Performance Verification of 

Production-Scalable EnergyEfficient Solutions

Winchester/Camberley Homes

Mixed-Humid Climate

D. Mallay and J. Wiehagen

Partnership for Home Innovation

July 2014
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ii

Performance Verification of Production-Scalable 

Energy-Efficient Solutions

Winchester/Camberley Homes Mixed-Humid Climate

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:

D. Mallay and J. Wiehagen

Home Innovation Research Labs

Partnership for Home Innovation

400 Prince George’s Blvd.

Upper Marlboro, MD 20774

NREL Technical Monitor: Stacey Rothgeb

Prepared under Subcontract No. KNDJ-0-40335-03

July 2014
iii

Acknowledgments

Home Innovation Research Labs acknowledges the support of the Building America Program in 

providing the funding to develop and test high performance homes. A special acknowledgement is 

recognized for Winchester Homes, Inc., their trade partners, and in particular Randy Melvin and 

Ed Boisseau who provided continual support for the project from the design stage through 

construction and testing.
v

Contents

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

List of Tables .............................................................................................................................................. vi

Definitions.................................................................................................................................................. vii

Executive Summary................................................................................................................................. viii

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

1.1 Overview ...................................................................................................................................... 1

1.2 Background................................................................................................................................... 1

1.3 Test House Design and Construction Goals................................................................................. 2

2 Test House Energy Features............................................................................................................... 4

2.1 Design Process and Energy Simulations ...................................................................................... 4

2.2 Construction and Energy Features................................................................................................ 4

2.3 Strategies To Achieve New Construction Test House Goals....................................................... 4

3 High Performance Solution Package ................................................................................................. 6

4 Verification Testing .............................................................................................................................. 8

4.1 Test Plan ....................................................................................................................................... 8

4.2 Infiltration Testing...................................................................................................................... 10

4.3 Heating and Cooling System Design and Duct Leakage Testing............................................... 11

4.4 Conditioned Air Distribution Testing......................................................................................... 12

4.5 Ventilation and Exhaust Fan Testing.......................................................................................... 15

4.6 Wall Cavity Moisture Performance ............................................................................................ 16

4.6.1 Sheathing Condensation Potential .................................................................................... 16

4.6.2 Interior Vapor Retarder..................................................................................................... 19

4.6.3 Preliminary Simulation Analysis...................................................................................... 20

4.6.4 Preliminary Measured Wall Cavity Moisture Performance.............................................. 21

4.6.5 Model Home Measured Energy Use................................................................................. 24

5 Energy Value....................................................................................................................................... 26

5.1 Initial Cost Analysis ................................................................................................................... 26

5.2 Future Cost Considerations ........................................................................................................ 26

6 Gaps and Lessons Learned............................................................................................................... 28

6.1 Overview .................................................................................................................................... 28

6.2 Wall Framing.............................................................................................................................. 28

6.3 Floor Framing............................................................................................................................. 28

6.4 Air Sealing.................................................................................................................................. 29

6.5 Heating, Ventilation, and Air Conditioning ............................................................................... 29

6.6 Plumbing..................................................................................................................................... 30

6.7 Quality Assurance....................................................................................................................... 30

7 Summary ............................................................................................................................................. 31

7.1 Conclusions ................................................................................................................................ 31

7.1.1 Overall Constructability and Potential for Continued Use of the High Performance 

Design ............................................................................................................................... 31

7.1.2 Wall Design To Meet Various Performance Levels......................................................... 31

7.1.3 Heating and Cooling Installation and Performance .......................................................... 31

7.1.4 Airtightness and Ventilation ............................................................................................. 32

7.1.5 Durability.......................................................................................................................... 32

7.1.6 System Testing Verification and Commissioning ............................................................ 32

7.2 Next Steps................................................................................................................................... 33

References................................................................................................................................................. 34

Appendix A: Energy Simulations ............................................................................................................ 35

Appendix B: Wall Cavity Moisture Sensors ........................................................................................... 38
vi

List of Figures

Figure 1. Winchester/Camberley NCTH .................................................................................................... 1

Figure 2. Indoor temperature profile during an extreme cooling period............................................. 14

Figure 3. Indoor temperature profile for 16-month monitoring period................................................ 15

Figure 4. Graphical description of sheathing temperature calculation............................................... 17

Figure 5. Theoretical condensation potential at interior surface of sheathing .................................. 18

Figure 6. Heating season measured condensation potential in test home ........................................ 19

Figure 7. WUFI simulation results for an R-23 wall in climate zone 4 ................................................. 21

Figure 8. MC of OSB sheathing in the climate zone 4 NCTH................................................................ 22

Figure 9. Temperature at the OSB sheathing in the climate zone 4 NCTH ......................................... 23

Figure 10. RH at the OSB sheathing in the NCTH (climate zone 4)...................................................... 24

Figure 11. Three additional houses built using NCTH features ........................................................... 31

Figure 12. Completed NCTH..................................................................................................................... 33

Figure 13. BEopt simulation results........................................................................................................ 35

Figure 14. Source energy savings for energy efficient design compared to the BA Benchmark .... 36

Figure 15. Annualized utility bill comparison for BA Benchmark and energy-efficient design........ 36

Figure 16. Source energy use for BA Benchmark and energy-efficient design................................. 37

Figure 17. Annual utility bills ................................................................................................................... 37

Figure 18. Omnisense S-900-1 sensor.................................................................................................... 38

Figure 19. Installed test wall moisture sensors ..................................................................................... 38

Figure 20. MC calibration curves............................................................................................................. 39

Unless otherwise noted, all figures were created by Home Innovation Research Labs.

List of Tables

Table 1. High Performance Home Design Strategies .............................................................................. 5

Table 2. Thermal Envelope Improvements............................................................................................... 6

Table 3. Mechanical System Improvements............................................................................................. 7

Table 4. Research Measurements and Equipment.................................................................................. 9

Table 5. Characterization Testing: House Leakage............................................................................... 10

Table 6. Characterization Testing: Duct Leakage.................................................................................. 12

Table 7. Example Measured Temperature by Level............................................................................... 13

Table 8. Average Temperatures for 3-Day Period, July 5–July 7, 2012 ............................................... 14

Table 9. Exhaust Fan Ratings and Operation......................................................................................... 16

Table 10. Summary of Gypsum/Paint Layer Permeance Tests ............................................................ 20

Table 11. Summary of Total Electric and HVAC System Energy for a Monitoring Period ................ 25

Unless otherwise noted, all tables were created by Home Innovation Research Labs.
vii

Definitions

ACH50 House Air Changes per Hour At 50 Pascals Pressure

AFUE

AGW

Annual Fuel Utilization Efficiency

Above Grade Wall

BA Building America

CFA Conditioned Floor Area

CFM25 Cubic Feet per Minute at 25 Pascals Pressure

CFM50 Cubic Feet per Minute at 50 Pascals Pressure

DPT Dew Point Temperature

ECM Electronically Commutated Motor

MC Moisture Content (of either wood framing or wood sheathing)

NCTH New Construction Test House

OSB Oriented Strand Board

RH Relative Humidity

SEER Seasonal Energy Efficiency Ratio

T Temperature

WHI Winchester Homes, Inc. 

WUFI Wärme und Feuchte instationär
viii

Executive Summary

Winchester/Camberley Homes collaborated with the Building America program and its Partnership

for Home Innovation to develop a new set of high performance home designs that could be 

applicable on a production scale. The new home designs are to be constructed in the mixed-humid 

climate zone 4 and could eventually apply to all of the builder’s home designs to meet or exceed 

future energy codes or performance-based programs. However, the builder recognized that the 

combination of new wall framing designs and materials, higher levels of insulation in the wall 

cavity, and more detailed air sealing to achieve lower infiltration rates changes the moisture 

characteristics of the wall system. In order to ensure long-term durability and repeatable successful 

implementation with few callbacks, this report demonstrates through measured data that the wall 

system functions as a dynamic system, responding to changing interior and outdoor environmental 

conditions within recognized limits of the materials that make up the wall system. A similar 

investigation was made with respect to the complete redesign of the heating, cooling, air 

distribution, and ventilation systems intended to optimize the equipment size and configuration to 

significantly improve efficiency while maintaining indoor comfort. Recognizing the need to 

demonstrate the benefits of these efficiency features, the builder offered a new house model to 

serve as a test case to develop framing designs, evaluate material selections and installation 

requirements, changes to work scopes and contractor learning curves, as well as to compare 

theoretical performance characteristics with measured results. 

In the production environment, the impact of the home redesign is significant both in cost and time. 

As interest in energy savings and environmental performance increases, and as building code 

requirements become more stringent, these new demands are now leading to large changes in 

envelope design, material selections, and performance metrics. When in previous enhancements 

the performance of the home could be increased through higher efficiency materials or systems, 

new building requirements are leading to a revamping of the entire building envelope and the space 

conditioning system. The evolving requirements are of such significance that design changes now 

must consider much more than a static insulation level or the rated efficiency of equipment, and 

begin to combine material properties with installation specifications, long-term durability 

assessments, and energy consumption estimates. This project is unique in that it lays the 

groundwork for higher performing wall designs that can be more easily modified to achieve a 

further increase in thermal performance levels without major redesign efforts. In addition,

performance results lend confidence in achieving stringent energy efficiency goals while 

maintaining durability. This project also demonstrates a reasonable and achievable heating, 

ventilation, and air conditioning design, installation, and commissioning that satisfies enhanced 

performance goals, including occupants’ comfort, and can be used in high performance house 

designs by the production builder.

Highlighted findings and lessons learned from the project include:

• Clear a pathway to the successful integration of an advanced wall design using 2 × 6

lumber, standardized rim header1 layout, optimized framing members,

2 offset interior 

 1 The rim header uses an engineered rim board design coupled with floor framing support specifications over 

openings to provide the header support. See NAHBRC 2012 for a detailed description of rim header testing. A 

methodology to prescriptively implement rim headers in the building code is underway.
ix

walls,

3 and wood structural sheathing by the architect, panel fabricator, and trade 

contractor.

• The advanced wall design exceeds minimum building code requirements for climate 

zones 1–5 both on a performance and a prescriptive basis and can be more easily 

modified for other higher performance solutions without large redesign costs.

• The durability of the wall cavity design in terms of the measured moisture characteristics 

in the cavity shows cyclic moisture content of 6%–18% with all wall orientations 

showing less than 10% moisture content in the summer months.

• The four floor level temperature gradient during a hot summer period showed modest 

temperature differences, less than 3°F between the main living areas of the house, and 

about 6°F when including the basement.

• The design and installation of the exhaust and ventilation fan systems require further 

refinement to consistently achieve rated flow rates.

• More coordination between the framing and heating, ventilation, and air conditioning 

trade contractors is necessary to decrease the complexity of installing the duct system 

with an engineered floor system.

This report outlines an advanced wall system design and installation, air sealing details, and the 

design and installation of the space conditioning and ventilation systems for a high performance 

home. The measured performance from tests on these systems indicates that the designs and 

installation methods are sufficiently mature to be incorporated by production builders in new home 

designs. The lessons learned from the test house show areas where particular attention should be 

made to avoid performance problems or the need for call-back repairs. The test house construction 

and test results can be used by builders as a basis to revise current home designs for a high 

performance home option in climate zones 3, 4, and 5. Researchers may use this report to add to 

the growing base of information on wall system moisture performance and for improvement of 

design tools to assess moisture characteristics in advanced wall systems.

 2 Optimized framing includes 24-in. o.c. studs, 2-stud corners, and reduced use of cripple framing. 3 Offset interior walls is a design methodology to move interior walls perpendicular to exterior walls 1 in. from the 

exterior walls providing space for a continuous sheet of gypsum board on the exterior wall.
1

1 Introduction

1.1 Overview

With the support of the U.S. Department of Energy Building America (BA) program, as part of the 

Partnership for Home Innovation, Home Innovation Research Labs (Home Innovation) partnered 

with production builder Winchester Homes, Inc. (WHI) and its Camberley Homes division to build 

a new construction test house (NCTH). This single-family, detached house is located in the mixedhumid climate (U.S. Department of Energy climate zone 4) of Silver Spring, Maryland. The threestory, Victorian-style model home was completed in 2011. 

The goals shared by the builder and the BA program for the test house were to design, construct,

and verify/evaluate the advanced high performance features of a production home design in the 

mixed-humid climate. 

This report details and summarizes the design features and the construction obstacles and provides 

verification testing results performed since the home’s completion. Testing results are used to 

evaluate technologies and system designs where sufficient data are available. The testing summary 

covers wall moisture characteristics, heating, ventilation, and air conditioning (HVAC) system 

performance characteristics, ventilation system operation, and additional infiltration testing.

Whole-house energy usage and heating and cooling energy data are compared to simulation 

estimates. 

1.2 Background 

The NCTH, pictured in Figure 1, was built in the Poplar Run subdivision in Montgomery County, 

Maryland, a suburb of Washington, D.C. Poplar Run will eventually include 700 homes. After 

gauging consumer acceptance of the advanced energy features in the test home, the builder will 

consider incorporating similar advanced energy features in some of the current designed 600 

homes as well as use the developed approaches as a design methodology for new home designs.

Figure 1. Winchester/Camberley NCTH
2

The three-story design has 3,228 ft2 of conditioned floor area (CFA) above grade, including a 605-

ft2 finished third floor with a sitting room, full bath, and bedroom. A finished basement brings the

total finished area to 4,441 ft2. Ceilings are 9 ft high for the first floor and basement, 8 ft high on 

the second floor, and 8 ft or sloped on the third floor. Above grade walls (AGWs) are wood-frame 

construction; the basement foundation is poured concrete and mostly below grade. All attic areas 

are vented. A unique design feature of this home is the octagonal, three-story turret containing an 

open stairwell that connects the basement to the second floor. Access to the third floor is by a 

separate stairway. The garage is detached from the house.

Since completion, the house has been open as a model for the development. Energy loads for the 

model home include multiple computers, digital TV displays operating continuously, lamps 

operating when sales staff are present, and space conditioning. The garage is configured as a field 

office for construction and sales and is outfitted with a heating and cooling system, computers, and 

other office equipment.

1.3 Test House Design and Construction Goals

The original performance goals for this house,

4 developed jointly by the builder and Home 

Innovation, was to improve energy efficiency by 30% over the current BA Benchmark by 

developing and implementing optimized framing, air sealing, insulation, and space conditioning 

system designs that could be cost-effectively constructed on a production basis using quality 

management practices. This performance goal aligns well with the goals of the BA program.5

Specific goals that the NCTH established during the planning phase include:

• Develop and implement a durable design that improves energy efficiency by at least 

30% over a comparable house that meets the 2009 International Energy Conservation 

Code (IECC 2009).

• Create a tight thermal boundary.

• Install insulation at levels that will be in accordance with future anticipated consumer 

demand and building code requirements.

• Develop an envelope design that can be adapted to higher insulation levels without 

costly architectural or structural redesign efforts.

• Optimize the wall design to improve thermal performance and minimize the potential 

for moisture accumulation inside the wall cavity while controlling incremental cost.

• Design the HVAC system to be located entirely in conditioned space to significantly 

reduce energy losses to unconditioned space, reduce duct lengths, and meet the 

home’s heating and cooling needs with a single HVAC system.

• Design the HVAC system to ensure occupant comfort in terms of temperature 

consistency, throughout the four-level home.

• Develop a cost-effective, integrated design that extracts construction efficiencies 

across building systems, such as reduced labor time for numerous trades when 

 4 Final Technical Report: Winchester/Camberley Homes NCTH – Design, Construction, & Short-term Testing, 

NAHB Research Center for the DOE Building America Program, March 2012. 5 See DOE 2011 
3

working with optimized framing systems, and which could be constructed on a 

production basis using quality management practices.

• Develop a test and monitoring plan to evaluate energy use, heating and cooling air 

distribution, and wall moisture performance.

• Earn Silver Certification under the National Green Building Standard (NGBS 2008).
4

2 Test House Energy Features

2.1 Design Process and Energy Simulations

WHI is committed to building a line of high performance homes that exceed current energy code 

requirements and look toward meeting future more stringent code requirements. Cost efficiencies 

in meeting such goals were achieved by developing a new product line that integrated the energy 

features rather than to modify an existing model. The team completely redesigned the NCTH 

thermal envelope from standard specifications and added a set of newly developed high 

performance construction features. The final energy efficiency solution package represented 

months of collaborative development among WHI and Home Innovation staff, trade contractor 

professionals, manufacturers, and product suppliers. The design process involved technical design 

input, laboratory testing, energy modeling and optimization, cost comparisons and other practical 

factors by team members. Energy savings were simulated using Building Energy OptimizationTM 

(BEoptTM) v1.0.1. Through BEopt software optimization and other analyses, a set of options that 

provided the highest predicted energy savings for the lowest investment costs was determined. 

These energy simulations, detailed in Appendix A, indicate that the BA energy savings goal was 

met based on modeling outputs.

2.2 Construction and Energy Features

WHI completed an extensive in-house cost analysis to select high performance home features. The 

cost analysis, along with the BEopt simulations and practical input based on the combined 

experience of the project team, allowed the builder to choose systems—based on wide-ranging 

factors including occupant comfort, constructability, durability, reliability, energy performance, 

and synergistic cost containment benefits such as reduced material and labor costs—that would 

perform as an integrated system.

The performance and cost analysis framework generally focused on meeting anticipated energy 

savings requirements in a manner that limited incremental cost and provided reliable and tangible 

results for the builder and homebuyer. 

Constructability was a very important factor in the builder’s decision-making process. Selected 

technologies, construction methods, and performance testing are all aspects of acute attention since 

the trade contractors must be able to incorporate any design changes in a manner that produces 

high quality outcomes and enhanced consumer satisfaction while minimizing code compliance 

failures and risks from negative long-term performance issues.

Based on the lessons learned through the NCTH design and installation process, the builder is 

planning incremental changes to existing house designs to incorporate high performance features. 

However, redesigning existing plans is often more challenging than working from a clean slate. 

The complexity of redesign extends to sales staff and homebuyers, who may not understand the 

difference between the layout of the model home and the redesigned model, particularly when 

interior walls are significantly changed.

2.3 Strategies To Achieve New Construction Test House Goals

During the design process, the project team identified design strategies that would meet the project 

goals of increased performance, constructability, durability and reliability. A summary of the 

project’s guiding design strategies is outlined in Table 1.
5

Table 1. High Performance Home Design Strategies

Design Strategy Solution Approach

Increased AGW Insulation • Enhanced and optimized framing to increase thermal 

performance

Improved Air Sealing • Detailed strategy balanced with cost and consistency of 

installation

Improved HVAC System 

Efficiency

• Reduced the number of HVAC systems from two to one

• Redesigned floor plan, framing, and ducts to locate entire 

system in conditioned space for significant energy savings

• Improved equipment operating efficiencies

• Improved ventilation, filtration, and occupant comfort

Quality Assurance and 

Control

• Planning stage design reviews included practical input 

from WHI, vendors, and trade partners

• Developed construction details and specifications

• Established construction monitoring points (reviews, 

inspections, and tests)

Repeatable Design • Specified features that optimized performance, cost, and 

practical implementation

Adherence to the design strategies provided both the guidance for technology and system selection 

as well as a metric for outcome evaluation.
6

3 High Performance Solution Package

Design solutions selected for the NCTH are summarized in Table 2 and Table 3. Major changes to 

improve the energy performance were centered on the envelope and HVAC systems. A more 

complete detail of the design changes is documented in two research reports.6,7

Table 2. Thermal Envelope Improvements

Feature Standard Practice NCTH

Foundation • R-10 walls • R-13 walls

Walls

• 2 × 4 frame, 16 in. on center

• R-13 batt insulation

• 2 × 6 frame, 24-in. on center

• Rim headers (DeRenzis et al. 2012)

• Reduced framing

• R-24 blown fiberglass insulation

• Offset interior walls8

Air Sealing

• Bottom plates sealed at deck

• Penetrations sealed

• Window rough openings 

sealed

• Panel joints and corners 

caulked

• Same as standard practice plus:

• Sealed frame at all critical areas using 

spray applied, elastomeric sealant9

• Airtight drywall approach10

• House wrap installed as air barrier

Windows • U-0.35, solar heat gain 

coefficient 0.35

• Low-e, U-0.31, solar heat gain 

coefficient 0.28

Doors • N/A • U-0.35, solar heat gain coefficient 0.36

Roof/Attic 

(Vented)

• Standard truss, 1-ft overhang

• R-38 blown fiberglass

• Ice and water shield at eaves 

and valleys

• Drip edges at eaves and rakes

• Raised heel truss, 2-ft overhang

• R-49 blown fiberglass insulation, full 

depth at eaves and sloped ceilings

• Ice and water shield at eaves and valleys

• Drip edges at eaves and rakes

 6 Final Technical Report: High-R Walls for New Construction Structural Performance Integrated Rim Header 

Testing, NAHB Research Center for the DOE Building America Program, April 2012. 7 Final Technical Report: Winchester/Camberley Homes NCTH – Design, Construction, and Short-term Testing, 

NAHB Research Center for the DOE Building America Program, March 2012. 8 Offset interior walls allow for a layer of continuous gypsum board to be used on exterior walls even where interior 

walls intersect. 9 One method for air sealing of the exterior wall framing is to apply an air sealing material to the front edges of top 

and bottom plates, to picture frame the cavity, and around openings. The material is generally non-expanding and 

offers no direct R-value to the wall. 10 The airtight drywall approach is an air sealing methodology to reduce air leakage from the interior of the house 

through separations in the drywall where it is attached to the framing members. 
7

Table 3. Mechanical System Improvements

System Standard Practice NCTH

Heating

(2) 80% AFUEa natural gas furnaces 

(one in vented attic and one in 

basement)

(1) 92.5% AFUE natural gas furnace 

with 2-stage gas valve and ECMb air 

drive, installed in basement

Cooling (2) 13 SEERc systems (1) 14-15 SEER system

Thermostat Programmable

Programmable with integral humidistat 

and controls to run the cooling system 

in dehumidification mode

HVAC Duct

(1) Flexible, insulated duct system 

in vented attic and (1) metal duct 

system in basement

(1) Single system 100% in conditioned 

space with supply trunk balancing 

dampers. Simplified central return with 

one grille per level and bedroom 

transfer grilles

Filtration Standard 1-in. filter (MERVd 1-4) High efficiency pleated filter (MERV 

10)

Mechanical

Ventilation

(1) Bath exhaust fan with 

programmable control

Supply type central fan integrated 

(ducted to the return) with damper and 

control11

Plumbing

65-gallon natural gas water heater, 

EFe 0.57; CPVCf branch and tee 

piping

50-gallon, power vent, natural gas 

water heater, EF 0.74 (est.); PEXg

manifold piping

Lighting 50% compact fluorescent lamps 80%+ compact fluorescent lamps a Annual fuel utilization efficiency

b Electronically commutated motor

c Seasonal energy efficiency ratio

d Minimum efficiency reporting value e Energy factor

f Chlorinated polyvinyl chloride

g Cross-linked polyethylene

The referenced reports provide background for the design solutions employed in this NCTH and 

describe implementation and construction issues discovered during site visits and in discussion 

with the builder and trade contractors.

 11 The ventilation system was initially set to operate at 60% of the ASHRAE 62.2 (ASHRAE 2010) ventilation rate 

for the house.
8

4 Verification Testing

While many of the energy efficiency features incorporated in the NCTH design were familiar to 

the builder and trade contractors, they were not standard practice. As a result, Home Innovation

developed a short-term verification testing plan to ensure that test results matched expected 

performance levels. For durability and confidence in the system performance, Home Innovation

established a longer-term testing plan to provide field data to demonstrate ongoing reliability and 

energy savings.

4.1 Test Plan

Testing and evaluating the design strategies employed in the NCTH are critical for understanding 

the reliability of the systems and if systems were successfully integrated into the finished product. 

Short- and long-term field tests address the following research questions:

• Based on the redesigned single-zone ducted air delivery system, how consistent are 

the interior temperatures on each of the four levels of the home? How do interior 

temperatures change throughout the day under summer and winter peak load 

conditions?

• Is measured energy use for space conditioning consistent with modeled estimates 

under similar ambient weather conditions? 

• Are the HVAC elements including furnace, compressor, thermostat, humidifier, fresh 

air supply damper, and exhaust fans operating as designed and in an optimal manner?

• How do the wall cavity environmental conditions change with seasonal interior and 

exterior conditions? Are sheathing moisture characteristics within expected swings?

• How do the wall cavity moisture characteristics compare with estimated or modeled 

results?

• Is there anecdotal evidence of market response to the costs, features, and interior 

conditions of the house from the builder, potential buyers, trade contractors, or 

manufacturer partners?

To answer all but the last question, the research measurements detailed in Table 4 will be taken. 

Builder feedback will be used to evaluate the last question.

Initial short-term test results, reported previously (see footnote 5 above), are summarized here to 

add context to the long-term and repeat test results. 
9

Table 4. Research Measurements and Equipment

Measurement 

Parameter Test Measurement Test Purpose

House Infiltration 

Rate

Blower door test and 

diagnostic evaluation

• After drywall – assess primary 

leakage paths and remediate

• At construction completion –

document overall infiltration rate and 

locate remaining major leakage paths

HVAC Duct 

Tightness and 

Overall Duct System 

Performance

Duct blaster test; air handler 

and diffuser flow rates

• Duct system rough-in – assess leakage 

and remediate; repeat tests

• At construction completion –

characterize overall air delivery 

system

Ventilation and 

Exhaust Fan System 

Performance

Balometer, hot wire 

anemometer, and pressure 

measurements

• At construction completion – measure 

supply ventilation airflow rate and 

exhaust fan flow rates. Measure house 

depressurization during exhaust fan 

operation

Whole-House

Electric

Energy transducer and 

recording devices

• Record whole-house electricity use

• Identify a demand profile

Space Conditioning 

Equipment

Energy transducer and 

recording devices

• Document the operation of the HVAC 

system relative to interior set points 

and exterior ambient drivers

Indoor Environment

Temperature/relative 

humidity (T/RH) sensors 

located on each floor and on 

the exterior of the home

• Analyze the operation of the HVAC 

system relative to interior and exterior 

T/RH drives

• Document the operation of the supply 

ventilation and humidification 

systems

• Analyze T stratification through the 

four-level home

• Assess ventilation performance

Wall Cavity 

Environment

T/RH/moisture content 

(MC) sensors placed in wall 

cavities of basement, first, 

second, and third floors, and 

roof

• Monitor wall cavity conditions and 

sheathing MC in high thermal value 

wall system with elastomeric air seal

• Characterize the diurnal and seasonal 

moisture performance 

• Provide data for comparison with 

moisture models

Other Repeat tests

• Additional short-term tests may be 

added based on ongoing analysis 

and/or field performance of similar 

other homes for comparison
10

4.2 Infiltration Testing

At various points during construction, Home Innovation conducted whole-house infiltration testing 

using a blower door to identify particular areas, if any, where remediation is likely to be necessary 

to meet whole-house infiltration criteria in the production environment. 

The first infiltration test was performed after drywall but before trim, floors, and ceiling 

penetrations were sealed. This test identified a significant leakage area in a third floor kneewall 

adjacent to a common HVAC chase that resulted in significant airflow between the attic and 

conditioned space at the angled top plate and sloped ceiling. This detail will require particular 

attention in all future air sealing efforts. A second infiltration test was conducted after further air 

sealing and the house was substantially complete except for the sealing of all ceiling penetrations. 

This test showed a significant reduction in air infiltration over the initial test. A final test was 

performed after completion; this test showed further reductions in air leakage. Finally, another air 

infiltration test was performed after 14.5 months of home operation to document any air leakage 

changes following heating and cooling cycles. Table 5 summarizes infiltration test results.

Table 5. Characterization Testing: House Leakage

Performance 

Metric NCTH Units

House Size 4,441 ft2 finished area

4,568 ft2 conditioned area

House 

Volume 41,847 ft3

Infiltration

Test 1a Test 2b Final 1c Final 2d

2,400 1,380 1,335 1,365 CFM50

3.4 2.0 1.9 2.0 ACH50

0.17 0.10 0.10 0.10 ACH natural

0.53 0.30 0.29 0.30 CFM50/ft2 CFA

a Prior to trim and sealing of all penetrations but after sheetrock installation

b After access panels and other kneewalls from the third-floor room to the attic were sealed c Final after all finishes complete

d 14.5 months following Final 1

The air infiltration measurement results indicate that the air sealing effort was successful in 

achieving the builder’s goal of no more than 3 ACH50. In addition, leakage areas that needed 

special detailing were identified. Leakage areas that were identified included the attic room 

kneewall framing, duct chase and closet framing adjacent to attic spaces, and ceiling penetrations 

adjacent to the attic. The builder used an elastomeric water-based foam product to air seal these 

areas as outlined in the previous report (see footnote 5). Based on the complexity of the framing, it 

was generally understood that use of such a product was highly advantageous to attain reliable air 

sealing that meets performance goals. 

Home Innovation conducted infiltration tests on models that include energy efficiency features 

similar to the NCTH but that have different layouts (models H2, H3, H4). The CFA of each model 

is within 4% of the NCTH. Two of the three models have an attic room and none has the complex 

turret design. The models were insulated and air sealed using the same approaches as the NCTH. 
11

During construction, these three models were not subject to the high level of scrutiny imposed on 

the NCTH, but all four models were air sealed by the same contractor. The H2, H3, and H4 models 

tested between 2.3 and 2.4 ACH50, providing anecdotal evidence of reliable and repeatable air 

sealing approaches to complex house designs.

As a comparison, the builder subsequently constructed a home (model B17) that has the same floor 

plan as model H3 but that was air sealed with caulking and spray foam rather than with elastomeric 

spray materials. Note that the model H3 and B17 does not have the large turret that is a design 

element in the NCTH. The turret adds multiple corner and angle joints constructed over three 

stories in height and presents a significant challenge to air sealing aside from the rest of the home. 

In model B17, the sealing contractor employed its customary practice of sealing window rough 

framing openings and other framing penetrations with spray foam, and caulking bottom plates at 

the deck, between top plates and panel joints. Infiltration testing showed that model B17 (which 

was insulated with batt insulation in the walls rather than packed fiberglass as was in model H3) 

tested at 3.1 ACH50, or about 30% higher than model H3. Whole-house air infiltration results, 

however, were close to the 3.0 ACH50 target air sealing level). Furthermore, during the air 

infiltration test in B17, air leakage around exhaust fans was measured at a total of 135 CFM (across 

five exhaust fans). If just half of this leakage was eliminated due to air sealing at the gypsum/fan 

interface, infiltration in B17 would be reduced to 3.0 ACH50. Yet, even though this result meets 

the builder’s infiltration goals, there remains the issue of consistently achieving satisfactory results 

on a production basis. From this example, it appears that standard air sealing methodologies can 

achieve what are considered low air infiltration levels. It remains to be demonstrated, however, if 

standard air sealing methods can achieve the required levels consistently and without remediation 

costs after the home is substantially complete.

4.3 Heating and Cooling System Design and Duct Leakage Testing 

To dramatically reduce equipment and distribution energy losses due to conduction and air 

leakage, the HVAC system was designed to incorporate all equipment and ducts within 

conditioned space. Standard builder practice was to install two HVAC systems, one in the 

basement and one in the attic. While the two-system approach is common in the region, simple to 

install (no supply ducts running between floors), and creates two independent zones for improved 

comfort, its benefits are more pronounced in conventional home designs for which comfort and

efficiency are not factored into the whole-house design. In high performance homes like the 

NCTH, a single, well-designed HVAC system can eliminate the need for additional equipment 

costs without sacrificing performance and comfort. 

Load calculations, equipment selection, and duct design were made in accordance with Air 

Conditioning Contractors of America Manual J (ACCA 2006), Manual S (ACCA 2004), Manual T

(ACCA 2009a), and Manual D (ACCA 2009b) standards. The project team selected a single 

HVAC and duct system located in the conditioned space with a 15 SEER cooling system and a 

92.5% AFUE natural gas furnace. The direct-vent furnace, which uses outdoor air for combustion 

and exhausts combustion air through a separate pipe, has a two-stage gas valve and ECM blower 

motor. The furnace was selected based on the cooling airflow requirements; in high-heat mode the 

furnace output is much higher than the design load, in low-heat mode, the furnace capacity 

matches design load well; the team anticipated that the furnace will operate primarily in low heat 

mode. During the cooling season, the programmable thermostat with integral humidistat can 

operate the furnace in dehumidification mode (reduced blower speed) to improve humidity control. 
12 

In the NCTH, a series of preliminary duct leakage tests were conducted before furnace installation

(see Table 6). The first test indicated higher than expected leakage. A second test, using theatrical 

smoke, identified leakage areas, and a third test measured the improvement after additional duct 

mastic was applied. During the preliminary tests, the house was not ready for a blower door test 

and therefore leakage to the outdoors could not be measured. After the furnace was installed, the 

final duct leakage test was more than double that measured in the last preliminary test. A portion of 

this increase may be attributed to additional leakage through the furnace, coil, and air cleaner 

cabinets. Additional leakage, likely a larger portion, may also be attributed to different duct testing 

protocols for the preliminary and final tests. During preliminary tests, outlets were sealed by 

adhering the masking material directly to the metal ducts. During final testing registers and grilles 

were sealed to finished floors and walls, which may have allowed additional leakage between these 

surfaces, particularly the gaps between the drywall and the metal duct at return grilles. Because the 

majority of duct was concealed behind drywall, further testing and repair were impractical. An 

additional rough test conducted after the installation of the furnace, filter, and coil, but before 

drywall, would have provided a valuable incremental test result. Duct leakage to outdoors, as 

expected for a tight home with ducts in conditioned space, was relatively low, less than 4% of air 

handler flow and less than 1 CFM25/100 ft2 CFA. Duct leakage testing results are summarized in 

Table 6. 

Table 6. Characterization Testing: Duct Leakage

Performance 

Metric NCTH Units

House Size 4,441 ft2 finished area

4,568 ft2 conditioned area

Duct leakage 

Rough 1a Rough 2a,b Rough 3a,c Finald

209 248 183 436 CFM25 total

4.6 5.4 4.0 9.5 CFM25/100ft2 CFA

N/A N/A N/A 43 CFM25 to outdoors

a All three rough duct tests were conducted after ducts sealed using mastic, before furnace installation, and before 

house was ready for blower door test, therefore duct leakage to outdoors was not available 

b Higher leakage results of test 2 were due to use of existing tape from test 1 as this test was performed using 

theatrical smoke for demonstration purposes (tape may have become loose in some areas)

c Test 3 was conducted after additional duct sealing using mastic

d Final test conducted after furnace installation and house was complete

4.4 Conditioned Air Distribution Testing

The ability of the single-zone, HVAC system with programmable thermostat/humidistat to operate 

as designed and provide adequate comfort was of significant interest to the project. Therefore, this 

testing sought to evaluate those HVAC design approaches that differed significantly from those of 

standard builder practice and to determine if the new approach matches the comfort levels achieved 

by the builder’s conventional two-system approach. The NCTH improvements are designed to 

enhance energy efficiency while limiting cost increases; however, it is critical that the system can 

provide acceptable comfort to the occupants through outdoor seasonal extremes.
13

One evaluation of comfort is temperature variations between levels in a multistory home. Since the 

NCTH contains three stories above grade plus a conditioned basement, the challenge for the singlezone duct delivery system is to provide a balanced temperature profile between levels. 

During the commissioning period, airflow at each diffuser was measured and dampers were 

adjusted. Measurements during one cooling period indicated that the temperatures on different 

levels of the home varied by time of day but typically were within 1°–3°F (see Table 7). Measured 

results were best when the two dampers for the lower levels were halfway closed. Based on 

temperature measurements and perceived comfort of the sales and builder staff, the duct design 

appears to be performing very well, particularly considering the four-level design. The 

effectiveness of the bedroom transfer grilles to provide a low pressure, return air pathway was not 

measured because interior doors were not installed at the time of testing.

Table 7. Example Measured Temperature by Level

Location

Temperature (°F)

June 21,

8:00 a.m.

June 21,

4:00 p.m.

August 17,

1:00 p.m.

1st Floor at Thermostat 70.6 71.6 72.2

2nd Floor Master Bedroom 70.4 71.6 72.1

3rd Floor Bedroom 70.7 72.6 73.5

Basement Recreation Room 69.7 70.9 72.3

Figure 2 depicts 15-minute average temperature data for 3 days in July and depicts cooling system 

operation. The 3-day period experienced extremely hot weather; the third day was a Saturday for 

which the home may have had many visitors and more introduction of outdoor air.

Figure 2 shows the temperature difference between floors. At times, generally when the air 

conditioner compressor was off, there was up to a 4°F differential between the first (blue) and third 

(green) floors. In general, the second floor (red) was slightly cooler than the first floor, likely due 

to higher internal gains and solar gain through windows. The air handler fan operates 

continuously,

12 so air is being mixed, but the temperature deviation in the third floor attic room is 

larger than the other floors. This is likely due to heat gain through the partially-cathedralized 

ceiling. Yet, the temperature profile shows that all above-grade floors trend together and respond 

similarly to the cooling equipment operation. Average temperatures for each level during the 3-day 

period, shown in Table 8, are within about 2°F with a wider separation in the basement area 

(indicating that, in summer, little cooling is needed in the basement). The outdoor temperature 

averaged 89°F and the attic temperature averaged even warmer (which is a driver for increasing 

temperature in the third floor room, in particular).

 12 The fan-only mode in the NCTH was set approximately 200 CFM higher than the standard fan only mode to 

maintain a higher level of mixing in the sales model. The effect of this detail on floor-floor temperature variations 

was not tested.
14

Figure 2. Indoor temperature profile during an extreme cooling period

Table 8. Average Temperatures for 3-Day Period, July 5–July 7, 2012

Temperature Measurement Location Average Temperature, °F

1st Floor (in Room With Thermostat) 72.1

2nd Floor (in Master Bedroom) 71.2

3rd Floor Attic Room 73.4

Basement Recreation Area 67.0

Basement Utility Room (HVAC Equipment Location) 65.7

Attic Space (Above Insulation, Vented) 96.1

Outdoor 89.0

Figure 3 depicts indoor temperatures for a 16-month period spanning two cooling seasons and one 

heating season. The first floor is highlighted in red, the second in black, and the third in green. The 

gray line, read on the right axis, represents the maximum temperature difference between the first, 

second, and third floors only. Temperature different between floors is highest in the heating season 

and during very hot periods in the cooling season.
15

Figure 3. Indoor temperature profile for 16-month monitoring period

The temperature profile indicates that the duct design and operation of the heating and cooling 

system produces modest temperature difference between floors. The design team had originally 

considered installing a thermostat-controlled zoned damper system to minimize temperature 

differences between floors, but it appears that the current design, with the continuous operation of 

the ECM fan motor, produces acceptably consistent temperatures across levels of the home.

4.5 Ventilation and Exhaust Fan Testing

Fresh air ventilation flow, measured using a hot wire anemometer, was lower than expected, even 

in the cooling mode when the fan should be drawing the most air (the cooling mode fan operation 

is the highest fan speed). One subsequent measurement in the heating mode showed an unexpected 

improvement, although the flow was still less than anticipated. Incoming ventilation air was 

measured between about 35 CFM and 70 CFM depending on the air handler operation. Daily 

average operation of the fresh air inlet damper has indicated a consistent airflow at all times of the 

year. The controller was set to operate the fresh air damper for 60% of the time. Monitoring 

equipment, which provided the status of the ventilation damper (open or closed), verified that the 

control was operating as intended.

Bath exhaust fan airflows initially tested significantly less than rated. Upon investigation, it was 

determined that an unnecessary control which limited airflow had been installed. Removing this 

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Maximum Temperature Difference, °F, Floors 1, 2 and 3 Only

Average Daily Temperature, °F

Indoor Temperature Profile NCTH Model

1st Floor 2nd Floor 3rd Floor Basement Utility Room Max T Difference
16

control improved the airflows considerably; however, all tested below the nominal factory ratings. 

Table 9 shows the results of exhaust fan measurements compared with factory ratings after the 

unnecessary control was removed.

Table 9. Exhaust Fan Ratings and Operation

Fan Location Rated Airflow, CFM Measured Airflow, CFM

Basement Bath 80 63

Powder Room 50 39

Master Bath (Main) 110 50

Master Bath WC 80 11

Hall Bath 80 42

Loft Bath 80 59

Range Exhaust 600 500

The results in Table 9 are not atypical from exhaust fan test results in other homes. The results 

clearly indicate that the design and installation of exhaust fans remains in need of improvement. At 

this time, however, there is no standard practice for verifying installed exhaust fan flow.

4.6 Wall Cavity Moisture Performance

Early investigations into the use of 2 × 6 framing in high performance home construction raised 

awareness of the importance of understanding the moisture characteristics of the wall cavity and 

designing the wall system to accommodate the natural movement of moisture in the wall cavity 

system. Members of the project team therefore, expressed interest in developing a more detailed 

understanding of the actual moisture characteristics in the wall cavity and additionally within the 

home. For this reason, and to add to ongoing field research on moisture characteristics in occupied 

homes, a more in-depth analysis of the moisture properties of the 2 × 6 framed wall system is 

underway at NCTH.

To evaluate the wall cavity moisture characteristics in the NCTH, sensors were installed at the 

interior sheathing surface. The sensors measure surface T/RH and the moisture content (MC) of the 

sheathing. (Refer to Appendix B for a description of the sensors and the calibration analysis used 

in the data processing.) 

Wall cavity sensors were installed in selected wall cavities on the three AGW areas (22 sensors), in 

the band area of the basement (2), in the attic space (1), and in selected roof sheathing areas (2). 

Indoor sensors were located on all four levels of the home and one exterior sensor was located near 

the garage. Sensors were installed in all orientations. One of the first-floor sensors was located in a 

northwest-facing wall section constructed of fully insulated, double 2 × 6 framing (nominal R-46).

In addition to the wall cavity sensors, indoor T/RH measurements were also taken on each level of 

the home. These indoor measurements provide data that can be used to document the cyclic 

interior moisture levels in various seasons based on the actual use of the home and the operation of 

mechanical equipment (heating, cooling, ventilation, fans).

4.6.1 Sheathing Condensation Potential

The project team was interested in the moisture characteristics of the 2 × 6 wall system developed 

for the high performance home design. Using a standard simplified condensation potential 
17

methodology, Home Innovation conducted an initial evaluation of the theoretical potential 

condensation characteristics in the wall cavity based on estimated interior temperature and 

humidity conditions and historical average weather data.13 The methodology assumes that the 

moisture in the wall cavity is directly based on the interior moisture conditions, regardless of the 

permeability characteristics of interior wall layers. The method uses standard calculations to 

determine wall sheathing temperature based on the level of insulation in the cavity.

Condensation is possible when the dew point temperature (DPT) of the air is higher than the 

surface temperature of the sheathing. In the heating season, the interior air T/RH directly affects 

the wall cavity moisture characteristics and the potential for increased MC of the sheathing. The 

configuration of the wall cavity, including interior vapor retarders, cavity insulation materials, and 

sheathing materials, will affect the ability of the wall cavity to handle the moisture load that enters 

the wall cavity through air leakage or diffusion. 

To determine the potential for condensation on the interior surface of the sheathing, the surface 

temperature can be calculated using exterior and interior temperature conditions and the R-value of 

the insulation materials. The temperature at the interior surface of the sheathing is a function of the 

relative insulation levels to the interior and exterior of the sheathing surface at the interior of the 

cavity (see Figure 4) and the indoor and outdoor environmental conditions. For the cavity path, the

temperature at any surface in the path is derived from the formula14:

Figure 4. Graphical description of sheathing temperature calculation

 13 Building Science Corporation, Guide to Insulating Sheathing, Revised January 2007. See also Insight issue May 

2011 (rev), www.buildingscience.com for a discussion on the actual condensing surface compared with calculations 

of the condensing plane within a wall cavity. 14 The calculation of the temperature at any point in the thermal pathway is based on well-known physical principles 

of heat or current flow across a resistance.

ROOO

Reeeeeeeeeeeee

R s s

R −f f

T

R −f f

R gg

Rc c

T

T − s
18

Teesfece e = ��

sum Rceeeee e−e

sum Rceeeee e−e

� × ∆Te−e� + Te

where:

Teesfece e ≡ temperature of the surface of interest

Rceeeee e−e ≡ sum of the path R-value from surface of interest to the exterior

Rceeeee e−e ≡ sum of the path R-value from the inside surface to the outside surface

∆Te−e ≡ Air temperature difference from the inside to the outside

Te ≡ Outside air temperature,

and where: Temperature is in °F and R-value is in ft2∙h∙°F/Btu.

For the NCTH located in climate zone 4, the potential for condensation based on monthly average 

outdoor temperatures is graphed in Figure 5. The wall system used for the dew point calculations is 

a 2 × 6 framed wall with R23 cavity insulation, exterior oriented strand board (OSB) sheathing and 

fiber cement siding, and interior gypsum with two coats of paint.

The green line represents the DPT of the indoor air at assumed winter conditions of 71°F and 47% 

RH. Curved lines represent the temperature at the sheathing for average monthly exterior 

temperatures, of various wall sections. The blue dotted line represents the actual monthly average 

temperature for the measurement period.

Under the assumed winter conditions, it is clear the potential for condensation on the interior 

sheathing surface exists during most of the winter heating season.

Figure 5. Theoretical condensation potential at interior surface of sheathing

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Sep Oct Nov Dec Jan Feb Mar Apr

Temperature/Dew Point Temperature, °F

Monthly Average Data

Historical Avg. Outdoor T, °F

Wall, 2x6, R23FG, OSB, °F

Wall, 2x6, R46FG, OSB, °F

DewPoint @ 71F/47%RH

Actual Avg. Outdoor T (2011-2012), °F

Condensationpotential between 

the dew point Temperature 

(green) and the wall cavity at the 

sheathing (red).

Interior dew point based on 

measured data
19

The difference between the actual sheathing temperatures and concurrent DPT for a full winter 

heating season are charted in Figure 6, based on moisture sensor readings of T/RH and calculations 

of DPT. When the DPT at the sheathing is higher than the sheathing temperature, the potential for 

condensation exists. In Figure 6, this condition is depicted by sheathing temperature difference (TDPT) that dips below the green line.

Figure 6. Heating season measured condensation potential in test home

Based on measured environmental conditions inside the wall cavities (excluding the one atypical 

wall section with R-46 insulation), the potential for condensation occurred for very few days in 

only a minor set of wall cavities during the heating season. The unoccupied home was actively 

humidified during the winter and the interior moisture and temperature conditions were very 

similar to the average conditions assumed in Figure 5. The results indicate that the theoretical 

calculation of condensation potential does not accurately represent the actual condensation 

potential across the winter heating season and therefore should be used cautiously when evaluating 

a particular wall design. Furthermore, the wall system design utilized in this test home in the first 

year following construction performs extremely well in terms of measured condensation resistance.

4.6.2 Interior Vapor Retarder

To better understand the actual moisture performance of some of the materials in the wall system 

and compare with assumptions, painted gypsum wall board was tested, since the layers of material 

in the wall system have a large effect on the amount of moisture that diffuses into the cavity. 

Constructed in climate zone 4, the NCTH is not required to have an interior vapor retarder per the 

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OSB/Cavity Temperature - Dew Point Temperature, °F

Daily Average Data, 10/1/11 - 4/30/12, 213 days

H1[1FlNE1]

H1[2FlNE1]

H1[2FlNE2bath]

H1[2FlNW1]

H1[1FlNW2]

H1[1FlNW3]

H1[2FlNW2]

H1[3FlNW]

H1[1FlSE1]

H1[1FlSE2]

H1[1FlSE3]

H1[1FlSE4]

H1[2FlSE1]

H1[2FlSE2bath]

H1[1FlSW1]

H1[2FlSW1]

H1[2FlSW2]

> Values less than 0 indicate condensation possible

> Maximum count for any wall cavity - 2 days (1%)

> Maximum number of wall cavities during a single day period with 

condensation potential - 5 of 17 cavities

> Maximum number of consecutive days with condensation potential for 

any cavity - 1 day

Note: Walls constrcuted of Siding, WRB, OSB, 2x6, 

R23 blown fiberglass, gypsum/paint.
20

International Residential Code.15 This wall design in this climate zone allows for moisture 

movement through the wall system to either the exterior (winter) or interior (summer). The 

standard paint specification is for two coats of latex paint. A section of painted drywall was 

removed from a test house similar to the NCTH and tested for permeability.16 Four samples were 

tested using both wet and dry cup methods to determine the permeance of the painted gypsum 

layer. The results from both methods are summarized in Table 10.

Table 10. Summary of Gypsum/Paint Layer Permeance Tests

Test Method Permeability, perm-in. Permeance*, perm

Dry Cup 18.14 36.45

Wet Cup –17.60 –35.54

* Based on the measured thickness of the gypsum/paint

The permeability of the gypsum/paint combination as tested is higher than data found in ASHRAE 

Fundamentals (2009) and other sources. However, these tests results are consistent with similar 

testing performed at Home Innovation on painted gypsum wallboard.

4.6.3 Preliminary Simulation Analysis

The Forest Products Lab, in collaboration with Home Innovation, is preparing a report that 

summarizes WUFI17 simulations of the moisture response of sheathing in various wall systems in a 

climate similar to climate zone 4. The simulations predict the MC of the sheathing and the cyclic 

nature of the MC. The use of such simulation software can provide a general understanding of the 

wall system performance but is highly dependent on the assumptions made by the programmer. 

Such assumptions include the estimate of indoor RH in the heating season, the type of weather year 

selected, the physical characteristics of material layers, and the orientation of the wall element.18

One of the wall systems investigated is configured in an identical manner to the NCTH walls. The 

researchers applied typical performance parameters to material layers. In some cases, for example 

when defining the permeance of painted gypsum, the researchers conducted parametric analyses to 

better understand a range of moisture performance of the OSB sheathing based on a range of 

drivers and material characteristics. Figure 7 shows the results of WUFI simulation of a 2 × 6 wall 

system with OSB sheathing, vinyl siding, R-23 fiberglass cavity insulation, and a gypsum/paint 

interior wall covering (with an assumed permeance of 10 perms). Results show the annual moisture 

response content of the sheathing following 3 years of simulation weather data.

 15 International Residential Code, IRC 2009, by the International Code Council, Chapter 6, Section 601.3. 16 ASTM Designation E96/E96M – 10, Standard Test Method for Water Vapor Transmission of Materials, was used 

as the test method to determine the water vapor permeance of the samples. 17 WUFI (Wärme und Feuchte instationär) is software that allows calculation of the transient coupled one- and two 

dimensional heat and moisture transport in multilayer building components exposed to typical weather. 18 A less well-known aspect of the software is the handling of air leakage and air movement through the wall system, 

which is known to affect the actual performance of the wall but is very difficult to simulate. 
21

Figure 7. WUFI simulation results for an R-23 wall in climate zone 4

4.6.4 Preliminary Measured Wall Cavity Moisture Performance

The NCTH was instrumented with moisture sensors located at the interior cavity side of the OSB 

sheathing. Sensors were located in all wall orientations and in various rooms. Measured moisture 

performance data in the wall cavities are available for a period of more than 1 year, encompassing 

full cooling and heating seasons. Sensors measure the T/RH at the sheathing surface and the MC of 

the sheathing.

Although the NCTH is not occupied, it is regularly open for use by sales staff and customers. A 

humidifier installed on the main air handler duct adds moisture to the airstream during heating 

periods. The ventilation system operates as commissioned and the air handler is set to fan-run 

mode to maintain air movement throughout the home on a continuous basis. These equipment 

operational features will affect the interior moisture levels and those in the wall cavity.
22

Figure 8. MC of OSB sheathing in the climate zone 4 NCTH

Figure 8 demonstrates the cyclic nature of the OSB moisture diffusion into the OSB sheathing over 

a full year period. Measured interior RH, an indicator of the potential for water vapor transmission 

into the cavity, aligned with, but is slightly higher than, typical RH used in the WUFI simulations 

(described above) and with estimates used in ASHRAE standards.19 The higher the indoor 

moisture levels, the higher the potential for moisture movement into the wall cavity in the winter 

months.

Similar to the simulation results in Figure 7, the MC of the sheathing increases as the exterior 

temperature decreases and the vapor driver into the cavity is from the interior to the exterior. The 

north and east orientations generally have a more pronounced seasonal change in MC, varying by 

approximately 6%. All of the measured cavities dry to below 10% MC in the summer period 

regardless of the highest MC recorded during the winter period. The wall section with the highest 

recorded MC is the one wall section that is a double 2 × 6 framing completely filled with insulation 

(a nominal R-46). This particular wall section (which is not common in this climate zone) has the 

lowest sheathing temperatures in the heating season due to the much higher level of insulation in 

the cavity.

The MC profile measured in the wall cavities (Figure 8) resembles the results of the simulation 

data (Figure 7) but with lower peak measurements and a less defined rise and fall between seasons. 

This is likely due to the actual weather conditions, which were warmer overall compared with 

 19 ASHRAE Standard 160, Criteria for Moisture-Control Design Analysis in Buildings, 2009. American Society of 

Heating, Refrigerating and Air-Conditioning Engineers.
23

simulation data based on historical averages. The actual performance of the wall system 

demonstrates the common cyclic moisture characteristics of the sheathing. 

Wall cavity temperature profiles for the same period as the MC data charted above are shown in 

Figure 9.

Figure 9. Temperature at the OSB sheathing in the climate zone 4 NCTH

The red dotted line is the outdoor temperature and the solid dark blue line (that average near 70°F), 

is the indoor temperature. The red dashed line on the lower portion of the chart is the temperature 

difference between the maximum and the minimum for the day and provides the relative difference 

in cavity temperature for various wall cavities in different orientations. The range of temperatures 

is as much as approximately15°F in the winter period. As expected based on the configuration of 

the wall system, the interior cavity OSB temperature closely tracks the exterior temperature.

Similarly, the RH in the cavity at the OSB sheathing is shown in Figure 10.

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Temperature, °F

Daily Average Data

Climate Zone 4A - Maryland - Wall Cavity Temperature

H1[1FlNE1] H1[1FlNE2] H1[2FlNE1] H1[2FlNE2bath] H1[1FlNW1R46] H1[1FlNW2]

H1[1FlNW3] H1[2FlNW2] H1[2FlNW1] H1[3FlNW] H1[1FlSE1] H1[1FlSE2]

H1[1FlSE3] H1[1FlSE4] H1[2FlSE1] H1[2FlSE2bath] H1[3FlSE] H1[1FlSW1]

H1[2FlSW1] H1[2FlSW2] H1[1Flint] H1[Outdoor] Cavity Temp. Span

Note: All walls

OSB, 2x6, R23 

blown fiberglass, 

gypsum/paint 

unless noted.

Temperature span wall cavities only 
24

Figure 10. RH at the OSB sheathing in the NCTH (climate zone 4)

The red dotted line represents the outdoor RH and the dotted blue line is indoor RH. The red 

dashed line on the lower portion of the chart is the wall cavity RH difference between the 

maximum and the minimum for the day and provides the relative difference in cavity RH for 

various wall cavities in different orientations. The range of RH, about 10%–30%, is fairly constant 

for much of the year.

4.6.5 Model Home Measured Energy Use

Monitored energy use and utility bills were used to roughly compare the electricity and gas use of 

the NCTH with simulation results. Because the NCTH is operated as a sales model and therefore 

includes significant additional lighting, miscellaneous electric, and HVAC systems, simulations 

were run using standard home operating assumptions but with three times the miscellaneous use of 

a typical residence. A summary of the total electric and heating, cooling, and ventilation system 

energy use is shown in Table 11.

Although measured energy use is higher than simulated, the measured data generally confirms that 

the house functions as designed based on the energy efficiency features of the home. Differences 

between simulated and measured data can generally be explained by ambient conditions (for 

example, measured cooling degree day is higher than simulated cooling degree day) and by air 

handler operation that increased cooling loads. 

0

10

20

30

40

50

60

70

80

90

100

8/1/2011 9/1/2011 10/1/2011 11/1/2011 12/1/2011 1/1/2012 2/1/2012 3/1/2012 4/1/2012 5/1/2012 6/1/2012 7/1/2012

Relative Humidity, %

Daily Average Data

Climate Zone 4A - Maryland - Wall Cavity Relative Humidity

H1[1FlNE1] H1[1FlNE2] H1[2FlNE1] H1[2FlNE2bath] H1[1FlNW1R46] H1[1FlNW2]

H1[1FlNW3] H1[2FlNW2] H1[2FlNW1] H1[3FlNW] H1[1FlSE1] H1[1FlSE2]

H1[1FlSE3] H1[1FlSE4] H1[2FlSE1] H1[2FlSE2bath] H1[3FlSE] H1[1FlSW1]

H1[2FlSW1] H1[2FlSW2] H1[1Flint] H1[Outdoor] Cavity RH Span

Note: All wallsOSB, 2x6, R23 

blown fiberglass, gypsum/paint 

unless noted.

Relative Humidity span for wall cavities
25

Table 11. Summary of Total Electric and HVAC System Energy for a Monitoring Period

Parameter Model Home Model 

Homea

Model 

Homeb

Measured Simulation Simulation

Analysis Period 11/10/2011 to 10/08/2012

Days in Period 334 334 days

Heating Degree Days 2,871 3,978

Cooling Degree Days 2,237 1,505

Total Electric Energy Use 34,847 kWh

Garage Office Electric Energy 

Use 5,866 kWh

Office Portion of Total 17% N/A N/A kWh

NCTH Electric Energy Use 28,981 23,389 9,368 kWh

Compressor Energy 4,646 2,723 1,686 kWh

Heating Gas Usec 282 312 485 therms

Air Handler (Furnace/Air 

Conditioner) Energy 1,234 809 448 kWh

Site Heating and Cooling Energy, 

Million Btu 48.263 43.251 55.781 MBtu

Ventilation Air Handler Energyd 2,121 230 230 kWh a Model home simulation has three times more miscellaneous electricity use than typical

b Typical home use in the model is based on BA Benchmark simulation protocols but with 71°F cooling to match 

simulated to measured performance

c Includes estimates for the fireplace use in the measured data

d Estimated fan energy for ventilation/air circulation

Due to the large electricity loads and resultant internal gains, and fewer observed heating degree 

days, the measured heating load on the furnace is lower than predicted. During the heating season, 

the furnace operated in low stage only and used approximately 162 therms of gas. The remaining 

120 therms of gas usage is attributed to the gas fireplace, which was used irregularly.

The major difference in the operation of the house compared to simulation results is the furnace fan 

operation. In the model, the fan operates constantly to circulate air. Based on measured data, the 

fan-only mode operated the furnace fan (a simplified ECM), at a higher flow rate than is typical for 

fan-only mode. The resulting fan electricity use contributes to a higher cooling load, a reduced 

heating load, and contributes to slightly more outdoor ventilation air when the fresh-air damper is 

open. The fresh-air damper was open 61% of the time.

Other anecdotal evidence suggests the NCTH is performing well. There are two other homes in the 

community used as sales models in a similar manner as the NCTH (including office space in the 

garage and similar lighting use patterns). Although the NCTH has additional electricity use for 

three large flat screen TV panels, which are not typically used in the other model homes, utility 

bills for the NCTH are approximately 20% less per ft2 than one model and approximately 10% less 

per ft2 than the other.
26

5 Energy Value

5.1 Initial Cost Analysis

During the design process, WHI completed an extensive in-house cost analysis. This allowed the 

builder to choose specific systems over other options (e.g., business as usual versus 2 × 4 with 

exterior rigid foam versus 2 × 4 with cavity spray foam). This analysis examined energy 

performance, occupant comfort, and synergistic cost containment benefits such as reduced material 

and labor costs. High performance features were selected and designed to perform as an integrated 

system. 

5.2 Future Cost Considerations 

As with most builders, there is an ongoing evaluation of the construction costs and benefits relative 

to new designs and products. Balancing the house features with construction details to develop a 

marketable product is often driven by changes in building codes, the development of new 

materials, and consumer preferences.

In evaluating the energy efficiency features of the NCTH in light of ongoing product development 

and construction specifications, the builder made a number of observations:

• The advanced framing system can be implemented without a large increase in cost when 

costs and benefits are considered together. Cost increases include additional insulation 

and trim materials. Benefits include labor savings and wall designs that are adaptable to a 

wider variety of wall insulation targets without major redesign efforts.

• Converting the framing system for an existing plan can be nearly as costly as developing 

a new floor plan, and it may be undesirable where extensive portfolios exist in a given

market. Another factor to consider is that floor area is important to consumers, and 

modifying interior area may be detrimental from a sales perspective. 

• Drivers for switching to advanced framing can often be related more to construction and 

bracing preferences of the builder and considerations for durability and use of familiar 

products and installation methods, rather than achieving insulation goals alone. An 

example of this decision process is the comparison between use of wood sheathing and a 

weather resistant barrier layer and an exterior foam panel with taped seams.

• The cost of air sealing is of growing significance especially when much lower levels of 

infiltration will be required by building codes and testing will be performed to assure 

goals are met. The air sealing methodology selected for the NCTH appears to be capable 

of meeting infiltration goals consistently and reliably. However, the cost of the system 

versus the value remains uncertain. The builder continues to investigate other means of 

achieving the same performance goals at lower cost.

• The design and installation of the HVAC system remains a challenge. The cost savings, 

or at least a neutral cost, of installing a single system instead of two systems has been 

realized. The efficiency gains of installing the ducts in conditioned space, the use of 

bedroom transfer grilles, and minimized duct runs are all aspects of the NCTH that the 

builder plans to gradually incorporate based on cost savings (both for the builder and 

consumer) and measured performance.
27

• The HVAC system design includes a fresh air system, but final specifications are still 

under development. One consideration of the return fresh air system is the necessity of 

incorporating an ECM, which has wider cost implications for the HVAC equipment.

The complexity of these cost issues along with the changing building code requirements and 

reliable and achievable performance goals are important to ongoing cost evaluations.
28

6 Gaps and Lessons Learned

6.1 Overview

The level of effort invested by the builder, its trades, and the researchers during the planning stage 

was considered important to the successful design and implementation of the energy features for 

the NCTH research project. The effort expended to monitor the home, especially the wall cavity 

monitoring, was a critical element in assuring durability and long-term performance of the 

advanced designs. This investment was deemed necessary for development of specifications for 

future changes in other home designs. The energy efficiency features were selected for durability, 

practical and repeatable installation, and cost effectiveness.

6.2 Wall Framing

By incorporating the advanced wall system, the builder achieved insulation levels that will meet or 

exceed future code requirements. The advanced framing system can accommodate higher 

performance goals, for example by adding exterior insulation or using higher R-value materials in 

the cavity. Use of 24-in. on-center spacing can simplify installation of electrical and plumbing 

materials as well as reduce the time to install wall finishes. Builder framing inspections showed a 

number of nailing and blocking issues that were addressed in the field and should be added to the 

framing contractor’s scope of work for subsequent houses.

Use of the rim headers on the first floor allowed for optimized framing around window and door 

openings. BA program laboratory testing supported the engineering work required to develop a 

standard methodology for rim header application. Specifications were required for rim header 

material at openings as well as nailing specifications for multiple rim elements and installation of 

joist hangers. While this home design was engineered, the methodology to develop prescriptive 

approaches to the use of rim headers was initiated through this effort. The framing contractor 

adapted to the design change without major complications implementing the double rim and joist 

hangers where needed over openings. One complication with the rim header design occurs when 

an opening is added in an exterior wall as occurred in this test house, in which case, standard 

framing techniques must be used.

Offsetting interior walls to eliminate corner breaks in the gypsum wallboard of exterior walls 

proved a successful design change. Both framing and sheetrock crews adapted easily to this design 

modification.

6.3 Floor Framing

The floor framing members were individually engineered and numbered to accommodate the floor 

plan. The software, developed and implemented by Weyerhaeuser Company, used for the design 

and layout of the floor joists incorporated main supply and branch duct runs, domestic and 

sprinkler plumbing pipe runs, and drain pipe runs to facilitate the incorporation of mechanical 

distribution in conditioned space. Floor joist elements were factory cut to align joist openings for 

each of these building elements. The floor framing design resulted in a rigid floor, and the 

numbered joists and rim boards, after a brief learning curve, made for efficient installation as 

reported by trade contractors.

One aspect of this design and installation method is the high level of precision needed in the layout 

and installation. Since the system is engineered, field modifications are less flexible and precise 
29

installation according to plans is necessary. This precision and attention to the framing layout can 

be a challenge.

6.4 Air Sealing

Air sealing new homes is of increasing importance due to the more stringent requirements in 

building codes and the requirement for testing to verify performance. The NCTH design presented 

a plethora of challenges for air sealing as the turret, the third floor loft, and the complicated roof 

framing all contributed to extensive air leakage paths where many angled framing members 

adjoined attic or exterior spaces. The air sealing system used in the NCTH was a spray applied 

elastomeric foam that allowed for a more comprehensive coverage of all interior surfaces adjoining 

exterior spaces. A major benefit of the system was the ability to inspect the air sealing coverage 

and identify locations where air sealing may be missing and, hence, problematic. Specific details 

on sealant coverage, for example if all bottom plates and cavity seams should be sealed, remain to 

be resolved. However, the general approach was found acceptable due to the excellent air leakage 

results and the relative straightforward installation methodology, especially for the complex 

framing design.

The installation of house wrap as a secondary exterior air barrier was not completely accomplished 

per the original design (sealing the top and bottom of house wrap was not completed). However, 

the test results in this NCTH and subsequent houses using the same air sealing system but with less 

inspection demonstrated the reliability of the system to achieve the desired outcome.

6.5 Heating, Ventilation, and Air Conditioning

The decision to install the entire heating and cooling system in conditioned space resulted in 

significant estimated energy savings over the BA Benchmark. HVAC system location, in fact, is 

one of the first design decisions that must be made in order to perform accurate heat loss and gain 

calculations, select equipment, and design the distribution system. The redesigned duct system was 

integrated with the redesigned floor plan and joist layout in order to accommodate a central duct 

chase. This chase, which was critical for installing the entire system in conditioned space, was also 

utilized for plumbing piping. 

The integration of the second and third floor duct layout with the floor joists required significant 

design stage effort and site coordination for the installation. A different approach to implement this 

design could be to cut an opening, at the factory, through the engineered rim board to 

accommodate the field installation of the duct after framing is complete. This approach may be 

complicated if an opening is required over a window where a rim header is used, however, a 

conventional header could be installed. Alternatively, the integrated duct and floor design could be 

eliminated if this duct were installed conventionally (below and perpendicular to the floor joist) 

with a bulkhead if the design can feasibly be constructed, especially from the initial development 

of the architectural plans. Clearly the duct design and layout remains an important issue for further 

design efforts and installation evaluations.

Duct leakage to outdoors was presumably through leakage points in the air barrier in areas that 

were physically connected to the ducts (for example at the rim areas or top of the central duct 

chase). Leakage to outdoors was low and therefore the energy penalty was not considered 

significant; however, total duct leakage remains an opportunity for further optimization of the 

system performance. 
30

Bath exhaust fan airflows which measure below nominal fan ratings may be a widespread issue 

(not limited to this project) and may be partially due to a lack of manufacturer guidance on duct 

design. Testing indicated a need to investigate improved exhaust fan ducting layout and component 

selection. Performance may be diminished by excessive duct static pressure; performance may be 

improved by using different duct or fittings (for example larger diameter pipe or a less restrictive 

vent hood). 

Lower-than-expected fresh air ventilation flow may be attributed to the return duct design, which 

was sized to reduce air velocity and therefore noise in accordance with Air Conditioning 

Contractors of America Manual D (ACCA 2009b) recommendations; this low-pressure-drop 

design may require a larger diameter fresh air duct to draw in adequate ventilation air. An overly 

restrictive fresh air intake hood may have contributed as well. The test results highlight a need for 

additional ducting considerations for a supply-type ventilation design to ensure sufficient 

ventilation. 

It is expected that the additional cost of higher efficiency heating and cooling equipment is more 

than offset by installing a single system, instead of two, and a simplified duct system. However, 

final cost figures are not available.

The startup of the furnace and air conditioning system, notably the calibration adjustments to the 

burner gas rates and blower flow rates in various modes, highlighted how critical a thorough 

commissioning procedure and written report are to ensure the equipment is operating properly and 

efficiently.

6.6 Plumbing

While the plumbing system performance in the NCTH was not analyzed, design improvements are 

possible. For example, locating the kitchen and baths in closer proximity would significantly 

decrease the pipe lengths to the outlets and enable the use of smaller diameter pipes. This redesign 

would save materials, installation labor time, and energy use. For the manifold distribution system, 

insulating the large diameter pipe between the water heater and the manifold should be considered. 

Due to its large diameter, this pipe can be a source of heat loss. Low flow fixtures will also 

contribute to lower water heating costs for the consumer.

6.7 Quality Assurance

The builder implemented many of the design changes directly on the building plans and within 

scopes of work for the trade contractors. This documentation is a necessary step for reliable and 

repeatable satisfactory outcomes. Design reviews, site reviews, and inspections are recommended 

for subsequent houses to help ensure that framing, air sealing, insulation, and mechanical systems 

are designed and installed for optimum performance goals. Commissioning and testing were 

valuable for NCTH performance and are recommended for heating and cooling systems, duct air 

delivery, ventilation fans, and whole-house air leakage in subsequent houses.
31

7 Summary

7.1 Conclusions

This test home project defined construction and energy efficiency goals to achieve a high 

performance home design. The project goals and research questions are summarized in the 

following key areas.

7.1.1 Overall Constructability and Potential for Continued Use of the High 

Performance Design

The goal for making major wall and mechanical system design changes was to provide the 

necessary framework to reliably and consistently achieve high performance goals on a production 

home basis. Using advanced design elements such as advanced 2 × 6 framing, rim headers, offset 

interior walls, and an optimized floor framing system, the builder and trade contractors 

successfully implemented these elements into their work scopes and into the quality control 

practices. Although the design changes were significant for the wall panelizer, framing trade 

contractor, HVAC trade contractor, and builder, the transition to the new system was made without 

major problems. The system design was also found to be sufficiently cost-effective so that it could 

be incorporated in new house designs or even in conversion of existing plans. These design 

strategies were implemented in at least three additional houses as shown in Figure 12.

Figure 11. Three additional houses built using NCTH features

7.1.2 Wall Design To Meet Various Performance Levels

One goal of the design effort was flexibility in achieving higher energy goals. The package of 

solutions used in the test house design has demonstrated that additional major design changes to 

the wall system or the HVAC system would not be needed to achieve higher energy savings goals 

or for meeting modestly more stringent future energy codes or above-code programs for energy 

savings and environmental performance. Selection of higher energy savings choices could be made 

by homeowners without requiring the builder to completely redesign the structure.

7.1.3 Heating and Cooling Installation and Performance

The complete redesign of the HVAC system focused on increasing the efficiency of the overall 

system, reducing duct losses, providing comfort throughout all levels of the home, and limiting any 

cost increases. These challenging goals were met through a rigorous design process that eliminated 

the need for a second system (typically located in unconditioned space), reduced duct losses, 
32

moved all ducts to the interior, and balanced the supply and return air to provide minimal 

temperature fluctuations between floors. The newly designed system for the house size and layout 

showed a significant increase in performance coupled with the advanced wall system, reduced the 

overall installed tonnage by at least 30%. The measured duct leakage to the exterior was minimal 

however efforts to obtain a sealed duct system required multiple tests and is an area where 

improvements can be made.

The total measured heating and cooling energy for the test home fell within estimates based on 

simulations indicating that the envelope and equipment design functioned as intended. 

7.1.4 Airtightness and Ventilation

The test house design effort also focused on developing an air sealing methodology that would 

result in infiltration rates of less than 3 ACH50 in a reliable, consistent, and cost-effective manner. 

The first two goals were met following multiple installation inspections by the builder and trade 

contractor and with successful implementation in three other homes in the development. However,

the last goal is still being analyzed to reduce the cost of achieving the lower infiltration rate. The 

performance goal was deemed necessary, however, and will remain an important design element in 

future homes. In addition to reducing infiltration, especially in very complex framing designs, a 

whole-house ventilation system design was developed and implemented. The result of this 

development effort is an improved and standardized ventilation system that will be implemented in 

new home designs and may likely be used in many existing home designs.

7.1.5 Durability

In particular for the new wall system design that significantly modified the framing dimension and 

insulation level, the concern of moisture accumulation in the structural sheathing was addressed.

The testing results showed that the sheathing will see varying moisture levels based on the 

changing exterior conditions and with interior moisture levels maintained by humidification. The 

cyclic moisture characteristics of the wall sheathing fell within acceptable ranges, from 7% to 18% 

in the 2 × 6 wall cavities and were well within the capability of the materials to handle moisture. 

The wall system was installed without vapor retarder materials enabling more complete insulation 

coverage while limiting cost increases.

The measured wall cavity moisture data indicated that based on actual winter outdoor and indoor 

T/RH, the DPT at the sheathing was rarely above the sheathing temperature and then only for brief 

periods of time. This measured result was significantly different when compared to standard DPT

calculations that indicate an extended period of condensation in the wall configuration. When 

comparing the measured wall cavity moisture characteristics with simulation results from WUFI 

software, the cyclic pattern of MC levels was confirmed; however, the peak MC for the sheathing 

in theoretical estimates was higher than measured results.

7.1.6 System Testing Verification and Commissioning

All permanent features (optimized framing, insulation, windows, plumbing piping, and single 

HVAC system with interior ducts) were designed, implemented and successfully tested and/or 

commissioned. The HVAC commissioning process in particular was found to be a necessary part 

of the redesign effort. This necessity grew out of the higher level of complexity for house 

component designs (such as the wall framing or duct layout), the technical advances of the 

equipment (both for controls and equipment setup), and the need for verification that target 
33

performance levels were met. This test verification and commissioning effort, however, is still 

under development by many builders and the cost of such verification comes without direct 

savings and such must be incorporated using a more cost-effective methodology.

The measured energy use of the model home was much higher than would be expected from an 

occupied home as lighting and other loads are much higher. Similarly, the temperature setting for 

the indoor environment was higher than might be expected in an occupied home. 

Figure 12. Completed NCTH

7.2 Next Steps

Home Innovation, working with WHI and the BA program, will continue monitoring the moisture 

performance of the wall system. Moisture information will be particularly valuable after the home 

is occupied as a residence.
34

References

ACCA (2004). Manual S, Residential Equipment Selection. Arlington, VA: Air Conditioning 

Contractors of America.

ACCA (2006). Manual J, Residential Load Calculations, Eighth Edition. Arlington, VA: Air 

Conditioning Contractors of America. 

ACCA (2009a). Manual T, Air Distribution Basics for Residential and Small Commercial 

Buildings. Arlington, VA: Air Conditioning Contractors of America.

ACCA (2009b). Manual D, Residential Duct Systems, Third Edition. Arlington, VA: Air 

Conditioning Contractors of America.

ASHRAE (2010). ANSI/ASHRAE Standard 62.2-2010, Ventilation and Acceptable Indoor Air 

Quality in Low-Rise Residential Buildings. Atlanta, GA: American Society of Heating, 

Refrigeration, and Air Conditioning Engineers.

ASTM (2009). MNL18-2nd. Moisture Control in Buildings: The Key Factor in Mold Prevention –

2nd Edition. Heinz R. Trechsel and Mark T. Bomberg, Editors. West Conshohocken, PA: ASTM 

International

DOE (2011). Building America Program Goals (2011). U.S. Department of Energy, Accessed 

December 2011: http://www1.eere.energy.gov/buildings/building_america/program_goals.html.

DeRenzis, A.; Kochkin, V.; Wiehagen, J. (2012). High-R Walls for New Construction Structural 

Performance: Integrated Rim Header Testing, NAHB Research Center, December 2012

IECC (2009). 2009 International Energy Conservation Code. Country Club Hills, IL: International 

Code Council.

NAHBRC (2012). Final Technical Report: High-R Walls for New Construction Structural 

Performance Integrated Rim Header Testing. Upper Marlboro, MD: NAHB Research Center.

NGBS (2008). National Green Building Standard: ICC (International Code Council) 700-2008. 

Washington D.C.: National Association of Home Builders.
35

Appendix A: Energy Simulations

The NCTH as built with both the optional finished basement and third floor showed 30% whole 

house energy savings over the BA Benchmark,

20 excluding any size adjustment factor. The 

preliminary energy simulations included both a cost optimization and source energy savings 

analyses. Through optimization, BEopt produced a set of options that provided the highest energy 

savings for the lowest investment costs, within the limits of the software and cost data. Figure 13

graphically depicts the simulation results.

Figure 13. BEopt simulation results

The “swoosh” shape of the graph indicates that the minimum annualized energy cost occurred at 

source energy savings of approximately 24% (indicated by blue dotted lines). Before reaching the 

minimum cost point, incremental investment in energy savings measures decreased annualized 

energy costs (mortgage plus utilities) at a roughly linear rate. Just beyond the minimum (after 

about 27% source energy savings), additional energy savings are attainable, but the investment 

needed to attain incremental efficiency gains rises sharply. For example, meeting the project goals 

of 30% energy savings required an approximately 10% higher annualized energy related cost than 

the annualized cost of reaching 27% savings requires. The results indicated that, for this home 

design in the Washington, D.C., area, the maximum practical energy savings for production 

builders is near the 30% level. Attaining higher energy savings requires a better understanding of, 

and experience with, new technologies, construction methods, and the benefits of efficiency 

investments.

The second simulation analysis consisted of preliminary source energy savings estimates. 

Although the test home was anticipated to reduce the home’s energy consumption by 30% over the 

BA Benchmark, the as-built design (which serves as a model home and, includes nearly 2,000 ft2

 20 The current BA benchmark home has insulation and air leakage minimums consistent with the 2009 International 

Energy Conservation Code, but is (and has always been) a whole-house analysis for both the reference house and the 

design house to determine energy savings.
36

of optional conditioned space) was subject to a size penalty that reduced overall projected savings. 

Because of the additional conditioned space, the BA program administers a penalty (which is 

manifested in a source energy reduction for the BA Benchmark design). Figure 14 shows source 

energy use for the BA Benchmark and the final house design. The size penalty reduced theoretical 

source energy savings by about 7%.

Figure 14. Source energy savings for energy efficient design compared to the BA Benchmark

(Adjusted source energy use includes a penalty for the energy efficient design’s additional square footage.)

The preliminary cost savings, which were not subject to a size penalty, were estimated to be about 

$1,100 per year. Components of the savings are depicted in Figure 15.

Figure 15. Annualized utility bill comparison for BA Benchmark and energy-efficient design

For a house having the same energy efficiency solution package as NCTH but that does not 

include the 700-ft2 above-grade finished attic space or the 1,300-ft2 finished basement, a 30% 

source energy savings (with a 1% size penalty) was predicted. Results are shown in Figure 16 and 

Figure 17.
37

Figure 16. Source energy use for BA Benchmark and energy-efficient design

Figure 17. Annual utility bills
38

Appendix B: Wall Cavity Moisture Sensors

Small wireless sensors (Omnisense S-900-1 shown in Figure 18 and Figure 19, shown as modified 

without leg extensions) were installed in walls in the NCTH to measure the following parameters:

• Cavity temperature (-40°F–185°F)

• Cavity RH (0–100%)

• Cavity DPT

• OSB sheathing MC (7%–40%).

21

T/RH are measured by an internal sensor located inside the plastic housing. The wood MC is 

determined using two screw pins driven into the sheathing and is based on the measured resistivity 

of the OSB material. The sensors are prepared at Home Innovation with a protective covering that 

inhibits moisture or other materials from entering the sensor body through the battery 

compartment. In this manner, the sensors have been successfully fielded in locations where 

expanding foam covers the sensor body.

Figure 18. Omnisense S-900-1 sensor Figure 19. Installed test wall moisture sensors

The manufacturer stated accuracy for the sensor models used is ± 2.0% RH and ± 0.3°C. Home 

Innovation has performed numerous calibrations to verify both sensor accuracy and the 

correlations with MC. MC was correlated with readings on handheld electrical conductance type 

moisture meters as well as MC readings with wet/oven dry sample measurement calculations. The 

wood MC value reported through the sensor technology is a wood moisture equivalent and is the 

water content of wood as a percentage of dry weight. The sensor manufacturer calibrates its 

devices based on wood species and temperature compensation relationships outlined by the U.S. 

Department of Agriculture.22 For calibration purposes, a set of sensors was installed in OSB 

 21 Calibrated from the manufacturer to USDA Douglas Fir. 22 James, William L., Electric Moisture Meters for Wood, Forest Products Laboratory, General Technical Report 

FPL-GTR-6

Internal 

Sensor

Antenna

MC Screws
39

samples and placed inside an environmental chamber capable of controlling T/RH. Figure 20

shows the set of sensors in the environmental chamber where T/RH were tightly controlled at 

various levels of humidity for calibration purposes. At various levels of humidity and when 

equilibrium was achieved (equilibrium MC) based on specimen weight consistency, a set of 

specimens were removed, weighed, oven dried, and weighed once again. The resultant ratio of the 

measurements provides the gravimetric MC of the specimen.

Figure 20. MC calibration curves

Figure 20 plots the sensor MC reading, the oven dry MC, and various reference curves from 

literature and shows the calibration relationship between the sensor reading and the measured OSB 

specimen MC. In all cases, the reported sensor reading is higher than the gravimetric calculation at 

most 2% MC. The National Institute of Standards and Technology reference curves (ASTM 2009) 

align well with the gravimetric measurements except at the 90% RH level where the National 

Institute of Standards and Technology reference is about 4% MC lower than measured calibration 

results. The results presented here include calibration of the sensor reading for OSB readings only, 

based on the gravimetric measurements as shown in Figure 20. Measurements from stud readings 

are left unchanged based on the sensor manufacturers’ calibration to solid lumber species.

Sensors were installed in test homes in wall sections identified by orientation with more sensors 

being placed in the north and east orientations. For multistory homes, sensors were placed in both 

the first- and second-story wall sections. Interior sensors provide T/RH data in the main living 

space and are located as close to the thermostat as practical. A second interior sensor is located in 

the main bathroom and where wall cavity sensors are located. If applicable, a third interior sensor 

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

0 10 20 30 40 50 60 70 80 90 100

mositure content, %

relative humidity, %

APA (Lit.)

NIST (Lit.)

Solid Wood (Lit.)

Sensor Reading

Gravimetric 

Measurement

y = 1.1555x + 0.1065

R2 = 0.9956

0

5

10

15

20

25

30

0 5 10 15 20 25

Specimen Gravimetric 

Moisture Content, %

Sensor Moisture Content Reading, %
40

is located in the basement area to provide temperature and humidity data below grade. An exterior 

sensor is used to record the ambient T/RH and is shielded using a white polyvinyl chloride cap.

Sensor data are transmitted at a minimum on a 15-minute basis. All data are uploaded continuously 

to a website capable of data storage. The raw data are processed to calculate the dew point and 

grains of moisture based on the T/RH. The MC data are calibrated to a standard wood MC based 

on the temperature at the wood surface.

The dataset stored on the website is downloaded periodically and averaged on a daily basis for 

further analysis and charting. Each sensor is associated with a wall room location and orientation 

and ultimately with a wall configuration.
DOE/GO-102014-4468 ▪ July 2014

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