Field Evaluation of 

Advances in EnergyEfficiency Practices for 

Manufactured Homes

E. Levy, J. Dentz, E. Ansanelli, G. Barker, 

P. Rath, and D. Dadia

ARIES Collaborative

March 2016
NOTICE

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ii

Field Evaluation of Advances in Energy-Efficiency Practices

for Manufactured Homes

Prepared for:

The National Renewable Energy Laboratory

On behalf of the U.S. Department of Energy’s Building America Program

Office of Energy Efficiency and Renewable Energy

15013 Denver West Parkway

Golden, CO 80401

NREL Contract No. DE-AC36-08GO28308

Prepared by:

E. Levy, J. Dentz, E. Ansanelli, G. Barker, P. Rath, and D. Dadia

Advanced Residential Integrated Energy Solutions (ARIES) Collaborative

1776 Broadway Suite 2205

New York, NY 10019

NREL Technical Monitor: Stacey Rothgeb

Prepared under Subcontract No. KNDJ-0-40347-05

March 2016
iii

The work presented in this report does not represent 

performance of any product relative to regulated 

minimum efficiency requirements.

The laboratory and/or field sites used for this work are 

not certified rating test facilities. The conditions and 

methods under which products were characterized for 

this work differ from standard rating conditions, as 

described.

Because the methods and conditions differ, the reported 

results are not comparable to rated product performance 

and should only be used to estimate performance under 

the measured conditions.
iv

Contents

List of Figures ............................................................................................................................................ vi

List of Tables .............................................................................................................................................. ix

Definitions................................................................................................................................................... xi

Acknowledgments ................................................................................................................................... xiii

Executive Summary.................................................................................................................................... 1

1 Introduction........................................................................................................................................... 3

2 Background and Literature Review .................................................................................................... 3

2.1 Literature Review............................................................................................................................. 3

2.2 Research Gaps and Relevance to Building America’s Goals .......................................................... 7

2.3 Research Questions.......................................................................................................................... 7

3 Whole-Building Performance Assessment........................................................................................ 8

3.1 Approach.......................................................................................................................................... 8

3.2 Experimental Method....................................................................................................................... 9

3.2.1 Designs ............................................................................................................................... 9

3.2.2 Acquisition........................................................................................................................ 13

3.2.3 Siting................................................................................................................................. 15

3.2.4 Commissioning ................................................................................................................. 15

3.2.5 Operation .......................................................................................................................... 17

3.2.6 Measurements................................................................................................................... 18

3.3 Monitoring Results ........................................................................................................................ 20

3.3.1 Cooling Season HVAC Energy ........................................................................................ 20

3.3.2 Cooling Season Comfort................................................................................................... 25

3.3.3 Heating Season HVAC Energy......................................................................................... 27

3.3.4 Heating Season Comfort................................................................................................... 32

3.3.5 Whole-House Ventilation ................................................................................................. 35

3.3.6 Moisture Measurements.................................................................................................... 35

3.3.7 Peak Electric Demand....................................................................................................... 38

3.3.8 Co-heat and Tracer Gas Testing ....................................................................................... 40

3.3.9 Heating System COP ........................................................................................................ 44

3.3.10 Humidification Testing ..................................................................................................... 50

3.3.11 Impact of Window Blinds................................................................................................. 54

3.3.12 Impact of Interior Door Position....................................................................................... 56

3.3.13 Convective Heat Transfer Through Open Doors.............................................................. 57

3.4 Data Analysis................................................................................................................................. 60

3.4.1 Climate Locations............................................................................................................. 60

3.4.2 Model Development and Calibration................................................................................ 62

3.4.3 Model Runs....................................................................................................................... 68

3.4.4 Modeling Results.............................................................................................................. 70

3.4.5 Cost Analysis.................................................................................................................... 75

4 Conclusions ........................................................................................................................................ 81

References................................................................................................................................................. 84

Appendix A: Commissioning Test Results ............................................................................................ 86

Appendix B: Monitoring Points and Equipment .................................................................................... 90

Appendix C: Impacts of Transfer Fans ................................................................................................... 92

Appendix D: Impacts of Blind Position................................................................................................... 96

Appendix E: Impacts of Door Position ................................................................................................. 101

Appendix F: Tracer Gas Test Data ........................................................................................................ 130

Appendix G: Co-Heat Testing Data ....................................................................................................... 134

Appendix H: Impacts of Window Blind Position.................................................................................. 137
v

Appendix I: Impacts of Controlled Heater Energy............................................................................... 142

Appendix J: Construction Drawings..................................................................................................... 145

Wall and Roof Insulation Details (House C)...................................................................................... 147
vi

List of Figures

Figure 1. Floor plan................................................................................................................................... 12

Figure 2. Lab house production .............................................................................................................. 13

Figure 3. Window flashing system in House C ...................................................................................... 14

Figure 4. Lab house site........................................................................................................................... 15

Figure 5. House C heat pump fan curve ................................................................................................. 17

Figure 6. Sensible load profiles............................................................................................................... 18

Figure 7. Cooling power relative to outdoor temperature for all three houses (Aug. 29–Sept. 15, 

2014)..................................................................................................................................................... 21

Figure 8. House A cooling energy consumption at various outdoor temperatures (Aug. 29–Sept. 

15, 2014)............................................................................................................................................... 23

Figure 9. House B cooling energy consumption at various outdoor temperatures (Aug. 29–Sept. 

15, 2014)............................................................................................................................................... 24

Figure 10. House C cooling energy consumption at various outdoor temperatures (Aug. 29–Sept. 

15, 2014)............................................................................................................................................... 24

Figure 11. House A room and outdoor temperatures during the typical cooling season (Aug. 29–

Sept. 7, 2014)....................................................................................................................................... 25

Figure 12. House B room and outdoor temperatures during the typical cooling season (Aug. 29–

Sept. 7, 2014)....................................................................................................................................... 26

Figure 13. House C room and outdoor temperatures during the typical cooling season (Aug. 29–

Sept. 7, 2014)....................................................................................................................................... 26

Figure 14. Heating power compared to outdoor temperature for all three houses 

(Jan. 6–13, 2015)................................................................................................................................. 29

Figure 15. House B backup electric resistance heating energy compared to outdoor air 

temperature......................................................................................................................................... 30

Figure 16. House C heat pump, transfer fan, and resistance heating energy compared to ambient 

temperature (Jan. 6–13, 2015) ........................................................................................................... 31

Figure 17. House C resistance heating energy compared to ambient temperature 

(Jan. 6–13, 2015)................................................................................................................................. 31

Figure 18. House C room and outdoor temperatures for the initial heating season analysis (Nov. 

12–17, 2014)......................................................................................................................................... 32

Figure 19. House C room and outdoor temperatures with resistance heat in remote rooms (Jan. 6–

13, 2015)............................................................................................................................................... 33

Figure 20. House A room and outdoor temperatures (Jan. 6–13, 2015).............................................. 34

Figure 21. House B room and outdoor temperatures (Jan. 6–13, 2015).............................................. 34

Figure 22. Moisture content and temperature/relative humidity sensors mounted in wall cavity ... 36

Figure 23. House B wall cavity conditions and wood moisture content (April 2014–April 2015)..... 37

Figure 24. House C wall cavity conditions and wood moisture content (April 2014–April 2015)..... 37

Figure 25. Monthly peak demand during coincident peak hours of the Tennessee Valley Authority 

system ................................................................................................................................................. 39

Figure 26. Monthly peak demand during all hours of the day.............................................................. 40

Figure 27. Tracer gas sampling equipment and sampling tube........................................................... 42

Figure 28. House B refrigerant coil in heating mode showing nonuniform temperatures................ 47

Figure 29. Air handling unit fan power for auto- and high-speed settings......................................... 48

Figure 30. Fan curve based on onetime flow and power measurements ........................................... 48

Figure 31. Comparison of mini-split COP (co-heat measurement method) with auto and high fan 

speeds ................................................................................................................................................. 49

Figure 32. Comparison of mini-split COP (air-side measurement method) with low and high fan 

speeds ................................................................................................................................................. 50

Figure 33. Vertical transfer fan duct........................................................................................................ 52

Figure 34. High, low, and primary room temperature sensors............................................................. 53

Figure 35. Window blinds 50% closed.................................................................................................... 54

Figure 36. Map of climate locations ........................................................................................................ 61

Figure 37. Annual energy consumption comparison—Columbus, Mississippi................................. 70
vii

Figure 38. Annual space-conditioning comparison—Columbus, Mississippi ................................... 71

Figure 39. Annual energy consumption comparison—Knoxville, Tennessee ................................... 72

Figure 40. Annual space-conditioning comparison—Knoxville, Tennessee...................................... 73

Figure 41. Annual energy consumption comparison—Bowling Green, Kentucky ............................ 74

Figure 42. Annual space-conditioning comparison—Bowling Green, Kentucky............................... 75

Figure 43. House C Bedroom 2 temperatures with and without transfer fan operation (cooling 

season) ................................................................................................................................................ 92

Figure 44. House C Bedroom 3 temperatures with and without transfer fan operation (cooling 

season) ................................................................................................................................................ 93

Figure 45. House C living room temperatures with and without transfer fan operation (cooling 

season) ................................................................................................................................................ 94

Figure 46. House C master bedroom temperatures with and without transfer fan operation (cooling 

season) ................................................................................................................................................ 95

Figure 47. House C master bathroom temperatures with and without transfer fan operation 

(cooling season)................................................................................................................................. 95

Figure 48. House C impacts of blind position in Bedroom 2 on room temperature compared to 

outdoor temperature (cooling season) ............................................................................................ 96

Figure 49. House C impacts of blind position on Bedroom 3 on room temperature compared to 

outdoor temperature (cooling season) ............................................................................................ 97

Figure 50. House C impacts of blind position on living room temperature compared to outdoor 

temperature (cooling season) ........................................................................................................... 98

Figure 51. House C impacts of blind position on master bedroom temperature compared to 

outdoor temperature (cooling season) ............................................................................................ 99

Figure 52. House C impacts of blind position on master bathroom temperature compared to 

outdoor temperature (cooling season) .......................................................................................... 100

Figure 53. House A impacts of door position on Bedroom 2 temperature compared to outdoor 

temperature (0.8 cfm/ft2

) (cooling season)..................................................................................... 101

Figure 54. House A impacts of door position on Bedroom 3 temperature compared to outdoor 

temperature (1 cfm/ft2

) (cooling season)........................................................................................ 102

Figure 55. House A impacts of door position on living room temperature compared to outdoor 

temperature (cooling season) ......................................................................................................... 103

Figure 56. House A impacts of door position on master bedroom temperature compared to 

outdoor temperature (0.5 cfm/ft2

) (cooling season)...................................................................... 104

Figure 57. House A impacts of door position on master bathroom temperature compared to 

outdoor temperature (1.2 cfm/ft2

) (cooling season)...................................................................... 105

Figure 58. House B impacts of door position on Bedroom 2 room temperature compared to 

outdoor temperature (0.7 cfm/ft2

) (cooling season)...................................................................... 106

Figure 59. House B impacts of door position on Bedroom 3 room temperature compared to 

outdoor temperature (0.8 cfm/ft2

) (cooling season)...................................................................... 107

Figure 60. House B impacts of door position on living room temperature compared to outdoor 

temperature—aspirator failture open period (cooling season) ................................................... 108

Figure 61. House B impacts of door position on master bedroom temperature compared to 

outdoor temperature (0.5 cfm/ft2

) (cooling season)...................................................................... 109

Figure 62. House B impacts of door position on master bathroom temperature compared to 

outdoor temperature (1.2 cfm/ft2

) (cooling season)...................................................................... 110

Figure 63. House C impacts of door position on Bedroom 2 room temperature compared to 

outdoor temperature (cooling season) .......................................................................................... 111

Figure 64. House C impacts of door position on Bedroom 3 room temperature compared to 

outdoor temperature (cooling season) .......................................................................................... 112

Figure 65. House C impacts of door position on living room temperature compared to outdoor 

temperature (cooling season) ......................................................................................................... 113

Figure 66. House C impacts of door position on master bedroom temperature compared to 

outdoor temperature (cooling season) .......................................................................................... 114

Figure 67. House C impacts of door position on master bathroom temperature compared to 

outdoor temperature (cooling season) .......................................................................................... 115
viii

Figure 68. House A impacts of door position on Bedroom 2 temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 116

Figure 69. House A impacts of door position on Bedroom 3 temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 116

Figure 70. House A impacts of door position on living room temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 117

Figure 71. House A impacts of door position on master bedrdoom temperature compared to 

outdoor temperature (heating season) .......................................................................................... 118

Figure 72. House A impacts of door position on master bathroom temperature compared to 

outdoor temperature (heating season) .......................................................................................... 119

Figure 73. House B impacts of door position on Bedroom 2 temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 120

Figure 74. House B impacts of door position on Bedroom 3 temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 121

Figure 75. House B impacts of door position on living room temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 122

Figure 76. House B impacts of door position on master bedroom temperature compared to 

outdoor temperature (heating season) .......................................................................................... 123

Figure 77. House B impacts of door position on master bathroom temperature compared to 

outdoor temperature (heating season) .......................................................................................... 124

Figure 78. House C impacts of door position on Bedroom 2 temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 125

Figure 79. House C impacts of door position on Bedroom 3 temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 126

Figure 80. House C impacts of door position on living room temperature compared to outdoor 

temperature (heating season) ......................................................................................................... 127

Figure 81. House C impacts of door position on master bedroom temperature compared to 

outdoor temperature (heating season) .......................................................................................... 128

Figure 82. House C impacts of door position on master bathroom temperature compared to 

outdoor temperature (heating season) .......................................................................................... 129

Figure 83. House C Bedroom 2 impacts of controlled heater energy ............................................... 142

Figure 84. House C Bedroom 3 of controlled heater energy.............................................................. 143

Figure 85. House C master bedroom impacts of controlled heater energy..................................... 144

Figure 86. House C master bathroom impacts of controlled heater energy.................................... 144

Figure 87. House A production print (House B is identical.).............................................................. 145

Figure 88. House C mechanical system schematic plan .................................................................... 146

Figure 89. Plan view of wall.................................................................................................................... 147

Figure 90. Top plate (gable wall section).............................................................................................. 147

Figure 91. Roof-to-wall connection (side wall section)....................................................................... 148

Figure 92. Floor-to-wall connection (side wall section)...................................................................... 148

Figure 93. Window sill ............................................................................................................................ 149

Figure 94. House C production print..................................................................................................... 150
ix

List of Tables

Table 1. Summary of Past Lab House Research ..................................................................................... 5

Table 2. Lab House Specifications............................................................................................................ 9

Table 3. Cooling and Heating Equipment Specifications ..................................................................... 11

Table 4. Commissioning Tests ................................................................................................................ 16

Table 5. Cooling Statistics (Aug. 29–Sept. 7, 2014)............................................................................... 22

Table 6. Transfer Fan Run Time (Aug. 29–Sept. 7, 2014)...................................................................... 22

Table 7. Cooling Energy Consumption (Aug. 29–Sept. 15, 2014) ........................................................ 23

Table 8. House A Supply Flows............................................................................................................... 27

Table 9. Heating Statistics (Average Ambient Temperature of 41.3°F) (Nov. 12–17, 2014)............... 27

Table 10. Heating Statistics with Resistance Heat in House C Remote Rooms (Average Ambient 

Temperature of 32.6°F) (Jan. 6–13, 2015)......................................................................................... 28

Table 11. Effective Ventilation Rates ...................................................................................................... 35

Table 12. Wall Cavity Maximum, Minimum, and Average Conditions (April 2014–April 2015) ......... 38

Table 13. Summary of Average Peak Demand Reduction During Peak Hours of the Tennessee 

Valley Authority System .................................................................................................................... 39

Table 14. Testing Schedule...................................................................................................................... 41

Table 15. Tracer Gas Test Results Summary......................................................................................... 43

Table 16. Tracer Gas Test Results Summary—With Systems Operating ........................................... 43

Table 17. Co-heat Test Results Summary (Btu/h/°F)............................................................................. 44

Table 18. Co-Heat Test Results Summary Adjusted for Infiltration..................................................... 44

Table 19. Summary of Heating System COPs........................................................................................ 46

Table 20. Mini-Split Heat Pump COPs at High and Low Fan Speeds .................................................. 49

Table 21. Humidification Test Results .................................................................................................... 51

Table 22. Analysis Period for the Impact of Transfer Fans on Room Temperatures in House C..... 51

Table 23. Transfer Fan Heat Delivery...................................................................................................... 54

Table 24. Window Blinds Analysis Period Conditions.......................................................................... 55

Table 25. Cooling Energy Reduction Due to Window Blinds ............................................................... 56

Table 26. Interior Door Position Analysis Periods ................................................................................ 56

Table 27. Convective Heat Flow Through Open Doors ......................................................................... 57

Table 28. Heat Loss to the Outside During 12 h ................................................................................... 58

Table 29. Heat Transfer into Rooms During 12 h: Calculations........................................................... 58

Table 30. Convective Heat Transfer Through Open Doors: Calculations........................................... 60

Table 31. Climate Locations Selected for Modeling.............................................................................. 61

Table 32. Model Calibration Errora in Space-Conditioning Energy...................................................... 62

Table 33. Envelope Inputs for House A, B, and C.................................................................................. 63

Table 34. Model Inputs—House A ........................................................................................................... 63

Table 35. Model Inputs—House B ........................................................................................................... 65

Table 36. Model Inputs—House C ........................................................................................................... 66

Table 37. Summary of Models ................................................................................................................. 68

Table 38. Assumptions for Model Runs.................................................................................................. 69

Table 39. Incremental Costs..................................................................................................................... 76

Table 40. Energy Savings and Payback—Columbus, Mississippi....................................................... 79

Table 41. Energy Savings and Payback—Knoxville, Tennessee ......................................................... 79

Table 42. Energy Savings and Payback—Bowling Green, Kentucky.................................................. 80

Table 43. Duct Leakage ............................................................................................................................ 86

Table 44. Total System Flow .................................................................................................................... 86

Table 45. Supply Register Flows ............................................................................................................. 87

Table 46. Ventilation Flows ...................................................................................................................... 87

Table 47. House A Envelope Leakage..................................................................................................... 88

Table 48. Transfer Fan Flows—House C ................................................................................................ 89

Table 49. Inventory of Monitoring Equipment, Data Loggers, and Sensors....................................... 90

Table 50. Tracer Gas Test Data.............................................................................................................. 130

Table 51. House A Co-Heat Testing Data.............................................................................................. 134
x

Table 52. House B Co-Heat Testing Data.............................................................................................. 135

Table 53. House C Co-Heat Testing Data.............................................................................................. 136

Table 54. Data Used for Multi-Variable Regression—Blinds Closed Period (Sept. 23‒29) ............. 137

Table 55. Predicted Cooling Energy Calculation with Normalized Data—Blinds Open Period (Aug. 

17‒23)................................................................................................................................................. 137

Table 56. Window Blinds Regression ................................................................................................... 138
xi

Definitions

°F Degree Fahrenheit

AC Air conditioner

ACH50 Air change per hour at 50 Pascals

AIM-2 The Alberta Air Infiltration Model 

ARIES Advanced Residential Integrated Energy Solutions Collaborative

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

Engineers

Avg. Average (tables only)

BEopt V 2.3.0.2 Building Energy Optimization version 2.3.0.3

Btu British thermal unit

CFH Cubic feet per hour

cfm Cubic feet per minute

COP Coefficient of performance

d Day

DHW Domestic hot water

DOE U.S. Department of Energy

EER Energy efficiency ratio

EF Energy factor

ft2 Square feet

h Hour

HSPF Heating seasonal performance factor 

HUD U.S. Department of Housing and Urban Development

HVAC Heating, ventilating, and air conditioning

IECC International Energy Conservation Code

kBtu One Kilo British thermal unit

kg Kilogram

kJ Kilojoule

kPa Kilopascal

kW Kilowatt

kWh Kilowatt-hour

MEF Modified Energy Factor 
xii

min Minute

MMBtu One million British thermal units

N/A Not applicable

s Second

SEER Seasonal Energy Efficiency Ratio

SHGC Solar heat gain coefficient

Temp. Temperature (tables only)

UA value Heat loss over the entire surface area

U-value Overall heat transfer coefficient

W Watt

yr Year

ZEMH Zero Energy Manufactured Home

ZERH Zero Energy Ready Home 
xiii

Acknowledgments

The Advanced Residential Integrated Energy Solutions Collaborative (ARIES) would like to 

thank those who contributed to this effort, including the following:

Lisa Haislip of the Tennessee Valley Authority and Bert Kessler from the Systems Building 

Research Alliance represented the project sponsors, the organizations committed to helping the 

manufactured-homebuilding industry find cost-effective ways to reduce energy use.

Stacey Rothgeb, Michael Gestwick, Lieko Earle, Jon Winkler, and Chuck Booten from the 

National Renewable Energy Laboratory provided invaluable technical guidance and project 

oversight.

A committee comprised of industry representatives provided ideas for and feedback on

approaches to developing advanced building techniques that had both commercial and energy 

savings potential. The group included Bert Kessler of Palm Harbor Homes, Robert Garcia of 

Fleetwood Homes, Mark Ezzo of Clayton Homes, Manuel Santana of Cavco, Jeff Legault of 

Skyline Homes, and Rob Luter of Kinro.

The project team thanks the many people from the Clayton family of companies that built, 

hosted, and assisted with the monitoring and maintenance of the test units, including David 

Brewer, Terry Owens, Brandon Frazier, Tommy Mehger, and Jim Bauer of SEhomes; Gavin 

Mabe of Clayton Homes; and Mike Wade of Cavalier Homes.

The following staff from product suppliers provided timely technical support and donated 

materials and products for the tests: Francis Babineau of Johns Manville, Brian Lieburn and 

Brian Mallon from the Dow Chemical Company, Joe Cefaly and Mike Bush from Mitsubishi 

Electric US, Tom Tjernlund and Tim Hoyez from Tjernlund Fans, Fred Irvin from AccuVent,

Craig Marden from Owens Corning, Mark Tackett from LP Corporation, Steve Richards from 

NORDYNE, and Tom Tracey and Terry Dullaghan from SENCO Brands, Inc.

The ARIES team was also assisted by engineer Kapil Varshney, who provided timely and 

valuable support.
1

Executive Summary

Through field-testing and analysis, this project evaluated whole-building approaches and

estimated the relative contributions of select technologies toward reducing energy use related to

space conditioning in new manufactured homes. Three lab houses of varying designs were built 

and tested side-by-side under controlled conditions in Russellville, Alabama. The tests provided 

a valuable indicator of how changes in the construction of manufactured homes can contribute to 

significant reductions in energy use.

The three side-by-side, unoccupied lab houses included heating, ventilating, and air-conditioning 

systems that simulated sensible loads. Each house represented a commonly specified set of 

features that impacts the energy used for space heating and cooling. The three homes had 

features that reflected the following levels of energy efficiency: a design meeting best-practice 

codes according to the U.S. Department of Housing and Urban Development (House A); a 

manufactured home conforming to typical ENERGY STAR® ratings (House B); and a design

meeting the U.S. Department of Energy Zero Energy Ready Home criteria (House C).

1 Except 

for the differences in the energy-related measures, the prototypes were identical (floor plan, 

orientation, construction). (See Table 2 for specifications.) The side-by-side tests provided a 

wealth of comparative data that yielded the following observations:

• Energy consumption. During the cooling period, House C used half the energy of the other 

houses. House B used slightly less energy than House A for cooling. House B and House C 

consumed about the same amount of heating energy, which was nearly one-third of the 

heating energy consumed by House A.

• Comfort. All three homes operated within indoor comfort guidelines specified by the Air 

Conditioning Contractors of America (±3°F temperature variation from the temperature at 

the thermostat during the cooling period) when the interior doors were open. House C used 

one-third of the heating energy of House A with superior comfort results. Some bedrooms in 

House A and House B had difficulty maintaining temperatures within ±2°F of the set point.

• Propensity for moisture problems. Wall cavity wood moisture content was slightly higher 

in House C than in House B, but it was still well within the safe limits. This was because of

the addition of exterior foam insulation to the walls in House C. (The expanded polystyrene 

foam insulation reduces the overall vapor permeability of the walls.) However, compared to

House B, the use of foam sheathing on House C also resulted in an average higher 

temperature (5.5°F) on the interior face of the foam during the heating season, mitigating 

condensation risk. Note that latent loads were not simulated.

• Peak load performance.

2 Peak demand in House C was significantly lower than it was in

the other two houses throughout the year. House B had somewhat lower peaks than did 

House A during most months. House A and House B winter peaks were similar during the 

winter months, suggesting that House B’s peak occurred when the heat pump was not 

operating and the house was relying solely on electric resistance backup. On average, during 

 1 House C was the first manufactured home in the United States to qualify for Zero Energy Ready Home 

designation.

2 Comments regarding peak load refer only to the demand resulting from the operation of the space-conditioning and 

ventilation equipment.
2

peak hours for the Tennessee Valley Authority system, House B had an 18% lower peak 

demand than House A, and House C had a 69% lower peak demand than House A.

• Real-world performance of heat pumps. The heating coefficient of performance (COP)

was calculated for both heat pumps using two independent methods: (1) airflow and 

temperature measurements and (2) co-heat testing measurements.

3 The co-heat testing

method was deemed more reliable. Using this method, the COP of both the traditional splitsystem heat pump and the ductless mini-split averaged approximately 2.5. This was well 

below what would be expected for the mini-split based on manufacturer data. However, 

when the mini-split air handling unit fan was forced to run on high speed, its COP increased 

to 4.11, indicating that low airflow could have been a cause of poor heat pump performance 

with this unit.4

• Estimate of costs and benefits. The cost premiums to the manufacturer (counting only the 

energy-efficiency measures) to build House C compared to House A and House B were 

$2,060 and $1,166, respectively. The price premiums for the homebuyer to purchase House 

C compared to House A and House B would be $6,607 and $4,339, respectively, assuming

that the houses were in regular production. The energy savings of House C compared to 

House A and House B range from 5.3 to 16.0 MMBtu/yr when they are located in 

International Energy Conservation Code Zone 3 and Zone 4. Within this range of conditions, 

the simple paybacks to the homebuyer associated with building House C compared to House 

A and House B ranged from approximately 8.8 to 17.5 yr.

 3 Co-heat testing was used to measure whole-house heat loss and therefore effective envelope U-values. These data 

were used to tune the simulation parameters. 4 It was not determined whether this finding can be generalized to other mini-split heat pumps.
3

1 Introduction

Through field-testing and analysis, this project evaluated whole-building approaches and

estimated the relative contributions of select technologies toward reducing energy use related to

space conditioning in new manufactured homes. Three unoccupied lab houses of varying designs 

were built and tested side-by-side under controlled conditions in Russellville, Alabama 

(International Energy Conservation Code [IECC] Climate Zone 3).

The tests compared the performance of the three houses (referred to herein as House A, House B,

and House C) built to different levels of thermal integrity. These tests allowed for a side-by-side 

comparison of actual whole-house performance focusing on the impacts that changes in envelope 

construction and heating, ventilating, and air-conditioning (HVAC) and distribution systems 

have on space-conditioning energy use. The houses had the following features: (1) House A was 

designed to best-practice thermal standards according to the U.S. Department of Housing and

Urban Development (HUD) and equipped with an electric furnace and a split-system air 

conditioner; (2) House B was designed to comply with the requirements of the ENERGY STAR®

program for manufactured homes, including an improved thermal envelope and a conventional 

split-system heat pump; and, (3) House C was designed to qualify for Zero Energy Ready Home

(ZERH) designation according to the U.S. Department of Energy (DOE) and included a highefficiency, single-point, ductless mini-split heat pump with a transfer fan distribution system 

instead of the traditional duct system for distribution. House A and House B used a standard duct 

system for air distribution.

2 Background and Literature Review

Energy is one of the major contributors to homeownership costs, and high energy costs create a 

pronounced financial burden on households that have modest incomes. Manufactured homes in 

particular are susceptible to excessive energy costs because industry energy standards, nationally

promulgated by HUD, were last updated in 1994. Programs such as ENERGY STAR and DOE’s

ZERH showcase ways to improve home efficiency and reduce energy costs. These efforts often 

incur higher construction costs (associated with enhanced efficiency) to achieve lower energy 

bills, a combination designed to yield lower net monthly homeowner costs.

2.1 Literature Review

In pockets of activity throughout the nation, researchers have conducted or are conducting field 

tests to explore better ways to build affordable, durable, comfortable, energy-efficient homes.

These activities include a few studies using manufactured homes. Some include field-testing 

homes that have varying envelope characteristics and an array of high-performance HVAC 

systems. A few of these efforts are described below.

• Research that sought to estimate the energy savings associated with changes in building 

envelope characteristics and HVAC system efficiency includes work by Oak Ridge National 

Laboratory (Gehl et al. 2012) comparing three site-built side-by-side homes in Farragut, 

Tennessee, that had similar floor plans. One home was a typical builder house, the second 

contained high-efficiency HVAC system components (including an air source heat pump and

sealed and insulated attic ducts fully inside the conditioned volume), and the third was built 

using optimum-value framing construction and was equipped with photovoltaic panels and a 
4

solar water-heating system. To simulate occupant load, the researchers programmed 

appliances, lights, and plug loads to run on a set schedule based on the Building America 

Research Benchmark protocol (Hendron and et al. 2006) (Hendron and Engebrent 2009). 

Compared to the standard home, Home 2 and Home 3 used 37% and 67% less energy, 

respectively.

• Similarly, Chasar, Chandra, and Parker et al. (2006) and Chasar, Chandra, and VanSchramm 

et al. (2010) compared three identical site-built homes of approximately 2,000 ft2 in San 

Antonio, Texas, a location that experiences both semiarid and humid subtropical conditions. 

Temperature and humidity data were recorded, and energy use was measured at a subsystem 

level, including heating, cooling, hot water, and major appliances. One of the homes was 

built to builder standard practice and served as the control home, and the other homes 

contained high-performance features. Researchers recorded utility peak electric load 

comparisons to assess the merits of various envelope and equipment improvements. The 

control home used natural gas for space and water heating, whereas one of the improved 

homes was equipped with a high-efficiency heat pump. Energy ratings for the homes yielded 

E-Scales (analogous to a Home Energy Rating System index) of 86 for the control home, 54 

for one improved home, and 37 for the third home. (The latter included a 2.4-kW 

photovoltaic array.) Relative to the control home, cooling energy savings ranged from 55% 

to 77% for the two improved homes. Total demand reductions observed from the control and 

improved homes ranged from 6 to 8 kW (62% to 83%) on the hottest day during the utility 

peak period. Peak air-conditioning loads in the improved homes on the same day were 

reduced by 1.2 to 2.9 kW (28% to 68%) compared to the control. A 2.4-kW grid-tied 

photovoltaic array on one home provided 60% of total electric energy needs during the 

hottest months, although the home was unoccupied during this period. During subsequent 

months when the home was occupied, the array provided approximately 30% to 40% of the

total home electric needs.

• In a study performed in Grand Forks, North Dakota (Chasar et al. 2004), eight duplex units 

were built with the goal of achieving up to 50% energy savings compared to the 1993 Model 

Energy Code. The actual comparison of energy use was provided by simulation with key data 

(such as infiltration rates) supplied by the field study. Of the eight homes, four were tighter 

and had more efficient HVAC systems and appliances than the Model Energy Code design,

and four were progressively tighter than the first group. The results were the basis for costeffectiveness assessments. Combined gas and electric savings compared to the base case 

ranged from 25% (first group of homes) to 35% (second group).

• The Florida Solar Energy Center (2004) in association with North Carolina Agricultural and 

Technical State University compared the energy used by two manufactured homes placed 

side-by-side in a controlled field study. One home conformed to HUD standards; the other 

contained measures intended to reduce energy use by approximately 50%. Modeling with 

Energy Gauge software predicted heating, cooling, and domestic hot water (DHW) savings 

of 57%; and field measurements yielded 53% savings. The homes were unoccupied, and the 

internal loads were simulated by incandescent lights on timers.

• The Zero Energy Manufactured Home (ZEMH) project examined two occupied, 1,600 ft2

,

double-section manufactured homes using identical floor plans (Lubliner and Hadley 2007).

Remote monitoring equipment was installed to track the performance of each home during a 
5

3-yr period. Both homes were built in 2002 by Kit Manufacturing. A comparison home was 

built to ENERGY STAR program requirements as part of the Northwest Energy Efficient 

Manufactured Housing Program. Total energy use of the ZEMH was 29.4 kWh/d, with 7.7 

kWh/d was covered by the photovoltaic array. The ZEMH showed 9% less energy use per 

year than the ENERGY STAR home, with 44% less space-heating energy consumption

despite having a higher occupant load than the ENERGY STAR home. The results were not 

normalized for occupant behavior.

• Pacific Northwest National Laboratory (2010) compared two identical, 1,500 ft2

manufactured homes located side-by-side to measure the impact of a variety of energy-saving 

measures on energy use and peak demand. A baseline home served as a control, typifying an 

average existing home in the Pacific Northwest. The second home was used to test new 

technologies. Occupancy was simulated following the protocol developed by the Pacific 

Northwest National Laboratory (Hendron and Engebrent 2009). Among the technologies 

evaluated were highly efficient windows (R-5) projected to save approximately 13% of the 

total whole-house energy use and reduce cooling-season peak demand by approximately 

25%. High-performance windows were also shown to improve thermal comfort through the 

moderation of radiant loads. However, the measure is expensive, and it has a long payback 

period (23 to 55 yr). The work continues, and the Pacific Northwest National Laboratory 

team plans to test other measures, including heat pump water heaters and low-emissivity 

storm windows. Table 1 summarizes the studies mentioned above and energy savings 

achieved.

Table 1. Summary of Past Lab House Research

Author(s) Location Description of Houses Home 

Size 

(ft2)

Occupancy 

Simulation 

(Yes/No)

Savings 

Relative 

to Case 1

Oak Ridge 

National 

Laboratory

(2011)

Farragut, 

TN

1. Typical builder house

2. Used energy-efficient 

appliances, windows, air-to-air 

heat pump, and insulated attic

3. Built using optimum-value 

framing construction with 

photovoltaic modules and solar 

water heating.

2,400 Hendron’s (2009) 

test protocol was 

used to simulate 

occupancy in all 

three houses 

throughout the 

testing period.

37% (2)

67% (3)

Chasar et al.

(2010)

San 

Antonio, 

TX

1. Typical builder house

2. High-performance home with 

9.5 HSPFa/18 SEERb heat pump, 

tankless DHW boiler, 100% 

fluorescent lights on 

timers/occupancy sensors, and 

energy-efficient appliances

2,000 All three houses 

were occupied

during most of 

the testing time.

55% (2)

77% (3)
6

Author(s) Location Description of Houses Home 

Size 

(ft2)

Occupancy 

Simulation 

(Yes/No)

Savings 

Relative 

to Case 1

3. Same as House 2 but with a 

tighter shell.

Chasar et al.

(2010)

Grand 

Forks, ND

1. Typical builder house (R-19 

wall insulation)

2. As above with tighter shell 

(2.8 ACH50c), 70% efficient 

energy recovery ventilator

3. As above with R-25 wall 

insulation, 2.4 ACH50 

infiltration.

1,840 Only computer 

models were used 

for each house; a 

theoretical base 

case house built 

to local minimum 

standards was 

devised to 

determine the

energy savings 

and costeffectiveness.

25% (2)

35% (3)

Florida 

Solar 

Energy 

Center

(2004)

Greensboro, 

NC

1. Basic HUD code standard

2. 50% more energy efficient.

1,528 The house 

included

incandescent 

lights for 1.5 

persons. Hot 

water draws were

twice per day.

53%‒

58% (2)

Lubliner/

Florida 

Solar 

Energy 

Center

(2007)

Cherry 

Lane, ID

1. ENERGY STAR HUD code 

home

2. ZEMH, built with highly 

efficient, cutting-edge 

technologies, including 

photovoltaic system, sun

tempering, solar water heating, 

heat recovery ventilator, and 

other ENERGY STAR

appliances.

1,600 No occupancy 

simulation or 

normalization

was done. The 

number of 

occupants in the

ZEMH was 

greater than it 

was in the 

ENERGY STAR

home.

9% (2)

a Heating seasonal performance factor

b Seasonal Energy Efficiency Ratio

c Air change per hour at 50 Pascals
7

2.2 Research Gaps and Relevance to Building America’s Goals

Relatively few efforts aimed at improving energy performance have looked at the challenge from 

a factory-built perspective and in particular the manufactured-home perspective. The best 

approaches for reducing energy use, improving indoor air quality, and increasing durability in 

homes constructed on-site are sometimes different from those built off-site. For example, the 

selection, design, and installation of the HVAC equipment and related distribution system are 

unique to factory building, and when they are viewed from an energy-efficiency standpoint they

are a weak link.

Building America has a goal of developing cost-effective home-technology solutions to reduce 

whole-house source energy consumption by 50% compared to the 2009 IECC. This effort aims 

to do so for space-conditioning energy in an affordable-housing segment. This work builds on 

knowledge related to the performance of point-source space conditioning for low-load homes, an 

area on which a number of Building America teams have focused. A thorough summary of the 

Building America literature on this subject is included in work by Building Science Corporation

(Ueno and Loomis 2015). Additionally, this work examines the impact of changes in thermal 

performance on collateral issues, particularly moisture performance, continuing the systems 

approach deeply embedded in Building America research.

2.3 Research Questions

This project addressed the following research questions:

• Can factory-built, manufactured homes meet the ZERH program requirements as defined? If 

not, what changes are suggested in the ZERH specifications to better reflect and take 

advantage of the unique aspects of factory building?

• What are the added costs and energy savings for manufactured ZERHs using ductless minisplit heat pumps compared to homes that adhere to best-practice HUD codes and ENERGY 

STAR manufactured homes?

• How does point-source space conditioning perform in a ZERH in terms of comfort? How do 

operational variables, such as opening and closing interior doors and window blinds and the 

operation of transfer fans, impact performance in heating and cooling modes?

• What is the in-situ coefficient of performance (COP) in heating and cooling modes of a 

ductless mini-split heat pump?
8

3 Whole-Building Performance Assessment

This section profiles the whole-building assessment process conducted during a full heating and 

cooling season in Russellville, Alabama. The discussion covers the approach and process for 

setting up the experiment (house design and procurement, siting, commissioning, operation and 

monitoring protocol), results, and data analysis. 

3.1 Approach

Three manufactured homes were built and colocated on a site adjacent to the SEhomes homebuilding facility in Russellville, Alabama. The houses varied only in the technologies being 

evaluated. They were operated for 15 months, and data was intensively monitored. The 

experiment assessed the following strategies for reducing energy use:

1. Thermal envelope technologies. The manufactured-home walls use exterior rigid foam 

insulation, enhanced air sealing, and highly insulated low-slope roofs utilizing a new 

dense-pack roof insulation technique.

2. Site-installed heat pumps. Site-installed, split-system heat pumps are used in the 

construction of manufactured homes in the Southeast, the location of the tests, and they

are required for homes qualifying for ENERGY STAR designation. However, their 

contribution toward energy use reduction and the specific performance characteristics of 

heat pumps when used with homes adhering to HUD code have not been verified in the 

field.

3. Ductless mini-split heat pumps. Ductless heat pumps can be fully installed and 

commissioned during home manufacturing in the plant and transported to the site, ready 

for operation. They are used in place of a typical furnace and split-system cooling 

equipment; the latter are completed at the site during the home setup. Ductless heat 

pumps offer the following advantages:

A. By replacing central ducted systems, ductless heat pumps eliminate the associated 

distribution issues and comfort problems that often accompany poor supply 

register locations and losses due to duct leakage.

B. They typically incorporate inverter-driven compressors and variable-speed fan 

technology, which results in very high efficiencies of up to 27 SEER and 12.5 

HSPF, much higher than standard heat pumps.

C. They free up space within the home usually devoted to heating and cooling 

equipment.

D. They provide both heating and cooling, offering a total space-conditioning 

solution in a single device.

E. They can be fully installed in the plant. This ensures that the home will have a 

heat pump, and it enables strict plant oversight and inspections that guarantee 

consistent installation quality and proper commissioning.

F. A single, wall-mounted outside compressor can be connected to numerous 

independently controlled air handling units, which facilitates flexible zoning of 

spaces and reduces over-/under-space conditioning.
9

G. The compressor is mounted outside, which reduces interior noise compared to 

most compact, unitary air-conditioning/heat pump systems.

H. They eliminate the possibility of mismatched indoor and outdoor equipment. 

I. They are available in small capacities (as low as 9,000 Btu/h) that are suitable for 

low-load buildings, such as small manufactured homes.

3.2 Experimental Method

3.2.1 Designs

Three side-by-side lab houses were built in Russellville, Alabama: one that conforms to bestpractice HUD standards (House A), one that complies with the manufactured-home ENERGY 

STAR program (House B), and one that meets DOE’s ZERH criteria (House C). The prototypes 

were identical (floor plan, orientation, construction) except for the differences associated with 

the measures listed in Table 2. Construction drawings are provided in Appendix J.

Table 2. Lab House Specifications

Items House A House B House C

Floor R-14 fiberglass 

blanket

R-28 fiberglass 

blanket

R-28 fiberglass blanket

Flooring 60% carpet; 40% vinyl 60% carpet; 40% vinyl 60% carpet; 40% vinyl

Wall 1⁄2-in vinyl-covered 

drywall, R-11 

fiberglass batts, 1⁄4-in

ThermalStar board (R1) (perm rating >5),

light-colored vinyl 

siding

1⁄2-in vinyl-covered 

drywall, R-13 

fiberglass batts, 1⁄4-in

ThermalStar board (R1) (perm rating >5), 

light-colored vinyl 

siding

1⁄2-in vinyl-covered 

drywall, R-13 + R-5 (1-in.

extruded polystyrene)

(perm rating 1.5),lightcolored vinyl siding

Windows U: 0.47, SHGC: 0.73;

single pane, metal

frame 

U:0.31, SHGC: 0.33, 

double pane, vinyl 

frame, low-emissivity,

air filled

U: 0.30, SHGC: 0.23, 

double pane, vinyl frame, 

low-emissivity, argon

filled

Ceiling R-22 blown fiberglass, 

vented roof cavity 

with asphalt shingles

R-33 blown fiberglass, 

vented roof cavity 

with asphalt shingles

R-45 blown fiberglass, 

dense-packed at eaves, 

vented roof cavity with 

asphalt shingles

Air Sealing Standard plant practice 

including foaming 

ceiling penetrations, 

caulking under bottom 

plates and between top 

plates and ceiling, 

marriage line gasket

Standard plant practice 

including foaming 

ceiling penetrations, 

caulking under bottom 

plates and between top 

plates and ceiling, 

marriage line gasket

Standard plant measures 

plus foaming around 

window and door rough 

openings, patching/ 

foaming floor 

penetrations, taping foam 

sheathing joints, caulking 
10

Items House A House B House C

foam sheathing to top and 

bottom plates, spray foam 

along marriage line

Mechanical 

Ventilation

Fresh air duct to air 

handling unit, no 

mechanical damper

Fresh air duct to air 

handling unit, no 

mechanical damper

45 cfm exhaust fan

SpaceConditioning 

Distribution

Metal in-floor ducts

sealed with mastic, R8 crossover duct 

between home 

sections

Metal in-floor ducts

sealed with mastic, R8 crossover duct 

between home 

sections

BR2 and BR3: Tjernlund

AS1 transfer fan, 21 W

MBR and MBath: 

Tjernlund AS2 transfer 

fan, 33 W
11

Table 3. Cooling and Heating Equipment Specifications

House A House B House C

Cooling 

Equipment

Intertherm DS4BD024KB

Cooling coil: C8 (B,D) 

AM01830U-B

Cooling capacity: 23.4

kBtuh

EER: 11.0

SEER: 13.0 

Intertherm air source 

heat pump DT4BD018K with backup 

electric resistance 

heaters

Cooling coil: C8 (B,

D) AM01830U-B

Cooling capacity: 18 

kBtuh

EER:11.0

SEER: 13.0

Heating capacity at 

47°F: 20.2 kBtuh; 

HSPF: 8.0

Heating capacity at 

17°F: 11.5 kBtuh

Mitsubishi variable-speed 

mini-split heat pump with 

outdoor unit assisted by 

temperature-controlled 

heaters when temperature 

falls below 69°F in the 

bedrooms

Outdoor unit: MUZFH15NA

Indoor unit: MSZFH15NA

Cooling capacity: 15 

kBtuh

EER: 12.5

SEER: 22.0

Heating capacity at 47°F: 

18 kBtuh; HSPF: 12.0

Heating capacity at 17°F: 

11 kBtuh

Heating 

Equipment

NORDYNE electric 

furnace, E3EB-010H, 

downflow set to low 

speed

Resistance heating 

capacity: 35 kBtuh

Air Handling 

Unit

NORDYNE electric 

furnace, E3EB-010H, 

downflow set to low 

speed

Resistance heating 

capacity: 10 kW

Air handling unit

wattage (heating 

elements +

blower):10.4 kW

NORDYNE electric 

furnace, E3EB-010H,

downflow set to low 

speed

Resistance heat 

capacity: 10 kW

Air handling unit

wattage (heating 

elements +

blower):10.4 kW

The floor plan for House A and House B is shown in Figure 1. The only changes to House C 

were the elimination of the furnace, relocation of the water heater to the furnace closet (to reduce 

DHW pipe lengths), and enlargement of the Bedroom 2 closet to include the former water heater 

compartment.
12

Figure 1. Floor plan
13

3.2.2 Acquisition

The homes were purchased from a single manufacturing plant and inspected during manufacture 

to ensure that the construction methods were consistent and uniform (Figure 2).

Figure 2. Lab house production
14

To ensure maximum protection against moisture and minimize envelope infiltration, window 

flashing systems were applied to the extruded polystyrene, as shown in Figure 3.

Figure 3. Window flashing system in House C
15

3.2.3 Siting

The homes were installed adjacent to the manufacturing plant for a period of approximately 15

months. The orientation and solar exposure were identical for all homes (Figure 4).

Figure 4. Lab house site

3.2.4 Commissioning

The homes were commissioned for the monitoring effort by establishing baseline conditions. A 

summary of commissioning test results is provided in Table 4, with additional details in

Appendix A. Due to the influence of ENERGY STAR requirements on manufactured homes, 

most of the manufactured-home plants in the United States use similar techniques for reducing 

enclosure and duct leakage in all newly constructed homes. Therefore, the enclosure leakage in 

House A is nearly the same as it is in House B. Thus, compared to older manufactured homes in 

the field, House A is considered a best-practice HUD home.
16

Table 4. Commissioning Tests

Test Equipment/Method Results

Enclosure 

Leakage 

Energy Conservatory blower door 

multipoint depressurization test

A: 4.7 ACH50

B: 4.6 ACH50

C: 3.8 ACH50

Duct Leakage Energy Conservatory duct blaster 

depressurization test

A: 54 cfm25 to outside

B: ~10 cfm25 to outside

C: N/A

Ventilation Rate Energy Conservatory FlowBlaster 

A: 44 intermittent

B: 32 intermittent

C: 45 continuous

Air Handling 

Unit Air Flow Energy Conservatory duct blaster

A: 980 cfm

B: 1,000 cfm 

C: variable

Supply Register 

Air Flows Energy Conservatory FlowBlaster See Appendix A

Note that the air handling unit air flow rates for House A and House B are high relative to the 

loads for optimal humidity control, even at the lowest speed. Nevertheless, this was the plant’s 

standard air handling unit used for production homes. This would result in lower moisture

removal in an occupied home; however, latent loads were not simulated in these unoccupied lab 

homes.

Air flow rates at a variety of power draws were measured for the variable-speed mini-split heat 

pump air handling unit in House C. These flows were later used in the investigation of heat pump 

COP. The resulting fan curve is shown in Figure 5.
17

Figure 5. House C heat pump fan curve

3.2.5 Operation

The homes were operated in an identical manner, including interior temperatures and simulation 

of occupant loads.

• Primary thermostat set points. The heating set point was 71°F, and the cooling set point 

was 76°F. To maintain an average house temperature (average of all rooms) of 76°F during 

the cooling season, the heat pump in House C was placed on a setback schedule of 75°F from 

8:00 p.m. to 10:00 a.m. and 73°F from 10:00 a.m. to 8:00 p.m. This was necessary to obtain 

average space temperatures comparable to House A and House B.

• Secondary heating (House C) set point. Auxiliary electric resistance heaters were used to 

supply backup heat to the House C bedrooms and master bathroom. These heaters were set to 

9°F.

• Transfer fans (House C) set point. Through-wall transfer fans in House C were set on 

independent thermostats in each room to which the fans delivered air. These thermostats 

were set to activate the fan at an upper set point of 76°F during the cooling season and at 

69°F during the heating season. Short-term tests were conducted with the fans deactivated to 

study their impact on room temperatures and energy use. Thermostat control was used so 

fans would run only when heating or cooling was needed in the rooms they served.

• Occupant loads. Sensible internal heat gain was simulated through the use of electric 

resistance heaters controlled by the data loggers. Figure 6 shows the schedule of loads.

Latent internal heat gains can also impact energy consumption and comfort; however, latent 

loading is more complex to simulate. Latent loads have been simulated through the use of 

ultrasonic humidifiers by the National Renewable Energy Laboratory (Fang et al. 2011). It was 

estimated that these homes would require approximately 1.5 gal/d of water delivered to the air. 

Because the homes were in a remote location and not attended regularly, there was limited 

opportunity to inspect the humidification equipment. Further, the homes were not connected to 
18

water service. Because the systems would have had to run unattended for long periods, large 

water tanks (100‒200 gal per home) using deionized water would have been required to reduce 

the need for humidifier maintenance, or frequent descaling would have been required. Risks 

associated with this approach include undetected leaks, malfunction of the humidification 

system, and biological growth in the water tanks. Therefore, internal latent loads were not 

simulated. However, a short-term humidification test was conducted in each home to assess the 

dehumidification capability of the equipment.

It is acknowledged that this may lead to greater variability in the results; eliminating latent 

internal loads could potentially impact the three houses differently. Additionally, measurements 

of moisture levels in the wall cavities were possibly underestimated along with attendant risks of 

condensation.

Figure 6. Sensible load profiles

• Interior doors. Because the field data was compared to single-zone Building Energy 

Optimization software (BEopt) model simulation, the interior doors were kept open for the 

majority of the testing period. To characterize the temperature distribution across the homes 

with the doors closed, short-term tests (5‒10 d) were conducted during the cooling and 

heating seasons with the doors closed.

• Window blinds. For the majority of the monitoring period, the blinds were kept 50% closed. 

Short-term tests were conducted with the blinds fully open and fully closed.

3.2.6 Measurements

The homes were monitored for 15 months with 1-min data uploaded on a daily basis. CR1000 

data loggers in conjunction with multiplexers were used for the data acquisition. Key metrics, 

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

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

W/h

Hour of Day

Sensible Gain Heater

Main

Sensible Gain Heater

Bedrooms
19

such as equipment operation and internal temperatures, were reviewed periodically to verify that 

the homes were operating as intended. Monitoring points and equipment included the following

(see also Appendix B):

• Air temperature. Watlow T-type thermocouples in conjunction with aspirated shields were

used to measure space air temperatures at five locations in each home at 5 ft above the floor 

(mounted on tripods) and at least 5 ft away from the heating/cooling/air distribution systems 

and exterior walls. A crawl space temperature sensor was placed at the center of the crawl

space approximately 1.5 ft above grade. An attic air temperature sensor was placed at the 

center of the attic above the insulation.

• Air temperature and relative humidity. A Campbell Scientific CS215 temperature and 

relative humidity probe was used to measure the temperature and relative humidity at one 

location in each home. The same sensor type was also used to measure the outdoor air 

temperature and relative humidity at one location in all three homes. To protect the outdoor 

sensor from the elements, a protection shield was used.

• Condensation. In House B and House C, Campbell Scientific CS215 temperature and 

relative humidity probes were used to measure the air temperature and relative humidity of 

the surface between the exterior sheathing (extruded polystyrene insulation) and interior 

fiberglass insulation on a north-facing wall approximately 32 in. above the floor. An 

Omnisense S900-1 sensor was used to measure the moisture content of the lower exterior 

corner of a stud in the same north-facing wall. The data from these sensors was used to

predict the propensity for moisture accumulation in the exterior wall.

• Power consumption. Power current transducers in conjunction with Wattnode energy-topulse transducers measured the power of HVAC equipment and total house power.

• Status. Hawkeye 300 (Veris H300) go/no-go current switches were used to measure the 

status of the reversing valves of the heat pumps.

• Current. The compressor and fan current were measured by Veris H721LC sensors.

• Solar radiation. A Campbell LI200X-L silicon pyranometer was used to measure the solar 

radiation at the site.

In addition to the long-term monitoring system, a series of short-term measurements were made:

• Co-heat testing. Short term co-heat testing in cold weather using portable electric resistance 

space heaters was conducted in all three houses to measure whole-house heat loss. The test 

data was used to obtain envelope U-value (overall heat transfer coefficient) information in 

each house and provide better quantification of simulation parameters. During the test, six 

portable heaters (one in each bedroom, one in the master bathroom, one in the living room, 

and one in the kitchen) were used to maintain 70°F throughout the test. Other heating 

equipment was switched off. Temperature sensors were used to turn the heaters on and off 

through the Campbell Scientific data loggers.

• Tracer gas decay testing. Infiltration was measured in all three homes utilizing tracer gas.

The objectives of the tracer gas testing were to determine infiltration levels in all three
20

houses for calibrating models and quantifying the effectiveness of the ventilation systems in 

all three houses.

• Humidification testing. The dehumidification capability of the equipment was tested. The 

objective of this test was to measure the humidity levels in each house during near-peak 

humidity conditions to assess the capability of the cooling equipment to maintain comfort 

conditions.

3.3 Monitoring Results

This section describes the results of the tests noted above. It characterizes typical performance in 

terms of HVAC energy consumption, comfort, moisture, and peak energy demand. The analysis 

section that follows generalizes the data to annual whole-house energy consumption at various 

locations using calibrated energy models.

3.3.1 Cooling Season HVAC Energy

A representative cooling season period that exhibited a wide range of outdoor temperatures was 

selected for analysis. During this period—from August 29, 2014, through September 15, 2014—

the interior doors were open and the window blinds were 50% closed.

A plot of cooling power relative to ambient temperature for this period shows that House C used 

less cooling energy than did the other houses at outdoor temperatures in excess of approximately

24°C (75°F) (Figure 7). House B used somewhat less cooling energy than did House A when 

temperatures rose above approximately 25°C. At lower temperatures, House A used less cooling 

energy than did House B. This inversion may have occurred because House A’s lower insulation 

values and higher ventilation rate allowed more natural cooling, whereas the better insulated 

House B held the heat longer. (Both homes had similar airtightness.) This was especially 

prevalent after sunset when the lower solar heat gain through the windows of House B no longer 

provided an advantage over House A. 
21

Figure 7. Cooling power relative to outdoor temperature for all three houses

(Aug. 29–Sept. 15, 2014)

Table 5 summarizes the cooling performance of all three houses. During this typical summer 

period, House C used half as much HVAC energy as did the other houses. House B used slightly 

less than House A did for cooling. Average indoor temperatures were similar and close to 

thermostat set points. Average relative humidity was slightly higher in House C, but it was still 

within acceptable limits. Note that during this period House C’s fresh air ventilation rate was 

approximately 3.5 times higher than that of the other houses (meeting the American Society of 

Heating, Refrigerating, and Air-Conditioning Engineers [ASHRAE] Standard 62.2-2010), which 

contributed to the higher humidity. If ventilation rates in House A and House B were to have met 

the standard, the difference between the cooling energy consumption of House C and the others 

would have been greater. Also, although relative humidity was higher in House C, it is likely that 

other indoor air quality pollutant levels were lower because of the higher fresh-air ventilation

rate.
22

Table 5. Cooling Statistics (Aug. 29–Sept. 7, 2014)

House A House B House C

Total Cooling (Avg. kWh/d) 15.0 14.5 7.4

Average Indoor Temp. (°F) 76.4 75.9 75.4

Cooling Set Point (°F) 76.0 76.0 73.0‒75.0

Avg. Relative Humidity (%) 46% 48% 59%

Air Handling Unit Fan Run Time 31% 37% 100%

Ventilation—Effective Continuous 

Rate (cfm) 14 12 45

3.3.1.1 Transfer Fan Operation

In House C, transfer fan thermostats were set to 76°F (24.4°C); that is, they would turn on when 

the thermostat controlling the fan reached that temperature. During these periods, the fans 

serving the rooms that had southern exposure (master bedroom and master bathroom) were on 

the highest percentage of the time (Table 6). The fan serving the northeast bedroom ran the least

frequently.

Table 6. Transfer Fan Run Time (Aug. 29–Sept. 7, 2014)

Transfer Fan Location Run Time (%)

Bedroom 2 (Northwest) 25

Bedroom 3 (Northeast) 12

Master Bedroom (Southeast) 55

Master Bathroom (Southwest) 49

3.3.1.2 Cooling Use When Outdoor Temperatures Were Below Indoor Cooling Target

The target temperature for all three houses during cooling was 76°F (24.4°C). The table and 

graphs below (Table 7, Figure 8, Figure 9, and Figure 10) identify hours during two weeks in the 

summer of 2014 when the cooling systems were operating coincident with outdoor air 

temperatures below this target cooling temperature. Opening windows during these conditions 

can provide free cooling and reduce overall HVAC energy consumption. As expected, the leakier 

and less thermally efficient the enclosure, the lower the proportion of cooling energy expended 

during these periods because daytime heat more rapidly dissipated to the outside. By opening 

windows and venting daytime heat that has built up, occupants would have had the opportunity 

to reduce cooling energy by up to 37% in House C, 33% in House B, and 22% in House A.
23

Table 7. Cooling Energy Consumption (Aug. 29–Sept. 15, 2014)

House A House B House C

Total Cooling (kWh ) 251 244 138

Time When Cooling Is Provided, 

When Outdoor Temp. Is Below 76°F (%) 11 21 51

Cooling Energy Consumption Not Required 

(% Cooling Energy During Hours as Defined 

in Row 2)

22 33 37

Figure 8. House A cooling energy consumption at various outdoor temperatures

(Aug. 29–Sept. 15, 2014)
24

Figure 9. House B cooling energy consumption at various outdoor temperatures

(Aug. 29–Sept. 15, 2014)

Figure 10. House C cooling energy consumption at various outdoor temperatures

(Aug. 29–Sept. 15, 2014)
25

3.3.2 Cooling Season Comfort

Hourly room temperatures were monitored to provide an indicator of thermal comfort. The 

graphs below (Figure 11, Figure 12, and Figure 13) show the indoor and outdoor temperatures in 

each house for a typical week during the cooling season when daily high ambient temperatures 

reached approximately 90°F. The horizontal red line indicates the desired room temperature 

(76°F). The horizontal dashed lines indicate the upper and lower bounds of the +/-3°F 

temperature variation in cooling recommended by the Air Conditioning Contractors of America

(1997). For the most part, all three houses were successful in maintaining indoor temperatures 

within this range. In House A, temperatures in the master bedroom and Bedroom 3 spiked the 

highest. Supply flows in these rooms were lower relative to the room sizes (Table 8). House B 

had the tightest range, indicating the best overall temperature control. House C showed the 

widest temperature fluctuation from one room to another, but only the master bathroom exceeded 

the upper bounds of the temperature range specified by the Air Conditioning Contractors of 

America. This room had the longest air pathway from the main living space, and it had southern 

exposure. The daily temperature fluctuations in the living and dining rooms are the result of the 

2°F daily setback employed in House C.

Figure 11. House A room and outdoor temperatures during the typical cooling season

(Aug. 29–Sept. 7, 2014)
26

Figure 12. House B room and outdoor temperatures during the typical cooling season

(Aug. 29–Sept. 7, 2014)

Figure 13. House C room and outdoor temperatures during the typical cooling season

(Aug. 29–Sept. 7, 2014)
27

Table 8. House A Supply Flows

Register Measured Supply 

Flow (cfm)

Room Size 

(sf)

Area Normalized 

Flow (cfm/sf)

Bedroom 2(Northwest) 136 142 1.0

Bathroom 2 Below measurement 

threshold 43 N/A

Kitchen 152 159 1.0

Dining Room 140 132 1.1

Master Bathroom 151 131 1.2

Master Bedroom 126 234 0.5

Living Room 116

232 1.0

Entry 124

Bedroom 3 (Northeast) 109 137 0.8

TOTAL 1,054 1,210 0.87

3.3.3 Heating Season HVAC Energy

Table 9 summarizes the initial heating performance of all three houses in November 2014 with

the interior doors open and the window blinds 50% closed. During this period, when average 

ambient temperature was 41.3°F, House C used 66% less HVAC energy than House A did and 

8% less than House B did. House B used 63% less than did House A in heating. Average indoor 

temperatures were slightly lower than the thermostat set point in House B and House C. Average 

humidity was similar in all three homes. During this period, House C’s fresh air ventilation rate 

was approximately four times higher than that of the other houses (meeting the ASHRAE

Standard 62.2-2010).

Table 9. Heating Statistics (Average Ambient Temperature of 41.3°F) (Nov. 12–17, 2014)

House A House B House C

Total Heating (Avg. kWh/d) 48.7 18.1 16.6

Avg. Indoor Temp. (°F) 71.3 69.9 69.5

Heating Desired Temp. (°F) 71 71 71

Avg. Relative Humidity (%) 28% 30% 33%

Air Handling Unit Fan Run Time 22% 33% 100%

Ventilation—Effective Continuous Rate (cfm) 10 11 45

It was observed that bedrooms were not maintaining acceptable temperatures in House C. (See 

Section 3.3.4 on comfort below.) Therefore, resistance heaters with dedicated thermostats set to 
28

69°F were added to those rooms. Table 10 summarizes the heating performance of all three 

houses from January 6‒13, 2015, with the addition of resistance heat in House C. Interior doors 

were open, and window blinds were 50% closed. During this period, when average ambient 

temperature was 32.6°F, House B and House C used a similar amount of heating energy and 

slightly less than half the heating energy of House A.

Average indoor temperatures were close to the thermostat set point in all houses. Average 

humidity was similar in all three homes. During this period, House C’s fresh air ventilation rate 

was approximately two to three times higher than that of the other houses.

Table 10. Heating Statistics with Resistance Heat in House C Remote Rooms (Average Ambient 

Temperature of 32.6°F) (Jan. 6–13, 2015)

House A House B House C

Total Heating (Avg. kWh/d) 66.6 32.3 31.8

Avg. Indoor Temp. (°F) 71.2 69.9 70.4

Heating Desired Temp. (°F) 71 71 71

Avg. Relative Humidity (%) 20% 21% 22%

Air Handling Unit Fan Run time 48% 47% 100%

Ventilation—Effective Continuous Rate (cfm) 21 15 45

Figure 14 shows heating power compared to ambient temperature. House B and House C used 

less heating energy than did House A at all outdoor temperatures. House B and House C used a 

similar amount of heating energy, but the trend lines indicate that as temperatures fell House C 

used less energy relative to House B. At colder temperatures, the heating system in House B 

relied more on electric resistance and less on the heat pump, whereas House C’s heat pump ran 

continuously (Figure 14). Figure 15 shows that in House B the backup electric resistance heat 

turned on when the outdoor air temperature fell below approximately 40°F, and it increased with 

decreasing temperatures. During this period, the heat pump showed stable and limited energy 

consumption. 
29

Figure 14. Heating energy compared to outdoor temperature for all three houses (Jan. 6–13, 2015)
30

Figure 15. House B backup electric resistance heating energy compared to outdoor air 

temperature 

Figure 16 shows average hourly electrical power used by the three components of the heating 

system in House C: the heat pump, the resistance heaters, and the transfer fans. The black line is 

the ambient temperature (°F). The heat pump and resistance heaters used similar amounts of 

heating energy, with resistance heating becoming a significant factor when the ambient 

temperatures fell below approximately 35°F. During this period, 46% of the space-conditioning 

energy use was attributable to the heat pump, 8% to the fans, and 46% to the resistance heaters.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 10 20 30 40 50 60

Heating energy kWh

Outdoor air temperature (°F)

Backup electric resistance

heating energy- House B

(kWh)

Heat pump energy- House

B (kWh)

Poly. (Backup electric

resistance heating energyHouse B (kWh))
31

Figure 16. House C heat pump, transfer fan, and resistance heating energy compared to ambient 

temperature (Jan. 6–13, 2015)

House C’s backup resistance heaters helped maintain temperatures in the bedrooms and the 

master bathroom at 69°F.

Figure 17 shows that when the outdoor air temperatures were below approximately 40°F, the

resistance heat consumption started climbing, and it surpassed the heat pump energy 

consumption when the ambient temperatures fell below approximately 25°F.

Figure 17. House C resistance heating energy compared to ambient temperature (Jan. 6–13, 2015)

R2 = 0.8608

R2 = 0.7551

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 10 20 30 40 50 60

Heating energy kWh

Outdoor air temperature (°F)

Backup electric resistance heating

energy- House C (kWh)

Heat pump heating energy- house C

(kWh)
32

3.3.4 Heating Season Comfort

As discussed above, an analysis of the indoor temperatures in House C revealed that the remote 

rooms were not maintaining acceptable temperatures (Figure 18). In particular, the master 

bathroom and master bedroom were falling well below the Air Conditioning Contractors of 

America acceptable heating variation from the set point limit (+/- 2°F from the set point in 

heating) when the outdoor temperatures fell below approximately 50°F. It was therefore decided 

to add electric resistance heat to the bedrooms and master bathroom controlled on independent 

thermostats to maintain at least 69°F in those rooms.

Figure 18. House C room and outdoor temperatures for the initial heating season analysis

(Nov. 12–17, 2014)
33

After the resistance heat was activated, the bedrooms still remained cooler than the main space 

(at or above the 69°F electric heat set point); however, the comfort metrics met the Air 

Conditioning Contractors of America guidelines (Figure 19).

Figure 19. House C room and outdoor temperatures with resistance heat in remote rooms

(Jan. 6–13, 2015)

For comparison purposes, the room temperatures in House A and House B are shown in Figure 

20 and Figure 21, respectively. Bedroom 2, Bedroom 3, and sometimes the master bathroom 

struggled (sometimes unsuccessfully) to maintain 69°F in both House A and House B.
34

Figure 20. House A room and outdoor temperatures (Jan. 6–13, 2015)

Figure 21. House B room and outdoor temperatures (Jan. 6–13, 2015)
35

3.3.5 Whole-House Ventilation 

Whole-house ventilation in House A and House B is achieved through the air handling unit, as is 

typical for manufactured homes. A fresh-air intake at the roof is connected via a 4-in-diameter 

flexible duct to the return side of the air handling unit. There is no mechanical damper. 

In House C, a continuously operating exhaust fan in the main living space provides ventilation in 

accordance with ASHRAE Standard 62.2-2010. This fan was initially planned for the master

bathroom to help draw conditioned air from the living space to the master suite, but code 

required it to be in a central location.

Table 11 compares the effective ventilation rates in each house to the requirements of HUD 

(2010) and ASHRAE Standard 62.2-2010. The rates in House A and House B were lower than 

the HUD recommendation of 0.035 ft3 per ft2

, and all three houses were lower than the HUD

minimum of 50 cfm.

Table 11. Effective Ventilation Rates

House

Whole-House Ventilation Flow 

(cfm)

Measured Requireda

A 22 50

B 13 50

C 45 50 a The required whole-house ventilation rate should be 0.035 ft3 per square foot of the conditioned space or a 

minimum of 50 cfm. Conditioned area = 1,210 ft2

.

3.3.6 Moisture Measurements

One risk of adding exterior foam insulation to the walls in House C was that the reduced vapor 

permeability of the foam sheathing (extruded polystyrene insulation) could lead to higher 

moisture content in the wall cavity. To explore the potential for condensation within the wall 

cavities with exterior foam sheathing, air temperature and relative humidity in a cavity between 

the sheathing and interior fiberglass insulation on a north wall was measured to estimate the

condensation potential in the cavity. A temperature and relative-humidity sensor was installed 

approximately 2.5 in. above the floor inside the cavity. The moisture content of a wood stud in 

the cavity was also measured at the same location using an Omnisense S900-1 moisture content 

sensor (Figure 22). 
36

Figure 22. Moisture content and temperature/relative humidity sensors mounted in wall cavity

Figure 23, Figure 24, and Table 12 show the data from the moisture content sensors in the wall 

cavities in House B and House C. Wood moisture content was slightly higher in House C, but it 

was still well within the safe limits of 19% (Forest Products Laboratory 2015). Additionally, the 

House C wall cavity temperature was moderated by the exterior insulation, which resulted in a 

minimum temperature that was 5.5°F higher than it was in House B, mitigating condensation 

risk.

House C’s moisture content tended to be somewhat higher in the summer, consistent with higher 

overall humidity in the house. House B had slightly higher readings in the winter. Note that the 

houses were unoccupied, and no moisture was added to simulate latent loads. Because the homes 

were newly constructed in the plant, wood was not subject to wetting, but it could have had 

residual natural moisture. Seasonal data seems to follow the expected trend—higher in the

summer and lower in the winter. Note that the vinyl-covered wallboard used in all three homes 

has been associated with moisture problems in warm, humid climates (Moyer et al. 2001).
37

Figure 23. House B wall cavity conditions and wood moisture content (April 2014–April 2015)

Figure 24. House C wall cavity conditions and wood moisture content (April 2014–April 2015)
38

Table 12. Wall Cavity Maximum, Minimum, and Average Conditions (April 2014–April 2015)

House Temp. (°F) Humidity

(%)

Wood Moisture 

Content (%)

Dew Point 

(°F)

B

Maximum 91.6 71.0 14.2 67.2

Minimum 27.0 38.2 7.0 7.9

Avg. 64.8 54.7 9.5 48.0

C

Maximum 86.2 77.4 14.6 73.3

Minimum 32.5 40.0 7.0 15.9

Avg. 65.2 62.2 11.6 52.1

3.3.7 Peak Electric Demand

Peak electric demand is calculated by the utility serving Russellville (Tennessee Valley 

Authority) as the single half-hour period with highest average power (kW) draw in the month. 

The coincident peak hours of the Tennessee Valley Authority system are as follows:

• Winter: December‒March, 6:00 a.m.‒8:00 a.m.

• Summer: June‒September, 2:00 p.m.‒5:00 p.m.

Figure 25 shows the peak demand for the three houses using the criteria from the Tennessee 

Valley Authority. Some data is missing from February and March because experiments run 

during those months interfered with normal house operation. Peak demand in House C was 

significantly lower than the other two houses during all months of the year. The heat pump in 

House C operated nearly continuously, so there was much less variation in power draw. House B 

had somewhat lower peaks than did House A during most months, but some winter peaks were 

similar, indicating that House B’s peak occurred when the heat pump was not running and the 

house was relying solely on electric resistance backup. On average, during the peak hours of the 

Tennessee Valley Authority system, House B had an 18% lower peak demand than did House A,

and House C had a 69% lower peak demand than did House A.

Interestingly, when broadening the range of hours to show peaks for any time of day, House B 

had higher winter peak demand than did House A during most months (Figure 26). 
39

Figure 25. Monthly peak demand during coincident peak hours of the Tennessee Valley Authority

system

Table 13. Summary of Average Peak Demand Reduction During Peak Hours of the Tennessee 

Valley Authority System

House Avg. Monthly Peak Demand 

During Peak Hours

Avg. Demand Reduction 

Compared to House A

A 3.1 N/A

B 2.6 18%

C 1.0 69%
40

Figure 26. Monthly peak demand during all hours of the day

3.3.8 Co-heat and Tracer Gas Testing

Short-term co-heat testing in cold weather using portable electric resistance space heaters was 

conducted in all three houses to measure whole-house heat loss. The test data was used to obtain 

envelope U-value information that was used to tune the simulation parameters. During the test, 

six portable heaters (one in each bedroom, one in the master bathroom, one in the living room, 

and one in the kitchen) were used to maintain 70°F throughout the duration of the test. Other 

heating equipment was switched off. Temperature sensors were used to turn the heaters on and 

off through the Campbell Scientific data loggers. Tracer gas decay testing was conducted 

simultaneously with the co-heat testing to differentiate convective from conductive heat loss.

These tests were conducted during four days in December 2014 (December 8‒11). Co-heat tests 

were run in each house on three nights. Tracer gas measurements were made in conjunction with 

some of the co-heat tests (Table 14).
41

Table 14. Testing Schedule

A B C

Dec. 8‒9 Co-heat Co-heat Co-heat

Dec. 9‒10 Co-heat Co-heat

Tracer gas

Co-heat

Tracer gas

Dec. 10‒11

Co-heat

Tracer gas

Co-heat Co-heat

Tracer gas

Dec. 11‒12 Tracer gas Tracer gas

3.3.8.1 Co-Heat Testing

The co-heat test procedure was as follows:

1. The continuous exhaust fan in House C was turned off.

2. Heating systems in all houses were turned off.

3. Electric space heaters, controlled by the data logger based on each room’s indoor 

temperature, were used to maintain constant indoor temperature overnight in all rooms.

Each room had its own heater and temperature sensor.

4. For two tests in each house, a simultaneous tracer gas test (see procedure below) was 

conducted to measure the infiltration rate during the co-heat testing period. 

5. Fans were used to evenly distribute the heat and the tracer gas.

6. The energy consumed by the heaters, fans, and data collection equipment was measured 

continuously.

7. The heat loss of the building, inclusive of infiltration, was calculated via the following 

equation:

UU = II/(TTTT – TTT)

Where:

UA = Heat loss in kW per degree C

IG = Total internal heat gain in kW

Tout = Ambient outdoor temperature (°C)

Tin = Average indoor temperature (°C).

3.3.8.2 Tracer Gas Testing

Infiltration was measured in all three homes utilizing tracer gas. The objectives of the tracer gas 

testing were to determine infiltration levels in all three houses for calibrating models and 

quantifying the effectiveness of the ventilation systems. Tracer gas testing was conducted 

simultaneously with co-heat testing so that envelope infiltration losses could be separately 

accounted for in the resulting heat loss estimates. The tracer gas test procedure was as follows:
42

1. The houses were set up per the co-heat procedure above on December 9‒10 and 

December 10‒11. For the December 11‒12 test, the space-conditioning systems were on.

2. Air sampling tubes were run to each room and connected to a Brüel and Kjær Model 

1302 Multi-Gas Monitor System. A Brüel and Kjær 1303 Multipoint Sampler was used in 

House C to separately measure the sulfur hexafluoride tracer gas concentration in each 

room (Figure 27). In House A and House B, the room sample tubes were connected to a 

common manifold.

3. Sulfur hexafluoride was released into the space to an approximate concentration of 3‒4 

ppm.

4. The tracer gas monitoring systems measured the sulfur hexafluoride concentration at 5-

min intervals.

5. The decay rate of sulfur hexafluoride was converted into a natural air change rate via the 

following equation:

AA A AAA = ( 1/ 2)

Where:

ACHnatural = natural air change rate per hour for hour n

ln = natural logarithm

C1 = Average sulfur hexafluoride concentration in parts per million for hour n-1

C2 = Average sulfur hexafluoride concentration in parts per million for hour n.

 

Figure 27. Tracer gas sampling equipment and sampling tube

The results of the tracer gas testing are summarized in Table 15 along with a comparison to the 

blower door testing and the natural air change rates predicted from the blower door test results

using the Alberta Air Infiltration Model (AIM-2) incorporated into BEopt V 2.3.0.2 (Walker and 

Wilson 1998). The tracer gas testing data are provided in Appendix E. Results for the multiple 
43

tests in House B and House C are consistent from one test to another, but they are higher than the 

annual average AIM-2 predictions. 

Table 15. Tracer Gas Test Results Summary

House A House B House C

Dec. 8‒-9 0.22 0.14

Dec. 9‒10 0.22 0.14

Dec. 10‒11 0.25 0.24

Overall Avg. 0.25 0.23 0.14

Blower Door Air Change Rate

(ACH50) 4.7 4.6 3.8

Air Change Rate Extrapolated

from Blower Door Testa

0.13 

(annually)

0.12 

(annually)

0.10 

(annually) a Based on AIM-2 used in BEopt V 2.3.0.2

One set of tracer gas tests was conducted with space-conditioning and ventilation systems 

operating (Table 16). The continuous exhaust ventilation fan in House C (45 cfm) resulted in a 

higher air change rate than in House A and House B. The air change rate in House B was higher 

with systems operating than with systems off. However, there was no measured increase in the 

House A air change rate when the system was operating compared to when the system was off.

Table 16. Tracer Gas Test Results Summary—With Systems Operating

House A

Dec. 11‒12

House B

Dec. 11‒12

House C

Dec. 8, 8‒10 a.m.

Estimated Continuous 

Effective Mechanical 

Ventilation Rate Based on 

Commissioning Tests and Air 

Handling Unit/Exhaust Fan 

Run Time (cfm)

22 13 45

ACH Natural from Tracer Gas 

Test 0.25 0.27 0.28

ACH Natural from Tracer Gas 

Tests Converted to cfm 40 cfm 44 cfm 45 cfm

The results of the daily co-heat testing are summarized in Table 17. 
44

Table 17. Co-heat Test Results Summary (Btu/h/°F)

Test A B C

Dec. 10 326 250 202

Dec. 11 299 237 212

The results of the co-heat testing are summarized in Table 18 along with a comparison to the UA 

value (heat loss over the entire surface area) predicted by the house designs. The co-heat testing 

data are provided in Appendix G. The results are in reasonable agreement.

Table 18. Co-Heat Test Results Summary Adjusted for Infiltration

House

Co-Heat 

Results (Incl. 

Infiltration 

Losses)

(Btu/h/°F)

Avg. 

Infiltration 

Rate per 

Tracer Gas 

Test (ACH

Natural)

Infiltration 

Heat Loss 

(Btu/h/°F)

Heat Loss per 

Co-Heat Test

(Without

Infiltration 

Loss) (Btu/h/°F)

Difference 

from Design 

UA Value

(%)

A 333 0.25 43 290 -3.2

B 256 0.24 41 215 -8.5

C 208 0.14 24 184 0.4

The heat loss factors predicted by the results of the co-heat/tracer gas tests were used to calibrate 

the BEopt models and to calculate the heating system COPs. 

3.3.9 Heating System COP

The COP of the heating system was calculated for all three houses using a co-heat method. For 

House B and House C, the COP of the heat pumps was also measured using airflow

measurements.

3.3.9.1 Co-Heat Tests

Co-heat tests were conducted during two nights to determine each house’s actual heat loss (UA) 

inclusive of infiltration and duct leakage. The hourly monitored data from the co-heat tests is 

provided in Appendix G. Ventilation systems were not operating during the co-heat tests.

To calculate the system COPs, the UAs derived from the co-heat tests were used to calculate the

heat losses during periods when the systems were operating. Because the derived UAs did not 

include the effects of fresh air ventilation, this was added to the heat loss based on measured 

ventilation flows and indoor-outdoor temperature differences. COPs were calculated for 1-h

periods from 1:00 a.m. to 6:00 a.m. when the impact of solar gains would be smallest. The 

equation used to calculate simple heat loss during system operation was:

Q = UU ∗ (TTTT − TTT) + V ∗ cp ∗ (TTTT − TTT)
45

Where:

Q = Simple heat loss 

UA = Area-weighted U value of the house’s envelope, including walls, roof, floor 

and fenestration, inclusive of infiltration

Tout = Outdoor ambient temperature

Tin = Average indoor temperature (average of all room temperature sensors)

V = Effective ventilation rate in cubic feet per minute—average for each hour

cp = Specific heat of air approximated as 1.085

Note that this equation assumes that there is no heat recovery in the ventilation heat flow through

the building assemblies. COPs were then calculated using the following equation:

CC = (Q – II) / Q

Where:

Q = Simple heat loss in kW

IG = Internal gains in kW, measured

Qc = Heat pump compressor energy in kW, measured

3.3.9.2 Air-Side Measurements

The COPs in House B and House C were also calculated based on measurements of the supply 

and return air temperatures, fan power measurements, and onetime fan curve generated by 

measuring the air flow at a range of fan speeds. The following equations were used:

qc,tot = mda(h – hs)

CC = qc,tot / qelec

Where:

qc,tot = Total heating rate (sensible + latent) (kW)

qelec = Electrical power drawn by outdoor unit (kW)

mda = Dry air mass flow rate (kg/s)

hr = Enthalpy of return air (kJ/kg dry air)

hs = Enthalpy of supply air (kJ/kg dry air)

Enthalpy was calculated using an assumed total atmospheric pressure of 98.9 kPa and 

measurements of the air’s temperature and relative humidity. Correlations for enthalpy as a 

function of air properties are taken from the 2001 ASHRAE Handbook—Fundamentals, SI P6.9,

Equation 32.

 5 Converts cubic feet per minute into pounds per hour and multiplies times specific heat of air: 1 cfm * 60 minutes 

per hour = 60 CFH * .075 pound per cubic foot (standard air) = 4.5 * 0.24 specific heat of air = 1.08. 
46

Air flow rate was calculated using a curve fit to the measured air flow rates as a function of 

electrical power draw of the fan. (See curve below.) The curve fit results in a prediction of 

volume flow rate. To calculate mda, the density of the air on the supply side was calculated from 

the measured temperature and relative humidity and assumed total atmospheric pressure of 98.9 

kPa. The mass flow rate of the dry air was then calculated:

mda = ƿvma/(1 + ɷ)

Where:

ƿ = Density of moist air (kg/m3

)

vma = Volume flow rate of moist air (m3/s)

ω = Humidity ratio of moist air (kg water/kg dry air)

The correlations for the density of air were taken from the 2001 ASHRAE Handbook—

Fundamentals, Chapter 6, Equation 11 and Equation 28.

3.3.9.3 Results

The UAs calculated from the co-heat tests and average COPs for each house under normal 

operation are shown in Table 19. The hourly data is provided in Appendix G. An estimate for the

COPs without the adjustment for ventilation is also included to provide a lower bound for the 

COP in the event that some natural heat recovery was present in the infiltration flow through the

building assemblies.

Table 19. Summary of Heating System COPs

House

Equipment Make and Model 

Number

A

NORDYNE

Electric Furnace 

(E3EB010H)

B

Intertherm Heat 

Pump

(DT4BD-018KB & C8 

(B,D)AM01830U-B)

C

Mitsubishi

(MSZ-FH15NA 

& MUZFH15NA)

UA (Incl. Infiltration) Btu/h/°F 313 245 209

COP (Co-Heat Method) and 

Dates of Measurement (With 

Ventilation Adjustment)

1.10

Jan. 1‒2

2.50

Jan. 1‒2, 5, 7, 14

2.49

Jan. 8‒12, 14, 

16, 25

COP (Co-Heat Method) and 

Dates of Measurement 

(Without Ventilation 

Adjustment)

1.00

Jan. 1‒2

2.26

Jan. 1‒2, 5, 7, 14

1.63

Jan. 8‒12, 14, 

16, 25

COP (Air-Side Method) and 

Dates of Measurements

Not measured 1.37

Jan. 22‒29

1.39

Jan. 20‒26

Expected COP, Based on 

Manufacturer Data

1, less that lost via 

duct leakage

(electric resistance)

3.2, less that lost via 

duct leakage

4.8
47

With the ventilation adjustment, the co-heat measured COP for House A was higher than 1.0, 

which would be the expected value for an electric resistance system with zero duct losses.

(Without the ventilation adjustment, it was 1.0.) The co-heat method COP for House B was

similar to what would be expected based on the manufacturer’s specifications. The air-side 

measurement was much lower. 

Air-side measurements may be less reliable than measurements based on co-heat because of the 

uncertain uniformity of supply air measurements. It was noted that the heat pump heating coil in 

House B was nonuniform in temperature (Figure 28), which may have led to nonuniform supply 

air. Supply air was measured at a single supply register, which may not have been perfectly 

representative of the average supply air temperature. Other potential uncertainties include 

possible temperature differences from one room to another, higher convective airflow due to air 

handling unit operation than existed during the co-heat tests, and variations in ventilation rates 

from those estimated. Further, the COP calculations in House A and House B included the 

effects of duct leakage; therefore, the House A COP should be lower than 1. This is an indication 

of the magnitude of error inherent in this measurement process. Nevertheless, the COPs 

calculated by the co-heat method are taken to be close to actual performance.

Figure 28. House B refrigerant coil in heating mode showing nonuniform temperatures

The co-heat and air-side COP measurements for House C are well below the expected COP 

based on manufacturer data. Discrepancies from these expectations are discussed in more detail 

below.

3.3.9.4 Mini-Split Heat Pump COP

One possible cause of low COP could be low fan speed and therefore low supply airflow. The 

fan speed was set to auto-speed mode, in which the air handling unit automatically selects the fan 

speed based on internal logic. During this period, however, the fan operated at low power (5‒7 

W) and commensurately low speeds (164‒190 cfm) all the time in this mode, even when the heat 

loads were high. 

To further investigate this phenomenon, additional testing was conducted with the fan placed in 

the high-speed setting. At high speed, the fan drew more power (9‒16 W), and flows increased to 

216‒306 cfm. Figure 29 shows the air handling unit fan power for the auto- and high-speed 

settings. Figure 30 shows the fan curve (approximate flows at a range of power levels) 

established by taking onetime flow and power measurements.
48

Figure 29. Air handling unit fan power for auto- and high-speed settings

Figure 30. Fan curve based on onetime flow and power measurements

The average COPs calculated from the air-side and co-heat (with ventilation adjustment) 

methods while the fan was set on high speed (January 27‒30) are provided in Table 20 along 

with a comparison to the auto-speed COPs.
49

Table 20. Mini-Split Heat Pump COPs at High and Low Fan Speeds

High Fan Auto Fan (Low)

Co-Heat Method COP 4.11 2.49

Avg. Ambient Temp. (°F) 36.8 30.7

Air-Side Method COP 2.25 1.39

Avg. Ambient Temp. (°F) 43.2 42.1

Forcing the fan to high speed increased the COP to an average of 4.11 (3.12 without ventilation 

adjustment) as measured by the co-heat method. The high fan speed COP as measured by the airside method also increased but not as dramatically. It is possible that as airflows increased, the 

supply air temperature became less uniform across the outlet and the single-point air-side 

measurement did not capture a truly average reading. Note that average ambient temperature was 

6.1°F higher during the high-speed period.

Plots of hourly COPs for both measurement methods with outdoor temperature for hours when 

the fan was on auto compared to high are provided in Figure 31 and Figure 32. The co-heat 

measurement method has fewer data points because only the hours of 1:00 a.m. to 6:00 a.m. were

used.

Figure 31. Comparison of mini-split COP (co-heat measurement method) with auto and high fan 

speeds

0

1

2

3

4

5

6

7

5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0

COP

Outdoor ambient temperature (°C)

High fan speed AUTO Fan speed
50

Figure 32. Comparison of mini-split COP (air-side measurement method) with low and high fan 

speeds

Another possible contributor to low COPs is higher than expected return air temperatures relative 

to average room temperature. During the period of January 6‒13 (the winter sample period), the 

average temperature in the living space measured in the center of the room at approximately 60

in. above the floor was 70.2°F; the average return air temperature entering the heat pump was 

74.8°F. There was clearly stratification of indoor air due to thermal buoyancy: the high-low 

thermocouples in the living room nearest the heat pump measured an average of 68.9°F at 12 in.

above the floor and 75.4°C at 84 in. above the floor during this period.

3.3.10 Humidification Testing

One humidifier was placed in each house in the kitchen and set to operate continuously at its 

normal high output. The humidifiers were weighed at the beginning and end of the test to 

determine the average moisture injection rate during the test period. The test began at 8:00 a.m.

on July 24, 2014, and ended at 6:30 a.m. on July 25. The average injection rates for each house, 

the average relative humidity, and ambient temperatures before and during the test are provided 

in Table 21.
51

Table 21. Humidification Test Results

24 h Before 

Humidification Test

During 

Humidification Test

House Avg. Moisture 

Injection Ratea

Avg. Relative 

Humidity (%)

Avg.

Ambient 

Temp. (°F)

Avg. 

Relative 

Humidity 

(%)

Avg. Ambient 

Temp. (°F)

A 195 g/h 38.5

75.7

39.4

B 240 g/h 43.0 46.5 71.4

C 210 g/h 47.8 54.8 a The average moisture injection rate for a three-bedroom home is approximately 200 g/h per the Building America

protocol.

In all three houses, there were only minor increases in measured indoor relative humidity. This 

indicates that the latent capacity of the cooling systems in each house was adequate to remove 

this rate of moisture injection. The sensible loads on the cooling systems were high because it 

was hot outside and the cooling systems were operating frequently to meet that load. The 

conclusion from this test is that this level of moisture removal (200 g/h) is within the capacity of 

the cooling equipment with the observed sensible heat ratio of approximately 0.75.

3.3.10.1 Impact of Transfer Fans in House C

The impact of transfer fans on the House C bedroom and master bathroom room temperatures 

was analyzed during both the cooling and heating seasons. Periods when all four fans were 

activated (i.e., being controlled by their dedicated thermostats) were compared to periods when 

they were all deactivated (Table 22). 

Table 22. Analysis Period for the Impact of Transfer Fans on Room Temperatures in House C

House Transfer Fans

Active Period

Transfer Fans

Deactivated Period

Cooling Season Dates July 21–23, 2015 July 16–8, 2015

Heating Season Dates Jan. 10–3, 2015 Jan. 18–21, 2015
52

3.3.10.1.1 Cooling Season

The purpose of the transfer fans during the cooling season was to deliver air from the living 

room, where the heat pump is located, to the bedrooms and master bathroom. The hypothesis is 

that the cooler living room air would reduce air temperatures in those rooms and that warmer air 

would be returned via open doors and transfer grilles back to the living room. Transfer fan flow 

rates were constant. (See Appendix C for flow rates.) Fans pulled air from the living room 

approximately 12 in. above the floor and delivered it to the bedrooms/master bathroom at 

approximately 12 in. from the ceiling. A vertical, sealed metal duct was constructed inside the 2

x 4 partition wall to transfer the air. 

During this cooling analysis period, the average air temperature near the floor level of the living 

room (where the transfer fan inlet was) was 73°F. However, the average temperature at the 

master bedroom fan outlet was 76.6°F, indicating that the air might have picked up heat from the 

fan motor or other source. The average central room temperature in the master bedroom was 

76.4°F, nearly the same as the air being delivered to the room. This is consistent with the 

comparison of room temperature data from fan-on and fan-off periods—there is no discernable 

difference in bedroom/master bathroom temperatures at similar outdoor temperatures. The series 

of graphs in Appendix C plot room temperatures compared to outdoor temperatures for both 

conditions. The only trend evident is a slight increase in room temperatures with increasing 

outdoor temperatures. Note that the interior doors were open during these measurements.

Figure 33. Vertical transfer fan duct

3.3.10.1.2 Heating Season

In House C, backup resistance heat was provided to the bedrooms and master bathroom. 

Therefore, it was not possible to examine the impact of transfer fans on bedroom temperature, 

which was always at least 69°F. The purpose of the fans in these conditions would be to reduce 

the need for resistance heat by bringing warmer living room air into the cooler bedrooms. 

Because the warmer living room air was heated by the more efficient heat pump, this would be 

desirable.
53

However, it was observed that the resistance heaters were on nearly all of the hours when the 

transfer fans were on, and they were off nearly all of times when the fans were off. Both were 

driven by outdoor temperature. Therefore, it was not possible to estimate the impact of transfer 

fans on the energy consumed by the temperature-controlled heaters during this period, but it 

would seem that the effect is negligible.

Note that the fans were configured for optimal cooling-season operation—i.e., they pulled air 

from near the floor level in the living room, which would be the coolest air in the room. The 

high-low temperature sensors showed consistent temperature stratification in the living room 

during the heating season, with the floor-level sensors reading 5.2°F lower than the ceiling-level 

sensors and 3.6°F lower than the central living room sensor.

Figure 34. High, low, and primary room temperature sensors

The heat transfer rate from the living room to the master bedroom and master bathroom due to 

transfer fans was calculated from flow and temperature measurements using the equation below. 

The results in Table 23 indicate that heat transfer through the fans was low.

QQ = F ∗ cp ∗ (T T − TTT)

Where:

Qf = Heat transferred to the bedroom in Btu per hour via the transfer fan

F = Fan flow rate in cubic feet per minute delivered to the bedroom/master bathroom

Tbd = Bedroom/master bathroom temperature (F)

Tlv = Living room temperature (F)

cp = Specific heat of air approximated as 1.086

 6 Converts cubic feet per minute into pounds per hour and multiplies by specific heat of air: 1 cfm * 60 minutes per 

hour = 60 CFH * .075 pound per cubic foot (standard air) = 4.5 * 0.24 specific heat of air = 1.08
54

Table 23. Transfer Fan Heat Delivery

Room Fan Flow 

(cfm)

Qf

(Btu/h)

Fan Outlet

(°F)

Room

(°F)

Master Bedroom 106 103 70.0 69.0

Master Bathroom 115 89 69.8 69.0

3.3.11 Impact of Window Blinds

3.3.11.1 Cooling Energy

The impact of window blind position on cooling energy was investigated by comparing the

cooling energy consumption of periods when the blinds were completely open to similar periods 

when the blinds were completely closed. Window treatments were white, horizontal venetian

blinds (Figure 35). During the closed periods, the blinds covered 100% of the windows, and the 

blind vanes were angled downward toward the outside. The hypothesis was that closed blinds 

would reduce solar gain and therefore cooling energy. The periods analyzed are described in 

Table 24.

Figure 35. Window blinds 50% closed
55

Table 24. Window Blinds Analysis Period Conditions

House Blinds Open Blinds Closed

Dates Aug. 17‒23, 2014 Sept. 23‒29, 2014

Avg. Ambient Temp. (°F) 78.6 67.1

Ambient Temp. Range (°F) 74.5‒80.6 62.6‒71.8

Avg. Indoor Temp. House A

(°F) 75.7 74.8

Avg. Indoor Temp. House B

(°F) 77.7 76.5

Avg. Indoor Temp. House C

(°F) 74.7 73.0

Avg. Direct Normal Solar 

Radiation (Btu/ft2) 1013 1102

Direct Solar Radiation 

Range (Btu/ft2) 341‒1,483 274‒1,869

The direct factors affecting the cooling energy consumption during these periods are ∆T (TindoorToutdoor) and solar radiation received. For “daily” cooling energy and temperature, we used the 

time periods just before sunrise on Day 1 to just before sunrise on Day 2 (6 a.m. to 6 a.m.),

because the solar energy falling on the house during Day 1 would influence the cooling energy 

past midnight on Day 1, well into the early-morning hours. As shown in Table 24, the average 

ambient temperature during the period when the blinds were open is nearly 11.5°F higher than it 

was during the period when the blinds were closed. To eliminate the effect of cooler 

temperatures on cooling energy consumption, the data was normalized (see Appendix H). This 

was done by making a linear fit of the daily cooling energy as a function of ∆T (Tindoor-Toutdoor) 

and the daily totals of direct normal solar radiation during the period when the blinds were 

closed. This linear fit was used to predict the cooling energy consumption using identical

outdoor temperature and direct normal radiation data as that used during the period when the 

blinds were open.

The sun angles are not very different from August to September, so using a surrogate measure of 

solar energy such as direct normal radiation is reasonable. A complete cooling-season savings 

estimate would require modeling sun angles, which was beyond the scope of this analysis; but 

these data give a strong indication that closing the blinds led to a significant reduction in cooling 

energy.

The resulting predicted reduction in cooling energy due to closing window blinds in each house 

is shown in Table 25. Cooling energy reduction was less in House B and House C than it was in 

House A because those windows have a much lower SHGC than do the windows in House A. 
56

Table 25. Cooling Energy Reduction Due to Window Blinds

House A House B House C

Blinds Open Cooling Energy (kWh) 129.6 91.0 60.4

Blinds Closed Cooling Energy (kWh)a 81.8 72.4 44.9

Savings (Blinds Closed vs. Blinds Open) (%) 36.9 20.4 25.7 a Predicted using the best-fit equation derived from the regression of delta T and daily totals of solar radiation as the 

independent variables and cooling energy as the dependent variable. 

3.3.11.2 Room Temperature

The impact of blind position (completely open or completely closed) on room temperatures in 

the cooling season was also investigated during the same two periods as described above. As 

expected, closed blinds led to lower room temperatures in House C in all the rooms (by an 

average of 2.6°F). In House A and House B, closed blinds did not result in significantly lower 

room temperatures because the space-conditioning distribution system overcame the effects of 

the blinds. Appendix C plots room temperature compared to ambient temperature under both 

blind configurations.

3.3.12 Impact of Interior Door Position

The impact of interior door position (open and closed) on room temperatures was investigated 

during the cooling and heating season. For the majority of the monitoring period, the doors were 

kept open; however, during selected periods, the doors were closed to compare the effects. These 

experiments were carried out during the periods shown in Table 26.

Table 26. Interior Door Position Analysis Periods

Doors Open Doors Closed

Cooling Season June 22–28, 2015 July 2–8, 2015

Heating Season Dec. 23–29, 2014 Dec. 13–19, 2015

3.3.12.1 Cooling Season

Bedroom 2 and Bedroom 3 in House A and House B showed no change to slightly lower 

temperatures when the doors were closed, indicating that the house had fairly well balanced 

cooling airflow. The master bedroom in House B showed somewhat elevated temperatures when 

the door was closed, which is consistent with the lower supply flow per square foot in that room.

House A did not show this trend despite the same relatively low supply flow. The master 

bathrooms in House A and House B both showed lower temperatures when the doors were 

closed, which is consistent with their high supply flow per square foot and long return-air 

pathway. In House C, Bedroom 2 and Bedroom 3 showed significant warming when the doors

were closed. The master bathroom did not show a difference with closed doors; the room is more 

distant from the central space, and less air was exchanged with the cooler living room when the

doors were open. Likewise, the master bedroom’s larger volume and connection to the master 

bathroom diluted the effect of the open door on room temperature. Plots comparing the bedroom
57

temperatures to the ambient temperatures under both door configurations (open and closed) are 

provided in Appendix C. Table 45 shows the supply flows per square foot of room area.

3.3.12.2 Heating Season

Keeping the doors open resulted in room temperatures closer to the heating set point than they 

were when the doors were closed. In House A and House B, when the doors were closed at the 

ambient temperature ranges observed during these periods, the temperature in all rooms except 

the living room fell below the set point. The outdoor temperature had little effect on the indoor 

temperatures. This indicates an undersized distribution system for heating in these houses. 

In House C, data was collected during periods when the resistance heat in the bedrooms and 

master bathroom were not active, which enabled an assessment of impact on room temperature. 

There was a clear trend of decreasing indoor temperatures in House C as outdoor temperatures 

decreased. The same trend as in cooling was evident: only Bedroom 2 and Bedroom 3 showed a

significant change when the doors were closed (in this case, they became cooler). The master 

bathroom and small bathroom showed a negligible impact when the doors were closed. Plots 

comparing the bedroom temperatures to the ambient temperatures under both door 

configurations (open and closed) for heating are provided in Appendix D.

3.3.13 Convective Heat Transfer Through Open Doors

To calculate the convective heat flow through open doors in House C, two test periods were 

considered while the house was heated by electric resistance heaters and the exhaust fan and heat 

pump were off: (1) all rooms heated to 69°F and (2) bedrooms and master bathroom heated to 

69°F with the living area heated to 71°F. The heating energy consumed by the heaters in the 

master bedroom, master bathroom, Bedroom 2, and Bedroom 3 were compared to each other 

during these periods (Table 27). The difference in the amount of energy consumed by the 

bedroom/master bathroom heaters between these two conditions was approximately equal to the 

heat flow into the bedrooms from the living room. To eliminate the effect of solar radiation, a 3-

h nighttime period from 3 a.m. to 6 a.m. was considered during the course of 4 d as specified in 

Table 27, for a total of 12 h.

Table 27. Convective Heat Flow Through Open Doors

Temp. Set Point

69°F Living Room

69°F Bedrooms/

Master Bathroom

71°F Living Room

69°F Bedrooms/

Master Bathroom

Analysis Period Feb. 3–6, 2015 Feb. 14–17, 2015

Avg. Outdoor Temp. (°F) 24.1 24.6

Avg. Crawl Space Temp. (°F) 39.6 33.6

Avg. Attic Temp. (°F) 23.9 27.5

Avg. Wind Speed (m/s) 0.6 0.9

Average ambient temperatures were similar between the two periods; however, there was a 

difference of 6°F in the crawl-space temperature and a difference of 3.6°F in the attic 

temperature between the two periods. The difference in attic temperature could be due to a
58

higher thermostat setting in the living room, which caused greater heat loss to the attic than

during the period of February 3‒6. The higher wind speed might have been the cause of the 

lower vented-crawl-space temperature of February 14‒17.

The difference in the heat loss to the outside from these rooms during the two cases (71°F living 

room and 69°F living room) was adjusted based on the known U values of the building 

components by using the following equation (results are shown in Table 28):

Q = U x x ∆T

Where:

Q = heating energy consumed by the heaters in the rooms in Btu 

U = U value of the surface area in Btu/h-F

A = area of the surface in square feet

∆T = temperature difference between the rooms and space where heat transfer takes place.

The heat transfer into the bedrooms and master bathroom for all 12 h considered, when the living 

room was set to 71°F and 69°F, is shown in Table 29.

Table 28. Difference in Heat Loss to the Outside Over 12 Hours Between Living Room Set Point at 

71°F and Living Room Set Point at 69°F

Heat Loss 

Through 

Attic (Btu)

Heat Loss 

Through 

Floor (Btu)

Heat Loss 

Through 

Windows 

(Btu)

Heat Loss 

Through 

Walls (Btu)

Total 

Differencea

Bedrooms 2 and 3 -59 554 113 188 796

Master Bedroom -103 972 169 247 1,286

Master Bathroom -54 520 56 168 690 a Calculated heat loss to the outside during the two test conditions

Table 29. Heat Transfer into Rooms During 12 h: Calculations

Row BR2 BR3 MBR Mbath

1 Heater energy: 71° living room; 

69°F bedrooms (Btu) 6,620 3,879 10,927 10,625

2 Heater energy: 69°F all rooms (Btu) 12,946 8,605 19,439 11,331

3 Difference between rows 1 and 2 (Btu) 6,326 4,725 8,512 706

4 Adjustment due to difference in heat loss to 

outside (from Table 28) (Btu) 796 796 1,286 690

5 Heat transfer into rooms (Row 3 minus Row 4) 

(Btu) 5,548 3,948 7,259 29
59

Plots of hourly heater energy use in each room as a function of outdoor temperature are provided 

in Appendix I. Note that there is no direct doorway between the master bathroom and the living 

room; therefore, heat transfer into this room is low.

Additional calculations were made to separate the conductive heat flow through interior 

partitions from the convective heat flow through the open door (Table 30). The resulting

effective airflow through the doors ranged from 140 to 281 cfm. This cfm translates into an air 

velocity of only about 20 ft/min (through half the area of an open door). This level of airflow is

very difficult to measure and so was not measured directly. Note that there are a number of 

phenomena that lead to uncertainties with these calculations, including temperature stratification, 

imperfect mixing of air within rooms, imperfect estimates of component U values, averaging of 

temperatures, and variations in infiltration to the outside among the two periods.
60

Table 30. Convective Heat Transfer Through Open Doors: Calculations

Row Units Bedroom 2 Bedroom 3 Master 

Bedroom

Master 

Bathroom

1

Avg. ∆T 

(TbedroomTliving)F 1.8 1.8 1.8 2.0

2

Avg. heat 

transfer 

into rooms

per hour

Btu/h-F 256 182 335 1

3 Wall area ft2 90 90 92 131

4 Door area ft2 16.2 16.2 16.2 0

5

U value of 

interior

wall

Btu/h-ft2-F 0.34 0.34 0.34 0.34

6 UA interior 

wall Btu/h-F 30.8 30.8 31.4 44.4

7

UA door 

opening 

(Row 2 less 

Row 6)

Btu/h-F 225 151 303 -44

8

Convective 

heat 

transfer 

through 

door

Btu/h 405 272 546 -87

9

Effective 

airflow 

through 

open door

cfm 209 140 281 N/A

3.4 Data Analysis

The objective of this analysis was to extrapolate from the measured data the impact on annual 

energy consumption of the primary measures installed in the lab houses in a range of climates in 

the Southeast living simulations.

3.4.1 Climate Locations

Three locations were selected to represent the range of climates within the service territory of the 

Tennessee Valley Authority. Table 31 lists the locations along with their respective IECC

climate zone, HUD climate zone, manufactured home ENERGY STAR climate region, normal 
61

heating degree days, and normal cooling degree hours. Maps illustrating the territory and climate 

zones of the Tennessee Valley Authority are provided in Figure 36.

Table 31. Climate Locations Selected for Modeling

Location

IECC 

Climate 

Zone

HUD 

Climate

Zone

Manufactured 

Home

ENERGY 

STAR

Climate 

Region

Heating 

Degree 

Days 

(Base 65°F)

Cooling 

Degree 

Hours 

(Base 74°F)

Columbus, 

Mississippi 3 1 4 2,720 26,043

Knoxville, 

Tennessee 4 2 3 3,666 14,214

Bowling Green, 

Kentucky 4 2 2 4,314 14,745

Figure 36. Map of climate locations
62

3.4.2 Model Development and Calibration

The three houses were modeled using BEopt version 2.3.0.2 with the Energy Plus (version 8-3-0) 

engine.

Models were calibrated by comparing their output to the measured field data for selected periods 

of time when the operating conditions were well known (i.e., during periods when resistance heat 

was used in all three homes). Aspects of the models were then adjusted to better align 

intermediate outputs (such as attic and crawl space temperatures) to their respective measured 

conditions and, finally, to compare the modeled to measured space-conditioning energy use of 

each home.

A measure of calibration accuracy is provided in Table 32. This indicates how accurately the 

calibrated model predicted overall space-conditioning energy for the selected periods. The 

periods were chosen when the houses were operating with consistent set points and equipment 

operation. The resistance heating period was calibrated first because the more precisely known 

heating energy input for all three houses reduced the number of variables to calibrate. After the 

resistance heating period was calibrated as closely as possible, the other two periods were 

calibrated, primarily by tuning the equipment efficiencies.

Table 32. Model Calibration Errora in Space-Conditioning Energy

Calibration Period

House Resistance Heating Only

(March 7‒17) (%)

As-Built Heating Systems

(Jan. 6‒13) (%)

Cooling

(Aug. 29‒Sept. 15) (%)

A -0.56 -9 0

B -2.3 1 -1

C 10.85 0.64a 0 a The model calibration error equals (modeled - measured)/measured.

b When the energy consumed by the temperature-controlled heaters is predicted by the model.

The model inputs are provided in Table 34, Table 35, and Table 36, along with the basis for the 

inputs and an explanation of the calibration adjustment to the inputs, if any.
63

Table 33. Envelope Inputs for House A, B, and C

Type of 

Calibration

House A House B House C Basis of Adjustment

Wall U: 0.077 U: 0.077 U: 0.059 Modeled UA value for attic ceiling, 

floor, walls, windows, and door 

adjusted to match the co-heat test 

results

Attic Ceiling U: 0.043 U: 0.031 U: 0.022

Floor U: 0.074 U: 0.043 U: 0.042

Window U: 0.47, 

SHGC:

0.73

U: 0.31, 

SHGC:

0.33

U: 0.3, 

SHGC:0.23

Door U: 0.4 U: 0.4 U: 0.4 U value for the door was doubled to 

account for two doors

Interior Shading 

(Heating/Cooling 

Shade Multiplier)

0.75 0.75 0.75 0.75 indicates a 25% reduction in 

solar gain when the blinds cover 

50% of the effective window area

Ratio of Effective 

Leakage Area (to 

Outside) in 

Unfinished Attic to 

Total Floor Area

0.0033 

(BEopt 

default)

0.0033

(BEopt 

default)

0.00001 Adjusted House C to increase attic 

temperature to match measured 

data

Air Leakage 7.7 

ACH50

7.7 

ACH50

5 ACH50 Adjusted such that the AIM-II 

Model in BEopt would predict air 

leakage that matches the measured 

air leakage during the tracer gas test 

period in Dec.

Table 34. Model Inputs—House A

Model Input Value Basis and Calibration Adjustment (If Any)

Calibration Period: Jan. 6‒13

Electric Furnace Capacity: 34.1

kBtu/h (10 kW)

Capacity: Autosize was modified to 10 kW

Mechanical 

Ventilation

21.56 supply Based on flow measurement and air handling unit

run time

Duct Leakage 

(To outside)

6.5 cfm25/100 ft2, 

all ducts insulated 

to R-12 located in 

pier and beam 

(approx. weighted 

avg. between R-8 

Original measurement was 54 cfm25 to outside or 

4.54 cfm25/100 ft2

Total duct leakage: 115 cfm25

Original model: 17% ducts insulated to R-8 

located in pier and beam, 83% ducts located in 

conditioned space
64

Model Input Value Basis and Calibration Adjustment (If Any)

x-over duct + R-14 

in-floor ducts

Changed to increase energy use

Heating Set Point 70.1 °F Based on average measured indoor temperature 

during this period

Plug Loads 153 kWh Sum of energy consumed by two sensible gain 

heaters and additional not measured internal gain

Calibration Period: Aug. 29‒Sept. 15

Central A/C

Rated and Installed 

SEER

13 Rated value; input not used; not considered for 

model—EER used for calculations

EER (kBtu/kWh) 7.1 Reduced from 11 to account for higher measured 

cooling use during this period

Rated Air Flow Rate 

(cfm/t)

705/2 = 353 Rated standard airflow for this model is 705 cfm 

based on specifications from the AirConditioning, Heating, and Refrigeration Institute

Tonnage = 2

Rated Supply Fan 

Power (W/cfm)

0.34 400 W/1,160 cfm 

Installed Supply Fan 

Power (W/cfm)

0.68 417/980 = 0.43

Adjustment to increase the fan energy in the 

modeled output to match the measured fan energy

Mechanical 

Ventilation

21.56 cfm supply Based on flow measurement and air handling unit

run time

Duct Leakage 

(To outside)

6.5 cfm/100 ft2

All ducts insulated 

to R-12 located in 

pier and beam

Original measurement was 54 cfm to outside or 

4.54 cfm/100 ft2

Original model: 17% ducts insulated to R-8 

located in pier & beam, 83% ducts located in 

conditioned space

Changed to increase energy use

Cooling Set Point 76.28°F Based on average measured indoor temperature 

during this period

Plug Loads 277.5 kWh Sum of energy consumed by two sensible gain 

heaters and additional not measured internal gain
65

Table 35. Model Inputs—House B

Model Input Value Basis and Calibration Adjustment (If Any)

Calibration Period: Jan. 6‒13

Air Source Heat 

Pump

Rated HSPF 

(Btu/ W-h)

8 N/A

COP 3.0 COP = 3.2 based on Jon Winkler’s 

recommendation

Measured COP is 1.6. Value adjusted to increase 

the heating energy consumption

Rated Air Flow Rate 

(cfm/t)

1160/1.68 = 690.47

heating

Rated standard airflow for the cooling coil = 580 

cfm based on specifications from the AirConditioning, Heating, and Refrigeration Institute

Air handling unit airflow per specification =

1,160 cfm

Rated Supply Fan 

Power (W/cfm)

0.34 400 W/1,160 cfm 

Installed Supply Fan 

Power (W/cfm)

0.8 460/1,000 = 0.46 

Adjustment to increase the fan energy in the 

modeled output to match the measured fan energy

Minimum Temp.

Below Which 

Compressor Turns 

Off

29 °F Reduced from 40°F to increase the efficiency of 

the heating system to ensure air source heat pump 

works for a longer period and matches measured 

data

Mechanical 

Ventilation

12.8 cfm supply Based on flow measurement and air handling unit

run time

Duct Leakage 

(To outside)

0.8 cfm/100 ft2

All ducts insulated 

to R-12 located in 

pier and beam

Original measurement was 9.5 cfm to outside, or 

0.80 cfm/100 ft2

Original model: 17% ducts insulated to R-8 

located in pier and beam, 83% ducts located in 

conditioned space

Heating Set Point 69.9 °F Based on average measured indoor temperature 

during this period

Plug Loads 122.6 kWh Sum of energy consumed by two sensible gain 

heaters and additional not measured internal gain

Calibration Period: Aug. 29‒Sept. 15 

Air Source Heat 

Pump
66

Model Input Value Basis and Calibration Adjustment (If Any)

Rated and Installed 

SEER

13 Rated value; input not used; not considered for 

model—EER used for calculations

EER (kBtu/kWh) 6.5 Reduced from 11 to account for lower efficiency 

measured during this period

Rated Air Flow Rate 

(cfm/t)

1,160/1.5 = 773 

cooling

Rated standard airflow for the cooling coil = 580 

cfm based on specifications from the AirConditioning, Heating, and Refrigeration Institute

(did not seem to affect results)

Air handling unit airflow per specification =

1,160 cfm

Rated Supply Fan 

Power (W/cfm)

0.34 400 W/1,160 cfm (did not affect results)

Installed Supply Fan 

Power (W/cfm)

0.80 460/1,000 = 0.46

Adjustment to increase the fan energy in the 

modeled output to match the measured fan energy

Mechanical 

Ventilation

12.8 cfm supply Based on flow measurement and air handling unit

run time

Duct Leakage 

(To outside)

0.8 cfm25/100 ft2

All ducts insulated 

to R-12 located in 

pier and beam

Original measurement was 9.5 cfm25 to outside,

or 0.80 cfm25/100 ft2

Total duct leakage: 36 cfm25

Original model: 17% ducts insulated to R-8 

located in pier and beam, 83% ducts located in 

conditioned space

Cooling Set Point 77.36°F Based on average measured indoor temperature 

during this period

Plug Loads 277.3 kWh Sum of energy consumed by two sensible gain 

heaters and additional not measured internal gain

Table 36. Model Inputs—House C

Model Input Value Basis and Calibration Adjustment (If Any)

Calibration Period: Jan. 6‒13

Mini-Split Heat 

Pump

Rated HSPF 

(Btu/ W-h)

4.2 Reduced from 12 HSPF to account for measured 

HVAC energy use and to account for the 

temperature controlled heaters in the bedrooms 
67

Model Input Value Basis and Calibration Adjustment (If Any)

Heating Capacity 

Offset 

(Btu/h)

3,000 Nominal heating capacity - nominal heating 

capacity = 18,000 - 15,000 

Minimum Heating 

Capacity

0.29 Min. capacity/nominal rated capacity = 

5,150/18,000

Maximum Heating 

Capacity

1.33 Max capacity/nominal rated capacity = 

24,000/18,000

Min Heating 

Airflow (cfm/t)

134 Min. heating airflow: 201cfm, t: 1.5

Max Heating 

Airflow

331.33 Min heating airflow: 497cfm, t:1.5

Supply Fan Power 

(W/cfm)

0.18 Full load amps: 0.67, cfm: 410 (from the AirConditioning, Heating, and Refrigeration 

Institute)

Minimum Temp. -13°F Specifications indicate 62% heating capacity at 

-13°F

Heating Set Point 70.4°F Based on average measured indoor temperature 

during this period

Plug Loads 157.5 kWh Sum of energy consumed by two sensible gain 

heaters, 4 transfer fans, and additional not 

measured internal gain. Energy consumed by 

temperature controlled heaters taken out 

Calibration Period: Aug. 29‒Sept. 15

Mechanical 

Ventilation

45 cfm exhaust

Mini-Split Heat 

Pump

Rated SEER 

(Btu/ W-h)

15.2 Reduced from 22 SEER to account for measured 

cooling energy

Minimum Cooling 

Capacity

0.436 Min. capacity/nominal rated capacity = 

6,450/15,000

Maximum Cooling 

Capacity

1.27 Max. capacity/nominal rated capacity = 

19,000/15,000

Min Cooling Airflow

(cfm/t)

180 Min. cooling airflow: 225 cfm, t: 1.25
68

Model Input Value Basis and Calibration Adjustment (If Any)

Max Cooling

Airflow

328.8 Min. cooling airflow: 411 cfm, t: 1.25

Supply Fan Power 

(W/cfm)

0.18 Full load amps: 0.67, cfm: 410 (from the AirConditioning, Heating, and Refrigeration 

Institute)

Minimum Temp. -13°F Specifications indicate 62% heating capacity at 

-13°F

Heating Set Point 74.12°F Based on average measured indoor temperature 

during this period

Plug Loads 301.114 kWh Sum of energy consumed by two sensible gain 

heaters, 4 transfer fans, and additional not 

measured internal gain

3.4.3 Model Runs

The calibrated models were then run for each of the three locations. Five models were prepared. 

Three of the models were created from directly measured data as described above. Two of the 

models were not built as test homes, so they were simulated by changing only the heating system 

type (electric resistance to heat pump or vice versa). Because the heating system efficiencies 

were well known from the measured data, this was done with a high degree of confidence. Note 

that the modeled home envelopes were not altered for code and program compliance in the 

different climate locations; rather, they were retained as built. A summary of the five models is 

provided in Table 37.

Table 37. Summary of Models

Model Thermal Envelope Space Conditioning Data Source

A1 HUD code Electric resistance furnace; split system 

ACa Measured

A2 HUD code Heat pump furnace; split system AC Simulated

B1 Manufactured home 

ENERGY STAR Electric resistance furnace; split system AC Simulated

B2 Manufactured home 

ENERGY STAR Heat pump furnace; split system AC Measured

C ZERH (IECC 2012) Ductless mini-split heat pump Measured a Air conditioner

The calibrated models had sensible gain heaters installed to account for the internal gains due to 

people, lights, and appliances. To estimate these internal gains in an occupied and functional 

home, some assumptions were made, as given in Table 38. 
69

House C had transfer fans installed in the three bedrooms and the master bathroom; these turned

on when the temperatures in those rooms fell below 69°F in heating or rose above 76°F in 

cooling. When analyzing the behavior of the transfer fans, it was found that they were on nearly 

44% of the hours during the cooling season and 90% of the hours during the heating season. This 

energy was translated into BEopt as miscellaneous plug loads to include in the model the energy 

use and internal gains due to these fans.

Table 38. Assumptions for Model Runs

Model A and A1 Model B and B1 Model C

Set Point Heating: 68°F

Cooling: 78°F

Heating: 68°F

Cooling: 78°F

Heating: 68° F

Cooling: 78°F

Bathroom Exhaust 

Rate 

(Default per 

Building America 

House Simulation 

Protocols)

32 cfm avg. 60 min/d

(intermittent)

26 cfm avg. 60 min/d

(intermittent)

50 cfm avg. 60 min/d

(intermittent)

Bath Fan Power 0.3 W/cfm/fan 0.3 W/cfm/fan 0.3 W/cfm/fan

Kitchen Range Hood 

Exhaust 

(Changes in Code)

80 cfm 77 cfm

110 cfm 60 min/d

(intermittent) (per 

HSP)

Water Heater Electric benchmark, 

50 gal, 0.90 EF

Electric standard, 50 

gal, 0.92 EF

Electric premium, 50 

gal, 0.95 EF

Lighting 100% incandescent 100% incandescent 80% compact 

fluorescent lighting

Refrigerator Benchmark =

434 kWh/yr

0.8 X benchmark =

347 kWh/yr

0.8 X benchmark =

347 kWh/yr

Cooking Range Benchmark (499 

kWh/yr, electric)

0.8 X benchmark (399 

kWh/yr, electric)

0.8 X benchmark (399 

kWh/yr, electric)

Dishwasher Benchmark 

(318 kWh/yr )

0.8 X benchmark 

(290 kWh/yr)

0.8 X benchmark 

(290 kWh/yr)

Clothes Washer Standard 

(MEFa = 1.41)

ENERGY STAR 

(MEF = 2.47)

ENERGY STAR 

(MEF = 2.47)

Clothes Dryer Electric (EF = 3.1) Electric (EF = 3.1) Electric (EF = 3.1)

Additional Plug 

Loads None None Transfer fan energy as 

described above

Appliance Operating 

Schedules

Per the Building America House Simulation Protocols

(National Renewable Energy Laboratory 2010) a Modified Energy Factor
70

3.4.4 Modeling Results

Figure 37 through Figure 42 show the results of comparing the five models for each of the three 

climates. The results are presented in terms of annual site energy consumption in MMBtu/Yr and 

annual space-conditioning energy in MMBtu/yr (also site energy). All three climates showed

similar relationships: Model A1 used the most space-conditioning and ventilation energy, 

followed by Model B1. The conventional heat pump models (A2 and then B2) were next in 

consumption. Model C had the least space-conditioning/ventilation consumption—generally less 

than half that of A1 and 20% to 35% less than the next most efficient model, B2. Because the 

mini-split heat pump in Model C is much more efficient than the conventional air-conditioning 

systems, the reduction in annual energy use was highest in the warmest climate (Columbus, 

Mississippi) and lowest in the coolest climate (Bowling Green, Kentucky).

Figure 37. Annual energy consumption comparison—Columbus, Mississippi

7.43 7.43 5.84 5.84 5.64

4.72 4.72

4.72 4.72 2.93

2.29 4.58

1.88 3.73

0.14

1.61

6.34

7.74

5.12

6.33

2.56

18.65 8.95

15.6 7.78

8.07

10.67

10.67 9.69

9.69

8.95

50.16

44.15

42.9

38.14

30.12

0

10

20

30

40

50

60

Home A 1 Home A 2 Home B 1 Home B 2 Home C 1

Site energy (MMBtu/yr)

Columbus, Mississippi

Vent Fan (E) Lg. Appl. (E) Lights (E) HVAC Fan/Pump (E)

Transfer fan (E ) Cooling (E) Heating (E) Hot Water (E)
71

Figure 38. Annual space-conditioning comparison—Columbus, Mississippi

2.29

4.58

1.88

3.73

0.14 1.61

6.34

7.74

5.12

6.33

2.56

18.65

8.95

15.6

7.78

8.07

27.34

21.33

22.65

17.89

12.60

0

5

10

15

20

25

30

Home A 1 Home A 2 Home B 1 Home B 2 Home C 1

Space conditioning (MMBtu/yr)

Columbus, Mississippi

HVAC Fan/Pump (E) Vent Fan (E) Transfer fan (E ) Cooling (E) Heating (E)
72

Figure 39. Annual energy consumption comparison—Knoxville, Tennessee

7.43 7.43 5.84 5.84 5.64

4.72 4.72

4.72 4.72 2.93

2.08 4.46

1.7 3.57

0.13

1.61

4.44

5.5

3.54

4.44

1.80

20.15 10.25

16.6 8.8

9.02

11.36

11.36 10.3

10.3

9.54

50.24

43.78

42.75

37.72

30.89

0

10

20

30

40

50

60

Home A 1 Home A 2 Home B 1 Home B 2 Home C 1

Site energy (MMBtu/yr)

Knoxville, Tennessee

Vent Fan (E) Lg. Appl. (E) Lights (E) HVAC Fan/Pump (E)

Transfer fan (E ) Cooling (E) Heating (E) Hot Water (E)
73

Figure 40. Annual space-conditioning comparison—Knoxville, Tennessee

2.08

4.46

1.7

3.57

0.13 1.61

4.44

5.5

3.54

4.44

1.80

20.15

10.25

16.6

8.8

9.02

26.73

20.27

21.89

16.86

12.78

0

5

10

15

20

25

30

Home A 1 Home A 2 Home B 1 Home B 2 Home C 1

Space conditioning (MMBtu/yr)

Knoxville, Tennessee

HVAC Fan/Pump (E) Vent Fan (E) Transfer fan (E ) Cooling (E) Heating (E)
74

Figure 41. Annual energy consumption comparison—Bowling Green, Kentucky

7.43 7.43 5.84 5.84 5.64

4.72 4.72

4.72 4.72 2.93

2.22 4.76

1.81 3.79

0.17

1.61

4.34

5.36

3.44

4.31

1.74

25.08

13.31

20.64

11.42

11.99

11.58

11.58 10.49

10.49

9.72

55.43

47.22 46.99

40.62

34.02

0

10

20

30

40

50

60

Home A 1 Home A 2 Home B 1 Home B 2 Home C 1

Site energy (MMBtu/yr)

Bowling Green, Kentucky

Vent Fan (E) Lg. Appl. (E) Lights (E) HVAC Fan/Pump (E)

Transfer fan (E ) Cooling (E) Heating (E) Hot Water (E)
75

Figure 42. Annual space-conditioning comparison—Bowling Green, Kentucky

3.4.5 Cost Analysis

Table 39 shows the itemized costs for each component that differs among the three houses. The 

total incremental cost to build House C compared to House A was approximately $2,500,

including non-energy-related measures needed to comply with ZERH criteria. This translates to 

an approximate $6,600 incremental price to the retail homebuyer.

2.22

4.76

1.81

3.79

0.17 1.61

4.34

5.36

3.44

4.31

1.74

25.08

13.31

20.64

11.42

11.99

31.7

23.49

25.94

19.57

15.73

0

5

10

15

20

25

30

35

Home A 1 Home A 2 Home B 1 Home B 2 Home C 1

Space conditioning (MMBtu/yr)

Bowling Green, Kentucky

HVAC Fan/Pump (E) Vent Fan (E) Transfer fan (E ) Cooling (E) Heating (E)
76

Table 39. Incremental Costs

Item House A $ 

Homeowner

House B $ 

Homeowner

House C $ 

Homeowner

Estimated 

Incremental 

Cost A to B

Estimated 

Incremental 

Cost B to C

Estimated 

Incremental 

Cost A to C

Cooling 

Equipment

AC 

installed,

2 t

$2,498 HP 

installed,

1.5 t

$3,015 Mini-split heat 

pump

$3,300 $518 $285 $803 

Mini-split heat 

pump 

installation

$0 N/A $0 $0 

Heating 

Equipment

Furnace 

installed + 

thermo

$333 Furnace 

installed + 

thermo

$333 Included in 

cooling

$0 $0 ($333) ($333)

$0 $0 $0 $0 $0 

Distribution Interior 

ducts,

material

$232 Interior 

ducts,

material

$232 Transfer fans 

with fan 

center and

duct material

$1,454 $0 $1,222 $1,222 

Interior 

ducts,

plant labor

$0 Interior 

ducts, plant 

labor

$0 Transfer fan 

thermostat

$176 $0 $176 $176 

Crossover 

duct,

material

$92 Crossover 

duct,

material

$92 Transfer fans, 

fan 

thermostat, 

wiring and 

duct 

installation

$0 $0 ($92) ($92)

Crossover 

duct, site 

labor

$38 Crossover 

duct, site 

labor

$38 N/A $0 $0 ($38) ($38)

Insulation—

Ceiling

R-14 

blown 

fiberglass

$404 R-28 

blown 

fiberglass

$579 R-45 densepack eaves,

blown 

$1,089 $175 $510 $685 
77

Item House A $ 

Homeowner

House B $ 

Homeowner

House C $ 

Homeowner

Estimated 

Incremental 

Cost A to B

Estimated 

Incremental 

Cost B to C

Estimated 

Incremental 

Cost A to C

fiberglass

Insulation—

Walls

R-11 batt 

fiberglass

R-13 batt 

fiberglass

$670 Foam + FG 

batt R-13

$1,606 $670 $936 $1,606 

Insulation—

Floor

R-14 

blanket 

fiberglass

$687 R-28 

blanket 

fiberglass

$1,374 R-28 blanket 

fiberglass

$1,374 $687 $0 $687 

AirTightening 

Measures

N/A $0 N/A $0 Prescriptive 

measures

$0 $0 $0 $0 

$53 $0 $53 $53 

Windows Clayton 

single plus 

storm

$1,382 Clayton 

vinyl, lowemissivity

air filled

$1,600 Clayton vinyl,

lowemissivity, 

argon filled

$2,200 $218 $600 $818 

Doors Standard $769 Standard $769 One door, low 

U-value

$507 $0 ($263) ($263)

Roof 

Ventilation

N/A $0 N/A $0 AccuVent 

baffles

$169.88 $0 $170 $170 

Interior 

Framing

2 x 3 

framing

$0 2 x 3 

framing

$0 Up-charge for 

2 x 4 framing 

for transfer 

fan walls

$220 $0 $220 $220 

Range Hood Standard $56 Standard $56 BROAN 30-in

range hood 

403001 white

$73.39 $0 $18 $18 

Water 

Heater

Standard $0 Standard $0 Standard $0 $0 $0 
78

Item House A $ 

Homeowner

House B $ 

Homeowner

House C $ 

Homeowner

Estimated 

Incremental 

Cost A to B

Estimated 

Incremental 

Cost B to C

Estimated 

Incremental 

Cost A to C

Carbon 

Monoxide

Alarms

N/A $0 N/A $0 Carbon 

monoxide

alarms

$176 $0 $176 $176 

Ventilation 

Fans

Ventline $46 Ventline $46 Air King x 2 $184.80 $0 $138 $138 

Gutters N/A $0 N/A $0 Gutters $450 $0 $450 $450 

Refrigerator Standard $775 Standard $775 ENERGY 

STAR model

$774.97 $0 $0 $0 

Dishwasher Standard $378 Standard $378 ENERGY 

STAR model

$378.42 $0 $0 $0 

Lights N/A $0 N/A $0 Compact 

fluorescent 

lighting in 

80%

$110 $0 $110 $110 
79

Because House C was designed to comply with ZERH criteria, it included some items that were 

not strictly related to energy efficiency, such as gutters, ventilation fans, and carbon monoxide 

alarms. Not counting these items, the premiums to build House C compared to House A and

House B were $5,843 and $3,575, respectively (price to homebuyer). The modeled energy 

savings of House C compared to House A and House B ranged from 5.29 to 15.97 MMBtu/yr 

depending on climate location. 

Table 40 through 

Table 42 compare the annual utility bill savings in dollars at the average statewide Tennessee 

electricity rate of 10.59¢/kWh (U.S. Energy Information Administration 2015) with the costs for 

energy measures only.

As shown in the modeling results and in Table 40, the energy savings from House C compared to

House B was the highest in the warmest climate (Columbus), which resulted in a payback period 

of 14.4 yr. House B and House C showed payback periods that ranged from 4.9 to 9.7 yr across 

the climates compared to House A. In Bowling Green, House C achieved the largest savings—

$664/yr—compared to House A. House B, the ENERGY STAR home, had the shortest payback 

period in all climates compared to House A.

Table 40. Energy Savings and Payback—Columbus, Mississippi

House

Annual 

Utility 

Cost

Savings 

Compared 

to House A

Incr. Retail 

Cost 

Compared 

to House A

Payback

Compared 

to House A

(yr)

Savings 

Compared 

to House B

Incr. Retail 

Cost 

Compared 

to House B

Payback 

Compared 

to House B 

(yr)

A $1,653 N/A N/A N/A N/A N/A N/A

B $1,280 $373 $2,268 6.1 N/A N/A N/A

C $1,031 $622 $5,843 9.4 $249 $3,575 14.4

Table 41. Energy Savings and Payback—Knoxville, Tennessee

House

Annual 

Utility 

Cost

Savings 

Compared 

to House A

Incr. Retail 

Cost 

Compared 

to House A

Payback 

Compared 

to House A 

(yr)

Savings 

Compared 

to House B

Incr. Retail 

Cost 

Compared 

to House B

Payback 

Compared 

to House B 

(yr)

A $1,656 N/A N/A N/A N/A N/A N/A

B $1,263 $393 $2,268 5.8 N/A N/A N/A

C $1,055 $601 $5,843 9.7 $208 $3,575 17.2
80

Table 42. Energy Savings and Payback—Bowling Green, Kentucky

House

Annual 

Utility 

Cost

Savings 

Compared 

to House A

Incr. Retail 

Cost 

Compared to

House A

Payback

Compared 

to House A 

(yr)

Savings 

Compared 

to House B

Incr. Retail 

Cost 

Compared to

House B

Payback 

Compared 

to House B 

(yr)

A $1,816 N/A N/A N/A N/A N/A N/A

B $1,356 $460 $2,268 4.9 N/A N/A N/A

C $1,152 $664 $5,843 8.8 $204 $3,575 17.5
81

4 Conclusions

Following are the research questions and responses:

1. Can factory-built, manufactured homes meet the ZERH requirements as defined? If not, 

what changes are suggested in the ZERH specifications to better reflect and take 

advantage of the unique aspects of factory building?

House C was built in compliance with the HUD code and DOE ZERH criteria. The use of a 

ductless heat pump simplified the compliance with ENERGY STAR version 3 HVAC 

requirements. Thermal envelope, ventilation, and indoor air quality requirements were not a 

barrier, although they did add costs.

2. What are the added costs and energy savings for manufactured ZERHs using ductless 

mini-split heat pumps compared to the HUD code and ENERGY STAR manufactured 

homes?

HVAC energy savings in House C achieved a 50% reduction compared to the HUD-code home 

(House A) despite the need for supplemental resistance heat. Room for improvement exists in the 

form of better air distribution during the heating season, reducing the need for supplemental 

resistance heating, and improved ductless mini-split COPs, achieved perhaps by increasing 

airflow rates.. Equipment improvements had a larger impact than envelope improvements. The 

premium (counting only the energy-efficiency measures) to build House C compared to House A 

and House B was $2,060 and $1,166, respectively, at manufacturer cost. The energy savings of 

House C compared to House A and House B ranged from 5 to 16 MMBtu/yr depending on 

climate location. Paybacks to the homeowner for House C compared to House A and House B 

ranged from 8.8 to approximately 17.5 yr based on retail costs.

3. How does point-source space conditioning perform in a ZERH in terms of comfort, and 

how do operational variables such as opening and closing interior doors and window 

blinds and the operation of transfer fans affect that performance in heating and cooling 

modes?

A. Thermal comfort. The point-source heat pump in House C performed reasonably 

well in cooling mode. House C showed the widest temperature fluctuation from 

one room to another, but only the master bathroom exceeded the upper bounds of 

the Air Conditioning Contractors of America temperature range (with the interior 

doors open). In heating mode, the bedrooms did not maintain acceptable 

temperature in House C; therefore, resistance heaters with dedicated thermostats 

set to 69°F were added to those rooms. This increased energy consumption when

the ambient temperature was below freezing. 

B. Relative humidity. Relative humidity was within acceptable limits in all houses 

all year. Latent loads were not simulated; however, short-term humidification 

testing in summer revealed little impact on indoor relative humidity despite the 

significant moisture loads being introduced into the buildings, which indicates 

that the cooling equipment had sufficient excess capacity to handle the latent 

loads during hot weather. 
82

C. Transfer fan operation impact on room temperatures. A comparison of fan-on 

to fan-off periods in House C did not show a difference in bedroom/master 

bathroom temperatures at similar outdoor temperatures during both seasons. The 

interior doors were open during these measurements so the heat transfer through 

the open doors may have dwarfed that through the fans.

D. Blind position impact on cooling energy. The data showed a strong indication 

that closing blinds reduced cooling energy needs. Cooling energy was reduced by 

20.4% and 25.7% in House B and House C, respectively. House A cooling energy 

was reduced by 36.9%. The higher savings in House A is theorized to be due to 

the higher solar heat gain coefficient in the House A windows and a 

proportionally greater impact on solar gain of the blinds in those circumstances.

E. Blind position impact on room temperatures in cooling. Closing blinds during

the cooling season led to lower room temperatures in House C in all the rooms. In 

House A and House B, closing the blinds did not result in significantly lower 

room temperatures, presumably because the space-conditioning distribution 

system overcame the effects of the blinds on room temperature.

F. Impact of door position on room temperatures. In House C during the heating 

season, keeping the doors open resulted in a lower difference in room temperature 

between the main space and the bedrooms. Bedrooms were 0.4‒1.8°F lower than 

the heating set point with the doors open and 4.0‒5.4°F lower with the doors 

closed. During cooling season, there was no clear impact on room temperatures of 

closing interior doors.

G. Convective heat transfer through open doors. Heat transfer through open doors 

with a two-degree F temperature difference between the main living space and 

bedrooms was estimated by measuring the run time of the electric resistance 

heater and adjusting it based on partition U-values. Effective airflow rates of 

approximately 140 to 281 cfm were calculated.

4. What is the in-situ COP in heating of a ductless mini-split heat pump?

The heating coefficient of performance was calculated for both heat pumps using two 

independent methods: (1) airflow and temperature measurements and (2) co-heat testing 

measurements. The co-heat testing method was deemed more reliable. Using this method, the 

COP of both the conventional split-system heat pump and the ductless mini-split were 

approximately 2.5. This was well below the expectation for the mini-split based on manufacturer 

data. However, when the mini-split air handling unit fan was forced to run on its high-speed

setting, its COP increased to 4.11, indicating that low airflow could have been a cause of the low 

heating efficiency of this unit.

5. Other conclusions

A. Moisture measurements. Wood moisture content was slightly higher in House C

compared to House B, but it was well within safe limits. Higher moisture content 

was due to the addition of exterior foam insulation to the walls in House C that

reduced the vapor permeability of the foam sheathing (extruded polystyrene
83

insulation). However, it also resulted in a 5.5°F higher minimum condensation 

surface temperature than in House B, mitigating condensation risk.

B. Peak loads. Peak demand in House C was significantly lower than it was in the 

other two houses during all months of the year. House B had somewhat lower 

peaks than did House A during most months, but some winter peaks were similar, 

indicating that House B’s peak occurred when the heat pump was not running and 

the house was relying solely on electric resistance backup. On average, House B 

had an 18% lower peak demand than did House A, and House C had a 69% lower 

peak demand than did House A during the utility’s peak hours.
84

References

National Renewable Energy Laboratory, Building America House Simulation Protocols (Oak 

Ridge, TN: U.S. Department of Energy's Building America Program, 2010).

Air Conditioning Contractors of America, Manual RS: Comfort, Air Quality, and Efficiency by 

Design (Arlington, VA: Air Conditioning Contractors of America, 1997).

Aries, M.B.C., and G.R. Newsham, "Effect of Daylight Savings Time on Lighting Energy Use: 

A Literature Review," Energy Policy 36(6) (2008): 1,858‒1,866.

Boudreaux, P.R., A.C. Gehl, and J.E. Christian, "Occupancy Simulation in Three Residential 

Research Houses," ASHRAE Transactions 118(2) (2011).

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of the Fifteenth Symposium on Improving Building Systems in Hot Humid Climates 

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GA: ASHRAE, 2004).

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1996), 8.47‒8.59.

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86

Appendix A: Commissioning Test Results 

Table 43. Duct Leakage

Duct Leakage (cfm)

House Total To Outside

A

115 cfm

Fan pressure: -50.3 Pa

54 cfm

Fan pressure: -8.9 Pa

B

36 cfm

Fan pressure: -31.9 Pa

8-11 cfm (low flow)

Fan Pressure: -1.2 Pa

C N/A N/A

Table 44. Total System Flow

Pressures Measured at Kitchen Register House A House B

Normal System Operating Pressure 46 pa 42.5 pa

Operating Pressure with Duct Blaster Connected 34 pa 29 pa

Matched System Pressure 45.5 pa 42 pa

Return Flow at Matching System Pressure 980 cfm 1,000 cfm

Fan Pressure -80.2
87

Table 45. Supply Register Flows

Register House A (cfm) 

(July 23, 2014) House B (cfm) Room Area (ft2

) House A Supply 

(cfm/ft2)

House B Supply 

(cfm/ ft2)

Northwest

Bedroom

136 120 142 1.0 0.8

Bathroom 2 LO 76 43 LO 1.8

Kitchen 152 130 159 1.0 0.8

Dining Room 140 133 132 1.1 1.0

Master Bathroom 151 156 131 1.2 1.2

Master 

Bedroom

126 123 234 0.5 0.5

Living Room 116 118

232 1.0 1.0

Entry 124 104

Northeast

Bedroom

109 93 137 0.8 0.7

TOTAL 1,054 1,053 1,210 0.87 0.87

Table 46. Ventilation Flows

House Whole-House Ventilation 

Flow (cfm)

Exhaust Fan Flow (cfm) Range Hood (cfm) Master Bathroom Bathroom 2

A 44 46 18 80

B 32 40 12 77

C 45 50 49 110
88

Table 47. House A Envelope Leakage

House A

Volume: 9,617 ft3 Test: Depressurization

Baselines (Pa) Target House 

Pressure (Pa)

Fan Pressure 

(Pa)

Flow @ Pressure 

(cfm) Ring Actual House Pressure (Pa) ACH

0.65 19 45.1 390 B -18.9 2.4

-0.7 29 87.7 550 B -29.1 3.4

-0.62 39 113 634 B -39.2 4.0

-1.5 49 167 748 B -49 4.7

0.07 59 205 857 B -59 5.3

House B

Volume: 9,617 ft3 Test: Depressurization

Baselines (Pa) Target House 

Pressure (Pa)

Fan Pressure 

(Pa)

Flow @ Pressure 

(cfm) Ring Actual House Pressure (Pa) ACH

0.34 19 44.4 388 B -19 2.4

0.36 29 90.1 538 B -29 3.4

0.28 39 116.5 649 B -39.1 4.0

0.62 49 150 740 B -49.4 4.6

0.22 59 196 818 B -59.8 5.1

-0.22

House C

Volume: 9,617 ft3 Test: Depressurization

Note: With range hood damper installed
89

Baselines (Pa) Target House 

Pressure (Pa)

Fan Pressure 

(Pa)

Flow @ Pressure 

(cfm) Ring Actual House Pressure (Pa) ACH

0.84 19 27.2 268 B -19.8 1.7

0.19 29 41.2 384 B -29.7 2.4

-0.25 39 64.7 475 B -39 3.0

-0.4 49 106.5 616 B -48.9 3.8

-0.12 59 151 716 B -59.3 4.5

Table 48. Transfer Fan Flows—House C

Original Fans

(March 30, 2014)

Original Fans

(July 22, 2014)

New Fans Max. Speed 

in Master Bedroom and Bathroom

July 22, 2014

Room Fan Side 

(cfm) Supply (cfm) Fan Side (cfm) Supply (cfm) Fan Side (cfm) Supply (cfm)

Master 

Bedroom

66 48 57 45 133 106

Master 

Bathroom

51 48 51 45 125 115

Northwest 

Bedroom

42 38 Not measured 37 N/A N/A

Northeast 

Bedroom

56 48 55 49 N/A N/A
90

Appendix B: Monitoring Points and Equipment

Table 49. Inventory of Monitoring Equipment, Data Loggers, and Sensors

Quantity Description/

Purpose

Make and Model of 

Monitoring Equipment 

(or Equal)

A B C Outdoors

3

Data logging equipment

Campbell Scientific data

logger, model: CR1000 1 1 1

3 Campbell Scientific data

logger, power supply 1 1 1

3

Campbell Scientific, 

multiplexer model: 

AM16/32B

1 1 1

15 Air temperature 

measurement Watlow thermocouples 5 5 5

2 Electric furnace power 

(100 amps)

Continental Control 

Systems,

ACT-0750-100

2

7 Air temperature/

relative humidity Campbell CS215 probe 1 4 1 1

19

Protection for outdoor air 

temperature and relative 

humidity sensor

Campbell Scientific, 41303-

5A radiation shield 6 6 6 1

1 Solar radiation sensor Campbell LI200X-L silicon 

pyranometer 1

4 Moisture content of wood Omnisense S900-1 2 2

6 Compressor and fan current 

measurements Veris, H721LC (10 amps) 2 2 2

2 Status heat pump reversing 

valve Veris, H300 1 1

6 Heat pump/

AC power (20 amps)

Continental Control 

Systems,

ACT-0750-20

2 2 2

6 Total house power 

(150 amps)

Continental Control 

Systems,

ACT-0750-150

2 2 2

7 Wattnode power meter Continental Control 

Systems, WNB-3Y-208-P 3 2 2
91

Quantity Description/

Purpose

Make and Model of 

Monitoring Equipment 

(or Equal)

A B C Outdoors

1 Bath fan run time Veris, H300 1

1 Electric furnace resistance 

element status Veris, H300 1

3 Serial-to-Ethernet interface 

for wireless communication Campbell Scientific, NL201 1 1 1

4 Monitor run time of throughwall air transfer fans Veris, H300 4
92

Appendix C: Impacts of Transfer Fans

Figure 43. House C Bedroom 2 temperatures with and without transfer fan operation

(cooling season)
93

Figure 44. House C Bedroom 3 temperatures with and without transfer fan operation

(cooling season)
94

Figure 45. House C living room temperatures with and without transfer fan operation

(cooling season)
95

Figure 46. House C master bedroom temperatures with and without transfer fan operation

(cooling season)

Figure 47. House C master bathroom temperatures with and without transfer fan operation 

(cooling season)
96

Appendix D: Impacts of Blind Position 

Figure 48. House C impacts of blind position in Bedroom 2 on room temperature compared to 

outdoor temperature (cooling season)
97

Figure 49. House C impacts of blind position on Bedroom 3 on room temperature compared to 

outdoor temperature (cooling season)
98

Figure 50. House C impacts of blind position on living room temperature compared to outdoor 

temperature (cooling season)
99

Figure 51. House C impacts of blind position on master bedroom temperature compared to 

outdoor temperature (cooling season)
100

Figure 52. House C impacts of blind position on master bathroom temperature compared to 

outdoor temperature (cooling season)
101

Appendix E: Impacts of Door Position 

Figure 53. House A impacts of door position on Bedroom 2 temperature compared to outdoor 

temperature (0.8 cfm/ft2

) (cooling season)
102

Figure 54. House A impacts of door position on Bedroom 3 temperature compared to outdoor 

temperature (1 cfm/ft2

) (cooling season)
103

Figure 55. House A impacts of door position on living room temperature compared to outdoor 

temperature (cooling season)
104

Figure 56. House A impacts of door position on master bedroom temperature compared to 

outdoor temperature (0.5 cfm/ft2

) (cooling season)
105

Figure 57. House A impacts of door position on master bathroom temperature compared to

outdoor temperature (1.2 cfm/ft2

) (cooling season)
106

Figure 58. House B impacts of door position on Bedroom 2 room temperature compared to

outdoor temperature (0.7 cfm/ft2

) (cooling season)
107

Figure 59. House B impacts of door position on Bedroom 3 room temperature compared to 

outdoor temperature (0.8 cfm/ft2

) (cooling season)
108

Figure 60. House B impacts of door position on living room temperature compared to outdoor 

temperature—aspirator failure open period (cooling season)
109

Figure 61. House B impacts of door position on master bedroom temperature compared to 

outdoor temperature (0.5 cfm/ft2

) (cooling season)
110

Figure 62. House B impacts of door position on master bathroom temperature compared to 

outdoor temperature (1.2 cfm/ft2

) (cooling season)
111

Figure 63. House C impacts of door position on Bedroom 2 room temperature compared to 

outdoor temperature (cooling season)
112

Figure 64. House C impacts of door position on Bedroom 3 room temperature compared to 

outdoor temperature (cooling season)
113

Figure 65. House C impacts of door position on living room temperature compared to outdoor 

temperature (cooling season)
114

Figure 66. House C impacts of door position on master bedroom temperature compared to 

outdoor temperature (cooling season)
115

Figure 67. House C impacts of door position on master bathroom temperature compared to 

outdoor temperature (cooling season)
116

Figure 68. House A impacts of door position on Bedroom 2 temperature compared to outdoor 

temperature (heating season)

Figure 69. House A impacts of door position on Bedroom 3 temperature compared to outdoor 

temperature (heating season)
117

Figure 70. House A impacts of door position on living room temperature compared to outdoor 

temperature (heating season)
118

Figure 71. House A impacts of door position on master bedroom temperature compared to 

outdoor temperature (heating season)
119

Figure 72. House A impacts of door position on master bathroom temperature compared to 

outdoor temperature (heating season)
120

Figure 73. House B impacts of door position on Bedroom 2 temperature compared to outdoor 

temperature (heating season)
121

Figure 74. House B impacts of door position on Bedroom 3 temperature compared to outdoor 

temperature (heating season)
122

Figure 75. House B impacts of door position on living room temperature compared to outdoor 

temperature (heating season)
123

Figure 76. House B impacts of door position on master bedroom temperature compared to 

outdoor temperature (heating season)
124

Figure 77. House B impacts of door position on master bathroom temperature compared to 

outdoor temperature (heating season)
125

Figure 78. House C impacts of door position on Bedroom 2 temperature compared to outdoor 

temperature (heating season)
126

Figure 79. House C impacts of door position on Bedroom 3 temperature compared to outdoor 

temperature (heating season)
127

Figure 80. House C impacts of door position on living room temperature compared to outdoor 

temperature (heating season)
128

Figure 81. House C impacts of door position on master bedroom temperature compared to 

outdoor temperature (heating season)
129

Figure 82. House C impacts of door position on master bathroom temperature compared to 

outdoor temperature (heating season)
130

Appendix F: Tracer Gas Test Data

Table 50. Tracer Gas Test Data

House C House B House A Notes

2014 Hour ppm ACH ppm ACH ppm ACH

Dec. 8 17 3.01 3.06 Normal operation of 

HVAC in all three houses. 

House C exhaust fan off

18 2.62 0.14 2.51 0.20

19 2.31 0.13 2.07 0.19

20 2.03 0.13 1.64 0.23

21 1.81 0.11 1.34 0.20

22 1.61 0.12 1.1 0.20

23 1.43 0.12 0.867 0.24

0 1.27 0.12 0.696 0.22

Dec. 9 1 1.11 0.13 0.553 0.23

2 0.972 0.13 0.443 0.22

3 0.851 0.13 0.339 0.27

4 0.743 0.14 0.273 0.22

5 0.655 0.13 0.214 0.24

6 0.573 0.13 0.171 0.22

7 0.493 0.15 0.145 0.16

8 0.409 0.19 House C exhaust fan on

starting at 7:30 a.m.

9 0.307 0.29 House C exhaust fan on

10 0.235 0.27 House C exhaust fan on

11 House C exhaust fan off

until Dec 11

12

13

14

15

16
131

House C House B House A Notes

17 3.09

18 3.1 2.44 0.24 Co-heating in all three

houses

19 2.68 0.15 1.91 0.24

20 2.31 0.15 1.5 0.24

21 2.06 0.11 1.2 0.22

22 1.73 0.17 0.953 0.23

23 1.51 0.14 0.759 0.23

0 1.31 0.14 0.609 0.22

Dec. 10 1 1.15 0.13 0.489 0.22

2 0.971 0.17 0.39 0.23

3 0.84 0.14 0.307 0.24

4 0.718 0.16 0.242 0.24

5 0.621 0.15 0.197 0.21

6 0.535 0.15 0.16 0.21

7 0.468 0.13 0.13 0.21

8 0.407 0.14 0.11 0.17

9 0.355 0.14

10 0.315 0.12

11 0.268 0.16

12 0.236 0.13

13

14

15

16

17 3.42 3.95

18 2.68 0.24 3.08 0.25 Co-heating in all three

houses

19 2.11 0.24 2.41 0.25

20 1.65 0.25 1.87 0.25

21 1.3 0.24 1.46 0.25
132

House C House B House A Notes

22 1.01 0.25 1.12 0.27

23 0.784 0.25 0.872 0.25

0 0.607 0.26 0.675 0.26

Dec. 11 1 0.477 0.24 0.525 0.25

2 0.371 0.25 0.408 0.25

3 0.292 0.24 0.321 0.24

4 0.23 0.24 0.252 0.24

5 0.183 0.23 0.199 0.24

6 0.147 0.22 0.151 0.28

7 0.117 0.23 0.121 0.22

8

9

10

11

12

13

14

15

16

17 Normal operation of 

HVAC in all three houses. 

House C exhaust fan on

18 3.21 2.82

19 2.51 0.25 2.23 0.23

20 1.85 0.31 1.75 0.24

21 1.43 0.26 1.34 0.27

22 1.15 0.22 1.06 0.23

23 0.859 0.29 0.815 0.26

0 0.658 0.27 0.637 0.25

Dec. 12 1 0.504 0.27 0.502 0.24

2 0.384 0.27 0.392 0.25
133

House C House B House A Notes

3 0.299 0.25 0.299 0.27

4 0.233 0.25 0.236 0.24

5 0.159 0.38 0.182 0.26

6 0.126 0.23 0.148 0.21

7 0.109
134

Appendix G: Co-Heat Testing Data

Table 51. House A Co-Heat Testing Data

Time 

Stamp

Outdoor

Temp.

Avg. 

Indoor 

Temp. 

Sensible 

Gain 

Heater

Sensible 

Gain 

Heater

Main 

Panel

Outdoor 

Unit

Air 

Handling 

Unit

Fan

Total 

Internal 

Gain

Calculated 

Simple UA

(°C) (°C) (kW) (kW) (kW) (kW) (kW) (kW) (kW/°C)

12/10/2014 2:00 3.1 23.0 0.304 0.197 3.467 0.011 0.001 3.467 0.174

12/10/2014 3:00 3.2 23.0 0.297 0.197 3.435 0.011 0.002 3.435 0.174

12/10/2014 4:00 3.2 23.0 0.283 0.197 3.417 0.011 0.002 3.417 0.172

12/10/2014 5:00 3.2 23.0 0.281 0.201 3.405 0.011 0.001 3.405 0.172

12/10/2014 6:00 3.3 23.0 0.300 0.209 3.268 0.011 0.001 3.268 0.166

12/11/2014 2:00 -1.7 23.0 0.001 0.002 3.933 0.000 0.001 3.933 0.159

12/11/2014 3:00 -1.3 23.0 0.001 0.002 3.934 0.000 0.001 3.934 0.162

12/11/2014 4:00 -1.9 23.0 0.001 0.002 3.936 0.000 0.001 3.936 0.158

12/11/2014 5:00 -2.8 23.0 0.001 0.002 4.043 0.000 0.001 4.043 0.156

12/11/2014 6:00 -3.1 23.0 0.001 0.002 4.037 0.000 0.001 4.037 0.154
135

Table 52. House B Co-Heat Testing Data

Time 

Stamp

Outdoor

Temp.

Avg.

Indoor 

Temp.

Sensible 

Gain 

Heater

Sensible 

Gain 

Heater

Main 

Panel

Outdoor 

Unit

Air 

Handling Unit

Fan

Total 

Internal 

Gain

Calculated 

Simple UA

(°C) (°C) (kW) (kW) (kW) (kW) (kW) (kW) (kW/°C)

12/10/2014 2:00 3.1 23.0 0.301 0.197 2.617 0.006 0.008 2.617 0.132

12/10/2014 3:00 3.2 23.0 0.292 0.197 2.680 0.006 0.008 2.680 0.135

12/10/2014 4:00 3.2 23.0 0.281 0.196 2.603 0.006 0.008 2.603 0.132

12/10/2014 5:00 3.2 23.0 0.279 0.199 2.603 0.006 0.008 2.603 0.132

12/10/2014 6:00 3.3 23.0 0.298 0.208 2.562 0.006 0.008 2.562 0.130

12/11/2014 2:00 -1.7 23.0 0.000 0.002 3.128 0.007 0.008 3.128 0.126

12/11/2014 3:00 -1.3 23.0 0.000 0.002 3.144 0.007 0.008 3.144 0.130

12/11/2014 4:00 -1.9 23.0 0.000 0.002 3.147 0.007 0.008 3.147 0.126

12/11/2014 5:00 -2.8 23.0 0.000 0.002 3.186 0.007 0.008 3.186 0.123

12/11/2014 6:00 -3.1 23.0 0.000 0.002 3.169 0.007 0.008 3.169 0.121
136

Table 53. House C Co-Heat Testing Data

Time 

Stamp

Outdoor

Temp.

Avg.

Indoor 

Temp.

Sensible 

Gain 

Heater

Sensible 

Gain 

Heater

Main 

Panel

Outdoor 

Unit

Air 

Handling 

Unit

Fan

Simple 

UA 

Heat 

Loss

Total 

Internal 

Gain

Calculated 

Simple UA

(°C) (°C) (kW) (kW) (kW) (kW) (kW) (kW) (kW) (kW/°C)

12/10/2014 2:00 3.1 23.0 0.287 0.196 2.158 0.024 0.004 2.184 2.134 0.107

12/10/2014 3:00 3.2 23.0 0.277 0.196 2.144 0.025 0.004 2.165 2.119 0.107

12/10/2014 4:00 3.2 23.0 0.267 0.196 2.128 0.024 0.004 2.171 2.104 0.106

12/10/2014 5:00 3.2 23.0 0.264 0.200 2.147 0.022 0.004 2.171 2.125 0.107

12/10/2014 6:00 3.3 23.0 0.283 0.208 2.162 0.022 0.004 2.165 2.140 0.108

12/11/2014 2:00 -1.7 23.0 0.001 0.001 2.565 0.032 0.004 2.713 2.533 0.110

12/11/2014 3:00 -1.3 23.1 0.001 0.001 2.633 0.037 0.004 2.663 2.596 0.113

12/11/2014 4:00 -1.9 23.0 0.001 0.001 2.647 0.035 0.004 2.731 2.612 0.113

12/11/2014 5:00 -2.8 23.0 0.001 0.001 2.590 0.032 0.004 2.833 2.558 0.111

12/11/2014 6:00 -3.1 23.0 0.001 0.001 2.624 0.030 0.004 2.867 2.594 0.113
137

Appendix H: Impacts of Window Blind Position

Table 54. Data Used for Multi-Variable Regression—Blinds Closed Period (Sept. 23‒29)

Avg. 

Temp. (°C) 

Delta T 

(Tindoor -T 

outdoor) 

House A 

(°C)

Delta T 

(Tindoor -T 

outdoor) 

House B

(°C)

Delta T 

(Tindoor -T 

outdoor) 

House C 

(°C)

Direct 

Normal 

Radiation 

Total 

(Wh/m2)

Total 

Cooling 

Energy 

House A 

(kWh)

Total 

Cooling 

Energy 

House B 

(kWh)

Total 

Cooling 

Energy 

House C 

(kWh)

Tue. 09/23/14 17.30 -5.9 -6.9 -5.1 5,895.29 4.03 3.37 2.63

Wed. 09/24/14 18.50 -5.1 -6.0 -4.1 5,665.66 4.97 4.23 3.10

Thu. 09/25/14 20.15 -3.7 -4.6 -2.7 4,716.51 6.49 5.46 3.70

Fri. 09/26/14 20.17 -3.8 -4.6 -2.6 1,619.95 4.76 4.57 3.40

Sat. 09/27/14 19.50 -4.5 -5.3 -3.3 864.44 3.79 3.82 2.82

Sun. 09/28/14 22.05 -2.2 -2.9 -0.7 1,044.04 5.03 5.17 3.78

Mon. 09/29/14 21.10 -3.3 -4.0 -2.1 4,535.68 8.29 7.08 4.73

Table 55. Predicted Cooling Energy Calculation with Normalized Data—Blinds Open Period (Aug. 17‒23)

Avg. Temp. (°C ) 

Direct Normal 

Radiation Total 

(Wh/m2)

Predicted Total 

Cooling Energy 

House A- if blinds 

were closed

(kWh)

Predicted Total 

Cooling Energy 

House B- blinds 

closed period

(kWh)

Predicted Total 

Cooling Energy 

House C

(kWh)

Sun. 08/17/14 24.07 1,075.37 8.21 7.77 5.09

Mon. 08/18/14 24.13 1,936.92 8.69 8.02 5.10

Tue. 08/19/14 25.99 2,874.63 11.57 10.28 6.39
138

Avg. Temp. (°C ) 

Direct Normal 

Radiation Total 

(Wh/m2)

Predicted Total 

Cooling Energy 

House A- if blinds 

were closed

(kWh)

Predicted Total 

Cooling Energy 

House B- blinds 

closed period

(kWh)

Predicted Total 

Cooling Energy 

House C

(kWh)

Wed. 08/20/14 26.91 3,969.03 13.25 11.52 7.04

Thu. 08/21/14 26.85 3,798.98 13.06 11.39 6.99

Fri. 08/22/14 26.74 4,678.43 13.43 11.62 7.11

Sat. 08/23/14 27.20 4,043.29 13.61 11.83 7.20

Total cooling (kWh) 81.83 72.42 44.91

Table 56. Window Blinds Regression

SUMMARY OUTPUT House A

Regression Statistics

Multiple R 0.848477

R Square 0.719914

Adjusted R Square 0.579871

Standard Error 1.014776

Observations 7

ANOVA

df SS MS F Significance 

F
139

SUMMARY OUTPUT House A

Regression 2 10.5874 5.2937 5.1406

64

0.078448

Residual 4 4.119078 1.0297

7

Total 6 14.70648

Coefficients Standard 

error

t Stat P-value Lower 

95%

Upper 

95%

Lower 

95.0%

Upper 

95.0%

Intercept 8.275608 1.449644 5.7087

17

0.0046

56

4.250751 12.30047 4.250751 12.30047

Delta T House A 1.241755 0.415736 2.9868

81

0.0404

63

0.087486 2.396025 0.087486 2.396025

Direct Normal Radiation Total 

(W/m2)

0.000609 0.000228 2.6681

73

0.0559

12

-2.5E-05 0.001242 -2.5E-05 0.001242

Multiple R 0.887946

R Square 0.788448

Adjusted R Square 0.682672

Standard Error 0.696203

Observations 7

SUMMARY OUTPUT House B

Regression Statistics
140

ANOVA

df SS MS F Significance 

F

SUMMARY OUTPUT House B

Regression 2 7.225825 3.6129

12

7.4539

45

0.044754

Residual 4 1.938792 0.4846

98

Total 6 9.164617

Coefficients Standard 

error

t Stat P-value Lower 95% Upper 

95%

Lower 

95.0%

Upper 

95.0%

Intercept 8.543596 1.113623 7.6718

91

0.0015

52

5.451682 11.635

51

5.451682 11.63551

Delta T House B 1.025916 0.265947 3.8575

94

0.0181

84

0.287528 1.7643

03

0.287528 1.764303

Direct Normal Radiation 

Total (W/m2)

0.000376 0.000158 2.3841

63

0.0756

46

-6.2E-05 0.0008

15

-6.2E-05 0.000815

SUMMARY OUTPUT House C

Regression Statistics

Multiple R 0.893938

R Square 0.799126

Adjusted R Square 0.698688
141

Standard Error 0.388353

Observations 7

SUMMARY OUTPUT House C

ANOVA

df SS MS F Significance 

F

Regression 2 2.399962 1.1999

81

7.9564

67

0.040351

Residual 4 0.603273 0.1508

18

Total 6 3.003236

Coefficients Standard 

error

t Stat P-value Lower 95% Upper 

95%

Lower 

95.0%

Upper 

95.0%

Intercept 4.386133 0.369196 11.880

24

0.0002

87

3.361082 5.4111

85

3.361082 5.411185

Delta T House C 0.577592 0.144814 3.9885

12

0.0162

85

0.175524 0.9796

59

0.175524 0.979659

Direct Normal Radiation 

Total (W/m2)

0.00022 9.1E-05 2.4132

45

0.0732

97

-3.3E-05 0.0004

72

-3.3E-05 0.000472
142

Appendix I: Impacts of Controlled Heater Energy

Figure 83. House C Bedroom 2 impacts of controlled heater energy 
143

Figure 84. House C Bedroom 3 of controlled heater energy 
144

Figure 85. House C master bedroom impacts of controlled heater energy 

Figure 86. House C master bathroom impacts of controlled heater energy
145

Appendix J: Construction Drawings

Figure 87. House A production print (House B is identical.)
146

Figure 88. House C mechanical system schematic plan
147

Wall and Roof Insulation Details (House C)

Figure 89 through Figure 93 show construction details indicating how the exterior continuous 

insulation was incorporated into the wall assembly.

Figure 89. Plan view of wall

Figure 90. Top plate (gable wall section)
148

Figure 91. Roof-to-wall connection (side wall section)

Figure 92. Floor-to-wall connection (side wall section)
149

Figure 93. Window sill
150

Figure 94. House C production print
DOE/GO-102016-4830 ▪ March 2016

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