Greenbelt Homes Pilot Energy 

Efficiency Program Phase 1 

Summary: Existing Conditions 

and Baseline Energy Use

J. Wiehagen, M. Del Bianco, and A. Wood

NAHB Research Center 

February 2013
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iii

Greenbelt Homes Pilot Energy Efficiency Program Phase 1 Summary:

Existing Conditions and Baseline Energy Use 

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: 

J. Wiehagen, M. Del Bianco, and A. Wood

NAHB Research Center

400 Prince George’s Blvd

Upper Marlboro, MD 20774

NREL Technical Monitor: Stacey Rothgeb

Prepared Under Subcontract No. KNDJ-0-40335-00

February 2013
iv

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v

Contents

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

List of Tables ............................................................................................................................................ viii

Definitions................................................................................................................................................... ix

Executive Summary................................................................................................................................... xi

1 Introduction........................................................................................................................................... 1

2 Background........................................................................................................................................... 1

3 Baseline Condition ............................................................................................................................... 5

4 Simulation Results and Energy Upgrade Cost Estimates.............................................................. 11

5 Phase 1 Energy and Environmental Monitoring.............................................................................. 15

5.1 Data Collection Equipment................................................................................................16

5.2 Measurement of Energy Use..............................................................................................16

6 Summary Indoor Temperature and Relative Humidity ................................................................... 20

7 Detailed Data Summary Energy Use: Measured and Utility Meter Readings for Three Building 

Types ................................................................................................................................................... 21

7.1 Masonry Block Building – Units B-1, B-2, B-3, B-4 ........................................................21

7.2 Wood Frame Brick-Veneered Building – FB-5 through FB-8 ..........................................25

7.3 Wood Frame Vinyl Building – FV-5 through FV-8 ..........................................................28

8 Detailed Data Summary Energy Use: Utility Meter Readings for Four Building Types .............. 31

8.1 Block Vinyl-Sided and Block Building Units BV-1, B-5, B-6, BV-2...............................31

8.2 Block Vinyl-Sided Units BV-3 through BV-6...................................................................33

8.3 Wood Frame Brick Units FB-1 through FB-4 ...................................................................34

8.4 Wood Frame Vinyl Units FV-1 through FV-4 ..................................................................35

9 Indoor Relative Humidity ................................................................................................................... 35

10 Building Crawlspaces ........................................................................................................................ 42

11 Summary ............................................................................................................................................. 46

12 Next Steps ........................................................................................................................................... 47

References................................................................................................................................................. 48

Appendix A: Typical Building Specifications......................................................................................... 49

Appendix B: Temperature and RH Sensor Locations ........................................................................... 53

Appendix C: Phase 1 Energy Simulations.............................................................................................. 55

Before and After Energy Features ...........................................................................................55

Energy Usage Simulation Results............................................................................................55

Per Building and Per Unit (4 per Building) .............................................................................55

Block Building – B-1, B-2, B-3, B-4.......................................................................................55

Block Vinyl-Sided Buildings – BV-3, BV-4, BV-5, BV-6 .....................................................57

Wood Frame Brick Building – FB-1 and FB-2 .......................................................................59

Wood Frame Vinyl-Sided Building – FV-1, FV-2, FV-3, FV-4 .............................................61

Wood Frame Vinyl-Sided Building – FV-5, FV-6, FV-7, FV-8 .............................................63

Appendix D: Average Hourly Indoor Temperatures .............................................................................. 65
vi

List of Figures

Figure 1. Block building, one end unit, front.................................................................................................. 5

Figure 2. Block building, one end unit, rear .................................................................................................. 5

Figure 3. Wood frame brick building, front elevation, two units .................................................................... 7

Figure 4. Wood frame brick building, front elevation, two units .................................................................... 7

Figure 5. Wood frame vinyl building, front elevation, three units .................................................................. 9

Figure 6. Wood frame vinyl building, rear elevation, three units................................................................... 9

Figure 7. Onset receiver (data download in progress)................................................................................ 16

Figure 8. Summary comparison of heating energy use estimates for the heating period November 2010 –

March 2011........................................................................................................................................... 19

Figure 9. B-1 Whole house and heating electric use analysis.................................................................... 22

Figure 10. B-2 Whole house and heating electric use analysis.................................................................. 22

Figure 11. B-3 Whole house and heating electric use analysis.................................................................. 23

Figure 12. B-4 Whole house and heating electric use analysis.................................................................. 23

Figure 13. B-1 through B-4 average daily electricity use based on HDDs in the period............................. 25

Figure 14. FB-5 Whole house and heating electric usage.......................................................................... 26

Figure 15. FB-6 Whole house and heating electric usage.......................................................................... 26

Figure 16. FB-7 Whole house and heating electric usage.......................................................................... 27

Figure 17. FB-8 Whole house and heating electric usage.......................................................................... 27

Figure 18. FB-5 through FB-8 average daily usage and HDD during the period........................................ 28

Figure 19. FV-5 Whole house and heating electric usage.......................................................................... 29

Figure 20. FV-6 Whole house and heating electric usage.......................................................................... 29

Figure 21. FV-7 Whole house and heating electric usage.......................................................................... 30

Figure 22. FV-8 Whole house and heating electric usage.......................................................................... 30

Figure 23. Average daily usage and HDD during the period; FV-5 through FV-8 ...................................... 31

Figure 24. BV-1, B-5, B-6 and BV-2 average daily usage and HDD for the heating period ....................... 32

Figure 25. BV-3 through BV-6 average daily usage and HDD for the heating period ................................ 33

Figure 26. FB-1 through FB-4 average daily usage and HDD during the period........................................ 34

Figure 27. FV-1 through FV-4 average daily usage and HDD for the heating period ................................ 35

Figure 28. Indoor relative humidity B-3 and B-4 ......................................................................................... 36

Figure 29. Indoor relative humidity BV-1 and B-5....................................................................................... 37

Figure 30. Indoor relative humidity B-6 and BV-2....................................................................................... 37

Figure 31. Indoor relative humidity BV-3 and BV-4 .................................................................................... 38

Figure 32. Indoor relative humidity BV-5 and BV-6 .................................................................................... 38

Figure 33. Indoor relative humidity FB-1 and FB-2..................................................................................... 39

Figure 34. Indoor relative humidity FB-3 and FB-4..................................................................................... 39

Figure 35. Indoor relative humidity FB-5 and FB-6..................................................................................... 40

Figure 36. Indoor relative humidity FB-7 and FB-8..................................................................................... 40

Figure 37. Indoor relative humidity FV-1 and FV-2..................................................................................... 41

Figure 38. Indoor relative humidity FV-3 and FV-4..................................................................................... 41

Figure 39. Crawlspace relative humidity; Units B-1 through B-4 ................................................................ 42

Figure 40. Crawlspace temperature; BV-1, B-5, B-6 and BV-2 .................................................................. 43

Figure 41. Crawlspace temperature and relative humidity BV-3 through BV-6s ........................................ 43

Figure 42. Crawlspace temperature and relative humidity FB-1 through FB-4 .......................................... 44

Figure 43. Crawlspace temperature and relative humidity FB-5 through FB-8 .......................................... 44

Figure 44. Crawlspace temperature and relative humidity FV-1 through FV-4 .......................................... 45

Figure 45. Crawlspace temperature and relative humidity FV-5 through FV-8 .......................................... 45

Figure 46. Modeled energy use B-1............................................................................................................ 56

Figure 47. Modeled energy use B-2............................................................................................................ 56

Figure 48. Modeled energy use BV-3 ......................................................................................................... 57

Figure 49. Modeled energy use BV-4 ......................................................................................................... 58

Figure 50. Modeled energy use BV-5 ......................................................................................................... 58

Figure 51. Modeled Energy Use BV-6 ........................................................................................................ 58

Figure 52. Modeled energy use FB-1 ......................................................................................................... 59
vii

Figure 53. Modeled energy use FB-2 ......................................................................................................... 60

Figure 54. Modeled energy use FV-1 ......................................................................................................... 62

Figure 55. Modeled energy use FV-3 ......................................................................................................... 62

Figure 56. Modeled energy use FV-4 ......................................................................................................... 62

Figure 57. Modeled energy use FV-7 ......................................................................................................... 64

Figure 58. Modeled energy use FV-8 ......................................................................................................... 64

Figure 59. B-1 Average Hourly Indoor Temperature – November 2010 through April 2011 ...................... 65

Figure 60. B-2 Average Hourly Temperature – November 2010 through April 2011 ................................. 66

Figure 61. B-3 Average Hourly Temperature – November 2010 through April 2011 ................................. 67

Figure 62. B-4 Average Hourly Temperature – November 2010 through April 2011 ................................. 68

Figure 63. B-5 Average Hourly Temperature – February 2011 through April 2011.................................... 69

Figure 64. B-6 Average Hourly Temperature – February 2011 through April 2011.................................... 70

Figure 65. BV-1 Average Hourly Temperature – February 2011 through April 2011 ................................. 71

Figure 66. BV-2 Average Hourly Temperature – February 2011 through April 2011 ................................. 72

Figure 67. BV-3 Average Hourly Temperature – February 2011 through April 2011 ................................. 73

Figure 68. BV-4 Average Hourly Temperature – February 2011 through April 2011 ................................. 74

Figure 69. BV-5 Average Hourly Temperature – February 2011 to April 2011 .......................................... 75

Figure 70. BV-6 Average Hourly Temperature – February 2011 to April 2011 .......................................... 76

Figure 71. FB-1 Average Hourly Temperature – February 2011 to April 2011........................................... 77

Figure 72. FB-2 Average Hourly Temperature – February 2011 to April 2011........................................... 78

Figure 73. FB-3 Average Hourly Temperature – February 2011 to April 2011........................................... 79

Figure 74. FB-4 Average Hourly Temperature – February 2011 to April 2011........................................... 80

Figure 75. FB-5 Average Hourly Temperature – December 2010 to April 2011 ........................................ 81

Figure 76. FB-6 Average Hourly Temperature – December 2010 to April 2011 ........................................ 82

Figure 77. FB-7 Average Hourly Temperature – December 2010 to April 2011 ........................................ 83

Figure 78. FB-8 Average Hourly Temperature – December 2010 to April 2011 ........................................ 84

Figure 79. FV-1 Average Hourly Temperature – February 2011 to April 2011........................................... 85

Figure 80. FV-2 Average Hourly Temperature – February 2011 to April 2011........................................... 86

Figure 81. FV-3 Average Hourly Temperature – February 2011 to April 2011........................................... 87

Figure 82. FV-4 Average Hourly Temperature – February 2011 to April 2011........................................... 88

Figure 83. FV-5 Average Hourly Temperature – December 2010 to April 2011 ........................................ 89

Figure 84. FV-6 Average Hourly Temperature – December 2010 to April 2011 ........................................ 90

Figure 85. FV-7 Average Hourly Temperature – December 2010 to April 2011 ........................................ 91

Figure 86. FV-8 Average Hourly Temperature – December 2010 to April 2011 ........................................ 92

Figure 87. BV-6 Average Hourly Temperature – February 2011 to April 2011 .......................................... 93

Unless otherwise noted, all figures were created by the NAHB Research Center team.
viii

List of Tables

Table 1. Typical GHI Construction and Pre-Retrofit Conditions ................................................................... 3

Table 2. Typical Build Specifications – 8 in. CMU Block Building (B-1 through B-4).................................... 6

Table 3. Typical Building Specifications – Wood Frame with Brick-Veneer (FB-5 through FB-8)................ 8

Table 4. Typical Building Specifications – Wood Frame with Vinyl Siding (FV-5 through FV-8)................ 10

Table 5. Tested Air Infiltration ..................................................................................................................... 12

Table 6. Global Simulation Parameters ...................................................................................................... 12

Table 7. Estimated Costs Per Building for Retrofits Proposed for the GHI Pilot Program ......................... 14

Table 8. Monitoring the Pre-Retrofit Units................................................................................................... 15

Table 9. Pilot Study Homes Energy Usage Summary ................................................................................ 18

Table 10. Average Heating Energy for Building Types............................................................................... 20

Table 11. Indoor Temperature/Humidity Conditions during the 2010/2011 Heating Season ..................... 20

Table 12. 8 in. CMU Block, BV-1, B-5, B-6, BV-2....................................................................................... 49

Table 13. 8 in. CMU Block, BV-3 through BV-6.......................................................................................... 50

Table 14. Wood Frame Brick Veneer, FB-1 through FB-4.......................................................................... 51

Table 15. Wood frame vinyl, FV-1 through FV-4 ........................................................................................ 52

Table 16. Block Building – B-1, B-2, B-3, B-4............................................................................................. 55

Table 17. Block Vinyl-Sided Buildings – BV-3, BV-4, BV-5, BV-6 .............................................................. 57

Table 18. Wood Frame Brick Building – FB-1 and FB-2............................................................................. 59

Table 19. Wood Frame Vinyl-Sided Building – FV-1, FV-2, FV-3, FV-4..................................................... 61

Table 20. Wood Frame Vinyl-Sided Building – FV-5, FV-6, FV-7, FV-8..................................................... 63

Unless otherwise noted, all tables were created by the NAHB Research Center team.
ix

Definitions

A/C Air conditioning

B An acronym used in this report to designate a unit in a block 

building (8” CMU)

BA U.S. Department of Energy’s Building America Program

BV An acronym used in this report to designate a unit in a block 

building with vinyl siding

CMU Concrete masonry unit

Co-op Cooperative 

CT Current transducer

DOE U.S. Department of Energy

EE Energy efficiency

° F Temperature in degrees, Fahrenheit

FB An acronym used in this report to designate a unit in a wood 

frame brick-veneered building

ft2 Square foot

FV An acronym used in this report to designate a unit in a wood 

frame vinyl-sided building

GHI Greenbelt Homes, Inc.

GPM Gallons per minute, a rate of water flow

HDD Heating degree day

IECC International Energy Conservation Code

IRC International Residential Code

kWh Kilowatt hours (typical measure of electricity usage; equal to 

1,000 watt hours)

HVAC Heating, ventilation, and air conditioning

NAHBRC-IP NAHB Research Center Industry Partnership
x

NREL National Renewable Energy Laboratory, a national laboratory 

of the U.S. Department of Energy. www.nrel.gov

Research Center NAHB Research Center 

RH Relative humidity, ratio of water vapor in the air to its 

temperature
xi

Executive Summary

A multiyear pilot energy efficiency retrofit project has been undertaken by Greenbelt Homes, 

Inc, (GHI) a 1,566 co-operative of circa 1930 and 1940 homes in Greenbelt, Maryland. The three 

predominant construction methods of the townhomes in the community are materials common to 

the area and climate zone including 8 in. concrete masonry unit (CMU) block, wood frame with 

brick veneer and wood frame with vinyl siding. GHI has established a pilot project that will 

serve as a basis for decision making for the rollout of a decade-long community upgrade 

program that will incorporate energy efficiency upgrades to the building envelope from the 

exterior and equipment with the modernization of other systems like plumbing, mechanical 

equipment, and cladding.

The pilot project has three phases focused on identifying the added costs and energy savings 

benefits of energy efficiency features that are to be installed during a planned community-wide 

replacement program commencing in 2015. Phase 1 consists of a baseline evaluation of the 

current operation, use, environmental conditions, and energy costs for a representative set of 28 

townhomes sited in seven buildings. Phase 2 will consist of the installation of the building 

envelope improvements identified in Phase 1, continued monitoring of the energy consumption 

for the heating season both before and after installation, and performing energy simulations 

supporting recommendations for HVAC and water heating upgrades to be implemented in 

Phase 3. 

Phase 1 of the GHI pilot program efforts, detailed herein, included field walk-through 

evaluations (recording existing conditions), energy simulations for projected savings with 

exterior insulation upgrades, building envelope energy improvement cost estimates and 

recommendations, and installation and maintenance of monitoring equipment and data. 

Simulation results combined with estimated upgrade costs and ongoing maintenance costs for a 

30-year period indicate a positive net cash flow for one or more of the selected options for each 

building type. (Building envelope upgrades that were acceptable to the membership required 

exterior application with the new claddings because occupants required limited disturbance.)

Payback periods for the least cost approach for each building type are less than 20 years (net of 

reserves). Energy savings estimates for the analyzed envelope improvements in Phase 1 range 

from 9% (per each frame brick building) to nearly 30% for each block building.

Average indoor temperatures for the baseline heating season range from 58oF to 70°F with twothirds of the homes having an average temperature less than 68°F. Anecdotal homeowner 

comments have indicated that reduced energy bills is the predominant reason for the unusually 

low indoor temperatures.

Energy use data is being recorded and analysis of the data that was captured for a period of the 

2010/2011 heating season is presented. Average heating energy across all units in a given 

building type ranges from over 6,000 kWh for the block buildings to just over 4,000 kWh for the 

wood frame vinyl buildings. The wood frame brick veneer buildings averaged about 5,000 kWh.

The wood frame buildings average about 4.5 kWh/ft2

, the block buildings with vinyl siding 

averaged about 5.0 kWh/ft2

, and the uninsulated block buildings average about 6.2 kWh/ft2. 
xii

One of the questions that arise from this and similar analyses is the comparison of simulated 

energy use estimates with actual field measurements. In general, the initial measurement period 

indicated an acceptable level of confidence that energy simulations developed for these older 

homes are generally representative of actual energy use in the homes. Therefore, it can be 

surmised that estimated energy savings of simulated upgraded energy features will represent the 

expected energy savings. Furthermore, an analysis of the utility meter data also shows a 

correlation between measured energy use and heating energy estimates from utility data. The 

utility data however, is based on weekly or bi-weekly records.
1

1 Introduction

Greenbelt Homes Inc. (GHI) is a 1,600-home private housing cooperative (co-op) located on 

over 250 acres in Greenbelt, Maryland, about 12 miles from the nation’s capital. The co-op is 

comprised of 1,571 homes originally constructed by the federal government between 1936 and 

1941; with 29 more that were added in the ensuing years. These homes are primarily arranged in 

rows of two-story (and a small number of three-story) townhouses. All 1,600 GHI memberowners together own the cooperative and share the operating costs. A monthly fee covers the 

operating expenses of the cooperative and funds replacements. The co-op maintains and repairs 

plumbing, electrical wiring, and building structural components. The homes are individually 

metered for electricity. Natural gas is not available inside the community.

Because of comfort issues and high energy costs, GHI established a multiyear pilot program to 

assist in determining the best performing and lowest cost options for improvements to the 

existing homes. The pilot program coincides with scheduled window and siding replacement.

This report details Phase 1 of the GHI pilot program including field walk-through evaluations, 

energy simulations, building envelope upgrade recommendations, and baseline monitoring.

The Building America (BA) Program and the stated community goals for the GHI pilot program 

converge both in desired performance levels and cost effectiveness. The NAHB Research Center 

(through the BA program) is providing support to identify the combination of highest energy 

performance to least cost ratio while considering related needs of comfort and minimal lifestyle 

disruption during upgrades. The BA program also supports effort in monitoring the performance 

of the homes to detail pre- and post-retrofit energy use.

This report summarizes the initial condition of each home, the energy simulations and estimated 

costs of upgrades to assess cost effectiveness of energy improvements, and the initial preupgrade heating season energy use and indoor environmental condition results for the pilot 

homes. This data is intended as baseline data for use in comparison of ongoing monitoring 

results when the efficiency upgrades are implemented. The energy use measurements include

both utility meter data and data from installed sensors and transducers. The data is analyzed to 

develop baseline performance curves for each of the seven buildings in the GHI pilot program.

The energy use and curve fits will later be used to analyze energy use following the upgrades and 

to develop the retrofit cost analyses including estimated payback periods and a return-oninvestment for the energy upgrades.

The pilot program analysis will guide the GHI community in the future housing revitalization to

more energy efficient homes. 

2 Background

GHI is working to identify opportunities to upgrade the existing homes in the community for 

energy savings, durability, and good indoor environmental quality. The community’s housing 

stock not only provides shelter but a connection to a unique lifestyle that spans and transcends 

generations. Many communities of homes aged over 50 years old have continued service life 

expectations well into the future, and for GHI, maintaining and improving their 60- to 70-yearold homes is a clear directive of the cooperative. However, these vintage homes, while well built, 

have construction features that often frustrate energy efficiency and indoor comfort goals.

Residents of some of the homes have chosen to maintain colder-than-desired interior 
2

temperatures in the heating season to reduce energy bills. Other residents have added numerous 

space heaters to supplement the main heating equipment. Most residents currently pay high 

energy costs and have the experience and expectations to believe that these costs will increase 

over time.

Given the age of the buildings, occupant complaints of discomfort and high energy costs, and 

strong sense of community that includes the housing style itself, an effort to improve the 

performance of the community housing stock is a growing priority. In addition, just as important 

as energy efficiency are indoor environmental quality and affordability goals that necessarily 

include a positive net present value requirement for the 30-year project.

GHI has established a pilot program that will provide results to aid in decision making for the 

roll out of a decade-long community upgrade program to improve efficiency of the building 

envelope and modernize equipment such as plumbing, mechanical equipment, and cladding. The 

GHI Buildings Committee determined initial criteria for pilot program eligibility: all four units in 

a building had to be represented; the homes were required to be owner occupied; and each of the 

three predominant building types were to be represented in the pilot group. GHI staff sent letters 

soliciting volunteers for the program and 32 members responded. One building had to be 

dropped when an owner moved overseas.

The pilot project has three phases focused on identifying the added costs and benefits of energy 

efficiency features that are to be installed during a planned community-wide replacement 

program commencing in 2015.

Phase 1 of the GHI pilot program consists of a baseline evaluation of the current operation, use, 

environmental conditions, and energy costs for a representative set of 28 townhomes sited in 

seven buildings. Efforts conducted during 2010/2011 included field walk-through evaluations

(recording existing conditions), energy simulation for projected savings, building envelope 

energy improvement cost estimates and recommendations, and installation and maintenance of 

monitoring equipment and data. This report summarizes these efforts and includes the results of 

energy use monitoring over the 2010/2011 winter season.

Phase 2 will consist of the installation of the building envelope improvements identified in Phase

1, monitoring energy consumption for the heating season following installation, and performing 

energy simulations supporting recommendations for HVAC and water heating upgrades.

Phase 3 will include the installation of the HVAC and water heating upgrades identified in Phase

2 and monitoring energy consumption for the heating season following installation.

The community embarked on a similar upgrade in 1980. At that time, central building oil boilers 

were abandoned in place. The homes were individually metered with 125-amp electric panels 

and heat was supplied to each home by wall-mounted electric baseboard units and fan-coil 

ceiling-mounted heaters in the bath and kitchen. Homes do not have central air-conditioners 

(A/C). Typically, one or more room-capacity A/C units are installed in wall openings or 

windows. The boiler rooms now house many of the circa-1990 50 or 52 gallon electric water 

heaters that provide hot water to individual homes. Hot water pipes in the crawlspaces of the 

brick and block units are 90% insulated. Water heaters in the wood frame vinyl-sided units are 

located inside the homes. Vinyl or aluminum double-pane windows were installed in the 1980 

upgrade. Table 1 details the general conditions predominate in the community’s housing today.
3

Table 1. Typical GHI Construction and Pre-Retrofit Conditions.

Construction 

Type General Conditions Total No. of Units

Block -

8 in. CMU

(B or BV)

• Formed concrete crawlspace foundations1, with structural 

concrete first floors over common crawlspaces

• Crawlspaces are 4 ft and retrofitted as closed crawlspaces 

with 1 in. to 2 in. of rigid extruded polystyrene foam applied 

to the perimeter walls

• Crawlspace walls extend under front and rear porch slabs 

(many exposed to ambient conditions)

• Structural concrete floors (1st and 2nd levels)

• Main house and porch slabs lack thermal breaks

• CMU walls, finished with plaster 

• Some interior common walls are wood-framed (where party 

walls breach the adjacent units’ footprint).

• Double glazed vinyl windows (1980)

• Exterior walls are painted (B) or have vinyl siding (BV)

• Flat concrete roofs retrofitted with 3 3⁄4 in. of 

polyisocyanurate insulating tapered sheathing and EPDM 

roofing, R-26

• Electric baseboard heating

• Room through-the-wall air conditioning

• Electric water heat

256

Wood frame

Brick-Veneer

(FB)

• Formed concrete crawlspace foundations, with structural 

concrete first floors over common crawl spaces 

• Crawl spaces are 4 ft and retrofitted as closed crawlspaces 

with 1 in. to 2 in. of rigid extruded polystyrene foam applied 

to the perimeter walls

• Crawlspace walls extend under front and rear porch slabs 

(many exposed to ambient conditions)

• Structural concrete first floor

• Main house and porch slabs lack thermal breaks

• Balloon- framed 2 × 4-16 in. o.c. walls with plasterboard 

interior finish

• Blown-in cellulose/rock wool insulation in walls (1980)

• Board wall and roof sheathing (1 × 6/1 × 8)

• Exterior brick veneer, no WRB

318

 1 Several units have full, rear walkout basements of CMU.
4

Construction 

Type General Conditions Total No. of Units

• Double glazed vinyl windows (1980)

• Gable roofs with slate shingles

• Ventilated attic with rock wool, cellulose, or fiberglass floor 

insulation, R-16 (1980)

• Electric baseboard heating

• Room through the-wall air conditioning

• Electric water heat

Wood frame

Vinyl-Sided

(FV)

• Common ventilated crawlspace of 8 in. CMU block, 4 1⁄2 

courses high (3 ft)

• 2 × 8-16 in. o.c. floor joists with mid-span dropped beam 3-

2 × 10 in. on CMU piers

• R-11 kraft-faced fiberglass batt insulation in floor joists 

(1980)

• Balloon-framed 2 × 4-16 in. o.c. walls 

• Blown-in cellulose insulation in walls (1980)

• Board wall and roof sheathing (1 × 6/1 × 8)

• Double glazed vinyl or aluminum windows (1980)

• Vinyl siding, no WRB

• Gable roof with asphalt shingles 

• Ventilated attic 

• Attics insulated with rock wool, cellulose, or fiberglass floor 

insulation, R-16 (1980)

• Electric baseboard heating

• Room through-the-wall air conditioning

• Electric water heat

992

(140 of 

these are 

apartments)
5

3 Baseline Condition

The first step of Phase 1 of the pilot program was to determine the existing condition of the 28 

homes to aid in developing energy simulations and upgrade recommendations. The pre-retrofit 

condition of the 28 homes was established through occupant interviews, compilation of the 

previous years’ utility bills, physical inspections, and air infiltration and water flow testing. 

Representative pre- and post-retrofit data for three of the seven buildings are covered in Table 2

through Table 4. Building elevations are shown in Figure 1 through Figure 6. Data for all of the 

buildings in the pilot program can be found in Appendix A. 

Figure 1. Block building, one end unit, front.

Figure 2. Block building, one end unit, rear.
6

Table 2. Typical Build Specifications – 8 in. CMU Block Building (B-1 through B-4).

Greenbelt Homes, Inc.

Walk-through: 11/18/2010 11/18/2010 11/18/2010 11/18/2010

Unit Code B-1 B-2 B-3 B-4

Feature/ Component Before Before Before Before

Year Built 1936 1936 1936 1936

House Type Town - End: C 3.9 Town - Interior 

C2.6

Town - Interior C 

2.6

Town - End C 3.9

Structural Wall Type 8 in. CMU 8 in. CMU 8 in. CMU 8 in. CMU w/wood 

frame add

Front Orientation South South South South

Finished ft2, Main 1,168 844 787 1,168 

Ft2 Addition 77 

No. Stories 2 2 2 2 

Bedrooms 3 2 2 3 

Baths 1 1 1 2 

Ceiling Ht 8'-4" 8'-3" 8'-2"

Foundation Concrete Crawl - 4' Concrete Crawl - 4' Concrete Crawl - 4' Concrete Crawl - 4'

Insulated Foundation? Yes- 2 in. xps- to 3 ft Yes- 2 in. xps- to 3

ft

Yes- 2 in. xps- to 3

ft

Yes- 2 in. xps- to 3

ft

Heated No No No No 

Foundation R-value R-5 R-5 R-5 R-5

Floor R-value 0 0 0 0 

Vented Crawlspace No No No No

1st Floor 5 in. structural slab 5 in. structural slab 5 in. structural slab 5 in. structural slab

2nd Floor 5 in. structural slab 5 in. structural slab 5 in. structural slab 5 in. structural slab

Attic Ceiling 5 in. structural slab 5 in. structural slab 5 in. structural slab 5 in. structural slab

Attic R-value 26 26 26 26 

Roof Rafter Flat Concrete Roof Flat Concrete Roof Flat Concrete Roof Flat Concrete Roof

Structural Wall 8 in. CMU 8 in. CMU 8 in. CMU 8 in. CMU

Siding Painted CMU Painted CMU Painted CMU Painted CMU

Building Dimensions 25 × 20 16 × 20 16 × 20 25 × 20

Addition Dimensions 11x7

Window Material Vinyl Slider Vinyl Slider single glazed vinyl 

sliders w/storms

vinyl sliders

Ft2 Windows 54/36/85/0 65/0/55/0 65/0/56/0 37/7/100/36

Window U-/SHGC .55/.70 .55/.70 .55/.70 .55/.70

Wall R-value 0 0 0 10

Front Door 3070 wood 3070 wood 3070 wood 3070 wood 

Rear Door 3070 wd/gls 3070 wd/gls 3070 wd/gls 3070 wd/gls 

Right Door 2868 ins.

Storm Door Yes, F&R Yes, F&R Yes, F&R Yes, F&R

Air Leakage, ACH50 4.7 3.3 2.4 4.8

Mech. Vent., Run time none none none none-unused

Water Heater 50 gal. State 50 gal. Rheem 50 gal. State 50 gal. State

Model CD065220RTV RHEPro52 CD065220RTV CD065220RTV

Energy Factor Use .88 eff/4952k 4724 kWh .88 eff/4952k .88 eff/4952k

Location Boiler Rm. Boiler Rm. Boiler Rm. Boiler Rm.

Cooling Type wall unit wall unit wall unit wall unit

Manufacturer Haier 24 × 15 Fedders Estar Kenmore Sharp 

Model 2nd Gibson A7U08W2A 30 × 24 ACQ189XPO

Location 1st rear and 2nd 2nd wall 2nd wall 2nd wall

Heating Type Elec. Base. Elec. Base. Elec. Base. Elec. Base.

Linear feet (@250 watts/foot) 32 21 23 36 

Ceiling Heat (K, Kitchen; B, 

Bath)

K,B K,B B

Thermostat Location on wall on units on wall on wall

Toilet flush (gallons per flush) 2.4 2.4 1.6 1.6

Shower/Sink Flow (gpm) 2.0/2.2 2.25/2.5 1.5/1.5 3.0/1.6
7

Figure 3. Wood frame brick building, front elevation, two units.

Figure 4. Wood frame brick building, front elevation, two units.
8

Table 3. Typical Building Specifications – Wood Frame with Brick-Veneer

(FB-5 through FB-8).

Greenbelt Homes, Inc.

Date: 11/4/2010

Unit Code FB-5 FB-6 FB-7 FB-8

Feature/ Component Before Before Before Before

Year Built 1941 1941 1941 1941

House Type Town-End; C2.8 Town-Interior; C2.7 Town-Int; C2.6 Town-End Left

Structural Wall Type 2 × 4 Frame w/Brick 2 × 4 Frame w/Brick 2 × 4 Frame w/Brick 2 × 4 Frame w/Brick

Front Southwest Southwest Southwest Southwest

Finished ft2, main 1,067 1,067 833 1,234

Addition, ft

2 70 n/a unconditioned n/a unconditioned

No. Stories 2 2 2 2

Bedrooms 2 2 1 2

Baths 1 1.5 1 1

Ceiling Ht. 7 ft-11 in. 7 ft-11 in.

Foundation Unvented 

Crawlspace

Unvented Crawlspace Unvented Crawlspace Unvented Crawlspace

Insulated Walls R-7.5 R-7.5 R-7.5 R-7.5

Heated no no no no

Vented no no no no

1st Floor Structural slab 5" Structural slab 5" Structural slab 5" Structural slab 5"

2nd Floor 2 × 8 joists 2 × 8 joists 2 × 8 joists 2 × 8 joists

Attic Ceiling 2 × 8 2 × 8 2 × 8 2 × 8 

Attic R-value R-19 R-19 R-19 R-19 

Roof Rafter 2 × 6; 8/12 2 × 6; 8/12 2 × 6; 8/12 2 × 6; 8/12 

Roof Sheathing 1 × 6 T&G 1 × 6 T&G 1 × 6 T&G 1 × 6 T&G

Structural Wall 2 × 4 Frame R-11? 2 × 4 Frame R-11? 2 × 4 Frame R-11? 2 × 4 Frame R-11?

Siding Painted Brick 

Veneer

Painted Brick Veneer Painted Brick Veneer Painted Brick Veneer

Windows Material vinyl vinyl dbl glazed vinyl dbl glazed vinyl dg

Building Dimensions 26.67 × 20 26.67 × 20 19.17 × 20 33.83 × 20

Addition, Dim. 7x10

Windows, ft2 81/0/95/36 66/0/81/0 62/0/61/0 73/27/96/0

Window SF Front .55/.75 66 62 73

Wall Sheathing 1 × 6 T&G 1 × 6 T&G 1 × 6 T&G 1 × 6 T&G

Wall R-value R-11 R-11 R-11 R-11

Front Door wood 3070 wood 3070 wood 3070 wood 3070

Rear Door 3070wd/gl 3070wd/gl 3070wd/gl 3070wd/gl

Storm Door F&R F&R F&R F&R

Air leakage, ACH50 6.1 8.8 11.9 5.5

Water Heater State 50gal. GE 50gal. GE 50gal. GE 50gal.

Model P6522ORTZ CD6522ORTV CD6522ORTV GE

Energy Factor/Use 4952 watts 4952 watts CD6522ORTV

Location Boiler Room Boiler Room Boiler Room

Cooling Type Unknown Friedrich Amana Carrier

Manufacturer KM24L30-A 120722IA XCE183D 8/05

Location 2nd hallway 2nd floor 2nd floor 2nd floor

Heating Type Elec. Bsebd. Elec. Bsebd. Elec. Bsebd. Elec. Bsebd.

Linear Ft. 

(@250watts/ft)

31 32 21 35

Ceiling Heat (K, 

kitchen; B, bath)

K, B B K, B K, B

Toilet Flush (gal./flush) 2.4 1.6 2.0 2.4

Shower/Sink Flow 2.5/no test 3.0/1.8
9

Figure 5. Wood frame vinyl building, front elevation, three units.

Figure 6. Wood frame vinyl building, rear elevation, three units.
10

Table 4. Typical Building Specifications – Wood Frame with Vinyl Siding

(FV-5 through FV-8).

Greenbelt Homes, Inc.

Date: 11/5/2010

Unit Code FV-5 FV-6 FV-7 FV-8 

Feature/ Component or Status Before Before Before Before

Year Built 1941 1941 1941 1941

House Type Town-End G-2R Town -Interior, G-2L Town -Interior, G-2R Town-End, G-2L

Structural Wall Type Frame 2 × 4 Frame 2 × 4 Frame 2 × 4 Frame 2 × 4

Front Northwest Northwest Northwest Northwest

Finished ft2, Main 792 792 792 792

Addition ft2. 378 0 264 264

No. Stories 2 2 2 2

Bedrooms 2 2 2 2

Baths 1.5 1 1.5 1.5

Ceiling Ht. 96 in. 96 in. 96 in.

Foundation Vented Crawl Vented Crawl Vented Crawl Vented Crawl

Insulated Floor R-13 R-13 R-13 R-13

Heated No No No No

Vented 8 × 16 vents (2) 8 × 16 vents (2) 8 × 16 vents (2) 8 × 16 vents (2)

1st Floor 2 × 8 joists 2 × 8 joists 2 × 8 joists 2 × 8 joists

2nd Floor 2 × 8 2 × 8 2 × 8 2 × 8

Attic Floor 2 × 6 2 × 6 2 × 6 2 × 6

Attic R-value 18.85 18.85 18.85 18.85

Roof Rafter 2 × 6 2 × 6 2 × 6 2 × 6

Roof Sheathing 1 × 8 T&G 1 × 8 T&G 1 × 8 T&G 1 × 8 T&G

Attic R-value 16 16 16 16

Building Dimensions 22 × 18 22 × 18 22 × 18 22 × 18

Addition Dimensions 21 × 18 n/a 22 × 12 22 × 12

Structural Wall 2 × 4 2 × 4 2 × 4 2 × 4

Siding Vinyl / 1/2" EPS Vinyl / 1/2" EPS Vinyl / 1/2" EPS Vinyl / 1/2" EPS

Windows Material Vinyl - 1980 Vinyl - 1980 Vinyl – 1980 Vinyl - 1980

Windows, ft2 45/26/117/0 34/0/95/0 33/0/90/0 33/0/67/40

Window U-/SHGC .55/.75 & .29/.21 .55/.75 .55/.75 .55/.75

Wall Sheathing 1 × 8 T&G 1 × 8 T&G 1 × 8 T&G 1 × 8 T&G

Wall R-value R-11 R-11 R-11 R-11

Front Door 3070 wd 1/2 glass 

and storm

3070 wd 1/2 glass 

and storm

3070 wd 1/2 glass and

storm

3070 wd 1/2 glass 

and storm

Addition Front Door Ins. 3068 none None none

Rear Door Ins. 21068 3068 Vinyl 3068 wood none

Rear/Side Storm Door no yes No yes

Right Door none none None Ins. 21068

Air Leakage, ACH50 14.0 14.8 10.1 11.2

Mech. Vent., run time no no No no

Water Heater 50/State 50/Ruud 50/State 50/Ruud

Model P65220RT2 RU 0902227702 P65220RT2 PF52C

Energy Factor Use 4,946 4,992 4,946 4,992

Location 2nd floor near bath Powder Room

Cooling Type NIHD1406A

(heat pump)

Rear BR wdw 

LG71EX0953

through wall A/C through wall A/C

Manufacturer York Hallwdw GE 

AEH08FMG1

Unknown unknown 24 in. × 12

in.

Efficiency 9.8 EER; 820 watts air infiltrating through

Location Stored in attic Front through

window

1st floor - rear

Removed out of season? no

Heating Type Heat Pump, York; Electric Baseboard Electric Baseboard Electric Baseboard

Linear feet (@250 watts/foot) 18 19 20 20

Ceiling Heat (K, Kitchen; B, Bath) B K,B B K,B

Thermostat Location interior walls interior walls interior walls interior walls

Toilet flush (gal. per) 1.6 1.6 2.4 1.6

Shower/Sink Flow (gpm) 1.6/1.6 1.5/1.6 2/1.4 3.5/2.2
11

4 Simulation Results and Energy Upgrade Cost Estimates

The next step of Phase 1 was to use the baseline conditions to develop energy simulations and 

cost estimates for the energy upgrade recommendations. A simulation tool, BEopt2 v1.01, was 

used to calculate annual energy usage based on the pre-retrofit conditions noted. GHI provided 

support data about the pilot homes including limited architectural plans, general information on 

wall and roof composition that was not visible through inspection, a copy of the Reserves 

Policies and Analysis (dated 9/15/2008)3, and other background information. Equipment 

specifications, dimensions, building orientation, and other apparent features were recorded by 

NAHB Research Center staff during site walk-through evaluations and short-term testing of the 

pilot project units. 

A minimum of one end and one interior unit was modeled in each building. Savings and costs for 

the whole building (four units) were estimated from these outcomes. Several buildings, such as 

BV-3 through BV-6 and FV-1 through FV-4 were made up of unique homes, thus modeling 

more than two of the four units was warranted. The global assumptions underlying the modeling 

were developed in consultation with GHI, as these economic factors are common to the 

administration’s decision making. Air infiltration testing results and global modeling 

assumptions that were used in the compilation of upgrade features and costs are shown in 

Table 5 and Table 6, respectively.

House leakage was measured using multipoint and single-point testing in accordance with 

ASTM E779-10 and ASTM E1827-96, depressurization only. Leakage to outdoors was 

determined using a pressure equalization method utilizing two blower door setups. Starting with 

an end unit, blower doors were set up in this first unit and the adjacent second unit. The first unit 

was depressurized to measure total leakage and then the second unit was depressurized at the 

same time and to the same value to cancel leakage between units and thereby showed leakage to 

outdoors for the first unit. The difference provided the leakage between the first and second 

units. The blower door from the first unit was then installed in the third unit. The second unit was 

depressurized to measure total leakage, the third unit was depressurized to cancel out leakage 

between the second and third units, and the leakage between the first and second units from the 

previous test was deducted to determine the leakage to outdoors for the second unit. The blower 

door from the second unit was then installed in the fourth unit and the leakage to outdoors for the 

third unit was determined in the same way. The fourth unit simply needed the total leakage to 

determine leakage to outdoors because the leakage between the third and fourth units was 

already known.

 2 BEoptTM Software, NREL, http://www.nrel.gov/buildings/energy_analysis.html. 3 Developed and maintained by GHI, the Policies and Analysis outlines the reserve fund for improvements by each 

GHI home type.
12

Table 5. Tested Air Infiltration.

Building Unit Location Area Volume

Net Leakage 

to Outdoors 

(ACH50)

% of Total Leakage 

to Adjacent Unit(s)

Block

B-1 End 1,168 9,344 4.7 16%

B-2 Interior 844 6,752 3.3 32%

B-3 Interior 844 6,752 2.4 42%

B-4 End 1,245 9,960 4.8 16%

B-5 Interior 844 6,752 4.3 23%

B-6 Interior 921 7,368 8.4 9%

Block 

w/Vinyl

BV-1 End 1,528 12,224 7.2 8%

BV-2 End 1,245 9,960 4.8 11%

BV-3 End 1,112 8,896 7.5 16%

BV-4 Interior 1,080 8,640 3.5 37%

BV-5 Interior 1,596 12,768 4.3 18%

BV-6 End 1,596 12,768 4.0 12%

Frame 

Brick

FB-1 End 1,080 8,640 10.4 18%

FB-2 Interior 1,080 8,640 6.8 27%

FB-3 Interior 1,080 8,640 7.4 n/a

FB-4 End 1,080 8,640 8.0 16%

FB-5 End 1,080 8,640 6.1 28%

FB-6 Interior 1,136 9,088 8.8 25%

FB-7 Interior 841 7,288 11.9 18%

FB-8 End 1,173 9,384 5.5 20%

Wood 

frame

Vinyl

FV-1 End 936 7,488 9.7 12%

FV-2 Interior 782 6,256 13.1 14%

FV-3 Interior 782 6,256 9.3 29%

FV-4 End 870 6,960 14.1 15%

FV-5 End 1,170 9,360 14.0 7%

FV-6 Interior 792 6,336 14.8 9%

FV-7 Interior 1,056 8,448 10.1 15%

FV-8 End 1,056 8,448 11.2 13%

Table 6. Global Simulation Parameters.

Parameter Value

Annual Rate of Inflation A 3.30%

Discount Rate A 5.00%

Interest Rate B 7.00%

Fuel Escalation Rate B 0.50%

Heating Set Point 68 °F

Air/Conditioning Set Point not modeled

Number of Occupants per Home Number of Bedrooms on the Architectural Plans

Cost of Electricity $0.15/kWh

A Provided by GHI staff B Energy Price Indices and Discount Factors for Life-Cycle Cost Analysis – 2010, Annual Supplement to NIST Handbook 

135 and NBS Special Publication 709, NISTIR 85-3273-25.

Office of Management and Budget Circular A-94 Appendix C, Revised December 2010.

Office of Management and Budget, Fiscal Year 2010 Analytical Perspectives, Budget of the U.S. Government.
13

The block buildings were consistently of tighter construction than any of the others. Block 

buildings that tested higher than 5ACH50 had wood frame additions that likely accounted for the 

higher leakage. (Two of the homes that tested for leakage of 4.8ACH50 also had additions.) Both 

the wood frame brick and wood frame vinyl buildings are balloon framed of 2 × 4s with 1 × 6 

horizontal board floor, wall, and roof sheathing. Thus, the wood frame buildings’ construction 

significantly contributes to the air infiltration pathways. (The wood frame brick units have 

poured concrete foundations and structural first floor slabs, which likely account for the tighter 

average construction of these compared to the wood frame vinyl buildings.)

The units located in block buildings are of the tightest construction yet built of the least 

thermally-resistant materials because only the roofs and crawlspace walls have insulation (R-26 

and R-5, approximately). Software simulations confirmed that the block buildings were 

estimated to have the highest annual energy usage load, and therefore, the best outlook for 

energy efficiency improvement with the addition of wall insulation. 

GHI’s Buildings Committee saw the opportunity to add exterior wall insulation to the homes 

with the pending siding, window, and door replacement scheduled to begin in 2015. The plan 

included bringing the block buildings’ wall insulation in line with that of frame buildings (R-11 

to R-13) and investigating the performance versus cost of adding additional exterior insulation to 

the frame brick and frame vinyl buildings. The community consensus was that energy upgrades 

should be accomplished with minimal inconvenience to the occupant, thus access from the 

outside was emphasized.

The completion of conditioned crawlspace wall insulation in the block and frame brick buildings, 

addition of ventilated crawlspace ceiling insulation in the frame vinyl buildings, and addition of

air seal and insulation in the attics of frame brick and vinyl buildings were added to simulations 

to complete each whole building envelope energy efficiency upgrade. Table 7 covers the 

presentation that the Buildings Committee shared with the pilot program participant owners.

Numbers have been compiled by building (set of four townhomes). Row 1 indicates building 

type and cladding alternative. Row 2 indicates the added wall R-value. Column 1 outlines the 

features of the upgrade which are detailed more extensively in Appendix C.
14

Table 7. Estimated Costs Per Building for Retrofits Proposed for the GHI Pilot Program.
15

5 Phase 1 Energy and Environmental Monitoring

In addition to the baseline conditions and simulations, a monitoring effort was implemented to 

quantify the energy performance of the pilot buildings and to establish the pre-retrofit energy 

usage in the homes. Ongoing data collection for energy, temperature, and relative humidity (RH)

is being logged in 15-minute intervals in the buildings. The equipment will remain in place 

through all three phases of the pilot program which is expected to encompass three heating 

seasons. Research Center staff performs weekly site visits to download data from loggers and 

record data from utility meters. Programmed equipment downloads log energy data for 

processing and storage at the National Renewable Energy Laboratory (NREL, a Department of 

Energy laboratory and partner in the pilot program). The data is processed biannually and 

summarized for each heating season. Table 8 indicates the areas of interest, data collection 

devices, and expected use for the information gathered during the monitoring phases of the pilot 

study. 

Table 8. Monitoring the Pre-Retrofit Units.

Parameter of 

Interest Test Method Purpose

Whole House 

Electric Energy Use

Current transducer and 

recording devices

• Record whole house electricity use

• Develop use profile for winter months

• Integrate energy use data with general weather data

• Provide comparison with energy simulation results

Space and Water 

Heating and Dryer 

Energy Use

Current transducers and 

recording devices

• Proportion heating energy use as a fraction of total 

energy use

• Summarize total internal heating energy and major loads

Indoor Environment

Temperature/Relative 

Humidity sensors – 2 to 

4 devices per unit, 

located 1st and 2nd 

floors

• Provide indoor conditions for energy analysis

• Assess interior moisture loading/dilution

• Support ventilation option development and control

• Assess range of indoor temperature settings

Foundation 

Environment

Temperature/humidity 

loggers, at least 2 

sensors in crawlspace

• Provide crawlspace foundation conditions for energy 

analysis

• Assess potential moisture issues

• Compare with air sealing/ventilation/insulation options 

in pilot renovation plan

Weather data has been obtained from a National Weather Service station located at College Park 

Airport, within five miles of the GHI project center; station KCGS.

4 A shielded outdoor 

temperature and RH sensor was installed at the GHI office on Hamilton Place. The data on site is 

very similar to that from the weather station. Weather data is used to calculate heating degreedays and directly for use in the analysis of the energy performance of homes.

 4 The station was selected for its proximity to the project and the fact that it was likely to be well-maintained due to 

its location at a busy municipal airport. See http://www.wunderground.com.
16

5.1 Data Collection Equipment

Each of the seven buildings in the GHI pilot study were fitted with Onset Computer wireless ZW 

sensors5 to record temperature or RH, placed in several locations and on each level inside the 

units. In many cases, two sensors have been placed on each level in rooms on each side of the 

central stairway. The sensors are designed to record the data in a preset interval and transmit the 

data wirelessly to a receiver located in the crawlspace. Due to varying signal reliability, ZW 

routers, which also function as sensors, were installed in crawlspaces to boost the signal from the 

individual sensors. Data transmitted from the individual sensors to the central receiver is 

retrieved weekly via a site visit and a direct computer link to the receiver (see Figure 7) to 

retrieve the stored data. 

The homes in three selected buildings, B-1 through 

B-4, FB-5 through FB-8, and FV-5 through FV-8, 

are equipped with WattNode watt hour 

transducers6 which were installed in the electrical 

panel boxes of each home in the fall of 2010. The 

transducers monitor the energy use of the primary 

heating circuits, dryer, water heater, and whole 

house. Electric usage is recorded by the 

transducers as a pulse output proportional to the 

electric watt-hours consumed by equipment 

connected to the circuit. Transducer signal pulse 

data is recorded on a per minute basis by a data 

logger, also located in the crawlspace/boiler rooms 

beneath the buildings. The remaining four 

buildings in the pilot program were outfitted with 

watt-hour transducers in May of 2011. The 

monitoring plan calls for all energy transducers to 

remain in place through two or more heating 

seasons. Due to lack of electric panel access in two 

of the 28 pilot homes, a supplemental whole-house 

energy monitor was installed at the main electric 

distribution equipment to record whole house 

electric use. In addition, electric meter readings 

were obtained on a weekly basis for all homes so that a comparison of energy use could be made 

following the first heating season, given that not all homes were monitored in detail for electric 

energy consumption.

5.2 Measurement of Energy Use 

The GHI pilot program is designed to measure the energy consumption, primarily in heating 

seasons, and ultimately evaluate the affordability of retrofit technologies selected specifically for 

each of the GHI building types in the pilot project. The recommended building envelope retrofit 

technologies selected for the energy upgrade have been based in part on the use of software 

simulations to estimate energy use in the buildings before and after the upgrade installations.

7

Homes within the pilot project group have been equipped to compile actual data that can be 

 5 Manufacturer, Onset Computer, http://www.onsetcomp.com 6 Continental Control Systems, LLC, manufacturer, http://www.ccontrolsys.com/w/Advanced_Pulse_WattNode 7 NAHB Research Center, Greenbelt Homes Inc. Pilot Project Energy Analysis, April 2011. See Appendix C

Figure 7. Onset receiver

(data download in progress).

ZW Receiver
17

analyzed both to the simulation estimates and to the actual ongoing measured results as the 

retrofits are implemented in each phase of the energy efficiency retrofit program.

Pilot program homeowners were also asked to submit utility bills covering the 2009-2010 

heating season for use as an approximate check of energy model accuracy. The utility bills and 

the recorded data have already served as a “reasonableness” check of software model outcomes 

for establishing baseline conditions used for the building envelope energy efficiency 

recommendations. At the pilot program completion, the measured utility data, along with utility 

bills, will provide a straightforward method for evaluating realized total energy and cost savings 

relative to retrofit costs and to provide a comparison with the cost savings estimated by the 

software models.

Another commonly used method of isolating the heating and cooling energy used within a home 

lies in analyzing the utility bills on an annual basis. Where each monthly invoice indicates actual 

usage for the period, utility bills will generally show that during April-May and SeptemberOctober in this climate, energy use is lower than the other months due to a decreased use of 

space conditioning energy. Usage in these “shoulder” or “swing” months is a good indication of 

the basic electrical loads within a home for water heating, lighting, appliance, and miscellaneous 

loads. The observed “base” load can then be subtracted from each month’s usage to determine 

the electric energy attributable to heating and cooling. As a comparison, the watt-hour 

transducers that were installed in the electric panels measure the energy use of the circuits 

supplying the baseboard and ceiling heaters.8 Table 9 summarizes energy usage data for the pilot 

program homes from November 2010 through March 2011 and incorporating various analytical 

methods:

• Heating energy based on previous years’ utility meter readings multiplied by estimated 

percentage of heating use (column 9, available for all homes)

• Measured heating use for a subset of homes (column 11)

• Estimated heating use predicted by simulation software (column 12). 

The data presented in Table 9 compares estimated heating energy based on actual whole-house 

energy use measurements, and for 12 of the 28 homes in the study (reduced by one month of 

heating energy, October 2010) the direct measured heating energy to the software heating energy 

use estimates. As noted by the measured data results, each building equipped with transducers 

appears to have an outlier—a unit with temperature and electric usage much lower than 

expected, indicating the home may be unoccupied. As far as the severity of the winter heating 

data, for the period measured (November 2010 – March 2011) the actual heating degree day 

(HDD) for the period was 1% higher than the long-term average data used in the simulation 

software. In addition to the various electricity consumption analyses that have been outlined in 

this report, energy use will be compared relative to the outdoor temperature in each year of the 

study so that seasonal variations in the seasonal weather patterns will not distort real results. 

 8 Not all ceiling heaters were able to be monitored. Electrical energy to dryers and water heaters was also measured, 

as these can be sources of indoor heat gain; supplementing the baseboard heaters. (Supplemental portable space 

heaters used on other circuits also provide heat gains to the home; however this data is not captured directly.) In 

homes where the water heaters are not located within the units, the water heater energy is not added to the indoor 

heat gains. Water heater data may be used to evaluate the savings from use of more efficiency water heating 

equipment in subsequent phases of the project.
18

Table 9. Pilot Study Homes Energy Usage Summary.

Heating Season Summary Energy Data Table1

Evaluation Period – November 2010 - March 2011 (October heating not included)

Unit

Code

Unit

Type

Floor

Area 

(ft2

)

Days 

in

Period

Meter

Electric

Use, 

kWh

Cost @

$0.15

Average

Cost/day

Heating

Season

Utility Meter 

Estimated

Data Logger 

Estimate Simulated

Heating

Energy

kWh

Heating

Percent

of Total

Heating

Energy

kWh

Heating

Percent

of Total

Heating

Energy

kWh

B-1 Block 1168 169 12,580 $1,887 $11.17 69% 8,707 72.4% 9,108 9,773

B-2 Block 844 169 8,260 $1,239 $7.33 82% 6,794 79.8% 6,591 6,113

B-3 Block 844 169 2,390 $359 $2.12 82% 1,966 35.5% 848 6,113

B-4 Block 1245 169 16,620 $2,493 $14.75 69% 11,503 80.8% 13,429 9,773

FB-5 Frame/Brick 1080 171 8,840 $1,326 $7.75 64% 5,691 72.5% 6,409 5,587

FB-6 Frame/Brick 1136 171 10,392 $1,559 $9.12 46% 4,730 43.3% 4,500 3,880

FB-7 Frame/Brick 911 171 1,983 $297 $1.74 46% 903 65.8% 1,305 3,880

FB-8 Frame/Brick 1250 171 9,600 $1,440 $8.42 66% 6,379 71.2% 6,835 5,587

BV-1 Block/Vinyl 1528 171 12,120 $1,818 $10.63 67% 8,068 7,660

B-5 Block 844 171 4,140 $621 $3.63 60% 2,503 6,113

B-6 Block 921 171 6,746 $1,012 $5.92 73% 4,935 6,113

BV-2 Block/Vinyl 1245 171 9,190 $1,379 $8.06 83% 7,615 9,020

BV-3 Block/Vinyl 1112 166 11,020 $1,653 $9.96 62% 6,876 7,660

BV-4 Block/Vinyl 1080 166 5,455 $818 $4.93 51% 2,794 5,220

BV-5 Block/Vinyl 1596 166 13,605 $2,041 $12.29 64% 8,657 7,447

BV-6 Block/Vinyl 1596 166 10,500 $1,575 $9.49 62% 6,552 9,020

FB-1 Frame/Brick 1080 169 10,100 $1,515 $8.96 69% 6,928 5,587

FB-2 Frame/Brick 1080 169 5,900 $885 $5.24 69% 4,096 3,880

FB-3 Frame/Brick 1080 169 7,865 $1,180 $6.98 60% 4,695 3,880

FB-4 Frame/Brick 1080 169 3,710 $557 $3.29 70% 2,608 5,587

FV-1 Frame/Vinyl 936 170 5,705 $856 $5.03 67% 3,842 5,387

FV-2 Frame/Vinyl 782 170 6,589 $988 $5.81 53% 3,518 2,787

FV-3 Frame/Vinyl 782 170 5,890 $884 $5.20 53% 3,145 2,787

FV-4 Frame/Vinyl 870 170 7,760 $1,164 $6.85 65% 5,052 5,240

FV-5 Frame/Vinyl 1170 166 8,105 $1,216 $7.32 65% 5,305 71.2% 5,771 6,013

FV-6 Frame/Vinyl 792 166 5,835 $875 $5.27 45% 2,649 49.4% 2,882 3,570

FV-7 Frame/Vinyl 1056 166 9,220 $1,383 $8.33 56% 5,151 43.0% 3,965 4,760

FV-8 Frame/Vinyl 1056 166 6,570 $986 $5.94 65% 4,282 71.5% 4,698 6,013

1 Notes: 

Simulated heating energy based on a constant 68°F interior temperature for the whole house

FB7 unoccupied, BV4 unoccupied for partial period

B3, B6, BV2, B6, FV1. FV8 have atypical heating set-points and/or total use

Estimated percent meter heating energy based on utility bills for previous year where available

Simulation Heating Energy is for full heating season

B ≡ Block Buildings; BV ≡ Block Vinyl Buildings; FB ≡ Frame Brick Buildings; FV ≡ Frame Vinyl Buildings

The summary energy consumption details for the first heating season of the GHI pilot program 

indicate a wide range of energy usage in the homes:

1. Based on 2009-2010 heating season utility bills and estimates for non-heating uses, the 

heating energy as portion of total energy is ranges from 45% to 83% (Table 9, column 8).
19

2. Applying these estimated heating use percentages to the recorded utility meter data for 

the 2010-2011 (Table 9, column 9) heating season shows estimated heating use for the 

period from November through March of between 2,503 kWh and 8,707 kWh, a factor of 

about 3.5 (excluding the homes that are primarily unoccupied and one home where the 

energy use is well above all other homes).

3. A comparison of the estimated heating energy based on meter readings to the 12 homes 

where data logger data is available shows an average of 102% data logger to meter 

readings (Table 9, column 11 and column 9) across the 12 homes and a standard 

deviation of 24%. The large standard deviation indicates that there are outlier homes, as 

is known. Removing the three outlier homes from the set shows an average energy use 

ratio data logger to meter estimate again of 102% with a standard deviation of 11%, 

indicating a very good approximation of the heating energy based on utility meter 

readings.

4. When comparing the simulation data estimates to the utility meter readings, the results 

are more varied with an average ratio of 148% for across all of the homes and a standard 

deviation of 109%. When removing the three outlier homes from the data set, the average 

ratio of simulated to meter energy use is 106% with a standard deviation of 21%, 

indicating a somewhat good approximation of energy use by the homes from the 

simulation estimates.

Figure 8 charts the data as described in the four summary points above.

Figure 8. Summary comparison of heating energy use estimates

for the heating period November 2010 – March 2011.

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

B-1B-2B-3B-4

FB-5FB-6FB-7FB-8

BV-1

B-5B-6

BV-2BV-3BV-4BV-5BV-6

FB-1FB-2FB-3FB-4

FV-1FV-2FV-3FV-4FV-5FV-6FV-7FV-8

Heating Energy Use Estimate, kWh

Pilot Home Reference

Meter estimate

Logger estimate

Simulation estimate
20

The average energy use (meter estimates) for all homes for the heating period from November 

2010 to March 2011 is 64% of the total energy use in the homes. Table 10 summarizes the meter 

estimate heating energy use data based on building type.

Table 10. Average Heating Energy for Building Types.

Home Type Heating Energy, kWh Size, ft2 Ratio, kWh/sf

Average Block 6,068 978 6.21

Average Block/Vinyl 6,760 1,360 4.97

Average Frame/Brick 5,018 1,112 4.51

Average Frame/Vinyl 4,118 931 4.43

6 Summary Indoor Temperature and Relative Humidity

Additional long-term monitoring includes indoor temperature and RH. The indoor temperature 

monitoring period for the 2010/2011 heating season started in early December for some homes 

and late January for the remaining homes and extended through most of April, 2011. The ending 

dates coincide with the last data download prior to commencing data analysis for the second 

report that was submitted to GHI, as well as a weather warming trend where daily highs started 

averaging in the 70’s (°F) and lows stayed above 50°F. Table 11 is a summary of the actual 

indoor temperatures recorded for the periods.

Table 11. Indoor Temperature/Humidity Conditions during the 2010/2011 Heating Season.
21

Table 11 indicates a range of indoor temperatures in the pilot program homes between 58oF to 

70°F, except for FB-7 which was unoccupied and unheated for part of the season and has the 

lowest daily average temperature of 55°F and highest standard deviation. Gauged by the standard 

deviation calculated for the other homes in the group, the daily indoor average temperature 

swings are modest. The most significant finding, based on the recorded building conditions, is 

that 64% of the occupied units maintained average indoor winter temperatures less than 68°F; a 

threshold generally viewed as the minimum set point for energy simulations (and comfort) and 

that which was used for the GHI pilot program simulations.

7 Detailed Data Summary Energy Use: Measured and Utility 

Meter Readings for Three Building Types

The baseline performance of each of the 28 homes was determined from the monitored data and 

the utility meter readings for each of the building types including block, wood frame with brick 

façade, and wood frame with vinyl siding.

7.1 Masonry Block Building – Units B-1, B-2, B-3, B-4

The masonry block building was the first equipped with sensors and transducers. Data was 

recorded for a five month period—a large portion of the 2010/2011 heating season. By chance, 

two adjacent units in the building maintained similar average indoor temperatures of 68.1°F (B1) 

and 68.9°F (B2) during the period. Records show one unit in the building at an average indoor 

temperature of 70.4°F (B4), and another one at 61.6°F (B3). The energy use for the whole house 

and just heating energy use relative to the difference between daily outdoor and indoor 

temperatures is plotted on the graphs in Figure 9 through Figure 12, which represent the four 

houses in Building B. In most homes, the relationship between the heating energy and the 

temperature difference is expected to be much more linear than between the whole house energy 

use and the temperature difference. However, in this building type the relationship is generally 

consistent due in part to the large heating percentage of the total energy use. Whole house energy 

use is included to indicate the daily consumption levels for the home.

All of the graphs show increasing energy use as the temperature difference between outdoors and 

indoors increases. The energy use for heating in masonry homes such as these may be somewhat 

out-of-sync with weather patterns because the large thermal mass of the building tends to cause a 

lag in transferring thermal energy across the walls and floors. However, use of a daily summary 

is necessary when actual measured temperature data is used because homes are usually operated 

on a cycle of usage patterns that recurs every 24 hours (diurnal).
22

Figure 9. B-1 Whole house and heating electric use analysis.

Figure 10. B-2 Whole house and heating electric use analysis.

y = 2.4784x - 11.862

R2 = 0.7621

y = 2.5683x + 4.7048

R2 = 0.7481

-20

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35 40 45 50

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 11/27/10 - 4/10/11)

Unit B-1 Heating Energy Use B-1 Whole House Energy Use Heating Fit Whole House Fit

y = 1.3202x + 6.2045

R2 = 0.6732

y = 1.4145x + 13.482

R2 = 0.6778

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25 30 35 40 45 50

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 11/27/10 - 4/10/11)

Unit B-2 Heating Energy Use B-2 Whole House Energy Use Heating Fit Whole House Fit
23

Figure 11. B-3 Whole house and heating electric use analysis.

Figure 12. B-4 Whole house and heating electric use analysis.

y = 0.3668x - 1.8293

R2 = 0.1794

y = 0.3622x + 8.6544

R2 = 0.1127

-5

0

5

10

15

20

25

30

35

40

45

-5 0 5 10 15 20 25 30 35 40

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 11/27/10 - 4/10/11)

Unit B-3 Heating Energy Use B-3 Whole House Energy Use Heating Fit Whole House Fit

y = 2.9622x + 1.2618

R2 = 0.6467

y = 3.0014x + 18.879

R2 = 0.6406

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25 30 35 40 45 50

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 11/27/10 - 4/10/11)

Unit B-4 Heating Energy Use B-4 Whole House Energy Use Heating Fit Whole House Fit
24

Figure 9, Figure 10, and Figure 12 indicate similar performance because the whole house and 

heating energy use are consistent as evidenced by the whole house and heating energy fit lines 

being parallel, or having a similar slope. The area between the fit lines is generally indicative of 

energy use for appliances, lights, water heating and miscellaneous. When the area is consistent, 

as shown by these graphs, it indicates that usage is more or less routine from day to day.

The linear fit formulas describe the relationship between temperature difference and energy use 

of the two data sets in each graph; therefore, the difference in the offset of the fit lines’ formulae 

approximates the daily average energy consumption within the home for uses other than heating. 

For example, in Unit B-2, the offset difference between the whole house energy use and the 

heating energy use is approximately 7 kWh, and is representative of the average daily use for all 

loads other than heating energy. 

Unit B-3, Figure 11, is unique in that it appears that the occupant(s) was/were either away for a 

large portion at the beginning of the heating season or simply did not use much heating. (Table 

10 indicates an average winter season indoor temperature less than 62° F.) The whole house 

energy use does not increase with the same proportion as the other homes in the building when 

outdoor temperatures decrease. 

The vertical axis on all of these graphs represents the daily heating and whole house electric 

energy usage. The range of electricity usage for these four homes is large—40 kWh to 160 

kWh—with interior points of 80 and 125 kWh. The maximum energy use for heating any one 

home in this group ranges from 32 kWh–140 kWh during the more severe weather period. The 

interior units use less electricity for heating because of the reduced exterior wall and window 

area and the reduced interior living area (interior units in this building are approximately 28% 

smaller than the end units). 

In addition to the data measured by the transducers, the utility meter readings were logged 

weekly for each of the units. The utility meter data correlates well with the measured data. The 

utility meter data has been used to analyze the heating energy use compared to the number of 

HDDs in Figure 13. The use of HDD helps to compare the temperature severity (or the 

difference between indoor and outdoor weather) when the time period is greater than one day. 

HDD is the cumulative measurement (for a period) of the difference between 65°F and the 

average daily temperature below 65°F. Each point on the graph indicates the average daily 

energy usage and the average daily HDD in a period defined by meter readings. The trend line 

for each unit indicates the relationship between the outdoor temperature severity and the average 

daily electric energy consumption. 
25

Figure 13. B-1 through B-4 average daily electricity use based on HDDs in the period.

Units B-4 and B-1 demonstrate the highest daily energy usage during the heating period. These 

are end units with approximately 25% more exterior wall surface, nearly 50% more roof surface 

area, and 28% more heated area than B-2 and B-3, thus higher energy usage for space 

conditioning is expected. 

7.2 Wood Frame Brick-Veneered Building – FB-5 through FB-8

The wood frame brick-veneered building that received temperature sensors and energy 

transducers in November 2010 shows similar average indoor temperatures in three of the units—

66°F, 65°F, and 66°F (Table 11). One of the units was unoccupied for the heating season, but the 

heat was on for some of the period and its average temperature was 55°F.

Figure 14 through Figure 17 chart the transducer data on whole house and heating energy use 

during the 2010/2011 heating season. Figure 18 compares the metered data and the HDD for a 

period.

B1 = 3.0219x + 6.6923

R2 = 0.9456

B2 = 1.5097x + 16.673

R2 = 0.9572

B3 = 0.3393x + 8.7373

R2 = 0.4957

B4 = 3.2397x + 25.948

R2 = 0.8959

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30 35 40

Average Energy Use Per Day in Measurement Period, kWh

Average Heating Degree Days per Day in Measurement Period 

B-1 B-2 B-3 B-4 Linear (B-1) Linear (B-2) Linear (B-3) Linear (B-4)
26

Figure 14. FB-5 Whole house and heating electric usage.

Figure 15. FB-6 Whole house and heating electric usage.

y = 1.0811x + 14.057

R2 = 0.4991

y = 1.1189x + 27.505

R2 = 0.4069

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 12/15/10 - 4/10/11)

Unit FB-5 Heating Energy Use FB-5 Whole House Energy Use Heating Fit Whole House Fit

y = 1.5863x - 9.7688

R2 = 0.719

y = 1.6091x + 24.083

R2 = 0.5087

-20

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35 40 45

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 12/15/10 - 4/10/11)

Unit FB-6 Heating Energy Use FB-6 Whole House Energy Use Heating Fit Whole House Fit
27

Figure 16. FB-7 Whole house and heating electric usage.

Figure 17. FB-8 Whole house and heating electric usage.

The daily energy usage range for the occupied homes is not large—90 to 115 kWh per day—and 

homes are of similar area. The maximum energy for space heating is, as would be expected, 

higher for the exterior units (75 to 85 kWh maximum daily usage) than the interior occupied unit 

y = 0.4333x + 10.151

R2 = 0.3051

y = 0.4251x + 14.988

R2 = 0.1227

0

10

20

30

40

50

60

-5 0 5 10 15 20 25 30

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 2/10/10 - 4/10/11)

Unit FB-7 Heating Energy Use FB-7 Whole House Energy Use Heating Fit Whole House Fit

y = 2.0817x - 4.44

R2 = 0.7561

y = 2.2131x + 9.3564

R2 = 0.7695

-10

0

10

20

30

40

50

60

70

80

90

100

110

-5 0 5 10 15 20 25 30 35 40 45

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 12/15/10 - 4/10/11)

Unit FB-8 Heating Energy Use FB-8 Whole House Energy Use Heating Fit Whole House Fit
28

(65 kWh). The larger-than-normal difference between the whole house and heating energy use 

(more than 20 kWh usage per day) for unit FB-6 (Figure 15) is generated by heating hot water.

Figure 18 compares the energy use recorded at the meter with the HDD for the period. The data 

correlates well with that presented in the previous graphs (Figure 14-Figure 17).

Figure 18. FB-5 through FB-8 average daily usage and HDD during the period.

The energy used in these wood frame brick (FB) units is significantly lower than for the block 

(B) units (Figure 9 through Figure 12) due the former having wall insulation. FB-5 and FB-8 are 

the end units with approximately 340 more square feet of exterior wall surface than interior 

units; however, all of the homes in this building have similar conditioned area (Table 3).

7.3 Wood Frame Vinyl Building – FV-5 through FV-8

One of the wood frame vinyl-sided buildings in the pilot program was also instrumented during 

the same week as the block building. The average indoor temperature for the four units ranged 

from 63°F to about 69°F (Table 10). One of the units has an air source heat pump and the 

homeowner does not use the baseboard heaters. The average indoor temperature of three of the 

four units was from 1 to 5 degrees below the 68°F simulation set point.

Figure 19 through Figure 22 indicate the detailed daily data for whole house and heating energy 

use. The maximum energy use recorded for any day is similar to that of the wood frame brick 

building but, the range for these wood frame vinyl homes is not as great as those of the other 

building types. The range of maximum daily use was 74–119 kWh per day (used in FV-6, and 

FV-5, respectively). The two other homes in the building recorded maximum daily energy use of 

75 and 104 kWh. The maximum heating energy use, however, was as would be expected, higher 

for the exterior units (108 and 63 kWh), than the interior units (47 to 52 kWh). The difference in 

heating energy use in the end homes can be attributed to the 6°F difference in average indoor 

heating set point.

FB5 = 1.259x + 26.091

R2 = 0.8627

FB6 = 1.7588x + 22.021

R2 = 0.9071

FB7 = -0.3244x + 20.581

R2 = 0.1415

FB8 = 2.1544x + 10.642

R2 = 0.947

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30 35 40

Average Energy Use Per Day in Measurement Period, kWh

Average Heating Degree Days per Day in Measurement Period 

FB-5 FB-6 FB-7 FB-8 Linear (FB-5) Linear (FB-6) Linear (FB-7) Linear (FB-8)
29

Figure 19. FV-5 Whole house and heating electric usage.

Figure 20. FV-6 Whole house and heating electric usage.

y = 1.6745x - 11.553

R2 = 0.6411

y = 1.8075x + 0.1158

R2 = 0.641

-10

0

10

20

30

40

50

60

70

80

90

100

110

120

0 10 20 30 40 50 60

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 12/16/10 - 4/10/11)

Unit FV-5 Heating Energy Use FV-5 Whole House Energy Use Heating Fit Whole House Fit

y = 1.3548x - 11.684

R2 = 0.8092

y = 1.2504x + 9.4266

R2 = 0.6339

-10

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35 40 45

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 12/16/10 - 4/10/11)

Unit FV-6 Heating Energy Use FV-6 Whole House Energy Use Heating Fit Whole House Fit
30

Figure 21. FV-7 Whole house and heating electric usage.

Figure 22. FV-8 Whole house and heating electric usage.

Comparison between the daily energy data recorded by the transducers (Figure 19 through 

Figure 22) to the utility meter records (Figure 23) indicates the agreement between the two 

methods. Figure 23 is a graph of the relationship between periodic utility meter records and the 

y = 1.5475x - 13.846

R2 = 0.7825

y = 1.804x + 11.111

R2 = 0.5968

-10

0

10

20

30

40

50

60

70

80

90

100

110

0 5 10 15 20 25 30 35 40 45

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 12/16/10 - 4/10/11)

Unit FV-7 Heating Energy Use FV-7 Whole House Energy Use Heating Fit Whole House Fit

y = 1.9035x - 11.757

R2 = 0.7984

y = 1.9035x - 0.9954

R2 = 0.7889

-10

0

10

20

30

40

50

60

70

80

-5 0 5 10 15 20 25 30 35 40

Total Daily Whole-House and Heating Energy Use, kWh

Indoor-Outdoor Temperature Difference, °F (period 12/16/10 - 4/10/11)

Unit FV-8 Heating Energy Use FV-8 Whole House Energy Use Heating Fit Whole House Fit
31

weather severity measured in HDD for the brick veneered building consisting of units FB-5 

through FB-8. 

Figure 23. Average daily usage and HDD during the period; FV-5 through FV-8.

The whole house energy used in the FV and FB units is similar since these units all have similar

wall and ceiling insulation. The interior unit, FV-7 shows the overall highest energy use;

however, the energy use is greater for non-heating loads and is consistent for energy used for 

heating as with other interior units.

8 Detailed Data Summary Energy Use: Utility Meter Readings for 

Four Building Types

Four buildings were unable to be outfitted with the electric energy transducers in time for the 

2010-2011 heating season. As with the previous three building types, electric meter readings 

were recorded for the remaining four buildings in the pilot study at regular intervals. The whole 

house energy use of the four buildings that were not outfitted with current transducers for the 

2010/2011 heating season are analyzed here based on observed meter readings and can be 

compared with the similar analysis above.

8.1 Block Vinyl-Sided and Block Building Units BV-1, B-5, B-6, BV-2

Vinyl siding has been installed on the end units of the block building (thus, they are named BV-1 

and BV-2). The two interior units remain constructed of 8 in. CMU block that has been painted 

(B-5 and B-6). Temperature sensors were installed in each of the homes for part of the heating 

season (February through April 2011). Energy use data was obtained via periodic utility meter 

readings (because energy transducers were installed in May 2011; after the heating season). The 

average indoor temperatures vary significantly from unit to unit. All are lower than the 68°F set 

point used in the simulation models. Figure 24 charts the whole house energy use during the 

FV5 = 1.9874x + 3.667

R2 = 0.9199

FV6 = 1.0261x + 15.077

R2 = 0.876

FV7 = 1.6714x + 17.404

R2 = 0.9542

FV8 = 1.6044x + 3.1107

R2 = 0.8319

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30 35 40

Average Energy Use Per Day in Measurement Period, kWh

Average Heating Degree Days per Day in Measurement Period 

FV-5 FV-6 FV-7 FV-8 Linear (FV-5) Linear (FV-6) Linear (FV-7) Linear (FV-8)
32

period of the heating season against the HDDs in the period on each unit. The trend line for each 

unit indicates the relationship between the severity of the outdoor temperature and the average 

daily whole house energy consumption.

The end units, BV-1 and BV-2, indicate the highest maximum daily energy usage during the 

period; however B-6, an interior unit, is a close third in energy usage. These three units have 

considerably different conditioned areas of 1,528, 1,245, and 921, respectively. Like the other 

block end units, the two in this building have more than twice as much exterior wall surface area 

as the interior units. 

Figure 24. BV-1, B-5, B-6 and BV-2 average daily usage and HDD for the heating period.

BV1 = 2.0974x + 23.174

R2 = 0.5934

B5 = 0.3756x + 17.38

R2 = 0.0995

B6 = 1.6489x + 3.3049

R2 = 0.7603

BV2 = 0.8993x + 24.01

R2 = 0.1345

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30 35 40

Average Energy Use Per Day in Measurement Period, kWh

Average Heating Degree Days per Day in Measurement Period 

BV-1 B-5 B-6 BV-2 Linear (BV-1) Linear (B-5) Linear (B-6) Linear (BV-2)
33

8.2 Block Vinyl-Sided Units BV-3 through BV-6

Temperature sensors were installed in each unit of the masonry block vinyl-sided building for 

part of the heating season (February through April 2011). Energy use data was obtained via 

periodic utility meter readings, as energy transducers were installed in May 2011; after the 

heating season ended. The average indoor temperatures in these units were closest of any of the 

buildings to those used in the energy simulations—69°F, 64°F, 70°F, and 66°F. Figure 25 charts 

the electricity used during utility meter measurement period normalized to the number of HDDs 

in that period. 

Figure 25. BV-3 through BV-6 average daily usage and HDD for the heating period.

BV3 = 2.2651x + 16.675

R2 = 0.8592

BV4 = 1.4274x + 0.5019

R2 = 0.7093

BV5 = 2.0013x + 37.023

R2 = 0.839

BV6 = 2.1072x + 22.641

R2 = 0.7228

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30 35 40

Average Energy Use Per Day in Measurement Period, kWh

Average Heating Degree Days per Day in Measurement Period 

BV-3 BV-4 BV-5 BV-6 Linear (BV-3) Linear (BV-4) Linear (BV-5) Linear (BV-6)
34

8.3 Wood Frame Brick Units FB-1 through FB-4

Temperature sensors were installed in each unit of this wood frame brick-veneered building for 

part of the heating season (February through April 2011). Energy use data was obtained via 

periodic utility meter readings, as energy transducers were installed in May 2011; after the end of 

the heating season. The average indoor temperatures vary considerably—70°F, 65°F, 66°F and 

58°F. Each of the homes in this building contains the same conditioned area, 1,080 ft2

. Figure 26

charts the electricity used during each utility meter measurement period normalized to the 

number of HDDs in that period. The FB-4 unit appears to be an anomaly both as an exterior unit 

and lower slope of energy use with reference to the weather severity. 

Figure 26. FB-1 through FB-4 average daily usage and HDD during the period.

FB1 = 1.9548x + 16.223

R2 = 0.9512

FB2 = 1.5763x + 0.6336

R2 = 0.8501

FB3 = 1.843x + 7.9586

R2 = 0.8445

FB4 = 1.0362x - 0.459

R2 = 0.4386

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30 35 40

Average Energy Use Per Day in Measurement Period, kWh

Average Heating Degree Days per Day in Measurement Period 

FB-1 FB-2 FB-3 FB-4 Linear (FB-1) Linear (FB-2) Linear (FB-3) Linear (FB-4)
35

8.4 Wood Frame Vinyl Units FV-1 through FV-4

Temperature sensors were installed in each unit of this wood frame vinyl-sided building for part 

of the heating season (February through April 2011). Energy use data was obtained via periodic 

utility meter readings, as energy transducers were not installed until May 2011 after the end of 

the heating season. Average indoor temperatures were 63°F, 69°F, 68°F, and 68°F. Whole house 

energy use is plotted against the HDDs in the period in Figure 27. 

Figure 27. FV-1 through FV-4 average daily usage and HDD for the heating period.

9 Indoor Relative Humidity

One interest for the research in the pilot home program is to document the indoor conditions that 

represent comfort of the homeowners. Anecdotal evidence from homeowner interviews has 

identified lower than typical indoor temperature settings due in large part to energy use. 

Commensurate with the lower indoor temperatures, there is a concern that many homes have 

higher than acceptable RH that result in condensation and other indoor air quality problems. 

Using comfort as the criteria, 2001 ASHRAE Fundamentals (8.12) sets 25%–60% RH as the 

range acceptable to 80% of the population. This is the range where few people can detect 

humidity in the air. Below 25%, dry nose, throat, and skin are noticeable, while above 60% 

people detect a stickiness, or clammy feeling, on their skin. The Air Conditioning Contractors of 

America (ACCA) generally supports this humidity range at which various air contaminants 

grow.9 More recently, building science experts suggest that heat season RH should be less than 

40% to prevent condensation on cold surfaces.10

 9 ACCA Consumer Education Series, Manage Your Humidity, 2003, http://www.superior-air.com/Humiweb.pdf 10 Krigger & Dorsi, Residential Energy, 2009, Saturn Resource Management, Inc.

FV1 = 1.5333x + 0.7295

R2 = 0.8891

FV2 = 1.1753x + 13.46

R2 = 0.9691

FV3 = 1.3262x + 6.8322

R2 = 0.6992

FV4 = 2.5314x - 6.1739

R2 = 0.2687

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30 35 40

Average Energy Use Per Day in Measurement Period, kWh

Average Heating Degree Days per Day in Measurement Period 

FV-1 FV-2 FV-3 FV-4 Linear (FV-1) Linear (FV-2) Linear (FV-3) Linear (FV-4)
36

Homes in the pilot study tended to show average indoor RH within the ASHRAE 

recommendation range, however, a majority of the units showed average household RH higher

than the more recently recommended limit of 40%; 14 of 26 homes recorded in Table 11 showed 

average heat season RH above 40%. Two of the block houses had RH levels over 60% (B-3 and 

B-5) for some duration of the heat season. Both of these units indicate significantly cooler indoor 

average temperatures than the pilot group of homes—62oF and 64°F. The GHI Report 1, 

Phase 111 proposed exhaust fans with timers as a method of diluting the humid indoor air by 

exhaust ventilation. (RH sensors in units B-1 and B-2 were not available for this measurement 

period.) Figure 28 through Figure 38 show the available RH data for each home.

Figure 28. Indoor relative humidity B-3 and B-4.

 11 NAHB Research Center report to the Board of Directors of Greenbelt Homes, Inc. April 2011
37

Figure 29. Indoor relative humidity BV-1 and B-5.

Figure 30. Indoor relative humidity B-6 and BV-2.
38

Figure 31. Indoor relative humidity BV-3 and BV-4.

Figure 32. Indoor relative humidity BV-5 and BV-6.

The indoor RH of the wood frame brick and wood frame vinyl buildings for the heating period 

are detailed in Figure 33 through Figure 38.
39

Figure 33. Indoor relative humidity FB-1 and FB-2.

Figure 34. Indoor relative humidity FB-3 and FB-4.
40

Figure 35. Indoor relative humidity FB-5 and FB-6.

Figure 36. Indoor relative humidity FB-7 and FB-8.
41

Figure 37. Indoor relative humidity FV-1 and FV-2.

Figure 38. Indoor relative humidity FV-3 and FV-4.
42

10 Building Crawlspaces

Figure 39 through Figure 45 chart the RH in the crawlspaces of the buildings in the pilot study. 

An acceptable range would be similar to the range identified for indoor conditions. 

Dehumidifiers have been recommended for the block (B) and wood frame brick (FB) building 

crawlspaces, as these are currently closed crawlspace foundations without mechanical ventilation 

or a heat source. Air dilution via ventilation grills was recommended for the wood frame vinyl 

(FV) buildings. The buildings are outfitted with the grills, but these have been blocked by deck 

band boards and built-up grade. A full vapor barrier to cover the entire crawlspace floor was 

added in the fall of 2011 to all buildings.

The data indicates that the dew point in the crawlspaces remains below the temperature in the 

crawlspaces, generally resulting in little condensation potential on surfaces. One group of block 

building, units BV-1 through BV-2, did not report the RH due to a sensor malfunction. Average 

daily temperatures for the crawlspace are reported.

Figure 39. Crawlspace relative humidity; Units B-1 through B-4.
43

Figure 40. Crawlspace temperature; BV-1, B-5, B-6 and BV-2.

Figure 41. Crawlspace temperature and relative humidity BV-3 through BV-6s.
44

Figure 42. Crawlspace temperature and relative humidity FB-1 through FB-4.

Figure 43. Crawlspace temperature and relative humidity FB-5 through FB-8.
45

Figure 44. Crawlspace temperature and relative humidity FV-1 through FV-4.

Figure 45. Crawlspace temperature and relative humidity FV-5 through FV-8.
46

11 Summary

The purpose of Phase 1 of the Greenbelt Homes Inc. (GHI) pilot program was to determine the 

pre-retrofit condition of older homes, develop simulation models to estimate energy and cost 

savings, make building envelope upgrade recommendations, and instrument the homes to 

determine a baseline energy use and compare with utility meter readings. The pre-retrofit condition 

of the 28 homes in the pilot program was established through occupant interviews, compilation of 

the previous years’ utility bills, physical inspections, and air infiltration and water flow testing. As 

a result, the pre-retrofit conditions are available in detail for each of the building exterior wall types 

including block, wood frame with brick façade, and wood frame with vinyl siding.

The energy simulations for each wall type were completed using BEopt v1.01. Equipment 

specifications, dimensions, building orientation, and other apparent features were recorded by 

Research Center staff during site walk-through evaluations and short-term testing of the pilot 

project units. A minimum of one end and one interior unit was modeled in each building. 

Estimated savings and costs for the whole building were tallied from these outcomes. Several 

buildings were made up of unique homes, thus modeling more than two of the four units was 

warranted. The results of energy modeling were assembled in a spreadsheet to aid GHI staff in 

presenting the upgrade options to its membership. 

The baseline monitoring included collecting energy data to establish pre-retrofit energy use.

Energy use data is being recorded and analysis covering data that was captured for a period of 

the 2010/2011 heating season was presented herein. Ongoing data collection throughout all 

phases of the pilot project includes energy, temperature, and RH data. Using the collected 

baseline data, the Research Center compared the estimated heating energy from the simulation 

tins with the actual whole-house energy use monitored data. The result was a close correlation 

between the simulations and the data.

The baseline performance of each of the 28 homes was determined from the monitored data and 

the utility meter readings for each of the building types including block, wood frame with brick 

façade, and wood frame with vinyl siding. For the block buildings, the data shows increasing 

energy use as the temperature difference between outdoors and indoors increases. The energy use 

for heating in masonry homes such as these may be somewhat out of sync with weather patterns 

because the large thermal mass of the building tends to cause a lag in transferring thermal energy 

across the walls and floors. The energy used in the wood frame brick (FB) units is significantly 

lower than for the block (B) units due the former having wall insulation. The whole house energy 

used in the wood frame vinyl (FV) and FB units is similar since these units all have similar wall 

and ceiling insulation. For all of the units, the maximum energy for space heating is, as would be 

expected, higher for the exterior units than the interior-occupied unit. In addition, the utility 

meter data correlates well with the measured data for all the units.

Indoor temperature, RH, was also collected as part of the monitored data. The most significant 

finding, based on the recorded building conditions, is that 64% of the occupied units maintained 

average indoor winter temperatures less than 68°F; a threshold generally viewed as the minimum 

set point for energy simulations (and comfort) and that which was used for the GHI pilot 

program simulations. The indoor conditions, representing the pre-retrofit comfort of the 

homeowners, were also assessed based on the indoor RH. Homes in the pilot study tended to 

show average indoor RH within the 2001 ASHRAE Fundamentals 25%–60% recommendation 

range. However, 14 of 26 homes recorded showed average household RH higher than the more 
47

recently recommended limit of 40%. Two of the block houses had RH levels over 60% for some 

duration of the heat season.

Relative humidity was also monitored in the crawlspaces of the buildings in the pilot study. An 

acceptable range would be similar to the range identified for indoor conditions. As a result, 

dehumidifiers have been recommended for the block (B) and wood frame brick (FB) building 

crawlspaces and air dilution via ventilation grills was recommended for the wood frame vinyl 

(FV) buildings. A full vapor barrier to cover the entire crawlspace floor was added in the fall of 

2011 to all buildings. The data indicates that the dew point in the crawlspaces remains below the 

temperature in the crawlspaces, generally resulting in little condensation potential on surfaces.

12 Next Steps

GHI has established a pilot project that will serve as a basis for decision making for the rollout of 

a decade-long community upgrade program that will improve the energy efficiency of the 

building envelope and equipment such as plumbing, mechanical equipment, and cladding. The 

pilot project has three phases focused on identifying the added costs and benefits of energy 

efficiency features, which are to be installed during a planned communitywide replacement 

program commencing in 2015. Phase 1 presented in this report consisted of an evaluation of the 

current operation, use, environmental conditions, and energy costs. 

The next steps will include Phase 2 and 3 of the GHI pilot program. Phase 2 will consist of the 

installation of the building envelope improvements identified in Phase 1, monitoring energy 

consumption for the heating season following installation, and performing energy simulations 

supporting recommendations for HVAC and water heating upgrades to be implemented in 

Phase 3. The whole-house monitoring will continue throughout the project, both with the 

building envelope upgrades in Phase 2 and the HVAC upgrades in Phase 3.
48

References

ASHRAE (2010). Addendum to ASHRAE/ANSI 55-2010: Thermal Environmental Conditions for 

Human Occupancy. Atlanta, GA: American Society of Heating, Refrigerating, and AirConditioning Engineers. 

Hendron, R. (2006). “Building America Performance Analysis Procedures for Existing Homes”. 

NREL/TP-550-38238: Golden, CO. National Renewable Energy 

Laboratory http://www.nrel.gov/buildings/pdfs/38238.pdf

Krigger, J; Dorsi, C. (2009). Residential Energy: Cost Savings and Comfort for Existing 

Buildings. 5th Edition..Helena, MT: Saturn Resource Management, Inc.

NAHB Research Center (2011). Test Plan: Energy Use Analysis and Performance Monitoring of 

the GHI Remodel Pilot Program. (internal only).
49

Appendix A: Typical Building Specifications

Table 12. 8 in. CMU Block, BV-1, B-5, B-6, BV-2.
50

Table 13. 8 in. CMU Block, BV-3 through BV-6.
51

Table 14. Wood Frame Brick Veneer, FB-1 through FB-4.
52

Table 15. Wood Frame Vinyl, FV-1 through FV-4.
53

Appendix B: Temperature and RH Sensor Locations

These drawings show example of floor plans and location of temperature/humidity sensors.
54
55

Appendix C: Phase 1 Energy Simulations

Before and After Energy Features

Energy Usage Simulation Results

Per Building and Per Unit (4 per Building)

Block Building – B-1, B-2, B-3, B-4

Table 16. Block Building – B-1, B-2, B-3, B-4.
56

Figure 46. Modeled energy use B-1.

Figure 47. Modeled energy use B-2.
57

Block Vinyl-Sided Buildings – BV-3, BV-4, BV-5, BV-6

Table 17. Block Vinyl-Sided Buildings – BV-3, BV-4, BV-5, BV-6.

Figure 48. Modeled energy use BV-3.

Unit Code

Feature/ Component

House Type

Structural Wall Type

Front Orientation

Finished Sq. Ft.

Addition Sq. Ft.

No. Stories

Bedrooms

Baths

Foundation

Foundation R-value R-5 R-10 R-5 R-10 No R-13 No R-13

Floor R-value 0 R-10 Porch Slab 0 R-10 Porch Slab 0 R-10 Porch Slab 0 R-10 Porch Slab

Vented Crawlspace

1st Floor 5" structural slab 5" structural slab 5" structural slab 5" structural slab

Attic R-value

Building Dimensions

Addition Dimensions

Window, Sq. Ft.

Window U-/SHGC .55/.70 .30/.30 .55/.70 .30/.30 .55/.70 .30/.30 .55/.70 .30/.30

Wall R-value 0 R-12 0 R-12 0 R-12 0 R-12

Front Door w ood 3070 2 lt. U=.23 w ood 3070 w /3lt. U=.23 w ood 3070 w / 3 lts U=.23 w ood 3070 w / 3 lts U=.23

Rear Door 3068 full glass 3070 w ood 1/2 gl U=.23 3070 w / 1/2 lt. U=.23 3070 w / 1/2 lt. U=.23

Air Leakage, ACH50 7.5 4.8 3.5 3.2 4.3 3.8 4.0 3.7

Mechanical Ventilation, run time 0.00% Ex.&timer 100% 0.00% Ex.&timer 100% 0.00% Ex.&timer 100% 0.00% Ex.&timer 100%

Hot Water $353 $353 $353 $353 $446 $446 $429 $429

Heating $1,149 $568 $783 $439 $1,117 $576 $1,353 $700

Lights $170 $170 $170 $170 $227 $227 $227 $227

Appliances $252 $252 $252 $252 $296 $296 $296 $296

Misc. Loads $392 $392 $392 $392 $472 $472 $472 $472

Vent Fan $11 $13 $19 $18

Total 2,316 1,746 1,950 1,619 2,558 2,036 2,777 2,142

Percentage Energy Savings 25% 17% 20% 23%

Heating Energy Savngs 51% 44% 48% 48%

Energy Cost Savings $570 $331 $522 $635

Annual Cost Savings for 4-Unit Block/Vinyl Building (2 with basements) $2,058

26.67x20 26.67x20 28.67x20w/bsmt. 28.67x20w/bsmt.

64/35/107/0 65/0/80/0 70/0/120/0 73/0/127/49

Concrete Crawl 3.5/4' Concrete Crawl 3.5/4' Walkout Bsmt Walkout Bsmt

No No n/a n/a

R-26 R-26 R-26 R-26

2 2 3 3

2 2 3 3

1 1 1 1

Southeast Southeast Southeast

1080 1080 1160 1160

32

Energy Costs (excluding Fan/Pump)

BV3

Before

BV3

After

BV4

Before

BV4

After

BV5

Before

BV5

After

BV6

Before

BV6

After

Town - End, C 2.8 Town - Interior, C 2.7 Town - Interior, C 3.7 Town - End, C 3.7

 8" CMU 8" CMU 8" CMU 8" CMU

Southeast
58

Figure 49. Modeled energy use BV-4.

Figure 50. Modeled energy use BV-5.

Figure 51. Modeled Energy Use BV-6.
59

Wood Frame Brick Building – FB-1 and FB-2

Table 18. Wood Frame Brick Building – FB-1 and FB-2.

Figure 52. Modeled energy use FB-1.
60

Figure 53. Modeled energy use FB-2.
61

Wood Frame Vinyl-Sided Building – FV-1, FV-2, FV-3, FV-4

Table 19. Wood Frame Vinyl-Sided Building – FV-1, FV-2, FV-3, FV-4.
62

Figure 54. Modeled energy use FV-1.

Figure 55. Modeled energy use FV-3.

Figure 56. Modeled energy use FV-4.
63

Wood Frame Vinyl-Sided Building – FV-5, FV-6, FV-7, FV-8

Table 20. Wood Frame Vinyl-Sided Building – FV-5, FV-6, FV-7, FV-8.
64

Figure 57. Modeled energy use FV-7.

Figure 58. Modeled energy use FV-8.
65

Appendix D: Average Hourly Indoor Temperatures

Figure 59. B-1 Average Hourly Indoor Temperature – November 2010 through April 2011.
66

Figure 60. B-2 Average Hourly Temperature – November 2010 through April 2011.
67

Figure 61. B-3 Average Hourly Temperature – November 2010 through April 2011.
68

Figure 62. B-4 Average Hourly Temperature – November 2010 through April 2011.
69

Figure 63. B-5 Average Hourly Temperature – February 2011 through April 2011.
70

Figure 64. B-6 Average Hourly Temperature – February 2011 through April 2011.
71

Figure 65. BV-1 Average Hourly Temperature – February 2011 through April 2011.
72

Figure 66. BV-2 Average Hourly Temperature – February 2011 through April 2011.
73

Figure 67. BV-3 Average Hourly Temperature – February 2011 through April 2011.
74

Figure 68. BV-4 Average Hourly Temperature – February 2011 through April 2011.
75

Figure 69. BV-5 Average Hourly Temperature – February 2011 to April 2011.
76

Figure 70. BV-6 Average Hourly Temperature – February 2011 to April 2011.
77

Figure 71. FB-1 Average Hourly Temperature – February 2011 to April 2011.
78

Figure 72. FB-2 Average Hourly Temperature – February 2011 to April 2011.
79

Figure 73. FB-3 Average Hourly Temperature – February 2011 to April 2011.
80

Figure 74. FB-4 Average Hourly Temperature – February 2011 to April 2011.
81

Figure 75. FB-5 Average Hourly Temperature – December 2010 to April 2011.
82

Figure 76. FB-6 Average Hourly Temperature – December 2010 to April 2011.
83

Figure 77. FB-7 Average Hourly Temperature – December 2010 to April 2011.
84

Figure 78. FB-8 Average Hourly Temperature – December 2010 to April 2011.
85

Figure 79. FV-1 Average Hourly Temperature – February 2011 to April 2011.
86

Figure 80. FV-2 Average Hourly Temperature – February 2011 to April 2011.
87

Figure 81. FV-3 Average Hourly Temperature – February 2011 to April 2011.
88

Figure 82. FV-4 Average Hourly Temperature – February 2011 to April 2011.
89

Figure 83. FV-5 Average Hourly Temperature – December 2010 to April 2011.
90

Figure 84. FV-6 Average Hourly Temperature – December 2010 to April 2011.
91

Figure 85. FV-7 Average Hourly Temperature – December 2010 to April 2011.
92

Figure 86. FV-8 Average Hourly Temperature – December 2010 to April 2011.
93

Figure 87. BV-6 Average Hourly Temperature – February 2011 to April 2011.
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