Transformations, Inc.: 

Partnering To Build 

Net-Zero Energy Houses 

in Massachusetts

K. Ueno, D. Bergey, and H. Wytrykowska

Building Science Corporation

September 2013
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iii

Transformations, Inc.: 

Partnering To Build Net-Zero Energy Houses in Massachusetts

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: 

K. Ueno, D. Bergey, H. Wytrykowska 

Building Science Corporation 

30 Forest Street

Somerville, MA 02143

NREL Technical Monitor: Cheryn Metzger

Prepared under Subcontract No. KNDJ-0-40337-02 

September 2013 
iv

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v 

Contents

List of Figures ........................................................................................................................................... vii

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

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

Executive Summary.................................................................................................................................... x

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

1.1 Devens Sustainable Housing ................................................................................................2

1.2 The Homes at Easthampton Meadow ..................................................................................7

1.3 Coppersmith Way Development ........................................................................................11

2 Air Leakage Testing ........................................................................................................................... 14

3 Construction Cost and Energy Modeling......................................................................................... 17

3.1 Construction Cost...............................................................................................................17

3.2 Energy Modeling and Cost Effectiveness of Energy Efficient Measures ..........................18

3.3 Performance Data...............................................................................................................20

4 Mini-Split Heat Pump Performance and Thermal Distribution....................................................... 21

4.1 Background ........................................................................................................................21

4.2 Experimental Design and Sensor Installation ....................................................................22

4.2.1 Townsend (2010–2011) .........................................................................................22

4.2.2 Unoccupied Homes (2011–Present) ......................................................................23

4.2.3 Occupied Homes (2012–Present) ..........................................................................24

4.3 Results 25

4.3.1 Data Overview/Boundary Conditions ....................................................................25

4.3.2 Distribution ............................................................................................................29

4.3.3 Mini-Split Energy Consumption ............................................................................32

4.4 Resident Survey .................................................................................................................37

4.4.1 Survey Results .......................................................................................................37

5 Moisture Monitoring of Twelve-Inch Double-Stud Walls................................................................ 38

5.1 Background ........................................................................................................................38

5.2 Experimental Design and Sensor Installation ....................................................................39

5.2.1 Overview ................................................................................................................40

5.2.2 Wall Sensor Package ..............................................................................................43

5.2.3 Additional Sensors and Data Collection Logistics ................................................47

5.3 Results 48

5.3.1 Data Overview and Boundary Conditions .............................................................48

5.3.2 Monitored Wall Results .........................................................................................49

5.3.3 Analysis and Interpretation ....................................................................................54

6 Financing Options for Photovoltaic Systems.................................................................................. 56

6.1 Transformations, Inc. Financing Options ..........................................................................56

6.2 Massachusetts Department of Energy Resources Solar Carve-Out Program ....................56

6.3 Other Incentives .................................................................................................................58

7 Basements Versus Above-Grade Construction Cost Comparison............................................... 60

7.1 Basement and Slab-on-Grade Construction Comparison ..................................................60

7.2 Cost Analysis .....................................................................................................................62

7.3 Basement Versus Above-Grade Advantages and Disadvantages ......................................63

8 Conclusion and Further Work........................................................................................................... 65

8.1 Overview ............................................................................................................................65

8.2 Moisture Monitoring of Twelve-Inch Double-Stud Walls ................................................65
vi 

8.3 Financing Options for Photovoltaic Systems .....................................................................66

8.4 Basements Versus Above-Grade Construction Cost Comparison .....................................66

References................................................................................................................................................. 68

Appendix A: Mini-Split Heat Pump Performance Surveys.................................................................... 70

Appendix B: Model Home (Lot 13) Home Energy Rating Certificate ................................................... 79
vii 

List of Figures

Figure 1. Devens sustainable housing site plan...................................................................................... 3

Figure 2. (L) Farmhouse (Lot 1); (R) Greek Revival (Lot 2)..................................................................... 3

Figure 3. (L) Victorian (Lot 3); (R) Farmhouse (Lot 4) ............................................................................. 4

Figure 4. (L) Greek Revival (Lot 5); (R) Saltbox (Lot 6) ........................................................................... 4

Figure 5. (L) Custom Saltbox (Lot 7); (R) Ranch (Lot 8).......................................................................... 4

Figure 6. Wall section with basement....................................................................................................... 6

Figure 7. The homes at Easthampton Meadow site plan........................................................................ 7

Figure 8. (L) Model Home (Lot 13); (R) Custom Home (Lot 30) .............................................................. 8

Figure 9. (L) Custom Home (Lot 43); (R) Easthampton (Lot 40)............................................................. 8

Figure 10. (L) Northampton (Lot 28); (R) Needham (Lot 31) ................................................................... 8

Figure 11. (L) Cottage (Lot 23) and Hadley (Lot 24); (R) Small Saltbox (Lot 17)................................... 9

Figure 12. (L) Wall section with slab-on-grade; (R) basement ............................................................. 10

Figure 13. Coppersmith Way development site plan ............................................................................ 11

Figure 14. (L) Groton (Lot 24); (R) Wellesley (Lot 25)............................................................................ 12

Figure 15. (L) Groton (Lot 29); (R) Greek Revival (Lot 30) .................................................................... 12

Figure 16. Wall section with basement................................................................................................... 13

Figure 17. (L) Model home garage side; (R) house side ....................................................................... 15

Figure 18. (L) PV inverter connection; (R) tankless water heater intake and exhaust vent.............. 15

Figure 19. Farmhouse BEopt optimization results—cost versus energy use.................................... 19

Figure 20. Farmhouse BEopt optimization results—cost versus energy use.................................... 20

Figure 21. (L) Exterior of houses at Devens; (R) Easthampton............................................................ 23

Figure 22. (L) Upstairs mini-split at Easthampton; (R) Watt-hour meter at Devens........................... 24

Figure 23. (L) Small Saltbox (Lot 17); (R) Cottage (Lot 23)................................................................... 25

Figure 24. Indoor and outdoor temperatures at Easthampton............................................................. 26

Figure 25. Indoor and outdoor temperatures at Devens....................................................................... 27

Figure 26. Devens basement temperature before and after basement insulation ............................. 28

Figure 27. Devens first-floor temperature before and after basement insulation.............................. 28

Figure 28. Easthampton temperature variations ................................................................................... 29

Figure 29. Easthampton frequency distribution of temperature differences ..................................... 30

Figure 30. Easthampton frequency distribution of temperatures........................................................ 30

Figure 31. Devens temperature variations ............................................................................................. 31

Figure 32. Devens frequency distribution of temperature differences ............................................... 31

Figure 33. Devens frequency distribution of temperatures .................................................................. 31

Figure 34. Devens distribution of first-floor temperatures................................................................... 32

Figure 35. Devens mini-split power by floor .......................................................................................... 33

Figure 36. Easthampton mini-split power by floor ................................................................................ 33

Figure 37. Devens first-floor power by basement insulation ............................................................... 34

Figure 38. Distribution of mini-split power............................................................................................. 34

Figure 39. Devens mini-split power time series..................................................................................... 35

Figure 40. Devens mini-split balance point............................................................................................ 36

Figure 41. Easthampton mini-split balance point.................................................................................. 36

Figure 42. THERM results for double-stud walls (based on Straube and Smegal 2009); condensing 

plane highlighted in gray ................................................................................................................... 38

Figure 43. THERM results for 4-in. exterior foam wall (based on Straube and Smegal 2009); 

condensing plane highlighted in gray.............................................................................................. 39

Figure 44. Typical installation of 1⁄2 lb/ft3 spray foam in double-stud walls ........................................ 40

Figure 45. Overhead (L) and front (R) views of Lot 3 test house ......................................................... 41

Figure 46. Test walls shown on second-floor plan, with guard bay insulation for separation......... 42

Figure 47. Test wall locations shown on exterior of house; south (L) and north (R) orientations... 42

Figure 48. (L) Temperature and MC sensor at sheathing; (R) sensors at mid-height of stud bay ... 43

Figure 49 (L) “Wafer” surrogate RH sensor at sheathing; (R) schematic of sensor, with 

dimensions in mm .............................................................................................................................. 44

Figure 50. South test walls after installation of sensors, showing double-stud layout .................... 44
viii

Figure 51. (L) Instrumentation diagram for 12-in. ocSPF; (C) 12-in. cellulose; (R) 51⁄2-in. ocSPF .... 46

Figure 52. Sensor measure interior (bedroom) T/RH sensors ............................................................. 47

Figure 53. (L) Exterior T/RH sensor; (R) data collection from exterior connection port ................... 47

Figure 54. Exterior and interior (test rooms and basement) temperatures ........................................ 48

Figure 55. Interior RHs (test rooms and basement) .............................................................................. 49

Figure 56. Exterior and interior (test rooms and basement) dew point temperatures ...................... 49

Figure 57. North side sheathing MCs, with exterior temperature for reference................................. 50

Figure 58. South side sheathing MCs, with exterior temperature for reference ................................ 51

Figure 59. South side “wafer” sensor moisture contents, with exterior temperature for reference 52

Figure 60. South side “wafer” sensor MCs, with exterior temperature for reference ....................... 52

Figure 61. North-facing wall exterior side RH, with exterior temperature for reference ................... 53

Figure 62. North-facing wall interior side RH, with interior RH and exterior temperature for 

reference.............................................................................................................................................. 53

Figure 63. PVWatts calculation for a house with a 10-kW system located in Easthampton, 

Massachusetts.................................................................................................................................... 58

Figure 64. Foundation wall with 31⁄2 in. of ccSPF insulation................................................................. 61

Figure 65. Slab-on-grade construction................................................................................................... 62

Figure 66. (L) Tankless water heater; (R) PV inverters in unfinished basement................................ 64

Unless otherwise noted, all figures were created by Building Science Corporation. 

List of Tables

Table 1. Air Leakage Test Results in the Devens Sustainable Housing Development...................... 14

Table 2. Air Leakage Test Results in the Homes at Easthampton Meadow Development................ 14

Table 3. Air Leakage Test Results in the Coppersmith Way Development......................................... 14

Table 4. Construction Costs .................................................................................................................... 17

Table 5. Devens Sensor Package............................................................................................................ 23

Table 6. Easthampton Sensor Package.................................................................................................. 24

Table 7. Test Wall Listing ......................................................................................................................... 40

Table 8. Vapor Permeability of Insulation and Assemblies.................................................................. 54

Table 9. Value of Solar Renewable Energy Certificates in Massachusetts......................................... 57

Table 10. Basement Construction Cost.................................................................................................. 62

Unless otherwise noted, all tables were created by Building Science Corporation. 
ix

Definitions

ACH Air changes per hour

ACP alternative compliance payment

ADA airtight drywall approach

ASHP Air source heat pump

BSC Building Science Corporation

Btu British thermal unit

ccSPF Closed-cell spray polyurethane foam

CFM Cubic feet per minute

COP Coefficient of performance

DOE U.S. Department of Energy

DOER Massachusetts Department of Energy Resources

ft2 Square foot, square feet

HDD Heating degree day

MC Moisture content

NREL National Renewable Energy Laboratory 

ocSPF Open-cell spray polyurethane foam

o.c. On center

OSB Oriented strand board

PCF Pounds per cubic foot

PV Photovoltaic

RH Relative humidity

RPS Renewable Portfolio Standard

SEER Seasonal energy efficiency ratio

SHGC Solar heat gain coefficient

SREC Solar Renewable Energy Certificate

T/RH sensor Temperature/relative humidity sensor

Wh Watt-hour

XPS Extruded polystyrene
x 

Executive Summary

Transformations, Inc. is a residential development and building company that has partnered with 

Building Science Corporation (BSC) to build new construction net-zero energy houses in 

Massachusetts under the Building America program.

There are three communities that are being constructed through this partnership: Devens 

Sustainable Housing (“Devens”), The Homes at Easthampton Meadow (“Easthampton”), and 

Phase II of the Coppersmith Way Development (“Townsend”). This report covers all of the 

single-family new construction homes that have been completed to date. 

The houses built in these developments are net-zero energy capable homes built in a cold 

climate. The set of measures offered by the developer exceeds the 30% energy saving goals set 

by the Building America program for new homes in the cold climate for 2013. The houses will 

contribute to developing solutions and addressing gaps in enclosures and space conditioning 

research; specific topics included the following: 

• To determine the range of temperatures experienced in bedrooms of homes heated by 

point sources, data loggers were installed at two unoccupied and two occupied houses. 

The first year of data from the unoccupied homes show that under favorable conditions, 

mini-split heat pumps can provide thermal comfort and uniformity equal to conventional 

forced-air systems. 

• The homebuyers’ perception of ductless mini-split heat pumps’ performance was 

examined using surveys that were distributed to the homeowners in all three 

developments. The occupants have reported high levels of comfort, consistent with the 

measured temperature uniformity. Most occupants seem to accept the concept of keeping 

bedroom doors open most of the time, facilitating thermal distribution and thus enhancing 

comfort.

• The moisture risks of 12-in. thick double-stud walls insulated with cellulose or open-cell 

spray foam were researched with moisture monitoring experiment at one of the houses in 

Devens. Eight months of data have been collected and analyzed to date (from December 

2011 through July 2012) in unoccupied conditions. The first winter showed sheathing 

moisture contents high enough to cause concern in the double-stud cellulose wall, but 

acceptable conditions in the remaining walls. However, all walls dried to safe ranges in 

the summer. In addition, it is possible that the cellulose wall can withstand high moisture 

content levels without damage due to borate preservatives and moisture storage. BSC is 

continuing to collect data (currently August 2013); further analysis will be contained in 

future BSC reports. The first winter measured data without occupancy (and thus interior 

moisture generation); the upcoming winter will demonstrate the effect of higher interior 

humidity levels.

• Hygrothermal modeling was not performed at this time, with eight months’ of data. The 

planned process is to only perform hygrothermal modeling (for comparison with 

monitored results) after the collection of at least one year of data, and preferably more (to 

account for the initial year’s unoccupied conditions). 
xi 

• BSC worked with Transformations, Inc. to evaluate the options that are available to 

homeowners for obtaining photovoltaic systems. The developer has put substantial 

research and effort into developing affordable and viable alternatives. Local incentives—

as well as state and federal tax credits—contribute to making the residential photovoltaic 

systems financially attractive. BSC explored the financing models provided by the 

developer and looked at each available option in detail. Cost values and payback time 

were analyzed and compared to evaluate what each of those options has to offer. 

Incentive programs differ substantially in each state; therefore, a number of resources 

were provided to homebuyers to learn the details about the available options. 

• To determine the relative costs of additional above-grade space and basement space, BSC 

worked with the developer to compare a number of options available to the homebuyers. 

The cost analysis began by comparing the per square foot cost data for constructing a 

basement and a slab-on-grade foundation. The difference between the two approaches 

was found to be $12 with the basement cost at $39 and the slab-on-grade cost at $27. 

Several options for adding above-grade space, including unfinished and finished space 

above the garage, and building a one-story addition, were also explored and were found 

to range between $1.30–$125/ft2

.
1 

1 Introduction

Transformations, Inc. is a residential development and building company that has partnered with 

Building Science Corporation (BSC) to build new construction net-zero energy houses in 

Massachusetts under the Building America program.

There are three communities that are being constructed through this partnership: Devens 

Sustainable Housing (“Devens”), The Homes at Easthampton Meadow (“Easthampton”) and 

Phase II of the Coppersmith Way Development (“Townsend”). This report covers all of the 

single-family new construction homes that have been completed to date in Devens and 

Easthampton, as well as three homes in Phase II in Townsend. Currently, there are six houses 

that have been completed in the Devens development, seven houses in the Easthampton 

community, and three houses in the Townsend development. 

Transformations, Inc. completed one community development and multiple custom homes prior 

to partnering with BSC. Since 2006, the developer has been developing strategies for costeffective super-insulated homes in the New England market. Several construction methods for 

walls, roofs, basements, as well as mechanical and ventilation systems have been tested by the 

developer. After years of using various construction techniques, Transformations, Inc. has 

developed a specific set of assemblies that is implemented in the houses in all three 

developments. These assemblies exceed the requirements of current building codes and are 

financially viable for the developer. 

The houses built in these developments are net-zero energy capable homes built in a cold climate 

and contribute to research on topics including high R-value double-stud walls, high efficiency 

ductless air source heat pump (ASHP) systems (“mini-splits”), including occupant satisfaction 

and feedback; financing of photovoltaic (PV) systems; and basements versus slab-on-grade 

construction. The research questions were as follows:

• What range of temperatures is experienced in bedrooms of homes heated by point 

sources?

• How do buyers perceive the performance of the ductless mini-split heat pumps? Are the 

room-to-room temperature differences in homes with ductless heat pumps apparent to the 

residents?

• Does the use of open cell spray foam (ocSPF), rather than cellulose, in the wall cavities 

of double-stud walls change the moisture content of the wall assembly? Does this change 

the risk assessment for this construction approach? 

• Do results of hygrothermal analysis correlate with field-measured moisture contents, in 

terms of risks of wintertime moisture accumulation in wood-based sheathings? 

• How can a PV array sufficient for net-zero performance be financed with no or minimal 

increase in annualized energy-related cost to the homeowner, through Solar Renewable 

Energy Certificates (SRECs) and novel finance agreements? How can this model be 

applied to regions outside of Massachusetts? 
2 

• Basements are a common feature of cold climate construction, but they present special 

challenges for insulation and water management. How does the per square foot cost of 

basements compare to adding above-grade space?

With the high efficiency features used in the construction of these homes, the houses meet the 

requirements of the U.S. Department of Energy’s (DOE) Version 2 of the Builders Challenge 

program—the DOE Challenge Home—under the prescriptive path. The program requires that the 

homes are 40%–50% more energy efficient than a typical new home and are certified through a 

third-party company. The program requirements are as follows:

• Fulfill the requirements of the ENERGY STAR® for Homes Version 3. 

• Comply with the requirements of the U.S. Environmental Protection Agency’s (EPA) 

Indoor airPLUS checklist. 

• Use ENERGY STAR-qualified appliances. 

• Use high performance windows that meet ENERGY STAR requirements. 

• Use insulation levels that meet 2012 International Energy Conservation Code. 

• Install ducts in conditioned space. 

• Use highly energy efficiency hot water equipment. 

• Install solar systems that follow requirements of EPA Renewable Energy Ready Home 

(in climates with significant solar insolation). 

1.1 Devens Sustainable Housing

The Devens development is a net-zero energy community located in Fort Devens, Massachusetts, 

where the developer was awarded the contract to build eight one- or two-story single-family 

houses of 1,064–1,820 ft2

. 
3 

Figure 1. Devens sustainable housing site plan

As of August 2013 all of the homes in the development have been completed and occupied. 

Figure 2. (L) Farmhouse (Lot 1); (R) Greek Revival (Lot 2) 

Greek Revival (Lot 2)

Victorian (Lot 3)

Custom Saltbox (Lot 7)

Ranch (Lot 8)

Saltbox (Lot 6)

Farmhouse (Lot 4)

N

Greek Revival (Lot 5)

Farmhouse (Lot 1)
4 

Figure 3. (L) Victorian (Lot 3); (R) Farmhouse (Lot 4)

Figure 4. (L) Greek Revival (Lot 5); (R) Saltbox (Lot 6) 

Figure 5. (L) Custom Saltbox (Lot 7); (R) Ranch (Lot 8) 
5 

The houses feature three or four bedrooms as well as an optional basement. The construction of 

the houses is shown in Figure 6. The enclosure characteristics include full basements with 2 in. 

of extruded polystyrene (XPS) rigid insulation (R-10) under the slab and 31⁄2 in. of closed cell 

spray foam (ccSPF) insulation (R-20) at the basement walls, a double-stud wall with 12 in. of 

ocSPF (0.5 per cubic foot [PCF]) insulation (R-46 nominal) and 18 in. of cellulose insulation in 

the attic (R-63). The mechanical system consists of two single-head mini-split units, a ventilation 

unit, as well as a tankless propane water heater. A PV array is also part of the house package. 
6 

Figure 6. Wall section with basement

The work performed in the Devens development that will be discussed in this report includes 

moisture monitoring of the double-stud walls and heat pump monitoring in the Victorian (Lot 3), 
7 

feedback from the homeowners on the heat pump performance, and air leakage testing results 

from all of the houses built to date. 

1.2 The Homes at Easthampton Meadow

The Easthampton development is a net-zero energy capable community located in Easthampton, 

Massachusetts. Transformations, Inc. partnered with Beacon Communities LLC (a Boston-based 

development company) to build 33 one- or two-story, single-family houses of 1,064–2,365 ft2

(Figure 7). The houses feature two, three, or four bedrooms; the development includes marketrate as well as affordable units.

Figure 7. The homes at Easthampton Meadow site plan

Seven houses have been completed at the Easthampton community (Figure 8 through Figure 11): 

• The Model Home (Lot 13) 

• Four market-rate homes: Custom Home (Lot 29), Custom Home (Lot 30 and 35), Custom 

Home (Lot 43) and Easthampton (Lot 40) 

• Five affordable homes: Small Saltbox (Lot 17), Cottage (Lot 23), Hadley (Lot 24), 

Northampton (Lot 28) and Needham (Lot 31). 

The following houses are currently under construction: 

• Market-rate homes: Ranch (Lot 12), Victorian (Lot 22), Victorian (Lot 26), Greek 

Revival (Lot 33), Greek Revival (Lot 34), Greek Revival (Lot 38) 

• Four affordable homes: Hadley (Lot 14), Cottage (Lot 15), Cottage (Lot 36) and Hadley 

(Lot 37). 

Model Home (Lot 13)

Custom 

Home 

(Lot 30

and 35) 

Small Saltbox 

(Lot 17) Custom 

Home 

(Lot 43)

Easthampton 

(Lot 40)

Cottage 

(Lot 23)

Hadley 

(Lot 24)

N

Needham (Lot 31)

Northampton (Lot 28) Cottage

(Lot 15)

Hadley

(Lot 14)

Hadley 

(Lot 37)

Cottage 

(Lot 36)

Custom Home 

(Lot 29)

Greek Revival 

(Lot 33)

Greek 

Revival 

(Lot 34)

Greek 

Revival

(Lot 38)

Victorian

(Lot 22) 

Ranch (Lot 12)
8 

Figure 8. (L) Model Home (Lot 13); (R) Custom Home (Lot 30) 

Figure 9. (L) Custom Home (Lot 43); (R) Easthampton (Lot 40)

Figure 10. (L) Northampton (Lot 28); (R) Needham (Lot 31) 
9 

Figure 11. (L) Cottage (Lot 23) and Hadley (Lot 24); (R) Small Saltbox (Lot 17) 

The slab-on-grade foundations include 6 in. of XPS rigid insulation (R-30) under the slab and 4 

in. of XPS rigid insulation (R-20) at the edge of the slab (Figure 12, left). Half-height and fullheight basements are optional if the particular lot is amendable, given local water and soil 

conditions. Walls are 12-in. double-stud walls with 12 in. of ocSPF (0.5 PCF) insulation (R-46 

nominal); the vented attics are insulated with 18 in. of cellulose insulation (R-63). The 

mechanical system consists of one or two single-head mini-split units, a ventilation unit, and a 

tankless gas water heater. A PV array is offered to the homebuyers for either purchase or lease.
10 

Figure 12. (L) Wall section with slab-on-grade; (R) basement

The work performed in the Easthampton development that will be discussed in this report 

includes heat pump monitoring at the Model Home (Lot 13), the Small Saltbox (Lot 17) and the 

Cottage (Lot 37). The research also covers feedback from the homeowners on the heat pump 

performance, and air leakage testing results from all of the houses built to date. 
11 

1.3 Coppersmith Way Development

The Townsend development is located in Townsend, Massachusetts and is made up of 41 singleand multifamily homes and has been divided into three phases (Figure 13). Phase I of the project 

consisted of 15 units with 13 units that were built by Transformations, Inc., and one lot and one 

existing house that were sold. It began in January of 2006 and was completed in August of 2008. 

Phase II with 15 homes is currently under way and Phase III of the project, which consists of 11 

homes, is planned for the future. The houses in Phase II of the project are one to two stories tall 

and feature two, three, or four bedrooms. 

Figure 13. Coppersmith Way development site plan

Transformations, Inc. had completed several homes in Phase II of the Townsend development 

prior to working with BSC. The team collaborated on three homes: Groton (Lot 24), Wellesley 

(Lot 25), and Groton (Lot 29) (see Figure 14 and Figure 15. ). As of July 2013, one additional 

house has been completed, the Greek Revival located on Lot 30, and one additional house is 

under construction, lot 28. 

Groton (Lot 24)

Groton (Lot 29)

Wellesley (Lot 25)

N

Greek Revival (Lot 30)

(Lot 28)
12 

Figure 14. (L) Groton (Lot 24); (R) Wellesley (Lot 25) 

Figure 15. (L) Groton (Lot 29); (R) Greek Revival (Lot 30)

The construction of the houses is similar to the houses in the Devens development with the 

exception of using natural gas for the tankless water heater in the Groton (Lot 24) (Figure 14). 
13 

Figure 16. Wall section with basement

The work performed in the Townsend development that will be discussed in this report includes 

heat pump monitoring over the winter of 2010–2011 at the Groton (Lot 24), as well as feedback 

from the homeowners on the heat pump performance and air leakage testing results from all 

three houses.
14 

2 Air Leakage Testing

A multipoint air leakage (blower door) test was performed at all of the homes built to date in all 

three developments. This was done for the purposes of quality control and continuing 

improvement. The testing was performed by BSC as well as third-party raters that work directly 

with the developer. The test results are listed in Table 1 through Table 3. 

Table 1. Air Leakage Test Results in the Devens Sustainable Housing Development

House House Name CFM50 ACH50 Square Inch Leak/

100 ft2

CFM50/

Square Foot Enclosure

Lot 2 Greek Revival 450 1.4 1.1 0.10

Lot 3 Victorian 579 1.9 1.4 0.13

Lot 6 Saltbox 425 1.2 1.0 0.09

Lot 7 Custom Saltbox 481 1.1 0.9 0.09

Table 2. Air Leakage Test Results in the Homes at Easthampton Meadow Development

House House Name CFM50 ACH50 Square Inch Leak/

100 ft2

CFM50/

Square Foot Enclosure

Lot 13 Model Home 363 1.3 0.9 0.08

Lot 30 Custom Home 304 0.8 0.6 0.06

Lot 43 Custom Home 400 1.5 1.0 0.10

Lot 17 Small Saltbox 160 1.0 0.6 0.06

Lot 23 Cottage 156 1.0 0.5 0.05

Lot 24 Hadley 150 0.7 0.5 0.05

Lot 40 Easthampton 186 0.9 0.7 0.07

Table 3. Air Leakage Test Results in the Coppersmith Way Development

House House Name CFM50 ACH50 Square Inch Leak/

100 ft2

CFM50/

Square Foot Enclosure

Lot 24 Groton 430 1.1 0.7 0.07

Lot 25 Ranch 439 1.2 0.8 0.08

Lot 29 Groton 320 0.8 0.6 0.05

BSC performed the blower door test in the Model Home (Lot 13) in Easthampton after the 

interior finishes were in place but prior to the installation of the mechanical systems. The testing 

equipment was set up in the side door to the garage (Figure 17) and the test was performed after 

sealing off the exposed appliance connections, such as the PV inverter connection and the notyet-connected tankless water heater intake and exhaust vents, as shown in Figure 18. 
15 

Figure 17. (L) Model home garage side; (R) house side

Figure 18. (L) PV inverter connection; (R) tankless water heater intake and exhaust vent

The results are presented in terms of CFM (cubic feet per minute) at 50 Pascals (Pa) test 

pressure, air changes per hour (ACH) at 50 Pa, square inches (EqLA) per 100 feet surface area 

leakage ratio, and CFM50/ft2 of enclosure area (all six sides).

The Greek Revival (Lot 2) in the Devens development was the first house to be constructed and 

initially had the highest CFM50 result—682. This was due to several penetrations, such as 

sprinklers and a second-floor top plate that were not sealed properly. Also, the airtight drywall 

approach (ADA, or the use of interior gypsum board with air sealing details as an air barrier; see 

Lstiburek 1983, Lstiburek 2000, Lstiburek 2005, Holladay 2010) was not utilized on this project.

After the final test was performed, the builder returned to the house to air seal the penetrations, 

which resulted in the improvement of 232 CFM50. 
16 

The Model Home (Lot 13) in Easthampton was the first house to be built in that development. 

The ADA was implemented in this house and all penetrations were sealed using caulk.

In the Townsend development, the two Groton houses built on lot 24 and 29 have the same 

footprint, but there is a noticeable difference between the CFM50 results in those homes. The 

ADA was utilized in the Groton on Lot 29. 

Typical range for Building America infiltration benchmark for the houses is 8.8–10.4 ACH50. 

The DOE Challenge Home infiltration benchmark for climate zone 5 is 2 ACH50. All houses in 

all three developments meet these requirements. 
17 

3 Construction Cost and Energy Modeling

3.1 Construction Cost

The following table includes information regarding the cost of material and labor for the various 

energy-efficient building components based on the developer’s previous projects. Incremental 

costs can be determined by subtracting upgraded option costs from the provided basic options. 

The mechanical system costs are installed costs.

Table 4. Construction Costs 

Component Option Cost

Attic Insulation Blown-in cellulose (R-63), ccSFP flash and seala $3.50/ft2

Wall Framing 2 × 6 @ 24 o.c.a $0.80/ft2

Wall Framing Double-stud wall, 2 × 4 @ 16 in. inside and 

outsidea $1.05/ft2

Wall Framing Double-stud wall, 2 × 6 @ 16 in. outside, @ 24 in.

insidea $1.07/ft2

Wall Insulation 1-in. polyisocyanurate (R-6.5), 51⁄2-in. cellulose 

(R-20)a $2.85/sf 

Wall Insulation 2-in. XPS (R-10), 9-in. cellulose (R-33)a $4.50/ft2

Wall Insulation 4-in. polyisocyanurate (R-26), 3-in. ccSPF (R-18), 

81⁄2-in. cellulose (R-31), zip wall systema $10.55/ft2

Wall Insulation 12-in. cellulose (R-45) $3.60/ft2b

Wall Insulation 12-in. ocSPF (R-46) $3.60/ft2b

Basement Ceiling 

Insulation 3-in. ccSPF (R-18), fiberglass (R-30)a $4.40/ft2

Basement Ceiling 

Insulation Fiberglass (R-38)a $1.50/ft2

Basement Wall Insulation 2-in. polyisocyanurate (R-13) $3.12/ft2

Basement Wall Insulation (2) layers of 11⁄2-in. rigid foam (R-20) $5.00/ft2

Basement Wall Insulation 3–31⁄2 in. of ccSPF with intumescent paint (R-20) $3.97/ft2

Basement Slab 2-in. EPS (R-8)a $1.23/ft2

Basement Slab 6-in. XPS (R-30) $3.58/ft2

Windows Paradigm, vinyl, triple-pane (R-5)a $412.53 each

Windows Harvey, vinyl, triple-pane (R-5) $240.00 each

Air Sealing Airtight drywall approach (ADA) $250/house

Water Management ZIP system wall sheathing, material cost only $0.49/ft2c

Heating/Cooling Mitsubishi mini-split ductless heat pump (one 

head per floor) Per MSZ-FE12NA/MUZ-FE12NA $2,950/head

DHW Navien tankless instantaneous water heater (NR180 (NG)) $1,900 

Ventilation Panasonic 30 cfm exhaust only fan with boost 

option, two fans (“basic requirement”) $250 each

Ventilation Panasonic ERV, spot open location 20–40 CFM, 

plus a bath fan, add to “basic requirement” $800 each

Ventilation Fantech 704 HRV, exhaust one bathroom, supply 

one location, add to “basic requirement” $1,500 each
18 

Component Option Cost

Ventilation

Fantech 1504 HRV in closet near bathroom, 

exhaust three bathrooms, supply one location, add 

to “basic requirement”

$1,600 each 

Ventilation

Fantech 1504 HRV in basement, exhaust three 

bathrooms, supply one location, add to “basic 

requirement”

$2,400 each 

Ventilation

Fantech 1504 HRV in basement, exhaust three 

bathrooms, supply three bedrooms, add to “basic 

requirement”

$3,000 each 

Ventilation

LifeBreath HRV in basement, exhaust three 

bathrooms, supply three bedrooms, add to “basic 

requirement”

$3,500 each 

Lighting Compact fluorescent lamps provided by ENERGY 

STAR/utility $0 

Appliances ENERGY STAR refrigerator, dishwasher, clothes 

washer and dryer Market

Photovoltaics Net in Massachusetts after incentives $1.80/Wattp

a Not used in current construction. b As noted previously in the report, the equivalent pricing between 12 in. of cellulose and ocSPF is the current 

pricing offered by the insulation subcontractor, and may not necessarily be representative of market conditions.

c Material cost only. 

3.2 Energy Modeling and Cost Effectiveness of Energy Efficient Measures

The goal of the Building America program for new homes in the cold climate is to achieve a

30% reduction in energy use by 2013 and 50% by 2017. 

The energy and cost-effectiveness analyses for the “Farmhouse” model were performed using 

BEopt (Christensen and Anderson 2006), the Building America performance analysis tool. This 

tool includes an optimization capability that uses user-supplied cost data and energy use 

information for a specified set of energy-saving measures to determine combinations of measures 

that are optimal or near optimal in terms of cost effectiveness. On a graph that plots the average 

source energy savings per year against the annualized energy-related costs, the optimal packages 

are those that form the lower bound of the plotted data points. BEopt uses a sequential searching

technique so that not every possible combination of options is simulated. 

For the BEopt optimization prepared for this report, the cost values listed in Table 4, which were 

provided by the developer, were used in combination with the default cost values for new 

construction. 

The BEopt optimization of the enclosure compared 12 in. of ocSPF insulation (R-46) and 12 in. 

of cellulose insulation (R-45) installed in the above-grade double-stud walls. Different R-value 

levels of cellulose insulation at the attic floor were also compared: R-63, R-49, and R-38. For the 

basement wall insulation, three options were selected: R-20 ccSPF, R-20 rigid insulation, and R10 rigid insulation. Window types compared in the optimization were Harvey low-e, triple-
19 

glazed units (U = 0.19; solar heat gain coefficient [SHGC] = 0.21), and standard low-e, doubleglazed windows (U = 0.34; SHGC = 0.30). 

Two space conditioning options for the heat pump were included for the optimization: mini-split 

ductless heat pump with seasonal energy efficiency ratio (SEER) 23/heating season performance 

factor 10.6 and mini-split ductless heat pump with SEER 16/heating season performance 

factor 8.6. Enclosure airtightness options included: “Tightest” (1.7 ACH50) and “Tighter” 

(3.3 ACH 50). 

The BEopt optimization simulated the combinations of options for the Farmhouse model and an 

optimization curve was created (Figure 19). The selected point represents the measures 

implemented in the homes in all three developments. The measures include R-46 walls with 

ocSPF insulation, R-63 of cellulose insulation in the attic, R-20 rigid insulation for the basement 

walls, and Harvey triple-glazed windows. The SEER 23 ASHP was selected for space 

conditioning, with the “Tightest” infiltration rate for the enclosure. The difference in source 

energy use between the “B10 Benchmark” and “Maximum Savings” projected by BEopt was 

110.7 MBtu/yr, or a 44.9% reduction (Figure 19). 

Figure 19. Farmhouse BEopt optimization results—cost versus energy use

The most optimal design in terms of annual energy related cost savings and source energy 

savings yields a 37.5% reduction, or 93.2 MBtu/yr (Figure 20). The measures for this option 

include R-45 walls with cellulose insulation, R-38 of cellulose insulation in the attic, R-10 rigid 

insulation for the basement walls, and Harvey triple-glazed windows. The SEER 16 ASHP was 

selected for space conditioning, with the “Tightest” infiltration rate for the enclosure.
20 

Figure 20. Farmhouse BEopt optimization results—cost versus energy use

The set of measures offered by the developer for the houses in the Devens, Easthampton, and 

Townsend developments exceeds the 30% energy savings goal set by the Building America 

program for new homes in the cold climate for 2013. With the high efficiency components these 

homes are very close to achieving the 50% reduction in energy use set for 2017. 

3.3 Performance Data

The estimated annual energy cost for the Model Home (Lot 13) was obtained from the Home 

Energy Rating Certificate and is projected to be $88 (see Appendix B). The cost was determined 

by the REM/Rate software package, which was created by Architectural Energy Corporation. 

The developer indicated that the incremental cost for energy efficiency measures implemented in 

the house as compared to a house built to 2012 International Residential Code is $3/ft2

. 
21 

4 Mini-Split Heat Pump Performance and Thermal Distribution

4.1 Background

Conventional furnaces and split-system air conditioners are an awkward fit to high efficiency 

homes being built today. It is common for such homes to have design loads below 1.5 tons, 

which is the smallest size of split cooling system generally available. High SEER systems are 

often unavailable below 2 tons. For furnaces, 40 kBtu/h (3.3 tons-equivalent) is the smallest 

common size. For reference, the houses analyzed in this report have cooling loads below 1 ton, 

and heating loads of less than 1.5 tons. Holladay (2011) discusses the problem of selecting space 

conditioning equipment for low-load houses, and proposes various solutions. 

Reduced mechanical system cost is often given as one of the benefits of increased building 

insulation and airtightness. Unfortunately, the upfront savings from reducing capacity with a 

conventional split system or furnace by 1 ton (to the smallest available) are modest, as most of 

the cost is in the labor of installation. 

As annual energy demand for space heating drops, the cost of installing and maintaining gas 

distribution becomes harder to justify. When monthly service charges and increased mortgage 

cost are counted as part of the heating cost, heat pumps and additional PV can be more cost 

effective than a gas furnace. This is true even in cold climates (e.g., Massachusetts), and even 

when the furnace would use somewhat less energy on a source (primary) basis.

Ductless split-system heat pumps (“mini-splits”) offer a tempting answer to all of these 

problems. They are available in sizes from 0.75 tons to 1.5 tons. Transformations, Inc. has found 

the installed cost to be about $3000 less than a fully ducted conventional system. Similar prices 

are reported in other areas where local convention is to use sheet metal ducts for space 

conditioning distribution. Many mini-splits have a rated coefficient of performance (COP) above 

the best ducted heat pumps available, and variable-speed compressors, which render them even 

more efficient at off-peak conditions. Recently, mini-splits have come to market that maintain 

high heat output at 5°F or below, making them viable for cold climates. The remaining—and 

substantial—challenge for wider deployment of mini-splits is the uncertainty surrounding 

thermal comfort in houses without distribution of hot and cold air to every room.

The energy consumed by an ASHP depends on the building load and the outdoor temperature. 

For heat pumps with variable-speed compressors (including the mini-splits studied in this 

project), the COP depends strongly on both of these variables. This is in contrast to the efficiency 

of combustion systems, which are only weakly dependent on duty cycle and essentially 

independent of outdoor temperature. 

Air sealing and super-insulation of buildings changes not only the total annual loads, but the 

distribution of those loads over time. With the exception of lighting, energy-efficient houses are 

assumed to have the same internal heat gains as existing or built-to-code houses. These internal 

gains reduce the heating load (or increase cooling load) at all times. When this is combined with 

the reduced enclosure load, the average outdoor temperature during heating is lower than 

otherwise.
22 

4.2 Experimental Design and Sensor Installation

BSC’s initial monitoring in Townsend (Bergey and Ueno 2011) informed the design of the 

present research. The current research is divided into two phases: houses constructed and 

instrumented in 2011 (for which a winter’s worth of data are available), and houses instrumented 

in the summer of 2012 (from which data have not yet been collected). 

4.2.1 Townsend (2010–2011) 

Over the winter of 2010–2011, one of the houses in the Townsend development, the Groton (Lot

24), was monitored in order to measure the performance of the mini-split ductless heat pumps. 

One of the desired outcomes was direct measurement of the heating and cooling balance points 

of the house—the outdoor temperatures above or below which no space conditioning is required. 

The initial monitoring failed to answer this question for two reasons. 

In the initially monitored house, the occupant used deep thermostat setbacks and setups. As a 

result, there are many cold hours when no heating is required, as the house cools to set point, and 

many relatively warm hours when the heat pump works at maximum output to recover from 

setback. During these cooling-off and warming-up periods, there are large room-to-room 

differences. The occupants report being quite comfortable, although the house does not meet 

standard targets for thermal comfort. However, we are reluctant to extrapolate this satisfaction to 

other occupants. 

Fewer than 20% of households nationally use setbacks, although anecdotal evidence suggests 

they are more common in New England (EIA 2005). The authors expect that many buyers of 

low-load homes will stop using setbacks due to the perception that the house is efficient without 

compromising on comfort. Further, we expect that occupants who find some rooms too cold will 

stop using setbacks. 

Setbacks are poorly suited to these homes for several reasons. The low air leakage and high 

enclosure R-values mean that indoor temperature drops slowly even without heating. This 

reduces the energy savings available from an overnight or daytime setback. Variable-capacity 

heat pumps are most efficient when delivering a low output over a long period. Delivering the 

same total heat over a shorter period uses substantially more energy. Winkler (2011) reports 

COP at high, medium, and low compressor output for two models of mini-split heat pumps, 

including the Mitsubishi FE12NA used by Transformations, Inc. Operating at a steady set point 

also reduces peak electricity demand, avoids the capacity limitations of the heat pump, and likely 

improves comfort. 

A second problem with the Townsend monitoring resulted from the mini-split heat pump’s very 

low minimum output, and correspondingly low power draw in this state. A simple current switch 

is sufficient to indicate when a single-stage heat pump is running or not running, and runtime 

fraction can be calculated for any chosen interval. However, with variable-speed equipment, the 

switch suffers many false negatives when the power draw is below the cutout current. Because 

the unit under test is designed to run continuously and modulate refrigerant flow according to 

demand, the collected data do not distinguish between high output operation and the lowest 

output: both states are registered as on time.
23 

4.2.2 Unoccupied Homes (2011–Present)

In 2011 BSC instrumented two unoccupied houses, the Victorian (Lot 3) in Devens and the 

Model Home (Lot 13) in Easthampton. Unoccupied houses were chosen to obtain clean baseline 

data without the setback issues described above. The Easthampton house is acting as the model 

home for the development, while the Devens home was sold in June 2012. Some sensors in the 

Devens house are shared with the wall moisture research described in Section 5, so the sensor 

packages in the two houses are slightly different. 

Figure 21. (L) Exterior of houses at Devens; (R) Easthampton

In each house, temperature is measured in each bedroom, in a central part of the first floor, and 

in the second-floor hallway. In Devens, outdoor temperature is measured on site (Figure 53, left), 

while in Easthampton, outdoor conditions are taken from the weather station at Westfield, 

Barnes Municipal Airport (KBAF). Table 5 and Table 6 provide more details of the sensors used. 

Table 5. Devens Sensor Package

Location Property Interval Notes

Master Bedroom (South) 

Temperature, 

relative humidity 

(RH)

1 h ± 0.1°C NTC thermistor 

± 2% capacitive sensor

North Bedroom Temperature, RH 1 h ± 0.1°C NTC thermistor

± 2% capacitive sensor

West Bedroom Temperature, RH 1 h HOBO U10-003

Second-Floor Hall Temperature, RH 1 h HOBO U10-003

First Floor Temperature, RH 1 h HOBO U10-003

Breaker Box Electrical power 5 min Leviton Mini Meter

HOBO Pulse Logger
24 

Table 6. Easthampton Sensor Package

Location Property Interval Notes

Master Bedroom (South) Temperature, RH 1 h HOBO U10-003

North Bedroom Temperature, RH 1 h HOBO U10-003

West Bedroom Temperature, RH 1 h HOBO U10-003

Second-Floor Hall Temperature, RH 1 h HOBO U10-003

First Floor Temperature, RH 1 h HOBO U10-003

Breaker Box Electrical Power 5 min Leviton Mini Meter

HOBO Pulse Logger

Each of these houses has a 12,000-Btu/h mini-split serving the first floor, and an identical unit 

serving the second floor (Figure 22). These are monitored independently, with a resolution of 5 

Wh (0.005 kWh). The data logger recorded energy consumption in each 5-min interval. For this 

report, the Wh measurements were aggregated to the 1-h interval of the temperature data.

Figure 22. (L) Upstairs mini-split at Easthampton; (R) Watt-hour meter at Devens

4.2.3 Occupied Homes (2012–Present)

In May of 2012, BSC installed sensors in two smaller (two-bedroom) occupied houses in 

Easthampton, the Small Saltbox (Lot 17) and the Cottage (Lot 23). At the time of installation, 

these two-story houses had only a single mini-split delivering air centrally on the first floor. Load 

calculations and anecdotal evidence from prior houses suggested this experiment to the 

developer. By the end of the summer, the developer had decided to install a mini-split on the 

second floor of each house, as is standard in the three-bedroom Easthampton houses. It appears 

that thermally driven buoyancy is effective in distributing heat from a first-floor mini-split head 

in winter, but causes discomfort in summer.
25 

Figure 23. (L) Small Saltbox (Lot 17); (R) Cottage (Lot 23) 

The sensor packages in these two houses are similar to that in the Easthampton model home.

Because they are occupied, we have added a HOBO State Logger to each bedroom door. A 

magnet on the door frame triggers a reed switch in the sensor, providing at least a rough idea of 

when and how long the door is shut. 

No data have yet been downloaded from the sensors in these two houses. The data over the 

winter of 2012–2013 will be compared to the data from unoccupied houses. Occupied houses are 

expected to have bedroom doors closed some (but not all) of the time, increasing temperature 

differences between rooms. Heat gains within closed rooms also affect the temperature 

distribution. Internal gains are expected to move the balance point toward colder weather, and 

simultaneously decrease energy used for heating.

4.3 Results

4.3.1 Data Overview/Boundary Conditions

4.3.1.1 Easthampton

Monitoring of the Easthampton house began in July 2011. Data were last downloaded in May 

2012 (Figure 24). The house in Easthampton lost power for two days, October 29–31, 2011, due 

to a record-setting snowstorm (red highlighted rectangle). The weather station data are also 

unavailable during this period. The house dropped from 68°F to a low of 60°F during this period, 

recovering somewhat during daytime hours. 
26 

Figure 24. Indoor and outdoor temperatures at Easthampton

4.3.1.2 Devens

Data collection at Devens began in December 2011, and data from HOBOs were last 

downloaded in May 2012, at the same time as the Easthampton loggers. Data from the Devens 

Campbell logger can be downloaded without entering the building and so were collected again in 

July 2012 (Figure 25).

Both Devens mini-splits were turned off on March 10, 2012. On the April 14, the second floor 

unit was turned on again, while the first floor unit remained off until April 24 (red highlighted 

rectangle). This two-week period is omitted from all further analysis, since it is quite different 

from typical operating conditions. 

Prior to February 17, 2012, the basement at Devens was uninsulated. A large spike in the 

basement temperature occurs on the day basement wall ccSPF insulation was installed (gray 

arrow; exothermic reaction).
27 

Figure 25. Indoor and outdoor temperatures at Devens

After insulation, both basement and first-floor temperatures are substantially warmer, given 

similar outdoor conditions (Figure 26 and Figure 27). Unfortunately, the later period (with the 

house fully insulated) also has much warmer weather. Since extremely cold weather presents the 

greatest challenge to heat pump performance, and the greatest chance of large temperature 

differences within the building, the earlier data are especially important. The two periods were 

therefore pooled for most of the further analysis. In particular, since second-floor temperatures 

and mini-split energy use were similar in both periods (Figure 37), pooling these measurements 

seems reasonable.
28 

Figure 26. Devens basement temperature before and after basement insulation

Figure 27. Devens first-floor temperature before and after basement insulation
29 

4.3.2 Distribution

Concerns about thermal comfort in homes without forced distribution largely focus on bedrooms. 

Residents spend long periods in bedrooms; bedroom doors are closed for long periods for 

privacy reasons; and even with doors open, airflow to bedrooms is more restricted than to spaces 

on the first floors of these houses. 

4.3.2.1 Easthampton

Figure 28 plots temperatures in several rooms in Easthampton against those in the second-floor 

hallway during the heating season. The heating season was taken to be the months of November 

through February, inclusive, as outdoor temperature was always below indoor temperature 

during these months. The thermostat is in the hallway, and it is presumed that the second-floor 

set point will be adjusted to maintain comfort in bedrooms. 

Figure 28. Easthampton temperature variations 

All rooms of the house are within ± 2°F of each other nearly all of the time. The variance within 

each room over time is larger than the variation between rooms at the same time. Figure 29 and 

Figure 30 show the distributions of temperatures in each room, and the distributions of the 

temperature differences relative to the second-floor hallway. The southwest bedroom is within ± 

1°F of the hallway more than 90% of the time. The south bedroom is never more than 1°F cooler 

than the hall, but spends nearly 20% of the time more than 1°F warmer. 

This solar gain is consistent with prior observations. The windows on these houses have SHGCs 

of 0.2, and U-values also around 0.2. Even with this relatively low SHGC, it is peak solar 

heating, rather than the coldest conditions of the year, that presents the greatest challenge for 

uniform space conditioning. 
30 

Figure 29. Easthampton frequency distribution of temperature differences

Figure 30. Easthampton frequency distribution of temperatures

While wintertime overheating can be a problem in houses with higher SHGCs and glazing ratios, 

it seems unlikely that the observed temperatures here would be a cause for complaint. The peak 

temperature in the south bedroom is only 72°F. Even if the hallway were kept at a more generous 

set point (for example, 72°F), the 3°F difference, resulting in a 75°F bedroom, is unlikely to be 

perceived as uncomfortable. 

4.3.2.2 Devens

In Devens, the bedrooms consistently ran cooler than the hallway, often by more than 2°F. The 

south bedroom is warmer than the hallway only 10% of the time, and even less often for the 

other bedrooms (see Figure 31 through Figure 34). The west bedroom is 2°F or more below the 

hallway 20% of the time, but for the other bedrooms 60% and 80% of the time. Note, however, 

that the bedrooms are warmer than those in Easthampton. The hallway at Devens was maintained 

around 72°F, while Easthampton was kept between 67°F and 68°F. 
31 

Figure 31. Devens temperature variations 

Figure 32. Devens frequency distribution of temperature differences

Figure 33. Devens frequency distribution of temperatures
32 

Figure 34. Devens distribution of first-floor temperatures

It seems likely that the depressed bedroom temperatures (relative to the hallway) are related to 

heat loss to the first floor. As described in Section 4.3.1, the first floor at Devens ran 

considerably cooler than the second, especially before the basement was insulated. Figure 35

plots the first-floor temperature, before and after insulation, for comparison with the plots above. 

However, since the two periods conflate different enclosure conditions with different outdoor 

conditions, only the central values of the distribution can be considered valid. The tails clearly 

occur at different extremes of weather. The first-floor set point was 70°F (Figure 29), whereas 

the second floor was heated to 72°F. The median temperature in the south and west bedrooms is 

quite close to 70°F. This may indicate that conduction through the floor had a greater influence 

on bedroom temperatures than did convection through the doors. This is important for 

understanding the effect of closing doors. 

4.3.3 Mini-Split Energy Consumption

In Devens, the first floor mini-split unit used 691 kWh over the four months of monitoring, while 

the second floor used only 320 kWh. Figure 35 shows that the first-floor unit drew more power 

than the second-floor unit over a wide range of outdoor conditions. In Easthampton, the two 

units drew similar amounts of power at similar times (Figure 36). This is consistent with the 

additional load imposed on the first floor at Devens by the basement (Figure 37), which does not 

have its own mini-split head. A Manual J load calculation (ACCA 2006) predicts that the 

basement, with 3 in. of ccSPF on the walls, adds a heating load of 3500 Btu/h, about 3⁄4 of the 

load for the first floor alone. Easthampton has a slab-on-grade foundation, with 6 in. of XPS 

under the slab, and substantially lower predicted heating load. 
33 

Figure 35. Devens mini-split power by floor

Figure 36. Easthampton mini-split power by floor
34 

Figure 37. Devens first-floor power by basement insulation

Figure 38 compares power drawn by the first-floor mini-split before and after the basement was 

insulated. Both periods have useful data with outdoor temperatures between 25°F and 45°F, and 

under these conditions, the basement insulation did not much change energy consumption. It 

seems plausible that the increased indoor temperature offset the decreased conductance. Data 

from the upcoming winter will be necessary to understand how the completed house performs in 

the coldest weather.

Figure 38. Distribution of mini-split power

Both mini-splits at Devens spend many hours drawing no power. The first-floor unit spends 

slightly more than half its time thus, despite high total energy consumption. The hours without 

power draw do not occur in contiguous periods but cyclically correspond to peaks in the first 

floor temperature (Figure 39). It seems clear from the Easthampton data—measuring the same 

product—that the heat pump is capable of ramping smoothly from 0 to 200 W. It is not known 

why the heat pump in Devens resumes operation at 200 W or higher, rather than ramping up 

more gradually. 
35 

Figure 39. Devens mini-split power time series

Due to the low thermal losses of these buildings, solar gain and interior occupant gains 

contribute substantially to meeting the heating load. As these are unoccupied buildings, we only 

observe the effect of solar gain. This reduction in space heating energy can be observed as a 

change of balance point—the outdoor temperature above which no supplemental heating is 

required. The heating balance point has historically been assumed to be 65°F, but it is likely 

lower for low-load homes. 

To smooth out startup effects and other noise in the data, the balance point for each house was

found from the average power and average outdoor temperature over each day, rather than using 

the hourly data directly (Figure 40 and Figure 41). Data above 50°F were also excluded from the 

fit, as weather very close to the apparent balance point is often dominated by sun and other 

conditions not being considered in the regression. 
36 

Figure 40. Devens mini-split balance point

Figure 41. Easthampton mini-split balance point

For the set points being used (72°F second floor, 70°F first), the house Devens is found to have a 

balance point of 52°F, and to draw 26 W for each degree below that temperature. This line fits 

the daily average data with R2 = 0.82. The Easthampton data are fit with a balance point of 64°F, 

using 9 W for each degree the temperature drops, and with R2 = 0.75. However, the set point in 

Easthampton is rather low (68°F), so the balance point in typical use is likely higher. 
37 

These data are equivocal regarding the hypothesized balance point trend in low-load houses. 

65°F is the typical balance point assumed in heating degree day (HDD) calculations. The Devens 

house appears to balance significantly lower than this, even without internal gains. But 65°F is 

within the 95% confidence interval of the Easthampton regression. There is no obvious reason to 

consider one of these houses more representative than the other. 

4.4 Resident Survey 

BSC sent a one-page survey to residents of the developments at Easthampton and Devens, as 

well as to residents of several older houses built by Transformations, Inc. and heated by minisplits. The survey is attached to this report as Appendix A. 

4.4.1 Survey Results

Eight homeowners responded to the survey. Four moved into Easthampton in 2012, and had not 

yet lived in their new homes through a winter. Three had spent one winter in their homes, and 

one had spent two winters. All but one reported that the new homes are more comfortable than 

their previous homes and the remaining homeowner rated the house as a 1 (Most Comfortable) 

on a five-point scale. 

Two respondents report turning off the air conditioning during the summer at night and when 

they leave the house. Both of these keep the second-floor unit running at night, while turning off 

the first-floor mini-split. One homeowner did not answer this section of the survey; the others 

maintain fixed set points. One respondent reported having tried nighttime setbacks during cold 

weather and stopped due to the slowness of morning recovery during the coldest weather. These 

data suggest that winter setbacks are not very common in houses heated with heat pumps. The 

survey responses do not indicate that the incompatibility of heat pumps and winter nighttime 

setbacks is considered a liability. Summer setbacks, whether or not they save significant energy, 

do not present the same challenge to heat pump operation, because they occur at times of 

reduced or zero load. 

Half of respondents report at least one room, almost always a bedroom, is somewhat 

uncomfortable in summer. Half of those comfort complaints were of the room being too cold, 

which may represent a lack of clarity in the survey. Of five homeowners who addressed winter 

comfort (including one who moved in March 2012), only one reported cold bedrooms. This is 

also the only respondent who reports keeping bedrooms always or mostly closed. 

It is not clear from these data whether the high proportion of open doors represents a prior 

preference or a learned response to the limited thermal distribution. Several respondents use fans 

and open doors to improve distribution, suggesting an awareness that closed doors could reduce 

comfort. None indicate dissatisfaction with open doors, even by closing doors when in the room 

and opening them when not. 
38 

5 Moisture Monitoring of Twelve-Inch Double-Stud Walls

5.1 Background

Double-stud walls insulated with cellulose or low-density spray foam can have R-values of 40 or 

higher. Compared to approaches using exterior insulating sheathing, double-stud walls are 

typically less expensive, but have a higher risk of interior-sourced condensation moisture 

damage. Insulation outboard of structural sheathing increases the winter temperature of the 

sheathing, while additional insulation inboard of the sheathing decreases its temperature (Straube 

and Smegal 2009). 

This is demonstrated in the thermal simulation results shown in Figure 42 and Figure 43, which 

show temperatures for a double-stud wall and a 4 in. exterior foam wall, assuming an interior 

temperature of 68°F and an exterior temperature of –4°F. The surface that is the most likely to 

experience condensation (interior side of exterior sheathing) is highlighted in each wall in gray, 

showing the relative risks of air leakage or vapor diffusion-based condensation. 

Figure 42. THERM results for double-stud walls (based on Straube and Smegal 2009); 

condensing plane highlighted in gray 

Structural sheathing

Foundation wall

Cellulose 

insulation 

(9.5")
39 

Figure 43. THERM results for 4-in. exterior foam wall (based on Straube and Smegal 2009); 

condensing plane highlighted in gray 

If a double-stud wall is compared with a 2 × 6 wall with the same type of stud bay insulation and 

no exterior insulating sheathing, it is clear that the double-stud wall sheathing experiences colder 

wintertime temperatures, and less heat flow. Both of these factors increase the risks of moisturerelated problems (Lstiburek 2008). Low-density spray foam, with similar R-value to cellulose, is 

believed to have lower moisture risk because its superior control of air leakage reduces the risk 

of wetting of the exterior sheathing due to interior-source moisture. However, the insulation 

material is still open to vapor diffusion: a 12-in. thickness of ocSPF 0.5 lb/ft3 has a vapor 

permeability of 7.3 perms (both wet and dry cup; ASHRAE 2009), while 12 in. of cellulose is 

roughly 7–10 perms (dry and wet cup). 

5.2 Experimental Design and Sensor Installation

The moisture monitoring experiment is being conducted at the Victorian house (Lot 3) at 

Devens. It is intended to assess the moisture risk of 12-in. thick double-stud walls insulated with 

cellulose and low-density spray foam. 

Transformations, Inc. has been building double-stud walls insulated with 12 in. of ocSPF (0.5/lb3

density). However, the company has been considering a change to netted and blown cellulose 

insulation for cost reasons. Cellulose is a common choice for double-stud walls due to its lower 

cost (in most markets). However, cellulose is an air-permeable insulation, unlike spray foams. 

For these reasons both materials were tested as a comparison.

4" polyisocyanurate 

insulation

Structural sheathing

Foundation wall

Fiberglass 

batt insulation 

(5.5")
40 

5.2.1 Overview

Three wall assemblies were selected for this experiment; they were duplicated on opposite 

orientations (north and south), for a total of six test wall sections (see Table 7). The three test 

insulation materials are as follows:

• 12-in. 0.5 PCF spray foam in double-stud wall (as per the remainder of the house; typical 

installation is shown in Figure 44). The spray foam was installed in three passes with 

time allowed between the passes for cooling.

• 12-in. netted and dry blown-in cellulose in double-stud wall. The density was not directly 

measured, but it was reported to be 3.5 PCF. Typical densities achieved for proper dense 

pack installations behind netting are 3.5–4.0 PCF (Tauer 2012). 

• 51⁄2 in. of 0.5 PCF spray foam at exterior of double-stud wall, to approximate 

conventional 2 × 6 wall construction and insulation levels, acting as a control wall (a.k.a. 

“shorted” bay). 

Table 7. Test Wall Listing

Wall

ID Orientation Insulation Nominal R-value Notes

N1 North 0.5 PCF spray foam, 12 in. 46 Same as rest of house 

N2 North Netted/blown cellulose, 12 in. 42

N3 North 0.5 PCF spray foam, 51⁄2 in. 21 “Control”

S1 South 0.5 PCF spray foam, 12 in. 46 Same as rest of house 

S2 South Netted/blown cellulose, 12 in. 42

S3 South 0.5 PCF spray foam, 51⁄2 in. 21 “Control”

Figure 44. Typical installation of 1⁄2 lb/ft3 spray foam in double-stud walls
41 

The remainder of the wall is constructed as per the builder’s conventional construction, with an 

oriented strand board (OSB)-based sheathing with an integrated drainage plane and taped seams 

(no separate house wrap), and vinyl siding. The interior finish is 1⁄2-in. gypsum board with latex 

primer and paint finish (Class III vapor retarder).

The control wall (51⁄2 in. 0.5 PCF foam) is mean to represent common construction (2 × 6 stud 

frame walls); this assembly has no history or reputation of endemic moisture failures. Data from

the control bay (with the same solar and rain exposure as the test walls) will assist interpretation 

of the results.

The test home is not oriented directly north-south (Figure 45), but the southernmost and 

northernmost walls were used for this research.

Figure 45. Overhead (L) and front (R) views of Lot 3 test house

The test walls were installed in second-floor bedrooms (Figure 46). The test bays are indicated 

by the dotted patterns, and the guard areas (noninstrumented portions) are filled with fullthickness spray foam to maintain separation between adjacent bays.

North-facing walls experience the least solar gain, while south-facing walls receive the most.

The two orientations place upper and lower bounds on the moisture problems, as solar gain is the 

major source of energy to dry the sheathing in well-insulated walls.
42 

Figure 46. Test walls shown on second-floor plan, with guard bay insulation for separation 

As shown in Figure 47 (right), the third bay (“control”) on the north side is partially sheltered at 

the bottom by the sloping garage roof. No better location was available, due to the positioning of 

windows, bathrooms, and garage. 

Figure 47. Test wall locations shown on exterior of house; south (L) and north (R) orientations

Interior T/RH 

(North)

North 1-Foam

North 2-Cellulose

North 3-5-1⁄2” Foam

South 3-5-1⁄2” Foam

South 2-Cellulose

South 1-FoamInterior T/RH 

(South)
43 

5.2.2 Wall Sensor Package

Four types of sensors are used to measure conditions within the walls: 

• Temperature sensors (10k NTC thermistors (accuracy ± 0.2°C) 

• Relative humidity (RH) sensors (thermoset polymer capacitive based sensors with 

onboard signal conditioning (accuracy ± 3%, 10%–90% RH)

• Wood moisture content (MC) (in-situ electrical-based resistance measurements 

between corrosion-resistant insulated pins). 

The specifics of these sensors are covered in detail by Straube et al. (2002). Figure 48 shows 

typical sensor types and installations. 

The left-hand image (Figure 48) shows a temperature and wood MC sensor installed at the 

exterior sheathing. The sensor with red shrink tubing is a temperature measurement (thermistor), 

and the blue wire leads run to wood MC pins. 

The right-hand image (Figure 48) shows typical conditions mid-height in the study bay, with 

both temperature RH, sheathing MC, and stud moisture content sensors visible. The 

temperature/relative humidity (T/RH) sensor can be identified by the yellow heat shrink tubing; 

the sensor consists of a vapor-permeable polyolefin house wrap envelope around the T/RH 

sensor.

Figure 48. (L) Temperature and MC sensor at sheathing; (R) sensors at mid-height of stud bay

Figure 49 shows the “wafer” sensor, installed at the inboard side of the sheathing to measure 

conditions at the likely condensation plane. Screws were used as temporary clamps to hold the

sensor in place until the adhesive set.
44 

Figure 49 (L) “Wafer” surrogate RH sensor at sheathing; 

(R) schematic of sensor, with dimensions in mm

The completed installation at the south walls is shown in Figure 50 prior to insulation. Stud bays 

were chosen to avoid anomalies such as electrical boxes, plumbing pipes, or corners of the 

building. Lateral air movement at the cellulose bay is controlled by full-thickness spray foam 

between test bays.

Sensor cables were stapled back to studs or sheathing to minimize thermal bridging and/or 

insulation displacement effects near the measurement location; cables were run away from the 

sensor perpendicular to the heat flow path, to minimize their effect (Straube et al. 2002).

Figure 50. South test walls after installation of sensors, showing double-stud layout 

Brass pin

35.0

19.0

25.0

Pin spacing

Signal

+12 V

Face view

4.75

Edge view

12.7
45 

The test wall instrumentation plan for this research is shown in Figure 51. 

• Sheathing moisture content is typically a key indicator for long-term durability and 

moisture risks; therefore, three sheathing MC/temperature sensors were installed at each 

wall (upper/middle/lower). 

• The outermost stud MC was monitored at inboard and outboard edges. 

• Temperature and RH were monitored at three depths in the stud bay 

(outboard/middle/inboard), which allows measurement of temperature and humidity 

gradients.

• The “wafer” sensor was installed at the inboard surface of the exterior sheathing, to 

measure surface humidity conditions at the likely condensing plane. 

• A temperature sensor was installed at the interface between the insulation and the interior 

gypsum board. 

The sensor complement is identical in the two 12-in. thick insulation (spray foam and cellulose) 

wall test bays. At the “shorted” or “control” bay (N3/S3), the sensor count is reduced. There is a 

“dead” air space between the interior gypsum board and the interior face of the stud bay spray 

foam. This is not an ideal comparison, but was required to keep the interior gypsum board in 

plane at this occupied house. Temperature and RH conditions within the void space are being 

recorded directly, for comparison with interior conditions. Only a single temperature sensor was 

placed between the inner face of the foam and the drywall, as negligible temperature or RH

gradients are expected across this void space. 

The base of wall N3 is shielded by the garage roof (Figure 47); the sensors at the “lower” 

sheathing location were shifted to the lowest exterior exposure in the stud bay.
46 

Figure 51. (L) Instrumentation diagram for 12-in. ocSPF; (C) 12-in. cellulose; (R) 51⁄2-in. ocSPF

Mid-Height 

Sensors

Upper Wall 

Sensors

Lower Wall 

Sensors

1" 1"

Gypsum T

Sheathing MC 

upper wall

Sheathing MC 

lower wall

Sheathing MC 

middle wall

Wafer middle 

wall (no T 

sensor)

Framing MCs 

(inboard/outboard)

RH outboard/

middle/inboard 6 1/2" 6 1/2"

Mid-Height 

Sensors

Upper Wall 

Sensors

Lower Wall 

Sensors

1" 1"

Gypsum T

Sheathing MC 

middle wall

Wafer middle 

wall

Framing MCs 

(inboard/outboard)

RH outboard/

middle/inboard

Sheathing MC 

upper wall

Sheathing MC 

lower wall

6 1/2" 6 1/2"

Mid-Height 

Sensors

Upper Wall 

Sensors

Lower Wall 

Sensors

1"

Interior surface T

Sheathing MC 

middle wall

Wafer middle 

wall

Framing MCs 

(inboard/outboard)

RH outboard/

middle/inboard

Sheathing MC 

upper wall

Sheathing MC 

lower wall

6 1/2" 6 1/2"
47 

5.2.3 Additional Sensors and Data Collection Logistics

In addition to the sensors in the walls, T/RH sensors were located in the living spaces in the 

north and south rooms where test walls are being monitored. The enclosure is shown in Figure 

52; the locations on the floor plan are shown in Figure 46. 

Figure 52. Sensor measure interior (bedroom) T/RH sensors 

An exterior T/RH sensor (Figure 53, left) provides outdoor conditions synchronized to the wall 

measurements; it is located within a solar radiation shield. The data logger is located in the 

basement; data are collected at 5-min intervals, and hourly averages are recorded. No battery 

backup for the data logger is provided; however, the unit has nonvolatile memory, and will 

resume data collection after a power failure.

Figure 53. (L) Exterior T/RH sensor; (R) data collection from exterior connection port

An RS-232 serial cable was passed through the wall to a weathertight box mounted on the 

exterior. This allows on-site data collection without entering the house, as shown in Figure 53, 

right. Remote collection over a network connection is planned once the house is occupied and 

assuming that the occupants have a network connection for other reasons.
48 

5.3 Results

5.3.1 Data Overview and Boundary Conditions

Eight months of data have been collected and analyzed to date (from December 2011 through 

July 2012). This captures data from the building’s first winter (albeit unoccupied conditions), 

through spring and summer. 

Interior and exterior temperature conditions are shown in Figure 54. Winter 2011–2012 

conditions were exceptionally mild (4400 HDD Base 65°F versus 5600 HDD climate normal). 

Interior temperature held steady through the winter in both north and south bedrooms in the 69°–

71°F range, except for a period in March when the mini-split units were inadvertently turned off. 

Basement temperatures ran in the 48°–56°F range through most of the winter before insulation 

was applied to the foundation walls in mid-February 2012. After application of insulation, 

temperatures were warmer, tracking closer to interior conditions, despite a lack of space 

conditioning in the basement. 

Figure 54. Exterior and interior (test rooms and basement) temperatures

Interior RH conditions are shown in Figure 55; interior wintertime RH levels fell to the 10%–

20% range for much of the winter, which are exceptionally dry conditions. There was no 

occupancy through the winter, and therefore no interior moisture generation (occupants, 

showering, cooking), explaining the low RH levels. However, drying of construction moisture 

was occurring during the winter. Basement RH levels were higher, as would be expected due to 

lower temperatures.

-20

0

20

40

60

80

100

12/7 1/26 3/16 5/5 6/24

Temperature (F)

Exterior T

Interior T-North

Interior T-South

Interior T-Bsmt
49 

Figure 55. Interior RHs (test rooms and basement)

Interior temperature and RH conditions were used to generate dew point temperatures (absolute 

air MC), which were plotted with outdoor temperatures (Figure ), Interior moisture conditions 

are very close to outdoor conditions, as would be expected without interior moisture generation. 

After basement insulation (February 2012), basement dew points were higher than above-grade 

spaces, which might be attributed to drying of the basement slab. 

Figure 56. Exterior and interior (test rooms and basement) dew point temperatures

5.3.2 Monitored Wall Results

Sheathing MCs for the north-facing walls are shown in Figure 57; they show the expected 

seasonal rise and fall, with peak MCs in wintertime. The north 12-in. ocSPF wall (N1) showed a 

peak wintertime sheathing MC near 12%–15%; the 51⁄2-in. ocSPF wall (N3) was similar to N1, 

but with slightly higher peak MCs (15%–20%). However, the 12-in. cellulose wall (N2) showed 

considerably higher MCs, in the 25%–28% range. 

0

10

20

30

40

50

60

70

80

90

100

12/7 1/26 3/16 5/5 6/24

Reltaive Humidity (%)

RH in N-C

RH in S-C

RH in Bsmt-C

-20

-10

0

10

20

30

40

50

60

70

80

12/7 1/26 3/16 5/5 6/24

Dewpoint Temperature (F)

Exterior DP

Interior DP-North

Interior DP-South

Interior DP-Bsmt
50 

Figure 57. North side sheathing MCs, with exterior temperature for reference

The anomalies seen in the cellulose (N2) wintertime behavior (sudden jumps in MC) coincide 

with freezing temperatures; it is likely that freezing of bound water in the sheathing results in 

different electrical resistance response, and thus measured MC.

In the summer, all wall sheathings dry to roughly the same MC levels (10% or lower range). 

-20

-10

0

10

20

30

40

12/7 1/26 3/16 5/5 6/24

Temperature (C) and MC (%)

T out

N1 12" ocSPF MC Upper

N1 12" ocSPF MC Mid

N1 12" ocSPF MC Lower

-20

-10

0

10

20

30

40

12/7 1/26 3/16 5/5 6/24

Temperature (C) and MC (%)

T out

N2 12" cellulose MC Upper

N2 12" cellulose MC Mid

N2 12" cellulose MC Lower

-20

-10

0

10

20

30

40

12/7 1/26 3/16 5/5 6/24

Temperature (C) and MC (%)

T out

N3 5.5" ocSPF MC Upper

N3 5.5" ocSPF MC Mid

N3 5.5" ocSPF MC Lower

N3 (51⁄2 in. ocSPF)

N2 (12 in. cellulose)

N1 (12-in. ocSPF)
51 

The south-facing walls are all considerably dryer than the north-facing walls, but with a 

similar pattern, where the 12-in. cellulose wall (S2) has slightly higher wintertime peak MCs

(Figure 58), All walls dry to the 8% range in the summer; the intermittent data seen during 

summertime indicate periods dryer than the measurement range of the data logger (wood 

electrical resistance is too high for logger setup).

Figure 58. South side sheathing MCs, with exterior temperature for reference

Other sensors were examined to confirm the sheathing MC behavior. The “wafer” sensor results 

for the three north-facing walls are plotted in Figure 59, which reflect conditions at the exterior 

sheathing-to-insulation interface.

-20

-10

0

10

20

30

40

12/7 1/26 3/16 5/5 6/24

Temperature (C) and MC (%)

T out

S1 12" ocSPF MC Upper

S1 12" ocSPF MC Mid

S1 12" ocSPF MC Lower

-20

-10

0

10

20

30

40

12/7 1/26 3/16 5/5 6/24

Temperature (C) and MC (%)

T out

S2 12" cellulose MC Upper

S2 12" cellulose MC Mid

S2 12" cellulose MC Lower

-20

-10

0

10

20

30

40

12/7 1/26 3/16 5/5 6/24

Temperature (C) and MC (%)

T out

S3 5.5" ocSPF MC Upper

S3 5.5" ocSPF MC Mid

S3 5.5" ocSPF MC Lower

S3 (51⁄2 in. ocSPF)

S2 (12 in. cellulose)

S1 (12 in. ocSPF)
52 

Figure 59. South side “wafer” sensor moisture contents, with exterior temperature for reference

The response of these wood-based sensors should be understood when interpreting these results. 

Based on previous work (Ueno and Straube 2008), the “wafer” sensors come to equilibrium with 

100% RH conditions (closed box containing water) at 28%–30% MC. However, immersing the 

sensors in liquid water increases their MC to the 40%–45% range. 

The “wafer” response is consistent with the sheathing MC measurements: 12 in. of 0.5 PCF foam 

remains the dryest through the winter, followed by 51⁄2 in. of 0.5 PCF foam. The cellulose wall 

shows much higher wintertime peak moisture levels, consistent with condensation occurring at 

the sheathing. In contrast, the 0.5 PCF foam walls remain below the 100% RH level. During the 

summer, all “wafer” sensors dry to the 10%–2% moisture content range.

The south-facing wall “wafer” results are shown in Figure 60; again, patterns are analogous to 

the previous sheathing MC measurements. 

Figure 60. South side “wafer” sensor MCs, with exterior temperature for reference

The cellulose wall shows higher moisture levels, but all walls remain below the 100% RHequivalent level. During the summer, the wafers dry to below 10% MC. 

0

10

20

30

40

50

60

70

80

90

100

0

5

10

15

20

25

30

35

40

45

50

12/7 1/26 3/16 5/5 6/24

Exterior Temperature (F)

Wafer Moisture Conent (%)

N1-12" ocSPF N2-12" Cellulose

N3 5.5" ocSPF Exterior T

0

10

20

30

40

50

60

70

80

90

100

0

5

10

15

20

25

30

35

40

45

50

12/7 1/26 3/16 5/5 6/24

Exterior Temperature (F)

Wafer Moisture Conent (%)

S1-12" ocSPF S2-12" Cellulose

S3 5.5" ocSPF Exterior T

100% RH wafer 
53 

The RH measurements can be used to further confirm the previous results; the RH measurements 

for the north-facing walls (outboard side) are plotted in Figure 61. The temperatures at the RH 

sensors follow the expected wintertime pattern: N1 and N2 are close to identical (tracking 

outdoor conditions), and N3 is slightly warmer (due to reduced insulation inboard of the sensor). 

During the summer, all RH sensors at the sheathing fall to the 50%–65% range, as the 

temperature gradient and moisture drive are inward, away from the sheathing. 

The RH results are consistent with previous measurements: the cellulose wall has higher 

humidity levels at the sheathing than the 0.5 PCF foam walls. The RH sensor is installed roughly 

1⁄2 in. away from the face of the exterior sheathing.

Figure 61. North-facing wall exterior side RH, with exterior temperature for reference

The inboard RH sensors for the north-facing walls are plotted in Figure 62, with exterior 

temperature and interior RH for reference. It appears that the RH levels essentially track interior 

conditions. The void space inboard of N3/S3 showed similar behavior. 

Figure 62. North-facing wall interior side RH, with interior RH and exterior temperature 

for reference

0

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

12/7 1/26 3/16 5/5 6/24

Exterior Temperature (F)

Relative Humidity (%)

N1-12" ocSPF N2-12" Cellulose

N3 5.5" ocSPF Exterior T

0

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

12/7 1/26 3/16 5/5 6/24

Exterior Temperature (F)

Relative Humidity (%)

N1-12" ocSPF N2-12" Cellulose

Exterior T Interior RH
54 

5.3.3 Analysis and Interpretation

One caveat on interpreting the data is that the boundary conditions were unrepresentative of 

typical conditions. First, winter 2011–2012 was much milder than normal (4400 HDD Base 65°F 

versus 5600 HDD climate normal). Second, the house was unoccupied, and therefore had no 

internal occupant moisture generation; wintertime interior RH conditions were consistently in the 

15%–20% range (very dry), at normal indoor temperatures (70°F). As a result, these results are 

not the “worst case” in terms of interior-sourced wintertime condensation risks. 

Even with these less-challenging conditions, the MCs at the sheathing of the north-facing 

cellulose wall peaked at levels high enough to cause concern. Wintertime peak measurements 

were in the 25%–28% range, while the other (0.5 PCF foam) walls remained below 20%. 

Traditional guidance is to keep wood MC below 20%; decay fungi are inhibited below this level 

(Carll and Highley 1999), with optimum growth occurring in the 25%–30% MC range. Decay 

fungi become active at MC levels above 28% (Straube and Burnett 2005). 

In addition, the “wafer” sensors show that sheathing condensation might be occurring at peak 

wintertime conditions in the cellulose wall, unlike the 0.5 PCF walls. Although high RH

conditions are associated with mold and decay, liquid water (i.e., condensation) greatly 

accelerates degradation of common building materials (Doll 2002).

However, the MCs should interpreted with temperatures in mind. Biological activity is inhibited 

at low temperatures, so high MCs in mid-winter pose less risk than in warmer seasons. Sustained 

high MCs at moderate temperatures pose the greatest durability risks. In the collected data, all 

walls dried to MCs well within the safe range during the summer. 

Another consideration is that cellulose is treated with borate salts as a preservative and fire 

retardant. Borates are highly effective at inhibiting mold growth; they appear to leach into 

adjacent materials (e.g., gypsum board and wood sheathing), providing some protection to them. 

One puzzling result was that the 12 in. of 0.5 PCF foam showed consistently drier wintertime 

conditions than the 51⁄2 in. of 0.5 PCF foam. Common wisdom is that double-stud walls have 

colder sheathing, and thus experience greater moisture risks than conventional (e.g., 2 × 6) walls.

However, these results might be explained by the vapor permeability of the assembly. Although 

0.5 PCF ocSPF is generally thought of as vapor permeable, at the thickness applied at the 

double-stud wall here, there is significant vapor resistance. Table 8 shows the vapor permeability 

of the insulation layer alone, as well as in series with a 10 perm vapor retarder (Class III vapor 

retarder).

Table 8. Vapor Permeability of Insulation and Assemblies

Wall ID Insulation Material Vapor Permeability 

(Insulation Only) 

Vapor Permeability 

(Add 10 Perm Class III 

Vapor Retarder)

N1/S1 12 in. 0.5 PCF foam 1.8–2.5 perms 1.5–2.0 perms

N2/S2 12 in. cellulose 7.0–10 perms 4.0–5.0 perms

N3/S3 51⁄2 in. 0.5 PCF foam 4.0–5.5 perms 2.9–3.5 perms
55 

It appears that at this thicknesses applied here, the ocSPF used here provides reasonable vapor 

control from interior-sourced moisture. Note that the spray foam values are not identical to the 

ASHRAE value stated previously; they are taken from manufacturer’s data.

The vapor permeance of the painted and primed gypsum was not measured at this site; however, 

measurements at previous sites showed results in the 7–11 perm (dry cup) range, consistent with 

the value used for a Class III vapor retarder (10 perm). Schumacher and Reeves (2007) reported 

permeance measurements of 8 perms for drywall with two coats of latex paint, and 30 perms for 

drywall samples finished with a knock-down coating (a.k.a. California Ceiling).

It must be noted that the spray foam is an air-impermeable material, while cellulose is air 

permeable (does not meet air barrier material requirement of 0.02 l/(s-m2) at 75 Pa). However, 

cellulose (at higher densities) is an effective airflow retarder. Whether interstitial airflow has any 

role in the moisture behavior in this wall is unknown, but it may be a factor. 

For reference, the use of a Class III vapor retarder is allowed by code in conventional 

construction, assuming a vented cladding (ICC 2009). In Zone 5, allowable assemblies include 

vented cladding (such as vinyl siding) over OSB, plywood, fiberboard, or gypsum sheathing. 

However, a double-stud wall has different behavior than conventional (2 × 4 or 2 × 6) 

construction. 

Hygrothermal modeling was not performed at this time, with eight months’ of data. The planned 

process is to only perform hygrothermal modeling (for comparison with monitored results) after 

the collection of at least one year of data, and preferably more (to account for the initial year’s 

unoccupied conditions).
56 

6 Financing Options for Photovoltaic Systems

6.1 Transformations, Inc. Financing Options

Transformations, Inc. offers three feasible options to the homeowners for obtaining PV systems. 

The developer has put substantial research and effort into developing affordable and viable 

alternatives. Local incentives—as well as state and federal tax credits—contribute to making the 

residential PV systems financially attractive (Scott 2011). These options aid the buyers in 

obtaining properly sized PV arrays for their homes at reasonable cost.

One option the developer offers is to lease the system. This option is best suited for homebuyers 

who may not have enough capital or be able to qualify for a higher loan. Transformations, Inc. 

works with three different providers that offer competitive terms for the lease. The lease term is 

approximately 18 years and subsequently the homeowner is able to buy the system out. This 

option allows the homeowner to purchase the power the PV system is producing at a discounted 

price of 10% with no need to maintain the system. 

Another option is to purchase the system, which allows homeowners to keep all of the energy 

that is generated by the system. This alternative is suitable for homebuyers who are able to 

borrow a greater amount because the PV system cost is either included in the price of the home 

or financed with a separate loan. Including the cost of the PV system in with the mortgage that 

currently offers annual percentage rates in the 3%–4% range for a 30-year fixed year mortgage, 

is often the best option for the buyer. However, some of the larger solar systems (18.33 kW) 

have had a harder time appraising out for the full value of the system and home. Therefore, 

Transformations, Inc. has used a backup alternative of having the homebuyer obtain a second 

mortgage for the PV array. Also, the developer works with a local lender who offers a home 

equity line of credit with 2.99% annual percentage rate for three years with no points, no closing 

costs, no annual fees, and up to 100% financing. 

In the Devens and Townsend developments, the PV system is part of the house package. In 

Easthampton, the homeowners have an option of adding PV arrays to their homes. Typically, 

homebuyers of the market rate homes choose to purchase the system and the homebuyers of the 

affordable homes decide to either lease it or not install it at all. Thus far, the two Custom Homes 

(Lots 30 and 43) have chosen to purchase the system. The Model Home (Lot 13) includes the 

lease option and the Easthampton (Lot 40) has yet to be sold and does not currently feature a PV 

array. The homeowners of the Small Saltbox (Lot 17) and the Hadley (Lot 24) are considering 

the lease option and the homeowners of the Cottage (Lot 23) decided to opt out. 

6.2 Massachusetts Department of Energy Resources Solar Carve-Out Program

The Renewable Portfolio Standard (RPS) launched by the Massachusetts Department of Energy 

Resources (DOER) offers the SRECs to eligible projects (EPA 2009). RPS requires that a 

portion of the state’s total electricity come from renewable resources—for example, residential 

PV systems. There are 33 states, plus the District of Columbia, that have established RPS 

requirements and the conditions of each program differ significantly. 

In Massachusetts, the DOER Solar Carve-Out program’s goal is to install 400 MW of solar 

electricity (Massachusetts Clean Energy Center 2012). An SREC is created for every megawatthour of solar electricity created and each SREC can be sold to the utility companies to meet the 
57 

demand set by the program. The installed PV system has to be registered with the state program, 

and once it starts producing the energy the homeowner is able to track the production and hire an 

aggregator who will sell the SRECs back to the utility. The aggregation fee is typically around 

5% of the SREC contract price. 

The value of an SREC is typically determined by the market demand; in Massachusetts the 

DOER has calculated the Alternative Compliance Payment (ACP) rate of the SRECs for the next 

10 years. The rates determined by the DOER represent penalty rates that utilities are obligated to 

pay if not able to meet the requirements of the Solar Carve-Out program. However, due to a 

higher solar energy market supply the value of the SRECs has decreased. The SRECs can be 

obtained at the Solar Credit Clearinghouse Auction for $300 (minus the 5% auction fee and the 

5% aggregation fee). 

Table 9 lists the values of the SRECs as determined by the DOER as well as the potential 

incentives for a 10-kilowatt (kWpeak) system installed in 2012. Currently in Massachusetts, new 

systems can obtain SRECs for 40 quarters (10 years). Over time, they will be reduced by as 

much as 4 quarters in any given year. The ACP rate represents the maximum incentive that 

SREC owners can obtain and the auction rate may be (but is not guaranteed to be) the minimum

incentive. 

Table 9. Value of Solar Renewable Energy Certificates in Massachusetts

Compliance Year 

ACP Rate*/MWh 

(Maximum Incentives)

Auction Rate/MWh

(Minimum Incentives) 

Per SREC Per Year Per SREC Per Year

2012 $550.00 $5,747.50 $300.00 $2,978.25

2013 $550.00 $5,747.50 $300.00 $2,978.25

2014 $523.00 $5,465.35 $300.00 $2,978.25

2015 $496.00 $5,183.20 $300.00 $2,978.25

2016 $472.00 $4,932.40 $300.00 $2,978.25

2017 $448.00 $4,681.60 $300.00 $2,978.25

2018 $426.00 $4,451.70 $300.00 $2,978.25

2019 $404.00 $4,221.80 $300.00 $2,978.25

2020 $384.00 $4,012.80 $300.00 $2,978.25

2021 $365.00 $3,814.25 $300.00 $2,978.25

Total Rebates $48,258.10 $29,782.50

* The ACP rates for SRECs are determined by the Massachusetts DOER for a period of 10 years. An aggregation 

fee of 5% is included in the calculation of both yearly values. An additional auction fee of 5% is included in the 

calculation of the yearly auction rate values. The SREC income is likely to land between the two sets of incentives 

but the minimum is not guaranteed by the DOER.

Eleven SRECs (11.2 MWh) are assumed to be generated per year based on a system located in 

Easthampton, Massachusetts (Figure 63). The calculation was prepared using the PVWattsTM 

Grid Data Calculator (Version 2), which has been developed by National Renewable Energy 

Laboratory (NREL) (NREL 2012). The calculator determines energy production and cost savings 

for PV systems in any location in the world. 
58 

Figure 63. PVWatts calculation for a house with a 10-kW system located in 

Easthampton, Massachusetts

Transformations, Inc. typically retains SRECs and uses their value to drive down the prices of its 

net-zero energy homes to slightly above those of conventional construction. This enables faster 

adaption of net-zero energy homes in Massachusetts.

6.3 Other Incentives

In addition to the SRECs, incentives are available from the Massachusetts Clean Energy Center 

for projects that use services from investor-owned utilities. The incentives are offered for the 

installation of a system up to 10 kWpeak, with a rebate capped at 5 kWpeak. In addition, there is 

also a Massachusetts state tax credit of $1,000 and a federal tax credit of 30% of the system cost 

available to the homebuyer.

The State of Massachusetts offers generous incentives for the PV systems, but the RPS programs 

are available in other states. However, since the program requirements in other states may be 

different than in the state of Massachusetts, homeowners, builders, and developers should inquire 

about the program requirements in their states to learn the details.

Also, other local or state incentives may be available to the homeowners for purchasing PV 

systems, and performing thorough research about the existing options is important in order to 

maximize the savings. Homeowners interested in the incentives should check with the state and 

local agencies as well as their utilities to find out about available energy efficiency programs in 

their areas. 
59 

The following is a list of website page links where information can be found about incentive 

programs in the individual states as well as the state of Massachusetts: 

• Database of State Incentives for Renewables & Efficiency

www.dsireusa.org

• Massachusetts Department of Energy Resources Solar Carve-Out Program 

www.mass.gov/eea/energy-utilities-clean-tech/renewable-energy/solar/rps-solarcarve-out/about-the-rps-solar-carve-out-program.html

• Massachusetts Clean Energy Center

www.masscec.com

• Mass Save

www.masssave.com
60 

7 Basements Versus Above-Grade Construction Cost 

Comparison

In the Devens and Townsend developments, basements are included in the original designs of the 

homes. The basic package for the houses in the Easthampton development includes slab-ongrade foundations. Most buyers, however, are interested in having basements; the buyers of the 

market-rate homes in the Easthampton development have asked to add basements to the designs 

of their new homes. Buyers typically perceive basements as an added value to the homes, and see 

the potential of finishing the space and using it as additional living space. 

Including a basement in the design of a home presents many challenges in regards to water 

management and insulation. Ensuring that the site water management or thermal performance of 

the space is properly addressed is important to the overall performance of the house. 

Various research projects have focused on examining the best practices for insulation and water 

management when building a basement. Multiple articles and research projects have developed 

robust details and approaches for addressing those issues (Lstiburek 2006; Smegal and Straube 

2010; Ueno and Lstiburek 2010; Aldrich et al. 2012). Case studies have been published 

demonstrating the implemented approaches on a number of projects. These documents do not, 

however, include information comparing the cost of adding a basement versus constructing a 

slab-on-grade foundation, and expanding the above grade living space. 

In the article published in the Journal of Light Construction in 2010, the author discussed best 

practices for constructing frost-protected shallow slab-on-grade foundations (Gibson 2010). The 

author estimated that compared to a full 850-ft2 basement, building a frost-protected shallow 

slab-on-grade foundation can save approximately $20,000. This is due to eliminating the 

foundation subcontractor, the concrete needed for a full foundation wall, the first-floor deck, as 

well as the excavation costs. This estimate, however, does not provide current cost values for a 

slab-on-grade foundation. 

7.1 Basement and Slab-on-Grade Construction Comparison

Transformations, Inc. has developed standard packages for both including a basement in the 

home design and building a house with a slab-on-grade. In the Easthampton development the 

future homeowners of the market-rate houses are able to customize their homes based on their 

desires and needs. The affordable homes are stemwall slab-on-grade construction.

For the full basements (Figure 64), the basement slab assembly consists of (from bottom to top): 

a layer of crushed stone with filter fabric, one layer of 2-in. XPS rigid insulation, a layer of 6-mil 

polyethylene, and the concrete slab. For moisture control, dampproofing is installed on the 

outside of the foundation wall, extending from the top of the footing to grade. A capillary break 

at the junction between the top of the footing and the foundation wall controls capillary rise from 

the footing to the interior. A 31⁄2-in. layer of ccSPF insulation is installed at the foundation wall 

and over the rim joist. The developer gives the homebuyers the option of finishing the space with 

studs and drywall; the unfinished option includes the required ignition barrier in the form of an 

intumescent paint.
61 

Figure 64. Foundation wall with 31⁄2 in. of ccSPF insulation

The slab-on-grade assembly (Figure 65) consists of (from bottom to top): a layer of crushed 

stone with filter fabric, three layers of 2-in. XPS rigid insulation, a layer of 6 mil polyethylene, 

and the concrete slab. Two layers of 2-in. XPS rigid insulation are installed at the slab edge; the 

edge insulation is hidden under the inner (nonstructural) framing of the double-stud wall. The 

stemwall footings are below local frost depth. 
62 

Figure 65. Slab-on-grade construction

7.2 Cost Analysis

The developer has provided per square foot cost data for constructing a basement as well as per 

square foot cost data for a slab-on-grade foundation (Table 10). The information is based on the 

“Farmhouse” model with a footprint of 24 ft × 36 ft (864 ft2

) located in the Easthampton 

development. That particular model was used for the construction of the Model Home (Lot 13), 

which has the slab-on-grade, and the Custom Home (Lot 30), which has the full basement. The 

cost difference between building a full basement versus a stemwall slab-on-grade is 

approximately $10,000 ($12/ft2

). Of course, this cost includes high performance water control 

measures, and durable insulation measures that create a warm, dry, comfortable—and therefore 

more usable—space.

Table 10. Basement Construction Cost

Basement Cost Slab-On-Grade Cost

Site Work $18,850 (including structural 

fill, geo fabric)

$14,350 (including structural fill, 

geo fabric)

Foundation Labor $3,750 $2,600

Foundation Concrete $5,950 $3,450

Slab Insulation $1,200 (2-in. XPS) $2,800 (3 layers of 2-in. XPS)

First Floor Deck 

Materials $800 (estimated) – 

Basement Wall 

Insulation $3,150 (31⁄2-in. ccSPF) – 

Total $33,700 $23,200

To compensate for the lack of a basement, Transformations, Inc. typically offers the homebuyers 

the use of an unconditioned room above the garage. The garage size varies based on whether it is 

a one-car garage with a footprint of 12 ft × 22 ft (264 ft2

) or a two-car garage with a footprint of 

22 ft × 24 ft (528 ft2

). The cost of turning the space into a usable storage room is marginal as it 
63 

only requires the addition of floor sheathing to this vented attic space. The approximate cost of 

the floor sheathing for a one-car garage is $350 and $700 for a two-car garage. This estimate 

includes cost of materials and labor. 

Another option of adding usable space to the house is to finish the unconditioned room above the 

garage. This alternative will provide the homebuyers with a finished living space but the cost is 

considerably higher. Given that the options for the finishes can vary significantly, the 

approximate cost to finish a room above a one-car garage (264 ft2

) is $10,000 and for a space 

above a two-car garage (528 ft2) the cost is $20,000. 

Another alternative that is available to the homebuyer is to increase the footprint of the home. 

This option, however, will raise the overall price of the house significantly. To determine the 

cost of adding extra square footage to a house, the cost values for a Farmhouse model were used. 

The market price of the Model Home in the Easthampton development is $287,000. In order to 

construct a 12 ft × 14 ft (168 ft2) one-story addition to the Farmhouse model it would cost 

approximately $21,000 (this estimate does not include cost of foundation). Of course, this 

increased footprint assumes that the lot setbacks will accommodate a house of this size.

To summarize the cost analysis for the “Farmhouse” model as described above, the cost per 

square foot related to constructing a full basement versus above-grade space is as follows:

• Full basement: $39 

• Slab-on-grade foundation: $27 

• Unconditioned space above garage: $1.30 for one-car garage and $1.70 for two-car 

garage 

• Finished space above garage: $38 for one-car garage and $76 for two-car garage

• 12 ft × 14 ft (168 ft2

) one-story addition: $125. 

7.3 Basement Versus Above-Grade Advantages and Disadvantages

Basements can be problematic in regards to water management and insulation, and they can be 

viewed as dark and negative spaces in the houses. However, when constructed properly they can 

provide excellent storage area, space for mechanical equipment, and secondary living space. One

of the interesting points of Transformations Inc.’s construction is, however, that their design 

minimizes the space required for mechanical equipment in the basement. Space conditioning is 

provided by ductless heat pumps (no basement space needed), and domestic hot water is 

provided by a wall-hung tankless unit (space only required for servicing). The PV inverters are

also located in the basement. 
64 

Figure 66. (L) Tankless water heater; (R) PV inverters in unfinished basement

Transformations, Inc. also presents an opportunity of finishing the basement and providing 

additional living space, which will increase the value of a home. Two factors to consider in the 

basement versus slab decision are regional homebuyer expectations and site conditions. 

As the experience to date in Easthampton has demonstrated, homebuyers in the New England 

region typically expect basements in their homes; slab-on-grade foundations are viewed as a 

lesser option. The lack of a basement for storing personal items and to house the mechanical 

equipment can be an issue for some. However, many homebuyers view basements only as 

storage spaces and would never consider them for providing additional living space. 

Homebuyers also consider the impact of basement space on resale value.

Another factor to consider is the site that the house will be built on. If the site is fairly flat it 

makes sense to build a slab-on-grade foundation, but if the terrain is more complicated, the cost 

of constructing a slab-on-grade may be similar to a full basement, as the excavation costs will be 

significant. 

Slab-on-grade foundation can be viewed as less problematic (in terms of water control issues),

and many homebuyers would prefer a smaller storage area located above grade. Spaces located 

above grade are typically considered as more healthy, clean, and attractive when compared to a 

basement. However, the cost of finished and conditioned space above grade is significantly 

higher than the basement incremental cost. On the other hand, unconditioned but enclosed 

storage space (attic) is substantially lower cost than a basement on a per square foot basis. 
65 

8 Conclusion and Further Work

8.1 Overview

The advanced efficiency package implemented by the developer in the Devens, Easthampton, 

and Townsend developments exceeds the 30% energy savings goal set by the Building America 

program for new homes in the cold climate for 2013. Based on the results collected to date, the 

two major components of the package—the double-stud walls filled with ocSPF insulation and 

the ductless mini-split heat pump equipment—have performed well. However, BSC is 

continuing the moisture monitoring research in the Devens development; data has been collected 

through June 2013, and further analysis will be contained in future BSC reports. Mini-Split Heat 

Pump Performance and Thermal Distribution

• What range of temperatures is experienced in bedrooms of homes heated by point 

sources?

Under favorable conditions, mini-split heat pumps can provide thermal comfort and 

uniformity equal to conventional forced-air systems (± 2°F). The required conditions 

include a super-insulated building enclosure, excellent airtightness, moderate solar gains, 

and uniform set points within the building. Although one heat pump per floor is a 

common configuration, conductance between floors drives a large part of the thermal 

distribution. The two floors cannot be operated independently, nor successfully maintain 

different set points. This report does not address the effect of closing doors, which is 

expected to be important.

• How do buyers perceive the performance of the ductless mini-split heat pumps? Are the 

room-to-room temperature differences in homes with ductless heat pumps apparent to the 

residents?

Although the winter of 2011–2012 was generally mild, the heat pumps performed well on 

several days near the design temperature, and did not reach maximum output. Occupants 

report high levels of comfort, consistent with the measured temperature uniformity. Most 

occupants seem to accept the concept of keeping bedroom doors open most of the time, 

facilitating thermal distribution and thus enhancing comfort. 

8.2 Moisture Monitoring of Twelve-Inch Double-Stud Walls

• Does the use of ocSPF, rather than cellulose, in the wall cavities of double-stud walls 

change the MC of the wall assembly? Does this change the risk assessment for this 

construction approach? 

Eight months of monitored results were available for the comparison between doublestud walls with 12 in. of ocSPF, 12 in. of netted and dry blown-in cellulose, or 51⁄2 in. of 

ocSPF. The first winter showed sheathing MCs high enough to cause concern in the 

double-stud cellulose wall, but acceptable conditions in the remaining walls. However, all 

walls dried to safe ranges in the summer. In addition, it is possible that the cellulose wall 

can withstand high MC levels without damage due to borate preservatives and moisture 

storage.
66 

The team has been collecting data to present date (June 2013); further analysis will be 

covered in future BSC reports. The first winter measured data without occupancy (and 

thus interior moisture generation); the second winter demonstrated the effect of higher 

interior humidity levels. If high MCs are seen in the winter of 2012–2013, it will be 

interesting to see if the sheathing dries back to the same levels in the following spring and 

summer.

If the experiment can continue through an additional winter (2013–2014), and the 

homeowner agrees, it may be interesting to apply vapor retarder paint to the interior 

gypsum board at the test walls. This would determine whether vapor permeability or 

some other mechanism (such as air leakage) dominates the sheathing MC behavior. 

• Do results of hygrothermal analysis correlate with field-measured MCs, in terms of risks 

of wintertime moisture accumulation in wood-based sheathings?

Hygrothermal modeling was not performed at this time, with eight months’ of data. The 

planned process is to only perform hygrothermal modeling (for comparison with 

monitored results) after the collection of at least one year of data, and preferably more (to 

account for the initial year’s unoccupied conditions). 

8.3 Financing Options for Photovoltaic Systems

• How can a PV array sufficient for net-zero performance be financed with no or minimal 

increase in annualized energy related cost to the homeowner, through SRECs and novel 

finance agreements? How can this model be applied to regions outside of Massachusetts?

Transformations, Inc. was able to create three very viable options for financing a solar 

array that can suit a number of buyers—the lease option and two purchase options. The 

developer recognized that in some instances potential buyers were having difficulties 

financing the systems and responded to the needs of the buyers by offering an alternative 

financing option. 

The incentives offered by various programs in the state of Massachusetts as well as state 

and federal tax credits aid homebuyers in acquiring PV systems for their homes at an 

affordable price. However, the incentive programs in other states may differ significantly.

Homebuyers should learn the details about the available incentive programs in their areas 

that will allow them to obtain a PV system and reach net-zero energy at a reasonable cost.

8.4 Basements Versus Above-Grade Construction Cost Comparison

• Basements are a common feature of cold climate construction, but they present special 

challenges for insulation and water management. How does the per square foot cost of 

basements compare to adding above-grade space?

There are a number of factors to consider when choosing between adding a full basement 

and building a slab-on-grade foundation. The incremental cost of a high performance 

(well insulated and water managed) basement is high compared to a well-insulated slab; 

the builder’s incremental cost was roughly $12/ft2

. Unconditioned attic storage space can 

be added at a low cost ($1.30–$1.70/ft2

); however, adding space conditioning and 

finishes would increase the cost of additional above-grade square footage considerably
67 

($38–$76/ft2). Enlarging the footprint of the house is another possible option but it is

significantly more expensive when compared to the other alternatives ($125/ft2

). 

The experience to date in Easthampton has demonstrated that homebuyers in the New 

England region typically expect basements. Excluding a basement from a home design 

can have significant impact on the value of the house in a region where basements are 

expected. However, the characteristics of a particular site where the house is going to be 

located are important factors, as the excavation costs can be substantial. 

When presented with an opportunity for including a basement in a home design, budget 

and the desirable or needed square footage play a big role in the decision making. The

available options for substituting the basement space with the additional above-grade area 

as well as advantages and disadvantages for building basements and slab-on-grade 

foundations, are intended to help builders and homebuyers assess the true cost as well as

value of constructing either option. 
68 

References 

[ACCA] Air Conditioning Contractors of America (2006). Manual J® Residential Load 

Calculations Eighth Edition, Version 2.00. Arlington, VA: Air Conditioning Contractors of 

America.

Aldrich, R.; Mantha, P.; Puttagunta, S. (2012). Measure Guideline: Basement Insulation Basics. 

Washington, DC: U.S. Department of Energy. 

ASHRAE. (2009). 2009 ASHRAE Handbook—Fundamentals. Atlanta, GA: American Society of 

Heating, Refrigerating and Air-Conditioning Engineers, Inc. 

Bergey, D.; Ueno, K. (2011). “New England Net Zero Production Homes.” 2011 ASHRAE 

Annual Conference, Montreal, QC, Canada, June 25-29, 2011. 

Carll, C.G.; Highley, T.L. (1999). “Decay of Wood and Wood-Based Products Above Ground in 

Buildings. Journal of Testing and Evaluation 27(2):150–158. 

Christensen, C.; Anderson, R. (2006) BEoptTM Software for Building Energy Optimization: 

Features and Capabilities. NREL/TP-550-39929. www.nrel.gov/buildings/pdfs/39929.pdf. 

Accessed June 23, 2011. 

Doll, C.S. (2002). Determination of Limiting Conditions for Fungal Growth in the Built 

Environment, PhD Thesis, Harvard School of Public Health, 2002. 

EIA. (2005). Residential Energy Consumption Survey: Preliminary Housing Characteristics 

Tables, 2009. Washington, D.C.: Energy Information Administration. 

EPA. (2009). “Renewable Portfolio Standards Fact Sheet.” Washington, D.C.: Environmental 

Protection Agency. www.epa.gov/chp/state-policy/renewable_fs.html. Accessed September 25, 

2012. 

Gibson, A. (2010). “Super-Insulated Slab Foundations.” Journal of Light Construction, April 

2010. Williston, VT: Hanley Wood, LLC. 

Holladay, M. (2010). “Energy Smart Details: Airtight Drywall.” Fine Homebuilding Magazine, 

September 2010, pp. 86–87. Newtown, CT: Taunton Press, Inc.

Holladay, M. (2011). “Heating Options for a Small Home.” Fine Homebuilding Magazine, 

February-March 2011. Newtown, CT: Taunton Press, Inc.

ICC. (2009). International Residential Code for One- And Two-Family Dwellings. Country Club 

Hills, IL: International Code Council. 

Lstiburek, J.W. (1983). “The Drywall Approach to Airtightness,” Second Canadian Building 

Science Technology Conference, Canadian Society of Civil Engineers, November 1983. 

Lstiburek, J.W. (2000). Builder’s Guide to Cold Climates. Somerville, MA: Building Science 

Press.
69 

Lstiburek, J.W. (2005). “Understanding Air Barriers.” ASHRAE Journal (vol. 47); pp. 24-30. 

Atlanta, GA: American Society of Heating, Refrigeration, and Air-Conditioning Engineers, Inc. 

Lstiburek, J.W. (July 2006). “Understanding Basements.” ASHRAE Journal 48:24–29. Atlanta, 

GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Lstiburek, J.W. (2008). “Building Sciences: Energy Flow Across Enclosures.” ASHRAE Journal

50:60–65. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning 

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Massachusetts Clean Energy Center (2012) “Commonwealth Solar II,” 

www.masscec.com/index.cfm/pid/11159//stCode/live/preview/yes/cdid/11241. Accessed 

September 24, 2012. 

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www.nrel.gov/rredc/pvwatts/grid.html. Golden, CO: National Renewable Energy Laboratory. 

Accessed September 25, 2012. 

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Straube, J.; Onysko, D.; C. Schumacher. (2002). “Methodology and Design of Field Experiments 

for Monitoring the Hygrothermal Performance of Wood Frame Enclosures.” Journal of Thermal 

Envelope and Building Science 26(2): 123–151. 

Straube, J.; Smegal, J. (2009). Building America Special Research Project: High-R Walls Case 

Study Analysis (Research Report – 0903). www.buildingscience.com/documents/ reports/rr0903-building-america-special-research-project-high-r-walls/. Accessed December 4, 2012.

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70 

Appendix A: Mini-Split Heat Pump Performance Surveys
------------------------

U"\ tr~Nt~t ..tOI Energy Eff1ctency &

ENERGY Renewable Er·ergy TRANSFORMATlOHS'" 

1 

Performance of the Mini-Split Air Source Heat Pumps 

Name \ Address 14 Cavite street 

Please provide answers and additional com"fnts for the questions 1 through 11 below: 

1. 	 When did you move into your house? Month _A_:p_r_il_ _ __________ _ Year 2012 

2. How comfortable are you in your house? Please select 1 through 5. 

WinterTime SummerTime 

Most Comfortable Least Comfortable Most Comfortable Least Comfortable 

os 

3. How does your comfort compare to the last place f u lived? 0 More Comfortable 

4. 	 What temperature is your thermostat set to? First floor (Heating/Cooling) __t!!}_ 

5. 	 Do you adjust the thermostat setpoint at night? _X_ _ N _ _ 

If yes, what temperature do you set it to? First Flo9r (Heating/Cooling) __/ OFF 

6. 	 Do you adjust the thermostat setpoint when not horne? Y _X__ N__ 

If yes, what temperature do you set it to? First Floor (Heating/Cooling) _ _ I OFF I 	 7. Do you use any other heating or cooling devices, sJch as space heaters, window AC units, portable fans, etc? Y __N_X_ _ 

If yes, what device and in which room? I 

I 8. Are parts of your house warmer or colder than you want? If yes, please select 1 through 5. 

Winter ~ Too Cold Just Right 

I 

I Living Room 01 02 03 

Dining Room 01 02 03 

Kitchen 01 02 03 

Bathroom 1 01 02 03 

Bathroom 2 01 02 03 I 	 Bedroom 1 01 02 03 

Bedroom 2 01 02 03 

Bedroom 3 01 02 03 

9. Do you open or close windows to improve comfort? 

Summer Time 0 Always Open 

WinterTime 0 Always Open 

10. How do you operate bedroom doors? 

When in Bedroom 0 Always Open 

When not in Bedroom O Always Open 

4 

4 

04 

04 

04 

04 

04 

4 

Too Warm 

05 

05 

os 

os 

Os 

Os 

Os 

Os 

Too Cold 

01 

0 1 

01 

01 

01 

01 

01 

0 1 

02 

02 

02 

02 

02 

02 

02 

0 2 

0 Mostly Open 

0 Mostly Open 

0 Mostly Closed 

0 Mostly Closed 

0 Mostly Open 

O Mostly Open 

0 Mostly Closed 

0 Mostly Closed 

11. Which of the following most affect your door operatio1choices? 

0 Keeping room warmer/cooler 0 Room too stl1ffy/odors building up 0 Privacy 

71

05 

0 About the Same 0 Less Comfortable 

Second Floor (Heating/Cooling) __/!.!}___ 

Second Floor (Heating/Cooling) __/!.!}___ 

Second Floor (Heating/Cooling) _ _ I OFF 

SummerTime 

Just Right Too Warm 

03 04 os 

03 04 os 

03 04 os 

[Z]3 04 o s 

03 04 os 

[Z]3 

03 

04 

04 

os 

Os 

03 04 Os 

0 Always Closed 

0 Always Closed 

0 Always Closed 

0 Always Closed 
 

 

 

 

 

 

 

 

 

 

Performance of the Mini-Split Air Source Heat Pumps 

Name _____________________________ Address __________________________________________________________ 

93 Adams Circle, Devens, MA 01434

Please provide answers and additional comments for the questions 1 through 11 below: 

1. When did you move into your house? Month __________________________________________ 

November

Year _______________________ 

2011

2.	 How comfortable are you in your house? Please select 1 through 5. 

Winter Time Summer Time 

Most Comfortable Least Comfortable Most Comfortable Least Comfortable 

1 2 3 4 5 1 2 3 4 5 

4. What temperature is your thermostat set to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

5.	 Do you adjust the thermostat setpoint at night? Y _______ N _______ 

If yes, what temperature do you set it to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

3. How does your comfort compare to the last place you lived? 

63 78 X

 More Comfortable  About the Same 

63

 Less Comfortable 

78

6.	 Do you adjust the thermostat setpoint when not home? Y _______ N _______ 

X

If yes, what temperature do you set it to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

7.	 Do you use any other heating or cooling devices, such as space heaters, window AC units, portable fans, etc? Y _______ N ___

X ____ 

If yes, what device and in which room? __________________________________________________________________________________ 

Space heater(winter) and fan(summer) in study room.

8.	 Are parts of your house warmer or colder than you want? If yes, please select 1 through 5. 

Winter Time Summer Time

Too Cold Just Right Too Warm Too Cold Just Right Too Warm 

Living Room 1 2 3 4 5 1 2 3 4 5 

Dining Room 1 2 3 4 5 1 2 3 4 5 

Kitchen 1 2 3 4 5 1 2 3 4 5 

Bathroom 1 1 2 3 4 5 1 2 3 4 5 

Bathroom 2 1 2 3 4 5 1 2 3 4 5 

Bedroom 1 1 2 3 4 5 1 2 3 4 5 

Bedroom 2 1 2 3 4 5 1 2 3 4 5 

Bedroom 3 1 2 3 4 5 1 2 3 4 5 

10. How do you operate bedroom doors? 

When in Bedroom  Always Open  Mostly Open  Mostly Closed  Always Closed 

When not in Bedroom  Always Open  Mostly Open  Mostly Closed  Always Closed 

9. Do you open or close windows to improve comfort? 

Summer Time 



 Always Open 



 Mostly Open 



 Mostly Closed 



 Always Closed 

Winter Time Always Open Mostly Open Mostly Closed Always Closed 

11.	 Which of the following most affect your door operation choices? 

 Keeping room warmer/cooler  Room too stuffy/odors building up  Privacy 

72
 

 

 

 

 

 

 

 

 

 

Performance of the Mini-Split Air Source Heat Pumps 

Name	 ____________________ Address __________________________________________________________ 

97 Adams Circle, Devens MA 01434

Please provide answers and additional comments for the questions 1 through 11 below: 

1. When did you move into your house? Month __________________________________________ 

June

Year _______________________ 

2012

2.	 How comfortable are you in your house? Please select 1 through 5. 

Winter Time Summer Time 

Most Comfortable Least Comfortable Most Comfortable Least Comfortable 

1 2 3 4 5 1 2 3 4 5 

4. What temperature is your thermostat set to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

3. How does your comfort compare to the last place you lived? 

75

 More Comfortable  About the Same 

75

 Less Comfortable 

5.	 Do you adjust the thermostat setpoint at night? Y _______ N _______ 

N

If yes, what temperature do you set it to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

6.	 Do you adjust the thermostat setpoint when not home? Y _______ N _______ 

N

If yes, what temperature do you set it to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

7.	 Do you use any other heating or cooling devices, such as space heaters, window AC units, portable fans, etc? Y _______ N ___

N ____ 

If yes, what device and in which room? __________________________________________________________________________________ 

8.	 Are parts of your house warmer or colder than you want? If yes, please select 1 through 5. 

Winter Time Summer Time

Too Cold Just Right Too Warm Too Cold Just Right Too Warm 

Living Room 1 2 3 4 5 1 2 3 4 5 

Dining Room 1 2 3 4 5 1 2 3 4 5 

Kitchen 1 2 3 4 5 1 2 3 4 5 

Bathroom 1 1 2 3 4 5 1 2 3 4 5 

Bathroom 2 1 2 3 4 5 1 2 3 4 5 

Bedroom 1 1 2 3 4 5 1 2 3 4 5 

Bedroom 2 1 2 3 4 5 1 2 3 4 5 

Bedroom 3 1 2 3 4 5 1 2 3 4 5 

10. How do you operate bedroom doors? 

When in Bedroom  Always Open  Mostly Open  Mostly Closed  Always Closed 

When not in Bedroom  Always Open  Mostly Open  Mostly Closed  Always Closed 

9. Do you open or close windows to improve comfort? 

Summer Time 



 Always Open 



 Mostly Open 



 Mostly Closed 



 Always Closed 

Winter Time Always Open Mostly Open Mostly Closed Always Closed 

11.	 Which of the following most affect your door operation choices? 

 Keeping room warmer/cooler  Room too stuffy/odors building up  Privacy 

73
8. 

IQ~ CQIQ 

1. When did you move Into your house? 

2, How comfortable are you In your house? 

Year 2012 

Winter Time Summer Time 

Most Comfortable Least Comfortable Most Comfortable Least Comfortable 

Os 	 Os 

3. How does your comfort compare to the last you lived? IZJ More Comfortable 0 About the Same 0 Less Comfortable 

4, 	 What temperature is your thermostat set 

Y 

to? , Floor (Heating Cooling)~~ Second Floor (Healing/Co ling)!!}_)~ 

5. Do you adjust the thermostat setpoint at __N_x__

If yes, what temperature do you set it to? Floor (Heating/Cooling) __!__ Second Floor (Heating/Cooling}--'--

6. 	 Do you adjus1 the thermostat selpolnl when _ _ N_x__

If yes, whal temperature do you set II to? (Heating/Cooling) __I _ _ Second Floor (Heallng/Cooling) ____)__ 

7, 	 Do you usEI any other heating or cooling such as space heaters, window AC units, port<~ble fans, etc? Y _x__ N__ 

If yes, vJha1 device and in which room? _P_+-b_le...;f_a_ns......;..to...,m---ov_e ___ th_e_a_ir_t.....;.o_w_h_e_re __ w_e_n_e....;e_d_it.:.:..____________________

want? if yes, please select 1 through 5. 

Summer Time 

Too Warm Too Cold Just Riobt TQS!W5!rm 

Living Room 01 0 2 03 04 05 01 Oz 03 04 05 

Dicing Room 01 02 (l}3 04 os 0 1 0 2 (ZJ3 04 os 

l$ilcben 01 0 2 [2]3 04 05 01 02 [Z]3 04 05 

Bathroom 1 01 02 03 04 os 0 1 0 2 03 0 4 os 

Bathroom 2 01 02 [Z]3 04 Ds 01 02 IZJ 3 04 O s 

Bedroom l 0 1 0 2 [Z]3 04 05 0 1 02 03 [{]4 os 

Bedroom 2 01 02 03 04 O s 01 0 2 03 [{]4 Os 

Bedroom_3 01 02 03 04 Ds 0 1 0 2 03 04 Ds 

9. Do you open or close windows to improve 

summer Iitne 0 Always Opsn 0 Mostly Open 0 Mostly Closed 0 Always Closed 

WinterTime 0 Always Open D Mostly Open 0 Mostly Closed 0 Always Closed 

10. Howdo you operate bedroom doors? 

When in Bedroom O Always Open D Mostly Open 0 Mostly Closed IZJ Always Closed 

When noUn..Sectr:oom O Always Open O Mostly Open 0 Mostly Closed [Z] Always Closed 

11. Which of the following most affect your door c.'loices? 

0 Keeping room warmer/cooler D Room stuffy/odors building up 0 PrJV()Cy 

8374
 

 

 

 

 

 

 

 

 

 

Performance of the Mini-Split Air Source Heat Pumps 

Address __________________________________________________________ 

Please provide answers and additional comments for the questions 1 through 11 below: 

1. When did you move into your house? Month __________________________________________ Year _______________________ 

2.	 How comfortable are you in your house? Please select 1 through 5. 

Winter Time Summer Time 

Most Comfortable Least Comfortable Most Comfortable Least Comfortable 

1 2 3 4 5 1 2 3 4 5 

3. How does your comfort compare to the last place you lived?  More Comfortable  About the Same  Less Comfortable 

4. What temperature is your thermostat set to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

5.	 Do you adjust the thermostat setpoint at night? Y _______ N _______ 

If yes, what temperature do you set it to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

6.	 Do you adjust the thermostat setpoint when not home? Y _______ N _______ 

If yes, what temperature do you set it to? First Floor (Heating/Cooling) _____/_____ Second Floor (Heating/Cooling) _____/_____ 

7.	 Do you use any other heating or cooling devices, such as space heaters, window AC units, portable fans, etc? Y _______ N _______ 

If yes, what device and in which room? __________________________________________________________________________________ 

8. Are parts of your house warmer or colder than you want? If yes, please select 1 through 5. 

Winter Time Summer Time

Too Cold Just Right Too Warm Too Cold Just Right Too Warm 

Living Room 1 2 3 4 5 1 2 3 4 5 

Dining Room 1 2 3 4 5 1 2 3 4 5 

Kitchen 1 2 3 4 5 1 2 3 4 5 

Bathroom 1 1 2 3 4 5 1 2 3 4 5 

Bathroom 2 1 2 3 4 5 1 2 3 4 5 

Bedroom 1 1 2 3 4 5 1 2 3 4 5 

Bedroom 2 1 2 3 4 5 1 2 3 4 5 

Bedroom 3 1 2 3 4 5 1 2 3 4 5 

9. Do you open or close windows to improve comfort? 

Summer Time  Always Open  Mostly Open  Mostly Closed  Always Closed 

Winter Time  Always Open  Mostly Open  Mostly Closed  Always Closed 

10. How do you operate bedroom doors? 

When in Bedroom  Always Open  Mostly Open  Mostly Closed  Always Closed 

When not in Bedroom  Always Open  Mostly Open  Mostly Closed  Always Closed 

11. Which of the following most affect your door operation choices? 

 Keeping room warmer/cooler  Room too stuffy/odors building up  Privacy 

75
davn t~ ,/a;Ls., 

/Jfct/1 C(j 

o r c-ur 

u~ OVUllif ..ro• Energy Efftctency & 

lRANSFORMAl!ONS" ENERGY Renewable Energy 

lcto En«gy Hornet 

Address c13 G~--"7/:1/ 4/)i_ 


Please provide answers and additional comments for the questions 1 through 11 below: 

1. When did you move into your house? 	 Month __ :j_~:::....=...u,=-~.I.........f /er__________ Year d(()/Q


2. 	 How comfortable are you in your house? Please select 1througY. 

WinterTime SummerTime 

Most Comfortable 	 Least Comfortable Most Comfortable Least Comfortable 

01 02 w 04 os [3'1 02 03 04 os 

3. 	 How does your comfort compare to the last place you lived? 0'More Comfortable 0 About the Same 0 Less Comfortable 

4. What temperature is your thermostat set to? First Floor (HeatingfCooling) "'6; 70 Second Floor (HeatingfCooling) ll:>Or 7 :,;­

5. Do you adjust the thermostat setpoint at night? Y ~ 

~ 

N__ 	 AI

6. 	

If 

Do 

yes, 

you 

what 

adjust 

temperature 

the thermostat 

do you 

setpoint 

set it to? 

when 

First 

not 

Floor 

home? 

(HeatingfCooling) 

Y N 

fcL)_!?jf_ 

dJ 

Second Floor (HeatingfCooling) 

'S'tN/!C 

we.' r__ 

75 .c-1' ._·?+{­

If yes, what temperature do you set it to? First Floor (HeatingfCooling) loOr o#- Second Floor (HeatingfCooling) (c(.""l 1 '-.,.({l 

7. 	 Do you use any other heating or cooling devices, such as space heaters, window AC units, portable fans, etc? Y v-- N 

tl_ · · · I If yes, what device and in which room? t"tl/1 durt	I'! r Itor I /1 /Jed /~/1/...S 01'1 I1 

J J 

8. 	 Are parts of your house warmer or colder than you want? If yes, please select 1through 5. 

WinterTime 	 SummerTime 

Too Cold Just Right Too Warm Too Cold Just Right ToQ Warm 

Living Room 01 02 03 04 05 01 02 ~ 04 os 

Dining Room 01 02 03 04 os 01 02 B3 04 05 

Kitchen 01 [2['2 03 04 Os 01 02 [03 04 05 

Bathroom 1 01 Ef2 03 04 05 01 02 03 04 05 1 (.1~ Bathroom 2 01 02 03 04 05 01 02 ~3 04 05 

Bedroom 1 01 02 @3 04 Os 01 02 [2}'3 04 05 

Bedroom 2 01 02 E:j3 04 Os 01 02 03 04 Os 

Bedroom 3 01 02 r13 04 05 01 02 ~ 04 Os 

9. Do you open or close windows to improve comfort? 

Summer Time 0 Always Open ~stlyOpen 0 Mostly Closed 0 Always Closed 

WinterTime 0 Always Open 0 Mostly Open 0 Mostly Closed ~iways Closed 

10. How do you operate bedroom doors? 

When in Bedroom 0 Always Open ~stlyOpen 0 Mostly Closed 0 Always Closed 

When not in Bedroom ~ways Open (S1"Mostly Open O Mostly Closed 0 Always Closed 

11. Which of the following most affect your door operation choices? 

O Keeping room warmer/cooler O Room too stuffyfodors building up l£fPrivacy 

76
U ~ CHAllltll"l 0< Energy EffJCiency &

ENERGY Renewable Energy 

Zero EMrgy H<>tnn 

Address S b~ lN1 ~1)1\f.tJd ,('nA ()N~ ~ Please p s for the questions 1 thro-Jgh 11 below: 

1. 	 When did you move into your house? Month SfL II k Year --':Jr....&_,Oio.,.L...!)'--f'------

2. 	 How comfortable are you in your house? Please select 1through J 

Winter Time Summer Time 

Most Comfortable 	 / Least Comfortable Most Comfortable , / Least Comfortable 

01 02 03 [}(4 05 01 02 11r3 04 05 

3. How does your oomfort compare to too last place you !Ned? Comfr ,• 0 About the Same 0 S2r'1ertable 

4. What temperature is your thermostat set to? First Floor (Heating/Cooling 10 Second Floor (Heating/Cooling) t.k:J}. 

5. 	 Do you adjust the thermostat setpoint at night? Y 2.__ N---,;,'"\ fX 

If yes, what temperature do you set it to? First Floor (Heatin!l!CJ>oling) Jlj_t]Q Second Floor (Heating/Cooling) f:Ll]_Q 

6. 	 Do you adjust the thermostat setpoint when not home? Y _'/-.__ N r/ 1J 

If yes, what temperature do you set it to? First Floor (Heating/Cooling) ~_j_J Second Floor (Heating Cooling) -­ / 

7. Do you use any other heating or cooling devices, such 	 . as .space heaters, window ~ units, portable fans, etc? Y N__ \ 

If yes, what device and in which room? .\ 

8. Are parts of your house warmer or colder than you want? If yes, please select 1through 5. 

WinterTime 	 SummerTime 

Too Cold 	 Too Warm Too Cold Just Right Too Warm 

Living Room 01 02 04 05 01 02 0(3 04 05 

Dining Room 01 02 w 4 05 01 02 w 04 05 

r 

0 

Kitchen 01 02 S3 04 05 01 02 ISf3 04 05 

Bathroom 1 01 02 03 l¥]4 05 01 02 [$:13 04 05 

Bathroom 2 01 02 03 05 01 02 t;;}3 04 05 

Bedroom 1 01 02 03 ~ 05 01 02 (JQ3 04 05 

Bedroom 2 01 02 03 ~4 05 01 02 ~3 04 05 

Bedroom 3 01 02 03 Q4 	 05 01 02 ci3 04 05

9. Do you open or close windows to improve comfort? 

Summer Time 0 Always Open th'Mostly Open 0 Mostly Closed 0 Always Closed 

WinterTime 0 Always Open 0Mostly0pen 0 Mostly Closed _NAtways Closed 

10. How do you operate bedroom doors? 

When in Bedroom glwaysOpen D Mostly Open O Mostly Closed ,.QJ"Atways Closed 

When not in Bedroom lways Open 0Mostly0pen D Mostly Closed O Always Closed 

11. Which of the following most affect your door operation choices? 

D Keeping room warmer/cooler D Room too stuffy/odors building up ~Privacy 

77
U~ DIPU!Wt ..IOO Energy Eff•c•ency &

ENERGY Renewable Energy 

Performance of the Mini-Split Air Source Heat Pumps 

Name _	 _Address

Please provide answers and additional comments for the questions 1 through 11 below: 

1. When did you move into your house? Month _ __;:?:::....__-_/_	 - _a_oi_Y_____ Year ___ "d_o_JI ___

2. How comfortable are you in your house? Please select 1 through 5. 

WinterTime 	 SummerTime 

Least Comfortable Most Comfortable Least Comfortable 

~02 03 04 05 

3. How does your comfort compare to the last place you lived? O More Comfortable if.ooutthe Same 0 Less Comfortable 

4. What temperature is your thermostat set to? First Floor (Heating/Cooling) 0&-I /0 Second Floor (Heating/Cooling) nhJ t!tn:_ 

5. 	 Do you adjust the thermostat setpoint at night? Y __N ./ 

If yes, what temperature do you set it to? First Floor (Heating/Cooling) __/__ Second Floor (Heating/Cooling) __/__ 

6. 	 Do you adjust the thermostat setpoint when not home? Y __N V 

If yes, what temperature do you set it to? First Floor (Heating/Cooling) __!__ Second Floor (Heating/Cooling) __/__ 

7. 	 Do you use any other heating or cooling devices, such as space heaters, window AC units, portable fans, etc? Y __N ~ 

If yes, what device and in which room? 

8. Are parts of your house warmer or colder than you want? If yes, please select 1through 5. 

WinterTime SummerTime 

Too Cold J~ght Too Warm Too Cold ~ght Too Warm

Living Room 01 02 04 05 01 02 04 05 

Dining Room 01 02 04 05 01 02 @( 04 os 

Kitchen 01 02 Gs 04 05 01 ~~ 04 os

Bathroom 1 01 02 w 04 05 01 2 03 04 os 

Bathroom 2 01 02 ~ 04 05 01 02 [13 04 05 

Bedroom 1 01 02 ~ 04 05 01 [3{ 03 04 05 

Bedroom 2 01 02 ~ 04 05 01 02 @' 04 05 

Bedroom 3 01 02 03 04 05 01 02 [3'3 04 05 

9. Do you open or close windows to improve comfort? 

SummerTime 0 Always Open 0 Mostly Open ~tty Closed 0 Always Closed 

WinterTime 0 Always Open 0 Mostly Open l]J-MOStiy Closed 0 Always Closed 

10. How do you operate bedroom doors? 

When in Bedroom O Always Open gfo~ 0 Mostly Closed 0 Always Closed 

When not in Bedroom O Always Open ' Mostly Open 0 Mostly Closed 0 Always Closed 

11. Which of the following most affect your door operation choices? 

O Keeping room warmer/cooler 0 Room too stuffy/odors building up SPrivacy 

78
79

Appendix B: Model Home (Lot 13) Home Energy Rating 

Certificate
/H~·. &~A'~ "'·f'f River Valley Way 

Easthampton , MA 01027 

5 Stars Plus 

Verified Condition 

Conditioned Area: 1795 sq. ft. 

Conditioned Volume: 14323 cubic t. 

Bedrooms: 3 

Mechanical Systems Features 

Registry ID: 

Rating Number: 

Certified Energy Rater: 

Rating Date: 3/14/11 

Rating Ordered For: 

Estimated Annual Energy Cost 

Verified Condition 

Use MMBtu Cost 

Heating 9.6 $504 

1.4 $72 

14.2 $201 

18.9 $996 

-32.0 $-1686 

$0 

$88 

· home meets or exceeds the minimum 

criteria for all of the following: 

EPA ENERGY STAR Version 2 Home 

2009 International Energy Conservation Code 

Percent 

576% 

82% 

230% 

1137% 

-1925% 

0% 

100% 

(Jj Air-source heat pump: Electric, Htg: 10.5 HSPF. Clg: 23.0 SEER. 

Air-source heat pump: Electric, Htg: 10.5 HSPF. Clg: 23.0 SEER. 

Water Heating : Instant water heater, Natural gas, 0.92 EF, 0.0 Gal. 

Duct Leakage to Outside: 0.00 CFM. 

Ventilation System: Supply Only: 120 cfm , 21 .1 watts. 

Programmable Thermostat: Heating : Yes Cooling : Yes 

Building Shell Features 

Ceiling Flat: R-89, R-24 Exposed Floor: R-42 

Vaulted Ceiling : R-58 Window Type : U:0.20, SHGC :0.26 

Above Grade Walls: U-0.021 Infiltration: 

Foundation Walls: NA Rate : Htg : 1.52 Clg : 1.52 ACH50 

Slab: R-20.0 Edge, R-30.0 Under Method : Blower door test 

Lights and Appliance Features 

Percent Interior Lighting: 100.00 Range/Oven Fuel : Electric Company 

Percent Garage Lighting: 0.00 Clothes Dryer Fuel : Electric Address 

Refrigerator (kWh/yr): 416.00 Clothes Dryer EF: 2.67 City, State, Zip 

Dishwasher Energy Factor: 0.77 Ceiling Fan (cfm/Watt): 0.00 Phone# 

The Home Energy Rating Standard Disclosure lor this home is available from the rating provider. Fax # 

REM/Rate- Residential Energy Analysis and Rating Software v13.0 

This information does not constitute any warranty of energy cost or savings. 

© 1985-2012 Architectural Energy Corporation, Boulder, Colorado. 

80
DOE/GO-102013-3902 ▪ September 2013

Printed with a renewable-source ink on paper containing at 

least 50% wastepaper, including 10% post-consumer waste.

buildingamerica.gov