, window pane, window frame), 

the average interior convection coefficient was found for the core heating and cooling seasons. This was 

October–April for heating in Colorado Springs and May–September for cooling in Las Vegas. For each 

surface type, the Colorado Springs and Las Vegas values were then averaged. Equivalent constant 

convective surface coefficients were calculated using area weighting as shown in Tables C1-2 through 

C1-4; area-weighted averages are indicated with bold font in the tables. 

 
84 

Table C1-2. Interior Convective Surface Coefficients for Vertical Surfaces

Surface Area (ft2

) hc (Btu/h·ft2·°F) 

 Col Springs Las Vegas Avg 

Exterior Wall Framed 258.5 0.305 0.315 0.310 

Exterior Wall Unframed 775.5 0.341 0.316 0.329 

Interior Wall 1024.0 0.272 0.295 0.284 

Door 40.0 0.371 0.324 0.348 

Area-Weighted Average 0.305 

Table C1-3. Interior Convective Surface Coefficients for Roof and Gables

Surface Area (ft2) hc (Btu/h·ft2·°F) 

 Col Springs Las Vegas Avg 

Gable 121.5 0.200 0.226 0.213 

Roof 1622.2 0.255 0.228 0.242 

Area-Weighted Average 0.240 

Table C1-4. Interior Convective Surface Coefficients for Horizontal Surfaces

Surface Area (ft2) hc (Btu/h·ft2·°F) 

 Col Springs Las Vegas Avg 

Raised Floor 1539.0 0.225 0.349 0.287 

Ceiling Framed 153.9 0.343 0.197 0.270 

Ceiling Batting 1385.1 0.299 0.185 0.242 

Attic Floor Framed 153.9 0.341 0.254 0.297 

Attic Floor Batting 1385.1 0.271 0.181 0.226 

Area-Weighted Average 0.255 

Disaggregated average values for the pane and frame (highlighted in bold below) were applied as shown 

in Table C1-5. Values for low-e windows were calculated similarly. 

Table C1-5. Interior Convective Surface Coefficients for Single-Pane Windows

Surface Area (ft2) hc (Btu/h·ft2·°F) 

 Col Springs Las Vegas Avg 

Window Pane 10.96 0.298 0.236 0.267 

Window Frame 4.04 0.475 0.389 0.432 

 

C.1.1.1 Difference Between Surface Heat Transfer Convective Calculation in EnergyPlus 

Version 4.0 Versus Version 3.1 

After several simulation trials of the test specification were completed, an updated version of EnergyPlus 

(Version 4.0) was released. Documentation accompanying the release indicates the correction of an error 

in the EnergyPlus algorithm used to calculate convective heat transfer coefficients on the interior surfaces 

of windows. The correction has a secondary effect (< 0.3%) on the EnergyPlus calculation of the window 

exterior surface convective coefficients. The effect of the Version 3.1 error on EnergyPlus results is 

shown in Table C1-6. The effect of the error on average reference program base case energy use 

(L200EX-P) and window retrofit energy savings (L200-L250EX-P) is shown in Figures C1-1 and C1-2 

for the physics heating and cooling cases, respectively. The DOE-2.1E and SUNREL reference results 

(used with EnergyPlus results to calculate average reference results) were generated by applying interior 

combined surface coefficients based on EnergyPlus versions 3.1 and 4.0, as shown for the labeled average 
85 

results bars. In these figures the y-axes for the window retrofit sensitivity results are magnified relative to 

the y-axes for the base case energy use results. 

Table C1-6. Effect of Window Interior Surface Convective Calculation for

EnergyPlus Version 3.1 Versus Version 4.0

EnergyPlus Version Version 

3.1 

Version 

4.0 

V3.1 – 

V4.0 

% Error 

([V3.1] – [V4.0])/(V4.0) 

Single-Pane Window Interior Surf. Coeffs. 

(Btu/(h·ft2

·°F)) 

 

hc 0.267 0.318 -0.051 -16.0% 

hs = hi + hc 1.115 1.166 -0.051 -4.4% 

Low-e Window Interior Surface Coeffs. 

(Btu/(h·ft2

·°F)) 

 

hc 0.222 0.264 -0.042 -15.9% 

hs = hi + hc 1.070 1.112 -0.042 -3.8% 

Annual Gas Use, with heating (MBtu/yr) 

L200EX-P (base case) 119.01 120.13 -1.12 -0.9% 

“L200EX-P” – “L250EX-P” 

(single-pane v. low-e window sensitivity) 

 10.86 11.85 -0.99 -8.4% 

Annual Electric Use, with cooling (kWh/yr) 

L200EX-P (base case) 10665 10676 -11 -0.1% 

“L200EX-P” – “L250EX-P” 

(single-pane v. low-e window sensitivity) 

1310 1316 -6 -0.5% 

 

Figure C1-1. Effect of window interior convective surface coefficient on average reference results 

for gas use and savings in cases with space heating

L200-L250EX-PH

0

2

4

6

8

10

12

14

16

18

20

VERSION 3.1 VERSION 4.0

Average Reference Savings (MBtu)

L200EX-PH

0

20

40

60

80

100

120

140

VERSION 3.1 VERSION 4.0

Average Reference Results (MBtu)
86 

 

Figure C1-2. Effect of window interior convective surface coefficient on average reference results 

for electricity use and savings in cases with space cooling

The differences caused by the EnergyPlus version 3.1 error, shown in Figures C1-1 and C1-2, are 

relatively small compared to the range of disagreement among reference results shown in Appendix G, 

Section G.1. Because of project time constraints, these errors were not addressed for the initial version of 

BESTEST-EX. An update to a future version of BESTEST-EX is recommended to correct default 

combined interior surface coefficients for windows. Such a revision will also require re-running 

BESTEST-EX working group simulation trials and generating new reference utility billing data for the 

calibration tests. This update should be considered in parallel with other recommendations for future work 

described in Appendix I.

C.1.2 Radiative Portion

To provide equivalent interior combined surface coefficients, radiative portions must be assumed. The 

infrared portion of the film coefficients is based on the linearized gray-body radiation equation (Duffie 

and Beckman 1980) 

hi = 4εσT3

 (C-4) 

where: 

 ε = infrared emissivity 

 σ = 0.1718×10−8

 Btu/(h·ft2·°F) (Stefan-Boltzmann constant) 

 T = average temperature of surrounding surfaces 

 (assumed 50°F [510°R] for outside, 68°F [528°R] for inside) 

 hi = infrared radiation portion of surface coefficient 

L200-L250EX-PC

0

200

400

600

800

1000

1200

1400

1600

1800

2000

VERSION 3.1 VERSION 4.0

Average Reference Savings (kWh)

L200EX-PC

0

2000

4000

6000

8000

10000

12000

VERSION 3.1 VERSION 4.0

Average Reference Results (kWh)
87 

C.2 Exterior Surface Coefficients 

C.2.1 Combined Heat Transfer Coefficients 

Using combined coefficients is a simplification of the convective and radiative heat transfer at the 

external surfaces. For example, there may be instances for a surface when there is a net energy loss 

through radiant exchange with the sky, but almost no temperature difference exists between the air and 

the surface or the ground and the surface. For situations such as these it is difficult to capture the physical 

behavior with one combined heat transfer coefficient that is multiplied by the surface-air temperature 

difference. 

However, combined exterior heat transfer coefficients (provided for programs that do not automatically 

calculate surface heat transfer) were calculated using the method described in Appendix C of HERS 

BESTEST. One notable difference from HERS BESTEST is the use of corrected wind speeds at the 

surface centroids (see Section C.3) instead of the meteorological wind speed from the weather file. 

First the time-average meteorological wind speeds were calculated for core heating and cooling seasons. 

This is October–April for heating in Colorado Springs and May–September for cooling in Las Vegas. The 

“core average” wind speeds are 4.44 m/s (9.93 mph) and 4.28 m/s (9.57 mph), respectively. The wind 

speeds were then corrected (see Section C.3) and used to calculate the exterior combined radiative and 

convective surface coefficients, ho, according to 

2

o ++= 321 VaVaah (C-5)

which is a second order polynomial in corrected wind speed V having coefficients ai (see HERS 

BESTEST Appendix C) that depend on the surface texture. 

Similar to the methodology used in HERS BESTEST (Appendix C), a brick or rough plaster surface 

texture was assumed for the raised floor, exterior walls, doors, gables, and roofs when calculating the 

coefficients of Equation C-5. In HERS BESTEST the exterior surface coefficients for the windows were 

calculated based on analysis using the program WINDOW 4.1 (1994). For BESTEST-EX the equivalent 

combined coefficients for the windows were calculated using Equation C-5, assuming a very smooth 

surface. The results of these calculations are summarized in Table C2-1. 

Table C2-1 can be further simplified to the area-weighted average (see Section C2.2 for description of 

area weighting) external heat transfer coefficients shown in Table C2-2. 

Table C2-1. Combined Exterior Heat Transfer Coefficients for Each Surface Type 

Surface Height (ft) 

Wind Speed 

Corr. Factor 

CO Ext Surf 

Coeff 

(Btu/(h·ft2

·°F)) 

LV Ext Surf 

Coeff 

(Btu/(h·ft2

·°F)) 

Avg. Ext Surf Coeff 

(Btu/(h·ft2·°F)) 

Floor 0.000 0.000 2.200 2.200 2.200 

Exterior Walls 4.000 0.451 3.656 3.603 3.630 

Windows (pane) 4.500 0.463 2.630 2.588 2.609 

Windows (frame) 4.500 0.463 2.630 2.588 2.609 

Doors 3.333 0.433 3.598 3.547 3.573 

Gables 9.500 0.546 3.966 3.902 3.934 

Roof 10.250 0.555 3.997 3.931 3.964 

Note: Exterior surface coefficients are calculated using the time average wind speed during the core 

heating and cooling seasons corrected to the centroid of each surface according to Section C.3. 

 
88 

Table C2-2. Combined Exterior Heat Transfer Coefficients After Area Weighting

Surface ho (Btu/(h·ft2

·°F))

Floor 2.200 

Exterior Walls/Doors 3.628 

Gables/Roof 3.962 

Window 2.609 

C.2.2 Disaggregation of Combined Coefficients Into Convective and Radiative 

Components

The combined exterior surface coefficients presented in Table C2-2 are disaggregated in Table C2-3 using 

the two different methods outlined below: 

1. “B-EX1” as described in Section C.2.2.1. 

2. “B-EX2” as described in Section C.2.2.2. 

A simplifying assumption for disaggregating convective and radiative portions of combined surface 

coefficients is that for the radiative portion for a given surface, the mean radiant temperature of the sky 

and other surrounding surfaces and objects equals the ambient air temperature. The actual mean radiant 

temperature is likely to differ from the ambient temperature. Additional research to refine calculation of 

equivalent combined surface coefficients that integrate radiative exchange with convective heat transfer 

of more advanced algorithms is needed. Such research should also consider developing future exterior 

surface coefficients based on the additive method for developing interior surface coefficients applied in 

Section C.1. 

If the program being tested requires use of disaggregated surface coefficients, either the “B-EX1” or “BEX2” coefficients may be used. Other disaggregated coefficients may also be used if there is a logical 

basis for selecting them. For historical reference, the original HERS BESTEST coefficients are also 

shown in italics under the heading “HERS.” 

A sensitivity test comparing the use of combined surface coefficients to more detailed surface heat 

transfer modeling was done with EnergyPlus. EnergyPlus simulations (using Case L200EX nominal 

inputs, except with full-year heating/cooling seasons) with the constant combined exterior surface 

coefficients with detailed calculation of radiation exchange disabled result in a Colorado Springs annual 

heating load that was 6.2% greater than the more detailed simulation using EnergyPlus’s “DOE2” exterior 

surface heat transfer algorithm. For Las Vegas, using the constant combined exterior surface coefficients 

results in a cooling load that agrees within 1% versus the more detailed simulation. The combined 

coefficients have better agreement with EnergyPlus’s “simple” model than its “DOE2” model. 

 
89 

Table C2-3. Disaggregated Exterior Film Coefficients for Opaque Surfaces 

(Btu/(h·ft2

·°F))

Exterior Walls/Doors, Outside (T = 50oF) (510oR) (ε = 0.9) B-EX1 B-EX2 HERS

hi = ho − hc for “B-EX1” 2.452 0.819 0.819 

hc = ho − hi for “B-EX2” 1.176 2.809 4.929 

ho 3.628 3.628 5.748 

Gables/Roof, Outside (T = 50oF) (510oR) (ε = 0.9) 

hi = ho − hc for “B-EX1” 2.574 0.819 0.819 

hc = ho − hi for “B-EX2” 1.388 3.143 4.929 

ho 3.962 3.962 5.748 

Raised Floor, Outside (T = 50oF) (510oR) (ε = 0.9) 

hi = ho − hc for “B-EX1” 2.068 0.819 0.819 

hc = ho − hi for “B-EX2” 0.132 1.381 1.381 

ho 2.200 2.200 2.200 

Windows: Very Smooth Surface Outside (T = 50oF) (510oR) (ε = 0.84) 

All Types of Windows 

B-EX1 B-EX2 HERS

hi = ho − hc for “B-EX1” 1.750 0.764 0.764 

hc = ho − hi for “B-EX2” 0.859 1.845 3.492 

ho 2.609 2.609 4.256 

C.2.2.1 Disaggregation Based on Calculated Convective Portion by EnergyPlus 

One way to disaggregate the combined surface coefficients, ho, into convective and radiative components 

is to estimate the convective component, hc. The radiative component hi is then hi = ho − hc. The 

coefficients calculated using this method are labeled “B-EX1” in Table C2-3. 

The “DOE2” exterior convection algorithm was used in EnergyPlus to generate reference results. 

According to EnergyPlus documentation, the DOE2 algorithm is a combination of the MoWiTT 

(Yazdanian and Klems 1994) and BLAST detailed algorithms. The “DOE2” algorithm improves on the 

simplified HERS BESTEST methodology (HERS BESTEST vol. 1, Appendices C and D), in which the 

combined exterior heat transfer coefficients are calculated based on the surface texture and 

meteorological wind speed. Instead, the “DOE2” algorithm uses a corrected wind speed (see Section C.3) 

and incorporates temperature-dependent natural convection (see Section C.1) in addition to wind-driven 

convection. Radiant exchange between the surface and the ground, sky, and air is modeled separately. 

For each surface the exterior convection coefficient, h ,glassc (a very smooth glass surface is initially 

assumed) is calculated using the relationship 

2 2

, )(

b

glassc n += aVhh z (C-6) 
90 

where hn is the natural convection coefficient (W/m2·K) calculated using the same methodology as the 

interior convection coefficients (See Section C.1). Vz is the wind speed (m/s) at the height of the centroid 

of the surface above ground (See Section C.3 for a description of the wind speed correction). The 

constants a and b depend on whether the surface is windward (a = 2.38, b = 0.89) or leeward (a = 2.86, 

b = 0.617). Any surface more than 100 degrees from normal incidence is considered leeward. 

The coefficient h ,glassc is then corrected based on the roughness of the surface using the equation 

)( += ,glasscfnc − hhRhh n (C-7) 

where Rf is surface roughness multiplier chosen from Table C2-4. 

Table C2-4. Surface Roughness Multipliers

Roughness Index Rf

Very Rough 2.17 

Rough 1.67 

Medium Rough 1.52 

Medium Smooth 1.13 

Smooth 1.11 

Very Smooth 1.00 

Because wind direction, wind speed, surface temperature, and outdoor temperature all change with time, 

the exterior convection coefficients in the EnergyPlus reference simulations vary with time. To develop 

example equivalent inputs for those programs that require constant disaggregated convective and radiative 

exterior surface heat transfer coefficients, EnergyPlus simulations using Case L200EX nominal inputs 

were performed and the time-varying exterior convection coefficients output by EnergyPlus were 

analyzed. For each surface type (exterior wall framed, exterior wall unframed, door, roof, gable, window 

pane, window frame, floor framed, and floor batting), the average exterior convection coefficient was 

found during the core heating and cooling seasons. This is October–April for heating in Colorado Springs 

and May–September for cooling in Las Vegas. For each surface type, the Colorado Springs and Las 

Vegas values were then averaged. Equivalent constant convective coefficients were calculated using area 

weighting as shown in Tables C2-5 through C2-8. 

Table C2-5. Exterior Convective Surface Coefficients for Vertical Surfaces 

Surface Area (ft2

) hc (Btu/(h·ft2·°F)) 

 Col Springs Las Vegas Average 

Ext Wall Framed 258.5 1.191 1.163 1.177 

Ext Wall Unframed 775.5 1.192 1.163 1.177 

Door 40.0 1.153 1.121 1.137 

Area-Weighted Average 1.176 

Table C2-6. Exterior Convective Surface Coefficients for Roof and Gables 

Surface Area (ft2

) hc (Btu/(h·ft2

·°F)) 

 Col Springs Las Vegas Average 

Roof 1622.2 1.391 1.387 1.389 

Gables 121.5 1.387 1.354 1.371 

Area-Weighted Average 1.388 

 
91 

Table C2-7. Exterior Convective Surface Coefficients for the Floor 

Surface Area (ft2

) hc (Btu/(h·ft2·°F)) 

 Col Springs Las Vegas Average 

Floor Framed 153.9 0.205 0.187 0.196 

Floor Batting 1385.1 0.125 0.126 0.125 

Area-Weighted Average 0.132 

Table C2-8. Exterior Convective Surface Coefficients for Windows 

Surface Area (ft2

) hc (Btu/(h·ft2·°F)) 

 Col Springs Las Vegas Average 

Window Pane 10.96 0.894 0.810 0.852 

Window Frame 4.04 0.923 0.833 0.878 

Area-Weighted Average 0.859 

To verify the equivalence of these inputs, the constant exterior convection coefficient values were used in 

EnergyPlus simulations that automatically calculate radiative exchange and compared to the more 

detailed EnergyPlus simulations using the “DOE2” exterior surface heat transfer algorithm (using Case 

L200EX nominal inputs, except for full-year heating/cooling seasons). Results for the annual heating and 

cooling loads in Colorado Springs and Las Vegas, respectively, agreed within 2%. 

C.2.2.2 Disaggregation Based on Calculated Radiative Portion Using HERS BESTEST 

Appendix D 

Another method to disaggregate the combined coefficients, ho, is to estimate radiative coefficients hi. The 

convective coefficients, hc, are then the difference hc = ho − hi. The coefficients calculated using this 

approach are labeled “B-EX2” in Table C2-3. Similar to Appendix D of HERS BESTEST, the infrared 

portion of the film coefficients is based on the linearized gray-body radiation equation (Duffie and 

Beckman 1980). 

hi = 4εσT3

 (C-4) 

where: 

 ε = infrared emissivity 

 σ = 0.1718 × 10−8

 Btu/(h·ft2·°F) (Stefan-Boltzmann constant) 

 T = average temperature of surrounding surfaces 

 (assumed 50°F [510°R] for outside, 68°F [528°R] for inside) 

 hi = infrared radiation portion of surface coefficient 

Other nomenclature used for Table C2-3 is: 

 hc = convective portion of surface coefficient 

 ho = total combined outside surface coefficient 

C.3 Wind Speed Correction 

In HERS BESTEST the equivalent exterior surface coefficients for the exterior walls, doors, and roofs are 

calculated using the mean annual weather station wind speed of 10.7 mph. The analysis using WINDOW 

4.1 assumes a slightly lower value of 9.0 mph. In reality, the wind speed over the surfaces of a building 

could be considerably lower than wind speed from the weather file. For the BESTEST-EX reference 

simulations, EnergyPlus converts the weather station wind speed to the local wind speed at the centroid of 

each surface according to the equation (ASHRAE 2001, F16.3) 
92 

meta a

met

met

met

z

z

VV 



 



 













 =

−

δ

δ (C-8) 

where V is the local wind speed, Vmet is the wind speed at the weather station, zmet is the height of the wind 

speed measurement (assumed to be 10 m), and z is the height of the surface centroid. δ and a are terraindependent coefficients found in ASHRAE (2001). The weather measurement is assumed to be in “flat, 

open country” (δ = 270 m, a = 0.14) and the site is assumed to be “suburbs” (δ = 370 m, a = 0.22). 

According to ASHRAE (2001), the descriptions for these terrain conditions are: 

Flat, open country: “Open terrain with scattered obstruction having heights generally 

less than 10 m, including flat open country typical of meteorological station 

surroundings.” 

Suburbs: “Urban and suburban areas, wooded areas, or other terrain with numerous 

closely spaced obstructions having the size of single-family dwellings or larger, over a 

distance of at least 2000 m or 10 times the height of the structure upwind, which ever is 

greater.” 

Equation C-8 is valid for an isolated building only. When the spacing-to-height values do not satisfy the 

terrain descriptions, the interference and shielding effects of nearby obstructions must be considered. As 

an example, the exterior walls of the conditioned zone in the BESTEST-EX model have a centroid height 

of approximately 1.22 m. Applying Equation C-8 gives 

( ) ≈ 451.0 VV met (C-9) 

 
93 

Appendix D Infiltration Modeling 

Infiltration caused by envelope leakage in residential buildings significantly affects the annual heating 

and cooling loads. Multiple methods exist for modeling infiltration given the results of blower door tests. 

Examples of methods and models are discussed in the following sections. 

D.1 Conversion of ACH50 to Natural Air Changes per Hour 

Some programs may use a rule-of-thumb conversion of ACH50 to natural air changes per hour. For 

example, one common approach is to use the approximation developed by Kronvall and Persily 

(Sherman 1998). 

20

ACH50 ACH ≈ (D-1) 

Assuming this simple relationship, the nominal constant equivalent ACH input for the pre-retrofit basecase building (Case L200EX) would be 0.975 ACH. However, an EnergyPlus simulation using nominal 

inputs and 0.975 ACH constant infiltration over-predicted the annual heating load in Colorado Springs by 

about 8%. This suggests that the factor in the denominator of Equation D-1 may need to be modified 

based on the characteristics of the climate and building (for example, see Sherman 1987). 

D.2 LBL Model (Sherman and Grimsrud) 

The “Basic Model” described in the 2005 ASHRAE Handbook of Fundamentals (p. 27.21) was used in 

EnergyPlus to model infiltration. This model is based on the LBL infiltration model developed by 

Sherman and Grimsrud in 1980. The infiltration airflow rate is calculated using the relation 

2 = −4 sPaL +Δ VCtCAQ metw (D-2) 

where Q is the airflow rate in CFM, AL-4Pa is the effective leakage area at 4 Pa, Cs is the stack coefficient, 

Δt is the indoor-outdoor temperature difference (absolute value, °F), Cw is the wind coefficient, and Vmet

is the wind speed measured at the weather station (mph). Cs and Cw depend on the distribution of leakage 

area in the house, height/terrain at the site/weather station, and shelter class of the building. The following 

assumptions were made (see 2005 ASHRAE Handbook of Fundamentals, p. 27.21): 

• Half of building leakage in walls 

• Equal leakage in floor and ceiling 

• One-story building (8 ft or 2.5 m) 

• Stack coefficient (Cs) = 0.0150 cfm2

/(in.4·°F), or in SI units as input into EnergyPlus: 

Cs = 0.000145 (L/s)2

/(cm4·K) corresponding with one-story house 

• Wind coefficient (Cw) = 0.0012 cfm2

/(in.4·mph2), or in SI units as input into EnergyPlus: 

Cw = 0.000032 (L/s)2

/(cm4(m/s)2) corresponding with: 

o “Terrain used for converting meteorological wind speed is that of a rural area with 

scattered obstacles” 
94 

o Shelter Class 5, “Typical shelter produced by buildings or other structures that are 

immediately adjacent (closer than one house height): e.g., neighboring houses on the 

same side of the street, trees, bushes, etc.” 

o One story house. 

• Effective leakage area (AL-4Pa) = 196.3 in.2

, as documented below. 

The effective leakage area at 4 Pa was calculated based on the Colorado Springs CFM50 nominal input

(4000 CFM50). First, the leakage area at 50 Pa was calculated using the equation (2005 ASHRAE 

Handbook of Fundamentals, p. 27.12) 

D r

PaL pC

CFM BA

Δ − = 2 )( 50

50

ρ (D-3) 

where B is a unit conversion factor (0.186), CFM50 is the airflow rate measured in CFM at 50 Pa, CD is 

the discharge coefficient (assumed to be 1.0), ρ is the density of air (0.060 lbm/ft3

 for 6171 ft altitude of 

Colorado Springs, using the equation of HERS BESTEST, Appendix B; for software that automatically 

calculates air density, the air density may have a different value) and r Δp is the reference pressure in 

inches of water (50 Pa × 1 in H2O per 249 Pa). Next, the leakage area at 50 Pa was converted to a leakage 

area at 4 Pa using the relationship (2005 ASHRAE Handbook of Fundamentals, p. 27.13) 

5.0

50

4

4

50

4 50

−

−

−

−

−

− − 















Δ

Δ















 =

n

Par

Par

PaD

PaD

PaL PaL

p

p

C

C AA (D-4) 

where n is the pressure exponent (assumed to be 0.65) and the flow coefficient at 4 Pa is also equal to 1.0. 

Using Equations D-3 and D-4, the effective leakage area at 4 Pa is: AL-4Pa = 196.3 in.2

. 

Applying the Las Vegas altitude of 2178 ft to adjust air density, and back-calculating based on AL-4Pa = 

196.3 in.2

, yield an equivalent 3714 CFM50 for Las Vegas. 

Other Models 

Software programs may use other infiltration models, such as AIM-2 (Walker and Wilson 1998) or a 

modified version of the two approaches discussed above. 

D.3 Equivalent Constant Infiltration Rates 

Equivalent constant infiltration rates are provided for programs that do not automatically calculate 

infiltration. Constant infiltration rates are based on the average of hourly weather-driven infiltration rates 

calculated by EnergyPlus over the core heating and cooling seasons for the Colorado Springs and Las 

Vegas climates, respectively; these are labeled as “E+ ACH” in Table D1-1. In this table, EnergyPlus 

simulations using its application of the Sherman-Grimsrud model (column labeled “S-G Load”) are 

compared with EnergyPlus simulations using the equivalent constant infiltration rate (column labeled 

“E+ACHload”). 

Table D1-1. EnergyPlus Infiltration Sensitivity Test Results 

 Las Vegas Colorado Springs

S-G Load E+ACHload S-G Load E+ACHload 

ELA (in.2) CFM50 (MBtu) E+ACH (MBtu) CFM50 (MBtu) E+ACH (MBtu) 

98.1 1857 58.0 0.246 57.7 2000 60.1 0.382 59.5 

137.4 2600 58.3 0.345 57.9 2800 65.2 0.534 64.4 

196.3 3714 58.9 0.492 58.2 4000 73.0 0.760 71.7 

215.9 4085 59.1 0.540 58.4 4400 75.5 0.835 74.2 
95 

Table D1-1 indicates 1%–2% agreement for use of constant values versus the detailed modeling. This 

table also indicates that infiltration has a greater effect on sensible heating load in Colorado Springs than 

on sensible cooling load in Las Vegas; this is because much of the infiltration is temperature-difference 

driven in the model. 

D.4 Comparison of Predicted Infiltration With Measured Infiltration 

Sensitivity tests were performed for heating load versus CFM-50 blower door measurements using the 

“Effective Leakage Area” model in EnergyPlus, which is based on the ASHRAE “Basic” residential 

infiltration model. Using the most sheltered assumption (Shelter Class 5), the savings appear to be about 

0.065 therms load/(CFM-50 reduction) for an ideal space heating system or 0.092 therms use/(CFM-50 

reduction) assuming a 70% furnace efficiency. These values are above the high end of estimates of 

0.050–0.060 therms use/(CFM-50 reduction) based on pre- and post-retrofit utility billing data (Blasnik 

2009). Further research is needed to investigate the causes of these differences and if other models may 

yield better agreement with measured field data. 
96 

Appendix E Window Modeling with WINDOW 5 

WINDOW 5.2 (2005) was used to help develop thermal and optical property specifications for the 

following windows used in BESTEST-EX: 

• Clear single-pane glass with aluminum frame with thermal break (see Section E.1) 

• Double-pane low-e glass with wood frame (see Section E.2). 

E.1 Single-Pane Window With Aluminum Frame With Thermal Break, Output From 

WINDOW 5 

The WINDOW 5 output listing below includes analysis results and inputs for the BESTEST-EX basecase (L200EX) single-pane window. The following inputs applied in the analysis are not listed: 

• “NFRC” calculation mode is applied 

• Environmental conditions are identical to “NFRC 100-2001”, except: 

o Fixed combined interior surface coefficient = 1.115 Btu/(h·ft2

·°F) 

o Fixed combined exterior surface coefficient = 2.609 Btu/(h·ft2

·°F). 

 Window 5.2a v5.2.17a Report Page 1 09/30/09 08:14:35 

 ID: 9 

 Name: B-EX Sngl Pane Actual Geometry 

 EnvCond: 8 B-EX sngl pane 

 

 Type: Custom Dual Vision Vertical 

 Tilt: 90 

 Width: 36.0 inches 

 Height: 60.0 inches 

 Area: 15.00 ft2 

 

 U-value: 0.774 Btu/h-ft2-F 

 SHGC: 0.679 

 Vt: 0.656 

 CI: N/A 

Data for Glazing Systems 

 COG 

ID Name Area #Lay Tilt Uc SCc SHGCc Vtc RHG 

 ft2 Btu/h-ft2 

------ --------------- ----- ---- ---- ------- ----- ----- ----- ----- 

 11 B-EX Single Pan 3.70 1 90 0.771 0.992 0.863 0.898 209 

 11 B-EX Single Pan 3.70 1 90 0.771 0.992 0.863 0.898 209 

Glass and Gas Data for Glazing System '11 B-EX Single Pane' 

ID Name D( ") Tsol 1 Rsol 2 Tvis 1 Rvis 2 Tir 1 Emis 2 Keff 

------ --------------- ----- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 

Outside 

 11826 L200EX-P Single 0.118 .837 .075 .075 .898 .081 .081 .000 .840 .840 .520 

Inside 

Frame Data 

 Frame Edge 

Location ID Name Source Area Area Uframe Uedge 

 ft2 ft2 Btu/h-ft2-F 

---------------- ------ ------------- ------------- ----- ----- ------- ------ 

Header 10 B-EX Alum Fra Generic 0.635 0.486 0.7850 0.7706 

Upper Left Jamb 10 B-EX Alum Fra Generic 0.547 0.428 0.7850 0.7706 

Upper Right Jamb 10 B-EX Alum Fra Generic 0.547 0.428 0.7850 0.7706 

Mullion 10 B-EX Alum Fra Generic 0.582 0.885 0.7850 0.7706 

Lower Left Jamb 10 B-EX Alum Fra Generic 0.547 0.428 0.7850 0.7706 

Lower Right Jamb 10 B-EX Alum Fra Generic 0.547 0.428 0.7850 0.7706 

Sill 10 B-EX Alum Fra Generic 0.635 0.486 0.7850 0.7706 
97 

Gas Data 

ID Name Type Cond Visc Cp Dens Pran 

 Btu/h- lb/ft- Btu/lb- lb/ft3 

 ft-F s F 

 x e-6 

______ ________________________ _____ ______ _______ _______ _______ ______ 

No gas data for Single Glazing 

Window 5.2a v5.2.17a Report Page 2 09/30/09 08:14:35 

Environmental Conditions: 8 B-EX sngl pane 

 Tout Tin WndSpd Wnd Dir Solar Tsky Esky 

 (F) (F) (mph) (Btu/h-ft2) (F) 

 ----- ---- ------ -------- ------ ---- ---- 

Uvalue -0.4 69.8 12.30 Windward 0.0 -0.4 1.00 

Solar 89.6 75.2 6.26 Windward 248.2 89.6 1.00 

Frame Library Data 

 U-value Edge GlzSys GlzSys Width 

ID Name Source Frame Edge Corr Width Uc (PFD) Abs 

 Btu/h- Btu/h- inches Btu/h- 

 ft2-F ft2-F ft2-F 

______ _____________ ____________ ______ ______ ____ ______ ______ _____ ____ 

 10 B-EX Alum Fra Generic 0.7850 N/A 5 N/A N/A 2.75 0.60 

Divider Library Data 

 U-value Edge GlzSys GlzSys Width 

ID Name Source Div Edge Corr Width Uc (PFD) Abs 

 Btu/h- Btu/h- inches Btu/h- 

 ft2-F ft2-F ft2-F 

______ _____________ ____________ ______ ______ ____ ______ ______ _____ ____ 

No Dividers for this Glazing System 

Optical Properties for Glazing System '11 B-EX Single Pan' 

Angle 0 10 20 30 40 50 60 70 80 90 Hemis 

Vtc : 0.898 0.898 0.897 0.895 0.887 0.868 0.820 0.703 0.439 0.000 0.820 

Rf : 0.081 0.081 0.081 0.083 0.090 0.107 0.154 0.270 0.534 1.000 0.146 

Rb : 0.081 0.081 0.081 0.083 0.090 0.107 0.154 0.270 0.534 1.000 0.146 

Tsol : 0.836 0.836 0.834 0.830 0.820 0.799 0.751 0.639 0.389 0.000 0.756 

Rf : 0.075 0.075 0.075 0.077 0.082 0.099 0.143 0.252 0.505 1.000 0.136 

Rb : 0.075 0.075 0.075 0.077 0.082 0.099 0.143 0.252 0.505 1.000 0.136 

Abs1 : 0.089 0.089 0.090 0.093 0.097 0.101 0.105 0.108 0.106 0.000 0.098 

SHGCc: 0.863 0.863 0.862 0.858 0.850 0.830 0.783 0.672 0.421 0.000 0.785 

Tdw-K : -1.000 

Tdw-ISO: -1.000 

Tuv : -1.000 

 Window 5.2a v5.2.17a Report Page 3 09/30/09 08:14:35 

 Temperature Distribution (degrees F) 

 Winter Summer 

 Out In Out In 

 ---- ---- ---- ---- 

Lay1 20.3 21.4 91.2 91.1 
98 

E.2 Double-Pane Low-e Window With Wood Frame, Output From WINDOW 5 

The WINDOW 5 output listing below includes analysis results and inputs for the BESTEST-EX low-e 

window applied for cases L250EX and L300EX. The following inputs applied in the analysis are not 

listed: 

• “NFRC” calculation mode is applied 

• Environmental conditions are identical to “NFRC 100-2001”, except: 

o Fixed combined interior surface coefficient = 1.070 Btu/(h·ft2

·°F) 

o Fixed combined exterior surface coefficient = 2.609 Btu/(h·ft2

·°F). 

 

 Window 5.2a v5.2.17a Report Page 1 09/30/09 09:57:36 

 ID: 8 

 Name: B-EX Low-e Dbl Actual Geometry 

 EnvCond: 9 B-EX low-e 

 

 Type: Custom Dual Vision Vertical 

 Tilt: 90 

 Width: 36.0 inches 

 Height: 60.0 inches 

 Area: 15.00 ft2 

 

U-value: 0.279 Btu/h-ft2-F 

 SHGC: 0.347 

 Vt: 0.517 

 CI: N/A 

Data for Glazing Systems 

 COG 

ID Name Area #Lay Tilt Uc SCc SHGCc Vtc RHG 

 ft2 Btu/h-ft2 

------ --------------- ----- ---- ---- ------- ----- ----- ----- ----- 

 10 B-EX Doulbe-Pan 3.70 2 90 0.222 0.504 0.438 0.704 104 

 10 B-EX Doulbe-Pan 3.70 2 90 0.222 0.504 0.438 0.704 104 

Glass and Gas Data for Glazing System '10 B-EX Doulbe-Pane Low-e' 

ID Name D( ") Tsol 1 Rsol 2 Tvis 1 Rvis 2 Tir 1 Emis 2 Keff 

------ --------------- ----- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 

Outside 

 11828 B-EX Low E Pane 0.118 .450 .340 .370 .780 .070 .060 .000 .840 .040 .520 

 2 Argon 0.500 .013 

 11826 L200EX-P Single 0.118 .837 .075 .075 .898 .081 .081 .000 .840 .840 .520 

Inside 

Frame Data 

 Frame Edge 

Location ID Name Source Area Area Uframe Uedge 

 ft2 ft2 Btu/h-ft2-F 

---------------- ------ ------------- ------------- ----- ----- ------- ------ 

Header 9 B-EX Wood Fra Generic 0.635 0.486 0.3960 0.2644 

Upper Left Jamb 9 B-EX Wood Fra Generic 0.547 0.428 0.3960 0.2644 

Upper Right Jamb 9 B-EX Wood Fra Generic 0.547 0.428 0.3960 0.2644 

Mullion 9 B-EX Wood Fra Generic 0.582 0.885 0.3960 0.2644 

Lower Left Jamb 9 B-EX Wood Fra Generic 0.547 0.428 0.3960 0.2644 

Lower Right Jamb 9 B-EX Wood Fra Generic 0.547 0.428 0.3960 0.2644 

Sill 9 B-EX Wood Fra Generic 0.635 0.486 0.3960 0.2644 
99 

Window 5.2a v5.2.17a Report Page 2 09/30/09 09:57:36 

Gas Data 

ID Name Type Cond Visc Cp Dens Pran 

 Btu/h- lb/ft- Btu/lb- lb/ft3 

 ft-F s F 

 x e-6 

______ ________________________ _____ ______ _______ _______ _______ ______ 

 2 Argon Pure 0.0094 14.11 0.12 0.1112 0.6704 

Environmental Conditions: 9 B-EX low-e 

 Tout Tin WndSpd Wnd Dir Solar Tsky Esky 

 (F) (F) (mph) (Btu/h-ft2) (F) 

 ----- ---- ------ -------- ------ ---- ---- 

Uvalue -0.4 69.8 12.30 Windward 0.0 -0.4 1.00 

Solar 89.6 75.2 6.26 Windward 248.2 89.6 1.00 

Frame Library Data 

 U-value Edge GlzSys GlzSys Width 

ID Name Source Frame Edge Corr Width Uc (PFD) Abs 

 Btu/h- Btu/h- inches Btu/h- 

 ft2-F ft2-F ft2-F 

______ _____________ ____________ ______ ______ ____ ______ ______ _____ ____ 

 9 B-EX Wood Fra Generic 0.3960 N/A 4 N/A N/A 2.75 0.60 

Divider Library Data 

 U-value Edge GlzSys GlzSys Width 

ID Name Source Div Edge Corr Width Uc (PFD) Abs 

 Btu/h- Btu/h- inches Btu/h- 

 ft2-F ft2-F ft2-F 

______ _____________ ____________ ______ ______ ____ ______ ______ _____ ____ 

No Dividers for this Glazing System 

 Window 5.2a v5.2.17a Report Page 3 09/30/09 09:57:36 

Optical Properties for Glazing System '10 B-EX Doulbe-Pan' 

Angle 0 10 20 30 40 50 60 70 80 90 Hemis 

Vtc : 0.708 0.708 0.698 0.686 0.668 0.633 0.554 0.402 0.188 0.000 0.588 

Rf : 0.112 0.112 0.110 0.113 0.125 0.149 0.195 0.300 0.530 0.999 0.178 

Rb : 0.123 0.123 0.122 0.126 0.141 0.170 0.234 0.379 0.648 1.000 0.210 

Tsol : 0.389 0.389 0.384 0.376 0.366 0.346 0.305 0.226 0.107 0.000 0.323 

Rf : 0.350 0.350 0.349 0.351 0.359 0.373 0.402 0.471 0.639 0.999 0.391 

Rb : 0.337 0.337 0.335 0.336 0.341 0.355 0.388 0.470 0.645 1.000 0.378 

Abs1 : 0.219 0.219 0.226 0.231 0.232 0.236 0.250 0.264 0.224 0.001 0.235 

Abs2 : 0.041 0.041 0.042 0.042 0.043 0.044 0.043 0.038 0.029 0.000 0.041 

SHGCc: 0.441 0.441 0.436 0.429 0.420 0.401 0.360 0.279 0.149 0.000 0.376 

Tdw-K : -1.000 

Tdw-ISO: -1.000 

Tuv : -1.000 

 Temperature Distribution (degrees F) 

 Winter Summer 

 Out In Out In 

 ---- ---- ---- ---- 

Lay1 5.6 5.9 108.3 108.7 

Lay2 54.9 55.2 90.2 90.0 
100 

Appendix F Random Selection of Explicit Inputs for Case 

 L200EX-C Reference Simulation Results 

Explicit inputs were randomly selected within the approximate input ranges (AIRs) assuming a triangular 

probability distribution. For this distribution the probability of selection is greatest at the nominal value 

and decreases linearly to zero at the minimum and maximum values. The triangular distribution may be 

either symmetric or asymmetric with respect to the nominal value; an asymmetric distribution is shown in 

Figure F-1. 

Figure F-1. Triangular probability distribution assumed for random generation of explicit inputs 

Three types of explicit input sets were generated for the L200EX-C base-case scenarios: targeted high, 

targeted low, and fully random space-conditioning energy consumptions. Given approximate input ranges 

(min, max) for selected inputs (see Table F-1), sets of explicit values were generated using the following 

approaches: 

1. Targeted High: Explicit inputs were selected randomly from the portion of the range (upper or 

lower) that led to increased space conditioning energy consumption versus nominal values. For 

inputs that have different effects in Las Vegas and Colorado Springs on the space conditioning 

loads (internal gains and solar absorptivity), the entire range was used. 

2. Targeted Low: Explicit inputs were selected randomly from the portion of the approximate input 

range (upper or lower) that led to decreased space-conditioning energy consumption versus 

nominal values. For inputs that have different effects in Las Vegas and Colorado Springs on the 

space conditioning loads (internal gains and solar absorptivity), the entire range was used. 

3. Fully Random: Explicit inputs were selected randomly from the entire range for each variable. 

The Microsoft Excel© 2003 “RAND” function was used to implement the triangular probability 

distribution and generate explicit input values within the AIRs listed in the test specification. According 

to Excel documentation, this pseudo-random number generator “returns an evenly distributed random 

number greater than or equal to 0 and less than 1.” Supporting information is available at 

http://support.microsoft.com/kb/828795.

The “fully random” inputs were generated assuming a triangular probability distribution in Excel using 

the equation: 

min)))-(max*nom)-(max*)RAND#-sqrt((1-max

ExplicitValue = IF(RAND#<= min min),-min)/(max-(nom + sqrt(RAND# min)),-(max*min)-*(nom

 (F-1) 

Min Nominal Max 
101 

where “min,” “nom,” and “max” are the minimum, nominal, and maximum values of the approximate 

input range, respectively. The theoretical basis for this equation is provided in Kotz and van Dorp (2004). 

In Equation F-1, “RAND#” refers to another cell where a random number is generated using the 

=RAND() function. The RAND() function should not be used within the equation above, because RAND# 

must be the same value each time it is used. If RAND() were used in the equation above, three different 

random values would be generated and the equation would not correctly implement the probability 

distribution.

Equation F-1 was modified for the selection of “targeted” explicit inputs. For targeting the upper portion 

of the approximate input range (nominal value or greater), the value for “min” in Equation F-1 was set to 

“nom.” For targeting the lower portion of the approximate input range (nominal value or less), the value 

of “max” in Equation F-1 was set to “nom.” Table F-1 shows which portions of the approximate input 

ranges were used for the three different methods of selecting explicit inputs: targeted high (“High”), 

targeted low (“Low”), and fully random (“Random”).

An Excel worksheet was created to generate sets of explicit inputs corresponding to targeted high, 

targeted low, and fully random cases. Each time the spreadsheet “recalculates,” new random numbers are 

selected. The spreadsheet automatically calculates the appropriate values of input variables that depend on 

the explicit inputs. For example, if a random R-value of 16.3 h·ft2

·

o

F/Btu is generated for the 

Ceiling/Attic/Roof R-value (see Table F-1), values for the attic fiberglass insulation thickness and joist 

thickness (see Table 1-6b) are calculated to match the selected Ceiling/Attic/Roof composite R-value. 

Explicit inputs were randomly selected for the parameters related to the variables listed in Table F-1 only. 

Even though inputs such as the attic fiberglass insulation and joist thickness have approximate input 

ranges in the test specification, the values of these inputs are not independent; they are uniquely 

determined once the values of the inputs in Table F-1 are generated. All explicit inputs and the calculated 

values for dependent inputs are not known by the participants testing software. 

Sets of explicit inputs were created using a computer program that systematically recalculates the 

workbook (refreshes the randomly selected explicit inputs) and then outputs the explicit values to a text 

file. In the computer program the process is automatically repeated for the number of cases requested by 

the user. The output text file was used by another computer program that automatically creates input files 

for the EnergyPlus, SUNREL, and DOE2.1E simulations. 

Using the methodology described above, 14 calibrated base-case scenarios were developed 

(developmental details follow):

• L200EX-C1H, targeted high space heating use 

• L200EX-C2H, targeted low space heating use 

• L200EX-C3H, fully random selection, near-nominal space heating use 

• L200EX-C4H, fully random selection, high space heating use 

• L200EX-C5H, fully random selection, low space heating use 

• L200EX-C6H, fully random selection, mid-high space heating use 

• L200EX-C7H, fully random selection, mid-low space heating use 

• L200EX-C1C, targeted high space cooling use 

• L200EX-C2C, targeted low space cooling use 

• L200EX-C3C, fully random selection, near-nominal space cooling use 

• L200EX-C4C, fully random selection, high space cooling use 
102 

• L200EX-C5C, fully random selection, low space cooling use 

• L200EX-C6C, fully random selection, mid-high space cooling use 

• L200EX-C7C, fully random selection, mid-low space cooling use 

Initially for both the heating and cooling cases, one targeted-high, one targeted-low, and 20 fully random 

sets of explicit inputs were generated (44 total sets). Each case was then simulated in EnergyPlus. The 

fully random cases were ranked according to annual space heating/cooling consumptions (sets of heating 

and cooling cases were considered separately). The fully random cases with space heating/cooling 

consumptions corresponding to the closest to nominal, highest, and lowest consumptions were initially 

selected for cases C3, C4 and C5 respectively (with a separate set of cases suffixed with “H” and “C” for 

heating and cooling, respectively). 

For selecting the mid-high cases C6H and C6C, and mid-low cases C7H and C7C, mid-high and mid-low 

space heating/cooling consumption target values were calculated by averaging space heating/cooling 

consumptions according to: 

2

))4()200(( "" CEXPL MidHigh + =

2

))5()200(( "" CEXPL MidLow + =

where L200EXP is the nominal result from the building physics test base case (Case L200EX-P), and C4 

and C5 are the highest and lowest results, as selected above (with a separate set of cases suffixed with 

“H” and “C” for heating and cooling, respectively). 

F.1 Non-HVAC (Base Load) Energy Use and Internal Gains 

Because base load energy use is often estimated from “swing” season or “off-” season utility data, 

uncertainty in base load energy use when a full year or more of utility billing data are available can be 

substantially less than the uncertainty range for sensible loads from electric and gas-fired appliances 

shown in Table F-1. Where monthly utility data are available, much of the uncertainty for internal gains 

may be attributable to the internal-gains-to-usage fractions, which is a relatively narrow band of 

uncertainty relative to the internal gains, and relative to some of the other parameters listed in Table F-1. 
103 

Table F-1. Approximate Input Ranges (AIRs), Nominal Inputs, and Portions of AIRs Used for 

Generating Explicit Input Sets Corresponding to Low, Random, and High 

Space-Conditioning Energy Consumption

Input Min Max L200EX 

Nominal Value 

Portion of AIR Used 

High 

(C1) 

Low 

(C2) 

Random 

(C3–C7) 

Ext. Wall R 

(h·ft2

·°F/Btu) 4.500 6.200 5.091 Lower Upper Entire 

Ceiling/Attic/Roof 

R (h·ft2

·°F/Btu) 7.100 19.300 13.673 Lower Upper Entire 

Effective Leakage 

Area @ 4Pa 

(in.2

) 

137.4 215.9 196.3 Upper Lower Entire 

Sens Loads 

Occupants 

(Btu/day) 

4347 13041 8694 Entire Entire Entire 

Sens Loads 

Elec 

(Btu/day) 

18234 80000 36468 Entire Entire Entire 

% Non-HVAC 

Electricity to 

Internal Gains 

60.0 90.0 75.0 Entire Entire Entire 

Sens Loads Gas 

(Btu/day) 7464 22392 14928 Entire Entire Entire 

% Non-HVAC Gas 

Energy to Internal 

Gains 

20.0 35.0 27.5 Entire Entire Entire 

Ext. Solar Abs. 0.5 0.8 0.6 Entire Entire Entire 

Space 

Conditioning 

Season (% of 

annual load) 

90 99 95 Upper Lower Entire 

Heating Set Point 

(°F) 60.0 75.0 68.0 Upper Lower Entire 

Furnace Efficiency 

(%) 60.0 80.0 70.0 Lower Upper Entire 

Cooling Set Point 

(°F) 71.0 86.0 78.0 Lower Upper Entire 

Cooling COP 2.5 3.5 3.0 Lower Upper Entire 

Note: All explicit inputs are selected independently for each space heating and space cooling base-case 

scenario, except heating set point and furnace efficiency are selected for space heating cases only, and 

cooling set point and cooling COP are selected for space cooling cases only.
104 

Appendix G Example Results

This appendix presents: 

• Building physics test cases reference results (see Section G.1) 

• Benefit of calibration discussion (see Section G.2) 

• Improvements to tested software and importance of simulation trials (see Section G.3). 

G.1 Building Physics Test Cases Reference Results 

Reference results were developed using: 

• DOE-2.1E Version JJHirsch PC 2.1En136 (DOE-2 Reference Manual 1981, DOE-2 Supplement 

1994) 

• EnergyPlus Version 3.1 (EnergyPlus Input Output Reference 2009) 

• SUNREL Version 1.14 (Deru et al. 2002) 

Figure G-1 and Table G-1 show the building physics (“-P”) cases reference results for the heating cases. 

Figure G-2 and Table G-2 show the “-P” reference results for the cooling cases. An electronic version of 

the results is provided with B-EX-Phase-1-Ref-P-Results.xls included with the accompanying electronic 

files. Cell addresses for finding this data within the .xls file are given in small font below the tables. 

Only the results for the “-P” test cases are shown in the figures and the tables. For the calibrated energy 

savings (“-C”) test cases, reference simulation results and randomly selected explicit inputs used in the 

reference simulations are intentionally not given for blind testing. 
105 

Figure G-1. Building physics heating tests: Reference simulation results 

Figure G-2. Building physics cooling tests: Reference simulation results

Annual Gas Usage or Savings

Buildings Physics Heating Tests

-25

0

25

50

75

100

125

150

L200EX-PH

base-case

L200 -

L210EXPH

air_seal

L200 -

L220EXPH

attic_ins.

L200 -

L225EXPH

wall_ins.

L200 -

L240EXPH

setback

L200 -

L250EXPH

windows

L260 -

L265EXPH

sol_abs

L200 -

L270EXPH

shading

L200 -

L300EXPH

combined

Case

Gas Usage or Savings (million Btu) 

E+

SUNREL

DOE2.1E

Annual Electricity Usage or Savings

Buildings Physics Cooling Tests

-1000

1000

3000

5000

7000

9000

11000

13000

15000

17000

L200EX-PC

base-case

L200 -

L210EXPC

air_seal

L200 -

L220EXPC

attic_ins.

L200 -

L225EXPC

wall_ins.

L200 -

L240EXPC

setback

L200 -

L250EXPC

windows

L260 -

L265EXPC

sol_abs

L200 -

L270EXPC

shading

L200 -

L300EXPC

combined

Case

Electricity Usage or Savings (kWh)

E+

SUNREL

DOE2.1E
106 

Table G-1. BESTEST-EX Building Physics Heating Tests Reference Results 

Table G-2. BESTEST-EX Building Physics Cooling Tests Reference Results

Total Annual Gas Consumption and Savings (million Btu/y)

Case EnergyPlus SUNREL DOE2.1E

L200EX-PH base-case 119.01 134.68 119.32

L200 - L210EXPH air_seal 17.14 15.88 15.33

L200 - L220EXPH attic_ins. 14.27 15.74 14.34

L200 - L225EXPH wall_ins. 19.10 25.00 18.69

L200 - L240EXPH setback 10.91 11.42 10.56

L200 - L250EXPH windows 10.86 17.50 9.92

L260 - L265EXPH sol_abs -4.08 -2.74 -2.58

L200 - L270EXPH shading -9.27 -11.66 -9.65

L200 - L300EXPH combined 66.38 77.81 65.34

 B-EX-Phase-1-Ref-P-Results.XLS: GasData! A256:F269 3-May-2010

Total Annual Electricity Consumption and Savings (kWh/y)

Case EnergyPlus SUNREL DOE2.1E

L200EX-PC base-case 10664 11966 10622

L200 - L210EXPC air_seal 140 103 156

L200 - L220EXPC attic_ins. 405 596 428

L200 - L225EXPC wall_ins. 454 656 259

L200 - L240EXPC setback 671 765 700

L200 - L250EXPC windows 1310 1840 1234

L260 - L265EXPC sol_abs 821 609 586

L200 - L270EXPC shading 1247 1508 1325

L200 - L300EXPC combined 3235 4161 3330

B-EX-Phase-1-Ref-P-Results.XLS: ELECclgData! A267:E280 3-May-2010
107 

G.2 Benefit of Calibration 

One goal of the BESTEST-EX process is to estimate the benefit of utility bill calibration. In this section 

the BESTEST-EX Working Group participant results from a preliminary field trial are analyzed to 

provide an estimate of this benefit. The general approach is to compare the errors of energy savings 

predictions using calibrated models versus the errors of predictions using uncalibrated models. Results

analyzed in this section are not final BESTEST-EX results. Rather, they represent a snapshot in time 

during a development process where modifications and improvements were being made to the test 

specification, reference simulation modeling, and participant software tools. 

“Nominal” values from the test specification tables (see Section 1) are used for inputs in the physics test 

cases. These nominal values are analogous to the reported values by an auditor or the default values in the 

software. Because nominal inputs are used for the physics retrofit cases, the physics test results can be 

thought of as “uncalibrated” energy savings predictions.

The nominal values reported by an auditor have uncertainty. For example, the nominal ELA for a 

residential building may be reported as 196 in.2

, but because of measurement uncertainty, variations in 

weather conditions, modeling assumptions, etc., the value is better-represented using an uncertainty 

range: e.g., ELA = 196 ± 20 in.2

. The “true” or “as-installed” value for the input is likely to fall within the 

input range. 

Audit software providers often calibrate or “true-up” the pre-retrofit base case model to utility bills by 

varying inputs away from the nominal, reported, or default values. For the utility bill calibration cases in 

BESTEST-EX, users are given nominal inputs, uncertainty ranges, and pre-retrofit billing data (generated 

by the reference programs using randomly selected explicit or “as-installed” inputs). The tested software 

calibrates the base case model to the utility bills by varying key model inputs away from the nominal, 

reported, or default values and then predicts energy savings for the different retrofit measures using the 

calibrated model. Because software tools calibrate to utility bills by varying the key model inputs, the 

calibration test results can be thought of as “calibrated” energy savings predictions. 

The analysis that follows is based on the results of the last full simulation trial of test cases with the 

BESTEST-EX Working Group participants before the publication of this test procedure. The draft of the 

test specification used in the simulation trial has the following important differences from the final 

version of the test procedure: 

1. The randomly selected reference simulation inputs for the calibration cases in the simulation trial 

are different from those selected for the calibration cases in the final version of the test procedure. 

2. External shading was not modeled in the combined physics cooling retrofit case (L300EX-PC) 

for the simulation trial. 

For the simulation trial, six results sets were submitted from five different software providers. All six 

results sets were complete for the heating test cases. However, one set was not complete for the cooling 

test cases and therefore was eliminated from all cooling analysis. Another program did not model a 

particular retrofit measure for the combined cooling cases and therefore was eliminated from analysis for 

that subset of cases (L300EX-PC and L300EX-CC). 

G.2.1 Analysis Approach 

The benefit of calibration analysis was performed under the following assumptions: 

1. Because the utility bills in BESTEST-EX are the average of the reference program simulations 

using the same set of randomly selected inputs for a given simulation trial, Working Group 

participant energy savings predictions are compared to average energy savings predictions of the 

reference programs. 
108 

2. Working Group participant results for the physics cases are applied as uncalibrated energy 

savings predictions. 

3. Working Group participant results for the utility bill calibration cases are calibrated energy 

savings predictions. 

To compare results from physics test cases and calibration test cases, the definition of the retrofit 

measures must be equivalent for both types of test cases. For example, in the physics wall insulation 

retrofit (L225EX-P), 3.5 in. of cellulose is blown into the wall cavity. Although the overall wall R-value 

for the wall insulation calibration cases (L225EX-C) can differ from the physics case, the retrofit measure 

is identical; 3.5 in. of cellulose is blown into the wall cavity. The same definition of the retrofit measure 

allows for a meaningful comparison between the physics (uncalibrated) and utility bill calibration 

(calibrated) results. In some instances there are differences between the retrofit specifications for the 

physics and calibration cases; these are: 

1. For the physics air-sealing retrofit (L210EX-P) the ELA is reduced from 196.3 in.2

 to 98.1 in.2, 

corresponding to a decrease in ELA of 98.2 in2

. The air-sealing retrofit for the calibration cases 

specifies a 100 in.2

 decrease in ELA from the randomly selected value. For the purpose of this 

analysis, the 1.8 in.2

 difference in ELA reduction between the physics and calibration test cases is 

neglected. 

2. External shading (L270-EX) is not included in the calibration cases and therefore is not 

considered in this analysis. 

3. The cool roof retrofit for the physics test cases is defined as a decrease in the roof solar 

absorptance from 0.8 to 0.2 (L260EX-P−L265EX-P). In the calibration cases it is defined as 

absolute change from the randomly selected value (between 0.5 and 0.8) to 0.2 (L200EX-C 

−L265EX-C). Because this measure is defined differently for the physics and calibration test 

cases, the individual cool roof retrofit case (L265EX) is excluded from this analysis. The cool 

roof retrofit is not excluded, however, from the combined retrofit cases (L300EX) because the 

definition of the retrofit measure is similar between the physics and calibration cases (the preretrofit value for the roof solar absorptance is the nominal value of 0.6). 

G.2.2 Graphical Comparison 

In this section results from the BESTEST-EX Working Group field trial are presented in graphical form. 

The benefit of calibration is examined for the following calibration scenarios: 

• C3 = Fully random explicit input selection, near nominal space heating/cooling consumption 

• C4 = Fully random explicit input selection, high space heating/cooling consumption 

• C5 = Fully random explicit input selection, low space heating/cooling consumption 

• C6 = Fully random explicit input selection, mid-high space heating/cooling consumption 

• C7 = Fully random explicit input selection, mid-low space heating/cooling consumption 

The targeted cases (C1 and C2) are not analyzed because the uncertainty of the key model inputs is 

artificially reduced by selecting explicit inputs from portions of the ranges that lead to high or low space 

heating/cooling consumption. The calibration scenarios are described in detail in Section 1.3.1.2 and 

Appendix F. 

Figures G-3 through G-7 and Figures G-8 through G-12 show the benefit of calibration for the heating 

and cooling calibration scenarios, respectively. The following abbreviations apply to the figures: 

 
109 

REF = Average of reference program energy savings predictions using randomly selected 

 inputs [million Btu or kWh] 

WG CAL = Average Working Group calibrated energy savings prediction [million Btu or kWh] 

WG UNCAL = Average Working Group uncalibrated energy savings prediction [million Btu 

or kWh] 

For the sets of individual results used to develop the average values shown, the error bars represent one 

standard deviation above those values. For format clarity, the error bar extensions for one standard 

deviation below the average values are not shown. 

Figure G-3. Field trial results for fully random, near nominal heating scenario (C3H) 

C3H (Fully Random, Near Nominal)

0

20

40

60

80

100

120

140

L200EX-C3H

base-case

L200 -

L210EXC3H

air_seal

L200 -

L220EXC3H

attic_ins.

L200 -

L225EXC3H

wall_ins.

L200 -

L240EXC3H

setback

L200 -

L250EXC3H

windows

L200 -

L300EXC3H

combined

Case

Gas Consumption (million Btu)

REF

WG CAL

WG UNCAL
110 

Figure G-4. Field trial results for fully random, high heating scenario (C4H) 

Figure G-5. Field trial results for fully random, low heating scenario (C5H) 

C4H (Fully Random, High)

0

20

40

60

80

100

120

140

160

180

L200EX-C4H

base-case

L200 -

L210EXC4H

air_seal

L200 -

L220EXC4H

attic_ins.

L200 -

L225EXC4H

wall_ins.

L200 -

L240EXC4H

setback

L200 -

L250EXC4H

windows

L200 -

L300EXC4H

combined

Case

Gas Consumption (million Btu)

REF

WG CAL

WG UNCAL

C5H (Fully Random, Low)

0

20

40

60

80

100

120

140

L200EX-C5H

base-case

L200 -

L210EXC5H

air_seal

L200 -

L220EXC5H

attic_ins.

L200 -

L225EXC5H

wall_ins.

L200 -

L240EXC5H

setback

L200 -

L250EXC5H

windows

L200 -

L300EXC5H

combined

Case

Gas Consumption (million Btu)

REF

WG CAL

WG UNCAL
111 

Figure G-6. Field trial results for fully random, mid-high heating scenario (C6H) 

Figure G-7. Field trial results for fully random, mid-low heating scenario (C7H) 

C6H (Fully Random, Mid-High)

0

20

40

60

80

100

120

140

160

L200EX-C6H

base-case

L200 -

L210EXC6H

air_seal

L200 -

L220EXC6H

attic_ins.

L200 -

L225EXC6H

wall_ins.

L200 -

L240EXC6H

setback

L200 -

L250EXC6H

windows

L200 -

L300EXC6H

combined

Case

Gas Consumption (million Btu)

REF

WG CAL

WG UNCAL

C7H (Fully Random, Mid-Low)

0

20

40

60

80

100

120

140

L200EX-C7H

base-case

L200 -

L210EXC7H

air_seal

L200 -

L220EXC7H

attic_ins.

L200 -

L225EXC7H

wall_ins.

L200 -

L240EXC7H

setback

L200 -

L250EXC7H

windows

L200 -

L300EXC7H

combined

Case

Gas Consumption (million Btu)

REF

WG CAL

WG UNCAL
112 

Figure G-8. Field trial results for fully random, near nominal cooling scenario (C3C) 

Figure G-9. Field trial results for fully random, high cooling scenario (C4C) 

C3C (Fully Random, Near Nominal)

0

2000

4000

6000

8000

10000

12000

14000

16000

L200EX-C3C

base-case

L200 -

L210EXC3C

air_seal

L200 -

L220EXC3C

attic_ins.

L200 -

L225EXC3C

wall_ins.

L200 -

L240EXC3C

setback

L200 -

L250EXC3C

windows

L200 - L300EXC3C combined

(w.o. shading)

Case

Electricity Use (kWh)

REF

WG CAL

WG UNCAL

C4C (Fully Random, High)

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

L200EX-C4C

base-case

L200 -

L210EXC4C

air_seal

L200 -

L220EXC4C

attic_ins.

L200 -

L225EXC4C

wall_ins.

L200 -

L240EXC4C

setback

L200 -

L250EXC4C

windows

L200 - L300EXC4C combined

(w.o. shading)

Case

Electricity Use (kWh)

REF

WG CAL

WG UNCAL
113 

Figure G-10. Field trial results for fully random, low cooling scenario (C5C) 

Figure G-11. Field trial results for fully random, mid-high cooling scenario (C6C) 

C5C (Fully Random, Low)

0

2000

4000

6000

8000

10000

12000

14000

L200EX-C5C

base-case

L200 -

L210EXC5C

air_seal

L200 -

L220EXC5C

attic_ins.

L200 -

L225EXC5H

wall_ins.

L200 -

L240EXC5C

setback

L200 -

L250EXC5C

windows

L200 - L300EXC5C combined

(w.o. shading)

Case

Electricity Use (kWh)

REF

WG CAL

WG UNCAL

C6C (Fully Random, Mid-High)

0

2000

4000

6000

8000

10000

12000

14000

L200EX-C6C

base-case

L200 -

L210EXC6C

air_seal

L200 -

L220EXC6C

attic_ins.

L200 -

L225EXC6C

wall_ins.

L200 -

L240EXC6C

setback

L200 -

L250EXC6C

windows

L200 - L300EXC6C combined

(w.o. shading)

Case

Electricity Use (kWh)

REF

WG CAL

WG UNCAL
114 

Figure G-12. Field trial results for fully random, mid-low cooling scenario (C7C) 

G.2.3 Quantitative Comparison 

Figures G-3 through G-12 are graphical representations of the benefit of calibration. Qualitatively, they 

show that calibration generally improves the accuracy of the average Working Group participant energy 

savings predictions relative to the average reference program energy savings predictions. The 

improvement tends to increase as the difference between uncalibrated energy consumption and reference 

utility bill consumption increases (i.e., as the degree of calibration increases). 

The benefit of calibration (BoC) can be quantified. For example, the mean absolute error for the calibrated 

and uncalibrated energy savings predictions can be calculated using the equations 

[million kWh]or Btu 1

1

=

= −

N

i

WGCALi REF

N

ERRcal (G1) 

[million kWh]or Btu 1

1

=

= −

N

i

WGUNCALi REF

N

ERRuncal (G2) 

Where: 

N = Number of Working Group participant results sets 

 WGCALi = Calibrated energy savings prediction of individual Working Group 

 program 

WGUNCALi = Uncalibrated energy savings prediction of individual Working Group 

 program 

REF = Average reference program energy savings prediction 

The mean absolute error does not distinguish between underprediction and overprediction because the 

absolute value is taken for each residual. 

C7C (Fully Random, Mid-Low)

0

2000

4000

6000

8000

10000

12000

14000

L200EX-C7C

base-case

L200 -

L210EXC7C

air_seal

L200 -

L220EXC7C

attic_ins.

L200 -

L225EXC7C

wall_ins.

L200 -

L240EXC7C

setback

L200 -

L250EXC7C

windows

L200 - L300EXC7C combined

(w.o. shading)

Case

Electricity Use (kWh)

REF

WG CAL

WG UNCAL
115 

The BoC can then be defined as the decrease in mean absolute error of participant energy savings 

predictions: 

BoC = ERRuncal − ERRcal [million kWh]or Btu (G3) 

When BoC is positive, energy savings predictions are improved by calibration. BoC has the same units as 

the consumption [million Btu or kWh] and therefore can be compared to overall energy savings and 

converted to monetary values based on fuel prices. This is one of many approaches that can be used to 

quantify the benefit of calibration. For example, the root mean square error, mean of the residuals, 

standard deviation of the residuals, etc. could be examined in future analysis. 

Table G-3 indicates the sign of BoC (“Y” when BoC is positive, “N” when BoC is not positive) for the 

different fully random scenarios and retrofit measures in the Working Group field trial. 

Table G-3. Benefit of Calibration (BoC) for Working Group Field Trial 

The following observations are based on Table G-3: 

• BoC > 0 for combined retrofit in 10 of 10 scenarios 

• BoC > 0 for attic insulation and wall insulation retrofits in 5 of 5 heating scenarios 

• BoC > 0 for low-e window retrofit in 5 of 5 cooling scenarios 

• BoC > 0 for 6 of 6 retrofits in the C5 (low consumption) space-heating scenario 

• Remaining retrofits and scenarios show mixed BoC

• Cases with greater savings (e.g., insulation in heating climate, windows in cooling climate) have 

greater BoC. 

BoC calculations for the combined retrofit cases (L300EX) are presented in Table G-4 to provide an 

estimate of the benefit of calibration. In addition to the decrease in mean absolute error (million Btu or 

kWh), results are also presented in Table G-4 as a percentage of the average reference energy savings 

prediction (“% Avg Ref Savings”) and as monetary values ($/yr) assuming $12.58/million Btu gas cost 

and $0.116/kWh electricity cost (EIA 2009a, 2009b). Cost conversion factors are discussed in Judkoff et 

al. (2010). 

 

IS BoC > 0? Heating Cooling

C3 C4 C5 C6 C7 C3 C4 C5 C6 C7

Air Seal YNYYYNNYNN

Attic Insulation Y Y Y Y Y N Y N N Y

Wall Insulation YYYYYYYYNY

Programmable Thermostat N Y Y Y N N Y N N N

Low-e Windows N N Y N Y Y YYYY

Combined Retrofit YYYYYYYYYY
116 

Table G-4. Benefit of Calibration for Combined Retrofit Cases (L300EX) 

in Working Group Field Trial

Decrease in Mean Absolute Error of Energy Savings Predictions 

(“BoC,” see Equation G3) 

 Heating, Colorado Springs C3H C4H C5H C6H C7H 

(million Btu) 3.1 16.5 18.6 8.3 6.3 

(% of Avg Ref Savings) 4.5% 18.0% 39.9% 9.8% 10.9% 

($/yr assuming $12.58/million Btu) $39 $208 $234 $104 $80 

 Cooling, Las Vegas C3C C4C C5C C6C C7C 

(kWh) 356.9 395.3 521.8 294.0 457.9 

(% of Avg Ref Savings) 13.0% 10.9% 20.8% 8.5% 17.3% 

($/yr assuming $0.116/kWh) $41 $46 $61 $34 $53 

As seen in Table G-4, calibration decreased the mean absolute error by 3.1–18.6 million Btu (heating) and 

294.0–521.8 kWh (cooling) for the fully random combined retrofit scenarios. In terms of percentage of 

the average reference program energy savings predictions, the decrease ranged from 4.5–39.9% (heating) 

and 8.5–20.8% (cooling). Translated into U.S. dollars assuming conversion factors for gas and electricity 

prices noted above, the benefit of calibration ranged from $39–234 (heating) and $34–61 (cooling). For 

the space-heating retrofits, the benefit was largest for the low and high base-case heating consumption 

scenarios, followed by the mid-low and mid-high scenarios, with the near-nominal scenario showing the 

least benefit. For the space-cooling retrofits, the benefit of calibration is positive, but does not vary as 

greatly with the degree of calibration required for a given scenario. 

The benefit of calibration for the heating cases is generally greater than the benefit for the cooling cases. 

One possible explanation is that the retrofit measures for the cooling cases lead to less energy savings in 

terms of the overall pre-retrofit energy consumption, especially for retrofits that have more impact in 

heating climates. Thus, even with a fairly substantial 9–21% BoC (% of Avg Ref Savings), the economic 

benefit is less substantial. 

G.2.4 Conclusions 

This analysis is one of many approaches that can be used to estimate the benefit of calibration. Results of 

the analysis are specific to the base case house and input ranges defined in the test, as well as to the 

randomly generated scenarios, and to the reference and Working Group simulations used for the 

simulation trial. Additionally, the mean absolute error does not distinguish between underprediction and 

overprediction. In this context, Figures G-3 through G-12 show how calibration affects the average 

energy savings predictions and can be examined for trends in overprediction and underprediction. 
117 

Based on this preliminary analysis, energy savings predictions are generally improved by calibration. 

Improvement is not seen for every retrofit measure and calibration scenario, but calibration tends to 

improve predictions for: 

• Scenarios where there is a large difference between utility bills versus the energy consumption 

predicted using an uncalibrated model (i.e., where a larger degree of calibration is required) 

• Individual retrofit measures with robust energy savings (e.g., insulation in heating climate, 

windows in cooling climate) 

• Combinations of retrofit measures that maximize energy savings. 

G.3 Improvements to Tested Software and Importance of Simulation Trials 

As a result of the BESTEST-EX simulation trials, the working group participants documented eight 

software revisions and two input errors. The proprietary nature of participant programs does not allow 

disclosure of details. However, the working group participants indicated that the diagnostic logic 

associated with specific parameter variations of the test cases helped to isolate problems. Additionally, 

NREL clarified portions of the test specification related to the documented input errors. Therefore, the 

simulation trials are beneficial in that BESTEST-EX is already driving improvements to retrofit software, 

and the simulation trials drive improvements to the test procedure.
118 

Appendix H Definitions 

approximate input: an input for which an approximate input range has been defined; see listing in 

Section 1.3.1.2. Also see approximate input range. 

approximate input range: the specified range of possible values for an approximate input that forms the 

basis uncertainty range for selecting calibrated approximate inputs for the tested programs (see Section 

1.3.1.2), and from which explicit inputs are randomly selected in accordance with the process described in 

Appendix F. Also see calibrated input and explicit input.

calibrated input or calibrated approximate input: inputs for tested programs that are determined based 

on specified approximate input ranges and nominal input values using calibration to obtain agreement 

with base-case reference utility billing data. Also see approximate input range and nominal input. 

cavity albedo: see solar lost through window. 

combined radiative and convective surface coefficient: constant of proportionality relating the rate of 

combined convective and radiative heat transfer at a surface to the temperature difference across the air 

film on that surface. 

direct solar radiation: the solar radiation received from the sun without having been scattered by the 

atmosphere or other objects such as the ground; this is also called beam or direct-beam radiation. 

diffuse solar radiation: the solar radiation received from the sun after its direction has been changed by 

scattering by the atmosphere or other objects such as the ground. 

effective coefficient of performance (COP): the ratio of sensible heat extraction from the space by the 

space cooling equipment divided by the electricity use measured at the meter, including all losses 

associated with system efficiency, air distribution, etc.; latent load is not considered. 

effective heating efficiency: the ratio of heat provided to the space by the furnace divided by the furnace 

gas use measured at the meter, including all losses associated with furnace efficiency, air distribution, etc. 

explicit input: inputs for simulations used to develop reference utility billing data that are randomly 

selected from within specified approximate input ranges according to the process described in Appendix 

F. Also see approximate input range. 

exterior film: as used in Section 1, see combined radiative and convective surface coefficient. 

extinction coefficient: the proportionality constant K in Bouguer’s Law ((dI) = (I K dx)) where I is the 

local intensity of solar radiation within a medium and x is the distance the radiation travels through the 

medium. 

film coefficient: see combined radiative and convective surface coefficient. 

hemispherical infrared emittance: average directional infrared emittance over a hemispherical envelope 

over the surface. Also see infrared emittance. 

incidence angle: angle defined by the intersection of a line normal to a surface and a ray that strikes that 

surface. 

index of refraction: relates the angle of refraction (x2) to the angle of incidence (x1) at the surface 

interface of two media according to Snell’s Law (n1sin(x1) = n2sin(x2)) where n1 and n2 are indices of 

refraction for each medium. 

infiltration: the leakage of air through any building element (walls, windows, doors, etc.). 

infrared emittance: the ratio of the infrared spectrum radiant flux emitted by a body to that emitted by a 

blackbody at the same temperature and under the same conditions. 
119 

interior film: as used in Section 1, see combined radiative and convective surface coefficient. 

interior solar distribution: the fraction of transmitted solar radiation incident on specific surfaces in a 

room. Also see solar distribution fraction. 

internal gains: heat gains generated inside the space or zone.

latent heat: the change in enthalpy associated with a change in humidity ratio, caused by the addition or 

removal of moisture. 

nominal input: an input value as specified for the building physics base case (Case L200EX-P, see 

Section 1.2.1). 

non-proportional-type thermostat: a thermostat that provides two-position (ON/OFF) control. 

raised floor exposed to air: floor system where the air temperature below the floor is assumed to equal 

the outdoor air temperature, the underside of the conditioned zone floor has an exterior film coefficient 

consistent with a “rough” surface texture and zero wind speed, and the conditioned zone floor exterior 

surface (surface facing the raised floor) receives no solar radiation. Also see Section 1.2.1.5. 

sensible heat: the change in enthalpy associated with a change in dry-bulb temperature caused by the 

addition or removal of heat. 

shading coefficient (SC): ratio of solar heat gain coefficient (SHGC) for a given window or window 

system to that for direct normal incident solar radiation for unshaded clear reference glass (SHGC = 

0.87). Also see solar heat gain coefficient. 

shortwave: refers to the solar spectrum; e.g., in this test procedure the terms solar absorptance and 

shortwave absorptance are used interchangeably. 

solar absorptance: the ratio of the solar spectrum radiant flux absorbed by a body to that incident on it. 

solar distribution fraction: the fraction of total solar radiation transmitted through the window(s) that is 

absorbed by a given surface or retransmitted (lost) back out the window(s). 

solar heat gain coefficient (SHGC): a dimensionless ratio of solar heat gains to incident solar radiation, 

including transmittance plus inward flowing fraction of absorbed solar radiation; for windows, SHGC is 

dependent on solar incidence angle. 

solar lost: see solar lost through window. 

solar lost through window: the fraction of total solar radiation transmitted through the window(s) that is 

reflected by opaque surfaces and retransmitted back out the window(s). 

zone air temperature: the temperature of just the zone air, not including infrared radiation from the 

interior surfaces; such a temperature would be measured by a sensor housed in a well-aspirated 

containment shielded by a material with a solar and infrared reflectance of one; well-mixed air is 

assumed. 
120 

Appendix I Recommendations for Future Work 

The BESTEST-EX Working Group (2009-2010) has given NREL many insights into the trends observed 

in the field for retrofit efforts in both the weatherization and private sector contexts. One important 

observation is the tendency for even the most advanced simulation programs to over-predict the energy 

use in pre-retrofit older poorly insulated homes, and to also over-predict savings from retrofits. 

Practitioners in the low income weatherization program, and related utility bill data, indicate that it is not 

uncommon for the prediction of energy usage and savings to be roughly double the average of actual 

measurements (Berry and Gettings 1998; Blasnik 2010; Dalhoff 1997; Pigg 2001; Sharp 1994). It is 

crucial, as the nation embarks on a large scale retrofit effort, to identify and correct the sources of these 

errors. To solve this question, a serious effort is needed to validate building energy simulation programs 

against high quality measured data. Empirical experiments are needed that range from gathering and 

analyzing detailed data (to address resolving building physics modeling related errors), to analyzing large 

statistical samples (to understand the average impact of occupant behavior on energy savings). 

Comparisons with empirical data will drive improvements to the state-of-the-art reference programs used 

in software-to-software comparative tests. Software-to-software comparative tests complement 

comparisons with empirical data because they provide robust capability for diagnosing software errors by 

directly analyzing sensitivity to input variations. (Judkoff and Neymark 2006) Software-to-software 

comparative tests are also useful for identifying simulation input specification requirements needed for 

developing useful comparisons with high-quality measured data (Judkoff et al. 2008; Neymark et al. 

2005). Therefore, in parallel with validating building energy simulation programs versus measured data, 

refinements to and expansion of the BESTEST-EX Phase 1 comparative test cases could address areas of 

building physics modeling and model calibration not covered in BESTEST-EX Phase 1. 

Recommendations for future work related to BESTEST-EX, discussed below, are divided into the general 

categories of: 

• Empirical data checks; see Section I.1. 

• Additional test cases; see Section I.2. 

• Revisions to existing test cases; see Section I.3. 

I.1 Empirical Data Checks 

Initial work on empirical data checking should address the following preliminary questions related to 

using empirical data to quantify the accuracy of simulation tools: 

• What defines good quality empirical data? 

o Satisfactory documentation of billing data and other measurements, and their related 

uncertainties, for accurate comparison with simulation predictions? 

 Is sub-metered data available? 

o Satisfactory documentation of the building, for sufficiently accurate characterization of 

simulation inputs? 

o Satisfactory documentation of occupant behavior? 

o Other? 

• How accessible are various existing data sets? 

• How much existing data is available where specific buildings were sufficiently documented and 

monitored pre- and post-retrofit? 

o Are pre-retrofit audits and post-retrofit testing documentation or audits available? 
121 

• Should new data be gathered in existing homes? 

• Should custom empirical validation experimental facilities be constructed that allow: 

o Empirical determination of simulation inputs? 

o Side-by-side parametric sensitivity tests? 

o Reconfigurable test buildings and instrumentation? 

After addressing comparison of simulation tools with empirical data, the following questions related to 

improving BESTEST-EX to better match empirical data may be addressed: 

• Are there input specifications in BESTEST-EX that need further update based on comparisons 

with reference simulations and existing empirical data? 

• How can BESTEST-EX and its reference simulation results be compared with existing empirical 

data for a given home? 

o Normalize existing data for floor area, climate, and other characteristics? 

• Is it possible to define a separate process for developing a test suite where simulation predictions 

are directly compared with empirical data? 

I.2 Additional Test Cases 

Additional test cases being considered for inclusion in future versions of BESTEST-EX are categorized 

by mechanical equipment and building thermal fabric (enclosure) tests as listed in Sections I.2.1 and I.2.2, 

respectively. Where possible, existing BESTEST/ASHRAE Standard 140 (ANSI/ASHRAE 2007; Judkoff 

and Neymark 1995a, 1995b; Neymark and Judkoff 2002, 2004; Purdy and Beausoleil-Morrison 2003) and 

RESNET (2007) test suites may be considered for direct use, or as the basis for additional cases. 

I.2.1 Mechanical Equipment Tests 

• Space heating equipment 

o System replacement (to higher efficiency) 

o Fuel switching (e.g. air- and/or ground-source heat pumps versus gas-fired furnace or 

hydronic systems) 

o Secondary items: pilot lights, humidifiers, etc. 

• Space cooling equipment 

o Humid climate system replacement 

o Dry climate system replacement 

• Duct sealing and insulation 

• Domestic hot water 

o Tank and pipe insulation 

o System replacement (to higher efficiency) 

o Supply temperature modeling 

• Ventilation 

o Fans 

o Air-to-air heat exchanger 
122 

I.2.2 Building Thermal Fabric (Enclosure) Tests 

• Internal window shading 

• Other floor constructions and related retrofits 

o Vented crawl space/closed, conditioned crawl space 

o HERS BESTEST (Judkoff and Neymark 1995a) slab-on-grade and basement cases 

o IEA 34/43 slab-on-grade tests (Neymark et al. 2008), selected “b”-series and “c”-series 

cases 

• Lighting and household appliances (not including space conditioning and DHW equipment) 

• Thermal mass 

• Hot/humid climate air-seal retrofit. 

I.3 Revisions to Existing Test Cases 

During development of the initial version of BESTEST-EX, a number of possible revisions were 

identified. Possible revisions are categorized by building physics tests and calibration tests as listed in 

Sections I.3.1 and I.3.2, respectively. Changes to building physics tests also affect the calibration tests. 

I.3.1 Possible Revisions to Building Physics Tests 

• Review the outcome of empirical data checks (see above Section I.1) to determine if changes are 

needed to the base building or retrofit specifications to better match empirical evidence. 

• Apply separate types of window retrofits for heating and cooling climates. 

• Revise the default combined interior surface coefficients (for programs that do not automatically 

calculate surface heat transfer); see Appendix C, Section C.1.1.1. 

• Consider refinements to default combined exterior surface coefficients (for programs that do not 

automatically calculate surface heat transfer). 

• Infiltration: 

o Investigate possible causes of the difference between air-sealing retrofit energy savings 

calculated by the reference simulations versus estimates derived from utility billing data; 

see Appendix D, Section D.4. 

o Consider addressing infiltration heat recovery. 

o More detailed examination of ASHRAE (2005) stack and wind coefficients. 

o Investigate varying terrain types and shelter classes. 

o Apply SUNREL’s weather-driven infiltration model to generate its results. 

o Consider reducing effective leakage area in Case L210EX-P by 100 in2

 rather than by 

98.1 in2

 to match L210EX-C, for better benefit of calibration comparison. 

• Apply non-constant ground reflectance to account for the presence of winter snow. 

• Revise the EnergyPlus reference simulations to include more precise window height input; 

preliminary sensitivity tests indicate this would lead to about a 2% increase in the interior 

combined heat transfer coefficient for single-pane window. 

• Add internal mass for furnishings. 
123 

• Include ANSI/ASHRAE Standard 140 (2007) modeler report templates, and consider an 

additional report template to document calibration methods without disclosing proprietary 

information. 

I.3.2 Possible Revisions to Calibration Tests 

• Consider developing a version of the procedure for testing programs with automated calibration; 

such a version would have calibrated savings results available so that results would not have to 

be reviewed by a third party. 

• Apply an 8760-hour varying internal gains schedule, in place of the current 24-hour varying day 

schedule repeated for all days; this adds more realistic difficulty to base-case utility bill 

calibration for the tested programs. 

• Include input uncertainty (approximate input ranges) for window U-value and SHGC. 

• Consider revising the current approximate input ranges; see Appendix F, Table F-1. 

• Include external shading in the space cooling cases. 

• Fix the exterior wall and gable solar absorptance at 0.6; only apply the current solar absorptance 

approximate input range to the roof. 
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Building Energy Simulation Test for Existing Homes (BESTEST-EX); 

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