Winchester/Camberley Homes 

New Construction Test House 

Design, Construction, and 

Short-Term Testing in a 

Mixed-Humid Climate

D. Mallay, J. Wiehagen, and A. Wood

NAHB Research Center Industry Partnership

October 2012
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iii

Winchester/Camberley Homes New Construction Test House

Design, Construction, and Short-Term Testing in a

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, J. Wiehagen, and A. Wood

NAHB Research Center Industry Partnership

400 Prince George’s Blvd

Upper Marlboro, MD 20774

NREL Technical Monitor: Stacey Rothgeb

Prepared under Contract No. KNDJ-0-40335-00

October 2012
iv

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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 Goals ..................................................................................................................................2

2 Design Development............................................................................................................................ 3

2.1 Design Process and Energy Simulations..............................................................................3

2.2 Cost Analysis.......................................................................................................................3

2.3 Energy Solutions Package....................................................................................................3

3 Thermal Envelope................................................................................................................................. 7

3.1 Framing................................................................................................................................7

3.2 Air Sealing ...........................................................................................................................9

3.3 Insulation and Fenestration................................................................................................12

4 Systems............................................................................................................................................... 13

4.1 HVAC System ...................................................................................................................13

4.2 Plumbing............................................................................................................................16

4.3 Lighting and Appliances....................................................................................................16

5 Implementation ................................................................................................................................... 17

5.1 Framing..............................................................................................................................17

5.2 Air Sealing and Insulation .................................................................................................18

5.3 HVAC ................................................................................................................................20

6 Testing................................................................................................................................................. 22

6.1 Test Plan.............................................................................................................................22

6.2 Infiltration Testing .............................................................................................................23

6.3 Duct Leakage Testing ........................................................................................................24

6.4 HVAC Equipment Testing (Startup) .................................................................................25

6.5 HVAC Duct Distribution Testing ......................................................................................25

6.6 Ventilation Testing.............................................................................................................25

7 Gaps and Lessons Learned............................................................................................................... 27

7.1 Overview............................................................................................................................27

7.2 Framing..............................................................................................................................27

7.3 Air Sealing .........................................................................................................................27

7.4 HVAC ................................................................................................................................27

7.5 Plumbing............................................................................................................................28

7.6 Energy Simulations and Cost Effectiveness......................................................................28

7.7 Quality Assurance..............................................................................................................28

8 Summary ............................................................................................................................................. 29

8.1 Overview............................................................................................................................29

8.2 Next Steps..........................................................................................................................30

References................................................................................................................................................. 31

Appendix A Energy Simulations......................................................................................................... 32

Appendix B Complexity of the Home’s Thermal Boundaries.......................................................... 35
vi 

List of Figures

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

Figure 2. Advanced wall framing............................................................................................................... 4

Figure 3. Supply trunk through floor joists and central duct chase...................................................... 5

Figure 4. Floor framing............................................................................................................................... 8

Figure 5. Wall panels .................................................................................................................................. 8

Figure 6. Continuous drywall method....................................................................................................... 8

Figure 7. Raised heel truss with increased overhang at eaves.............................................................. 9

Figure 8. Complex thermal air boundary (1 of 3) ..................................................................................... 9

Figure 9. Complex thermal air boundary (2 of 3) ................................................................................... 10

Figure 10. Complex thermal air boundary (3 of 3) ................................................................................. 10

Figure 11. Air sealing................................................................................................................................ 11

Figure 12. House wrap installed as air barrier....................................................................................... 12

Figure 13. Wall and attic insulation......................................................................................................... 12

Figure 14. Furnace and first-floor return grille at central chase .......................................................... 14

Figure 15. HVAC supply trunk installed in second-floor framing ........................................................ 15

Figure 16. High-efficiency water heater.................................................................................................. 16

Figure 17. Floor framing........................................................................................................................... 17

Figure 18. Floor framing and wall panels ............................................................................................... 17

Figure 19. Wall panels .............................................................................................................................. 18

Figure 20. Wall panels and trusses ......................................................................................................... 18

Figure 21. Air sealing at blocking below third-floor knee wall and knee walls .................................. 19

Figure 22. Air sealing at basement rim area........................................................................................... 19

Figure 23. Installing wall cavity blown insulation and checking density............................................ 20

Figure 24. Installing HVAC trunk through floor joists........................................................................... 20

Figure 25. Blower door test apparatus and duct test using theatrical smoke.................................... 23

Figure 26. Three additional houses built using the NCTH features..................................................... 29

Figure 27. Completed test house ............................................................................................................ 30

Figure 28. BEopt simulation results........................................................................................................ 32

Figure 29. Source energy savings for energy efficient design compared to the B10 benchmark ... 33

Figure 30. Annualized utility bill comparison for B10 benchmark and energy efficient design....... 33

Figure 31. Source energy use for B10 benchmark and energy efficient design ................................ 34

Figure 32. Annual utility bills ................................................................................................................... 34

Figure 33. NCTH thermal envelope, Section A-A................................................................................... 35

Figure 34. NCTH thermal envelope, Section B-B................................................................................... 36

Figure 35. NCTH thermal envelope, Section C-C................................................................................... 36

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

List of Tables

Table 1. Cost-Effective Energy Solutions Summary ............................................................................... 5

Table 2. Thermal Envelope......................................................................................................................... 7

Table 3. Critical Areas to Apply Sealant ................................................................................................. 11

Table 4. Systems ....................................................................................................................................... 13

Table 5. Research Measurements and Equipment ................................................................................ 23

Table 6. Characterization Testing: House Leakage............................................................................... 24

Table 7. Characterization Testing: Duct Leakage.................................................................................. 24

Table 8. Example Measured Temperature by Level............................................................................... 25

Unless otherwise noted, all tables were created by NAHB Research Center.
vii

Definitions

ACCA Air Conditioning Contractors of America

ACH Air changes per hour

ADA Airtight drywall approach

AFUE Annual fuel utilization efficiency

AHRI Air-Conditioning, Heating, and Refrigeration Institute

ANSI American National Standards Institute

Btu British thermal unit

CFL Compact fluorescent lighting

CPVC Chlorinated polyvinyl chloride

ECM Electrically commutated motor

EF Energy factor

ERV Energy recovery ventilator

ft2 Square foot

h Hour

HRV Heat recovery ventilator

ICC International Code Council

IECC International Energy Conservation Code

iwg Inches of water gauge pressure

Low-e Low-emissivity

MBtu Thousand Btu

MERV Minimum efficiency reporting value (for media-type air filters)

NAHB National Association of Home Builders

NCTH New construction test house

NGBS National Green Building Standard (ANSI ICC 700-2008)

OSB Oriented strand board

PEX Cross-linked polyethylene

SEER Seasonal energy efficiency ratio

SHGC Solar heat gain coefficient

SPF Spray polyurethane foam

TXV Thermostatic expansion valve

WHI Winchester Homes, Inc. and its Camberley Homes division
viii

Executive Summary

The NAHB Research Center partnered with production builder Winchester/Camberley Homes to 

build a new construction test house (NCTH) with the support of the U.S. Department of Energy 

Building America Program.1 This single-family detached house, located in the mixed-humid 

climate zone of Silver Spring, Maryland, was completed in June 2011. The primary goal for this 

house was to improve energy efficiency by 30% over the Building America B10 benchmark by 

developing and implementing an optimized energy solutions package design that could be cost 

effectively and reliably constructed on a production basis using quality management practices. 

This report outlines the features of the house, discusses the implementation of the energy 

efficient design, and reports on the short-term testing results. During the interactive design 

process of this project, numerous iterations of the framing, air sealing, insulation, and space 

conditioning systems were evaluated for energy performance, cost, and practical implementation. 

The final design featured numerous advanced framing techniques and high levels of insulation. 

In addition, the HVAC system was built entirely within conditioned space. Short-term testing 

confirmed a very tight thermal envelope and efficient and effective heating and cooling. Relevant 

heating, cooling, humidity, energy, and wall cavity moisture data will be collected and presented 

in a future long-term report. 

 1 See http://www1.eere.energy.gov/buildings/building_america/program_goals.html for more information.
1 

1 Introduction

1.1 Overview

With the support of the U.S. Department of Energy Building America Program (see footnote 1), 

as part of the NAHB Research Center Industry Partnership, the NAHB Research Center 

(Research Center) 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 mixed-humid region (climate zone four) of Silver Spring, 

Maryland. The three-story (four levels including a basement) Victorian-style house, built as a 

model home, was completed in 2011. 

This report outlines the energy efficiency features of the house, discusses construction and 

installation, and reports on short-term characterization testing. Long-term monitoring and 

additional cost analysis will be detailed in a future report. 

1.2 Background 

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

Maryland, a suburb of Washington, D.C. This subdivision will eventually contain 700 homes, 

100 of which are expected to incorporate the energy efficient design of this house. Based on 

consumer acceptance and measured performance of this research project, some of the remaining 

600 homes may also include these advanced energy features.

Figure 1. Winchester/Camberley NCTH

The three-story design had 3,228 ft of conditioned floor area above grade, including a 605 ft 2 2

finished third floor with a sitting room, a full bath, and a fourth bedroom. A finished basement 

brought the total to 4,441 finished ft2. The finished third floor and basement were included 

builder options. Ceilings were 9 feet for the first floor and basement, 8 feet for the second floor, 

and 8 feet or sloped for the third floor. Above-grade walls were frame construction; basement 

foundations were poured and mostly below grade. All attic areas were vented. A unique design 

feature of this home was the octagonal, three-story turret that housed the open stairwell 

connecting the basement to the second floor. Access to the third floor was by a separate stairway. 

The garage was not attached to the house.
2

1.3 Goals

The primary performance goal for this house was to improve energy efficiency by 30% over the 

Building America B10 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. The Building America 

goals align well with the builder’s long-term goals for performance and construction quality. 

Specific goals for the NCTH were established during the planning phase:

• Develop and implement a durable design that improved energy efficiency by at least 30% 

over a comparable house that meets the 2009 International Energy Conservation Code 

(IECC; see International Code Council [ICC] 2009). 

• Create a tight thermal boundary and increase insulation levels to be in accordance with 

expected higher levels in future editions of energy codes or from consumer demand.

• Develop an envelope design that would be flexible in adapting 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 cost increases.

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

reduce energy losses (leakage and convection losses from equipment and ducts) to 

unconditioned space, reduce duct run lengths, and eliminate the need for a second system. 

• Design the HVAC system to ensure occupant comfort in this four-level design. 

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

building systems that could be constructed on a production basis using quality 

management practices.

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

distribution, and wall moisture performance.

• Earn the American National Standards Institute (ANSI)/ICC 700-2008 (2009) National 

Green Building Standard (NGBS) Silver Level Green Certification.
3

2 Design Development

2.1 Design Process and Energy Simulations

The builder was committed to including high performance home features to significantly exceed 

current energy code requirements and decided to develop a new product line that integrated the 

energy features instead of modifying an existing model. The thermal envelope was completely 

redesigned from standard specifications and a set of high performance construction features was 

developed for the new house design. The final energy efficiency solution package represented 

months of development by the Research Center, WHI staff, trade contractor professionals, 

manufacturers, and product suppliers. The design process involved technical input, energy 

modeling, and optimization by the Research Center and input on costs and other practical factors 

by team members. Energy savings were simulated using BEopt v1.1.2 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 are detailed in 

Appendix A and indicate that the Building America energy savings goal was met.

2.2 Cost Analysis

During the design process, WHI completed an extensive in-house cost analysis, which 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, among others). This analysis 

included energy performance, occupant comfort, and synergistic cost containment benefits such 

as reduced material and labor costs. The high performance features were selected and designed 

to perform as an integrated system. 

A detailed cost analysis is planned for the future long-term monitoring test report for this project. 

WHI is currently completing three additional houses of similar design that include the energy 

savings features of the NCTH. Once these are complete, the Research Center will work with 

WHI to finalize the cost analysis, allowing investigators to more fully understand the incremental 

costs. Understanding a builder’s cost approach is not necessarily a straightforward analysis 

because of the pricing structure for the different materials and the lack of comparative pricing for 

the framing system. Additionally, there is no reference point for “builder standard practice” 

because the homes are a new product line and unique to the builder. 

2.3 Energy Solutions Package

The project planning stage included four builder-directed design review meetings conducted at 

the Research Center. Attendees included the project manager, the operations manager, the site 

superintendent, design and purchasing personnel, structural engineers, floor component and wall 

panel vendors, and trade contractors. Numerous iterations of the framing, air sealing, insulation, 

and HVAC systems were evaluated for energy performance, cost, and practical implementation. 

For example, the meeting participants decided early in the process that wall panels would have 

structural sheathing without foam on the exterior. The builder was concerned about the structural 

durability of foam sheathing products without oriented strand board (OSB) and the durability of 

cladding attachment over rigid foam with or without OSB. Based on this decision and 

recognizing the need for higher insulation levels for this climate zone in the future, a nominal 

 2 See http://beopt.nrel.gov/ for more information.
4

2-in. × 4-in. wall cavity would require higher density insulation such as closed-cell spray 

polyurethane foam (SPF) insulation. After evaluating the cost for a 2-in. × 4-in. wall with SPF, 

this option was ruled out in favor of a 2-in. × 6-in. frame wall with batt or blown insulation.

Once this decision was made, the wall panels were redesigned to optimize performance, 

including engineered structural rim boards, elimination of nonstructural nailers where possible, 

and other advanced framing techniques (detailed in Table 2) to increase room for insulation and 

provide a higher level of air sealing. To avoid nonstandard length studs and maintain ceiling 

heights, a conventional second top plate was included in this new design. Figure 2 shows the 

construction of the wall design using this advanced framing technique. 

 

Figure 2. Advanced wall framing

Another example of this iterative design process was the early decision to install the entire 

HVAC system in conditioned space to reduce energy losses. This required redesigning the floor 

plan and floor framing to accommodate a central duct chase to serve all four levels. This chase 

was sized to accommodate the vertical sections of the supply and return trunk ducts within. 

Additionally, a bulkhead along the first floor ceiling to conceal the supply trunks serving the 

second and third floors was not architecturally acceptable. 

As a result, the horizontal sections of the supply trunks serving the upstairs (second and third 

floors) were integrated within the second-floor framing (installed perpendicularly through 

factory cutouts through the floor joists) so that all of this upstairs duct would be above the firstfloor ceiling plane. A bulkhead at the first floor ceiling would not be required. The supply trunks 

serving the downstairs (first floor and basement) were installed in the basement in a more 

conventional manner (below and perpendicular to the first-floor joists) because a bulkhead to 

conceal this duct was deemed acceptable in finished portions of the basement. 

Specialized design software was used to prepare accurate drawings showing exact locations of 

the mechanicals (including plumbing and sprinkler piping) within the floor system, including the 

central duct chase. These drawings were then used at the factory to number and cut all joists and 

rim boards to exact lengths, and to precisely cut openings through the I-joists as required. Figure 

3 shows the central duct chase and integrated duct and floor-joist design. This high-level 

integration of structural and mechanical systems required a complete duct design during the 
5

planning stage to size the chase and joist openings. Similar planning was necessary for the 

plumbing and sprinkler piping.

 

Figure 3. Supply trunk through floor joists and central duct chase

This iterative approach to evaluating benefits and trade-offs of alternative designs was applied to 

insulation and air sealing products and methods, floor and truss framing, windows, HVAC 

equipment, and the water heater and plumbing distribution system. Table 1 summarizes the 

design, and Table 2, Table 3, and Table 4 give additional details.

Table 1. Cost-Effective Energy Solutions Summary

Design Consideration Solution

Increased Insulation • 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 equipment systems from the 

traditional two HVAC systems 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

• Included practical input from WHI, vendors, and trade 

partners during planning stage design reviews

• Developed construction details and specifications

• Established construction monitoring points (reviews, 

inspections, and tests) 

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

practical implementation

Many of the new construction details were included in the drawing package. Goals and 

expectations for the trade contractors were mutually agreed on, and site reviews, inspections, and 

tests were scheduled for quality assurance. The level of effort invested during the planning stage 
6

was considered important for the successful design and implementation of the solution package 

for this test house as well as subsequent houses. 
7

3 Thermal Envelope

The thermal envelope design consisted of an integrated framing package with considerations for

air sealing and openings. The package also maintained the Victorian architectural style while 

allowing as much insulation as possible in the exterior walls and attic. Table 2 shows the thermal 

envelope design compared with standard regional practice. 

Table 2. Thermal Envelope

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

• Structural rim headers

• Reduced framing

• R-24 blown fiberglass insulation

• Continuous drywall method 

Air Sealing

• Bottom plates sealed at deck

• Penetrations sealed

• Window rough openings 

sealed

• Same as standard practice plus the 

following:

 Sealed frame at all critical areas (see 

Table 3) using spray-applied, watersoluble, elastomeric sealant

 Airtight drywall approach

 House wrap installed as air barrier

Windows • U-value = 0.35, SHGC = 0.35 • Low-e, U-value = 0.31, SHGC = 0.28

Doors • n/a • U-value = 0.35, SHGC = 0.36

Roof/Attic

(Vented)

• Standard truss, 1-ft overhang

• R-38 blown fiberglass

• 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

Notes: Low-e, low-emissivity; SHGC, solar heat gain coefficient

3.1 Framing

Floor framing was optimized using I-joists, 24-in. on center as shown in Figure 4. The reduced 

cost of fewer floor joists was partly offset by selecting 7⁄8-in. floor decking (instead of 3⁄4-in.) to 

ensure rigid floors. Floor joists and rim boards were cut to exact lengths and numbered at the 

factory for efficient installation. Cutouts through the joists for the HVAC duct, the plumbing, 

and the sprinkler piping were also made at the factory.
8

 

Figure 4. Floor framing

The factory-built wall panels shown in Figure 5 were redesigned to reduce thermal bridging and 

increase insulation volume. Walls were 2-in. × 6-in. wood frame, 24 in. on center, with 1⁄2-in. 

OSB sheathing. Structural rim headers eliminated first-floor headers and jack studs; unnecessary 

blocking, studs, and cripples were also eliminated. Second-floor headers were engineered to 

minimize dimensions to reduce initial cost, reduce thermal bridging, and increase wall insulation. 

Second top plates and a house wrap were installed in the field. Cladding was fiber cement siding.

 

Figure 5. Wall panels

The continuous drywall method was specified to further reduce framing air losses. All interior 

partition walls were installed 1 in. from the exterior walls, allowing the wallboard to be slid 

through this space along the exterior walls shown in Figure 6. These walls were structurally 

attached using metal plates above the top plates. Electric and plumbing trade partners’ 

specifications required that electric wiring or pipes were not to be installed in this space. 

 

Figure 6. Continuous drywall method
9

In the basement, wood frame walls were site-built and held 1 in. from the poured foundation. In 

the attic, raised heel roof trusses with the 2-ft overhangs shown in Figure 7 accommodated fulldepth insulation and insulation baffles at the eaves and notably at the sloped ceilings of the third 

floor.

 

Figure 7. Raised heel truss with increased overhang at eaves

3.2 Air Sealing

To achieve very low infiltration rates given the frame walls and complex thermal boundary, 

identifying critical areas for air sealing was essential. This house design was considered 

architecturally complex to air seal primarily because of the third floor and turret as shown in 

Figure 8, Figure 9, and Figure 10. The third floor had front and rear knee wall attics, partially 

sloped ceilings, and a separate attic above the flat ceiling. The top of the turret and the third floor 

were separated by the front attic. Additionally, the following were all adjacent to the same attic: 

the stairs to the third floor, the HVAC chase, a knee wall framed cavity, a gable knee wall for a 

second-floor bedroom with a cathedral ceiling, and two closets with lower ceilings. This 

complex design created the need for the installation and sealing of numerous air barriers 

including the blocking of floor joists below third-floor knee walls. 

 

Figure 8. Complex thermal air boundary (1 of 3)
10

 

Figure 9. Complex thermal air boundary (2 of 3)

 

Figure 10. Complex thermal air boundary (3 of 3)

The primary air sealing strategy was to create an effective air barrier exterior to the insulation. A 

secondary strategy was to provide an interior air barrier using the airtight drywall approach 

(ADA). The product selected for both was a spray-applied, low-expanding, water-soluble, 

elastomeric sealant (sealant) applied at all critical area seams of the wood frame. Table 3 outlines 

the critical areas where the sealant was applied, and Figure 11 shows examples of air sealing. 
11 

Table 3. Critical Areas to Apply Sealant

Critical Area Specific Location for Sealant

Exterior Walls

Stud cavities: top and bottom plates at sheathing

Stud cavities: studs at sheathing seams

Face of top plates, between top plates

Face of studs at wall panel connections

Bottom plates at floor deck

Electrical boxes and other exterior penetrations

Partition Walls Face of top plates adjacent to a vented attic

Rim Areas

Rim board at floor deck and top/sill plate

Floor-joist air barriers below third-floor knee walls

Sill plates at the foundation

Basement frame wall cavity, top plates at foundation wall

Knee Wall Air Barriers

Third floor, front and rear

Third-floor stairs

Gable knee wall of second floor, front bedroom cathedral ceiling

Portions of turret walls

Framed Cavity Air Barriers

Behind the fireplace

Behind tubs at exterior walls

HVAC chase, wall and sloped ceiling

Closet ceilings adjacent to attic

Knee wall cavity created by second knee wall

Additional Areas for ADA

Face of bottom plates

Face of window and door rough openings on exterior walls

Electrical boxes in exterior walls

 

Figure 11. Air sealing

As a tertiary air sealing strategy, house wrap was installed as a secondary exterior air barrier, 

which also serves as the drainage plane. All house wrap seams were taped, and the top and 

bottom edges were sealed to the frame. To seal the bottom edge, first flashing tape was applied 

to the sheathing with a 1-in. overhang below the sill plate, and then house wrap was shingled 
12

Figure 13. Wall and attic insulation

over and sealed to the flashing tape as shown in Figure 12. To seal the top edge, house wrap was 

held 2 in. from the top of the sheathing and then covered with flashing tape. The flashing tape 

was also mechanically secured with staples. 

 

Figure 12. House wrap installed as air barrier

Windows and doors were installed and flashed in a conventional manner per manufacturer 

instructions. Attic access panels and ceiling penetrations adjacent to attics, including electrical 

boxes, speakers, and recessed lights, were sealed after drywall using gaskets, foam, or caulk.

3.3 Insulation and Fenestration

After air sealing, above-grade wall cavities 

were netted and blown using R-24 dense-pack 

fiberglass insulation. The triangular voids 

between the wall panels of the octagonal turret 

were filled using spray foam insulation from a 

can because these walls had been installed 

with a 3⁄4-in. gap between panels to allow for 

the installation of the spray foam. Basement 

walls were insulated using R-13 fiberglass 

batts. Attic insulation, including the sloped 

ceilings of the third floor, was increased to R49 by using fiberglass batt insulation in some 

sloped ceiling locations and blown fiberglass 

insulation in other locations. Attic insulation in 

a few locations was installed before drywall using netting because access to these attic areas 

would be very limited after drywall installation. Windows were double hung, vinyl, and 

improved to low-e, a U-value of 0.31, and an SHGC of 0.28. Figure 13 shows the installed 

insulation and fenestration. 
13

4 Systems

The systems design included heating, cooling, duct, ventilation, plumbing, and lighting. The goal 

of the systems design was to improve equipment operating efficiencies, ventilation, filtration, 

and occupant comfort. Two significant design details for the test house systems include (1) 

locating the ducts entirely in conditioned space and designing the duct location in conjunction 

with the framing design and (2) properly sizing the HVAC system given the thermal envelope of 

the house, which allowed one HVAC system to be installed where typical regional practice 

would install two systems. Table 4 outlines the systems for the WHI test house. 

Table 4. Systems

System Standard Practice NCTH

Heating Two 80% AFUE natural gas 

furnaces (one in vented attic and one 

in basement)

One 92.5% AFUE natural gas furnace 

with two-stage gas valve and ECM 

air drive, installed in basement

Cooling Two 13 SEER systems One 15 SEER system

Thermostat Programmable Programmable with integral 

humidistat and controls to run the 

cooling system in dehumidification 

mode

HVAC duct One flexible, insulated duct system 

in vented attic and one metal duct 

system in basement

One 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 (MERV 1–4) MERV 10 high-efficiency pleated 

filter

Ventilation One bath exhaust fan with 

programmable control 

Mechanical ventilation with damper 

and control

Plumbing 65-gal natural gas water heater, EF = 

0.60; CPVC branch and tee piping

50-gal, power vent, natural gas water 

heater, EF = 0.74; PEX manifold 

piping

Lighting 50% CFL 80+% CFL

Notes: AFUE, annual fuel utilization efficiency; ECM, electrically commutated motor; SEER, seasonal energy 

efficiency ratio; MERV, minimum efficiency reporting value; EF, energy factor; CPVC, chlorinated polyvinyl 

chloride; PEX, cross-linked polyethylene; CFL, compact fluorescent lighting

4.1 HVAC System

The HVAC system was designed so that all equipment and ductwork would be located within 

conditioned space to significantly reduce equipment and distribution energy losses resulting from 

conduction and leakage. Standard WHI practice used two independent systems―one in the

basement to condition the first floor and basement, and a second in the attic (furnace and ducts) 

to condition the second and third floors. This approach, common in this region, provides 

effective heating and cooling comfort (two independent zones) and is simple to install (no supply 

ducts running between floors). The additional equipment costs are typically considered a tradeoff 

to the expectation of satisfactory occupant comfort and expediency. Installing two systems 

expedites the design stage and does not require site efforts to integrate the systems within 
14

conditioned space, but one system could often easily meet the heating and cooling load 

calculations. The WHI NCTH design was a single HVAC and duct system located in the 

conditioned space with the expected result, in addition to energy savings, of equipment cost 

savings. 

High-efficiency equipment was specified: a 15 SEER cooling system and a 92.5% AFUE natural 

gas furnace. The furnace shown in Figure 14 was direct vent (a two-pipe design that uses outdoor 

air for combustion) with a two-stage gas valve and an ECM air drive. The furnace was selected 

based on the cooling air flow requirements. In high-heat mode the furnace output was much 

higher than the design load; in low-heat mode, however, the output matched much more closely 

with the calculated load. The programmable thermostat with its integral humidistat had the 

capability of running the furnace in dehumidification mode (reduced blower speed) to improve 

moisture control during the cooling season. Electronic zone dampers were specified to ensure 

occupant comfort in this four-level house design. Load calculations, equipment selection, and 

duct design were in accordance with the recommendations of the Air Conditioning Contractors 

of America’s (ACCA’s) Manual J (2006), Manual S (2004), Manual T (1992), and Manual D 

(2009). 

 

Figure 14. Furnace and first-floor return grille at central chase

The centrally located duct chase shown in Figure 14 served all four levels. A simplified return 

duct system, consisting of one central return per level, was installed in the chase. Bedroom 

transfer grilles, baffled to minimize light and noise, provided a return air pathway. The return 

duct was intentionally sized in accordance with ACCA Manual D, Table A1-1, Air Velocity for 

Noise Control recommendations and acoustically lined to ensure quiet operation, an important 

consideration with the furnace installed in the basement directly below the first-floor return 

grille. 

Figure 14 shows how the vertical section of the upstairs (second and third floors) supply trunk 

duct was also installed in the chase. The horizontal sections of the upstairs supply trunk duct 

were integrated within the second-floor framing as shown in Figure 15. Supply branch ducts 

were installed between the joists, and vertically through interior walls for the third floor, to 

perimeter floor registers. 
15

Figure 15. HVAC supply trunk installed in second-floor framing

The downstairs (first-floor and basement) supply trunk was installed in a more conventional 

manner: below and perpendicular to the first-floor joists. As a result, a bulkhead was required to 

conceal this trunk in the finished portions of the basement. Supply branch ducts were installed 

between floor joists to perimeter floor registers on the first floor and ceiling registers in the 

basement. All ducts were sealed using mastic.

Fresh air ventilation for moisture control and indoor air quality was provided using a supply-type 

central fan-integrated design. The design is capable of meeting ASHRAE Standard 62.2 

ventilation recommendations (ASHRAE 2010). An insulated metal duct delivered outdoor air to 

the HVAC return plenum through a motorized damper opened or closed by an electronic control. 

This design allowed outdoor air to be filtered, conditioned, and well distributed during a call for 

heating or cooling, and the source of outdoor air would be known (unlike exhaust-only systems 

that rely on makeup air infiltrating through the house envelope). The ventilation control would 

also activate the damper and furnace blower when the heating or cooling run times did not satisfy 

the desired ventilation rate. A balanced ventilation system based on the use of an energy 

recovery ventilator (ERV) or heat recovery ventilator (HRV) was ruled out as too costly. The 

expectation for the selected supply-type ventilation was that positive house pressure would not 

be excessive and would tend to be alleviated via exhaust fan ducting, in effect providing a 

partially balanced system. As such, the system would not contribute to potential moisture drive 

into the wall cavities.

A high-efficiency (MERV 10), media-type, pleated air filter was installed to improve air quality. 

The filter cabinet had a gasketed access door and its location adjacent to the furnace allowed for 

simple filter replacement. Because the builder was concerned that the abundant wood floors and 

trim might dry too much and crack during the heating season, a central humidifier was installed. 

Bath exhaust fans were ENERGY STAR and rated to be quiet (0.8 sone at 0.1 in. of water gauge 

pressure [iwg] static pressure). Wall switches with timers were installed for these fans to ensure 

adequate moisture removal. These switches had a 20-minute fan-on delay and were capable of 

being programmed for supplemental ventilation, if desired.
16

4.2 Plumbing

Domestic hot water was provided by the 50-gallon, natural gas, power vented water heater 

shown in Figure 16. The estimated EF was 0.74 (manufacturers are not required to provide EF 

ratings for units with inputs exceeding 75,000 Btu/h). The water heater was centrally located, 

low-flow plumbing fixtures were installed, and a PEX manifold distribution system was installed 

to minimize energy and water use.

Figure 16. High-efficiency water heater

4.3 Lighting and Appliances

High-efficiency lighting was increased to more than 80% of total lighting by specifying 

dimmable fluorescents in recessed fixtures and fluorescent lamps in other standard fixtures. 

Recessed lighting fixtures were upgraded to sealed units to reduce air leakage (the incremental 

cost was attributed to the lighting option budget). Appliances were all ENERGY STAR rated. 

Additionally, the house design included one natural gas direct vent fireplace with a sealed glass 

panel. 
17

5 Implementation 

5.1 Framing 

The floor component manufacturer conducted an on-site installation review the morning of floor 

framing to ensure that the numbered joists and rim boards shown in Figure 17 and Figure 18

were efficiently and accurately installed. Two components were missing from the delivery and 

some minor field modifications were required, but this did not appear to affect the construction 

schedule. The floors and numbered wall panels shown in Figure 19 and Figure 20 were installed 

in 2 days. The roof trusses and framing were also numbered for efficient installation. After 

framing was complete, WHI staff observed and corrected some rim, header, and wall nailing 

issues. The 7⁄8-in. floor decking, which was installed over the 24-in. on center floor joists, 

resulted in an observably stiff floor. 

 

Figure 17. Floor framing

 

Figure 18. Floor framing and wall panels
18

 

Figure 19. Wall panels

 

Figure 20. Wall panels and trusses

5.2 Air Sealing and Insulation

The primary air sealing challenge was the difficulty of identifying a continuous thermal and air 

sealing boundary for this complicated house design. A notable effort was made to include the air 

sealing boundary on the drawings (see Appendix B); however, the three-dimensional aspect of 

the boundary made an on-site review, just before air sealing, imperative. This review included 

the framing contractor (responsible for installing the air barriers) and insulation contractor 

(responsible for sealing the air barriers) because they needed to coordinate their efforts. 

After air sealing, a walk-through showed that the majority of critical areas had been sealed. 

Because of the high expectations for this house, a number of areas needed to be touched up 

before installing insulation, including portions of top plates and header cavities, and portions of 

air barriers at knee walls, joist blocking, and framed cavities. Identifying areas that needed to be 

touched up was not intended as criticism of the product or trade contractors; instead, it was 

intended to highlight the challenge of identifying a continuous thermal and air barrier with such 

an architecturally complex design. A key advantage of using a product and method such as this 

sealant was the ability to visually inspect after air sealing and, if necessary, make corrections 

before insulation and drywall installation. Figure 21 shows an example of the complexity of air 

sealing these areas. 
19

 

Figure 21. Air sealing at blocking below third-floor knee wall and knee walls

Sealant was not consistently applied to the faces of the framing at the bottom plates and around 

windows and doors (although bottom plates were sealed at the floor deck). These areas were 

specified to be sealed in accordance with the ADA, but the contractor did not consider this 

necessary. Although sealant was applied in the gap between the rough framing and the windows 

and doors, these gaps might have been more effectively sealed using low-expansion spray foam 

insulation instead. Research Center personnel did not consider it necessary to apply sealant to the 

interior faces of the bottom cords of second- and third-floor roof trusses (although it would not 

have been detrimental). The sill plate at the foundation wall could not be sealed from the interior 

because the basement wall framing had already been installed (see Figure 22); instead, sealant 

was applied from the exterior at this critical area. 

Figure 22. Air sealing at basement rim area 

Sealing the house wrap to function as a secondary exterior air barrier was initially considered a 

simple, additional method to reduce infiltration. During construction, some areas of the house 

wrap were not completely air sealed as planned because they were challenging or overlooked, 

but an effort to correct all of these areas was not considered critical because the sealant was used 

as the primary air sealing strategy. 

To insulate the wall cavities, netting was stapled to the faces of all exterior wall framing. Next, 

the loose fiberglass insulation was blown into each cavity, using a hose from a truck outdoors, 

through one slit in the netting (see Figure 23). Wall cavity density was measured as the work 
20

progressed to ensure that the target insulation levels were achieved (see Figure 23). For attic

insulation, netting was installed at the ceiling plane where fiberglass batts had not already been 

installed. Next, loose fiberglass was blown into these areas. All wall and ceiling insulation was 

complete before drywall installation. 

 

Figure 23. Installing wall cavity blown insulation and checking density

5.3 HVAC 

During the design phase, the participants did not consider it acceptable to cut openings through 

the second-floor structural rim boards to allow the upstairs supply trunks to be slid into place. 

For this reason, the HVAC trade contractor installed these trunks in sections, through the joist 

cutouts, as the second-floor joists were being installed. This implementation approach required 

an additional site trip for the HVAC contractor. 

Figure 24. Installing HVAC trunk through floor joists

The electronic zone dampers originally specified were eliminated as too costly. Manual dampers, 

accessible from the furnace room, were installed instead in the three supply trunks. Two trunks, 

one for the front and one for the rear, supplied the first floor and the basement. The third trunk 

was dedicated to the second and third floors. This allowed air flow balancing between the two 
21

lower levels (first floor and basement) and the two upper levels (second and third floors), but not 

between the second and third floors. 

All ducts were sealed with mastic as planned. Before the furnace was installed, a rough duct 

leakage test indicated higher than expected leakage. A second rough test was conducted using 

theatrical smoke. The HVAC contractor was on site to visually identify the leakage areas in need 

of repair. After additional mastic was applied to these areas, a third rough test measured the 

improvement (see Section 6.3 for test results).

A standard efficiency, nominal 13 SEER cooling system was installed instead of the 15 SEER 

that was originally specified. This substitution was the result of a contract-related decision 

between the WHI purchasing department and the HVAC contractor. The ECM in the furnace 

typically improves the rated SEER, and although this system is likely operating above 13 SEER, 

this equipment combination (gas furnace, condensing unit, evaporator coil, and thermostatic 

expansion valve [TXV]) had not been rated by the Air-Conditioning, Heating, and Refrigeration 

Institute (AHRI). Note that the condenser and the coil are a rated AHRI match, but they had not 

been additionally rated with this furnace.
22

6 Testing

6.1 Test Plan

Many of the energy efficiency features incorporated into the house design were new to the 

builder and trade contractors. As a model home, the house will likely see extremes in energy 

usage that result from the anticipated additional heating, cooling, lighting, and miscellaneous 

loads. Using this NCTH for testing and evaluating products and methods is critical in addressing 

the following research questions: 

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

interior temperatures on each of the four levels of the home and how do these 

temperatures change throughout the day during summer peak cooling days and winter 

peak heating days?

• Is the measured energy use for heating and cooling consistent with modeled estimates 

given similar ambient weather conditions? 

• Are the HVAC elements—furnace, compressor, thermostat, humidifier, and fresh air 

supply damper—operating as designed and in an optimal manner?

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

exterior conditions and are the sheathing moisture characteristics within expected 

swings?

• How do the wall cavity moisture characteristics compare with modeled results in WUFI 

software?

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

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

manufacturers?

To answer all but the last question, a team will take the research measurements detailed in Table 

5. Feedback from WHI will be used to evaluate the last question.
23

Table 5. Research Measurements and Equipment

Measurement Equipment Test Type

Infiltration Rate Minneapolis Model 3 blower door and 

DG700 manometer

Short-term 

characterization test

Duct Loss Minneapolis Series B duct blaster and 

DG700 manometer

Short-term 

characterization test

Air Handler and Duct Flow 

Rates

Trueflow grid, balometer, hot wire 

anemometer

Short-term 

characterization test

Temperature, Humidity, 

Moisture Content Omnisense S-900 wireless sensor Long-term monitoring

Electric Energy Watt Node transducers and associated 

current transformer sizes Long-term monitoring

Gas Valve On-Time Low-current switch Long-term monitoring

Data Recording—

Temperature/Humidity/

Moisture Content

Omnisense Gateway connected to 

protected website Long-term monitoring

Data Recording—Energy, 

Runtime, and Others

Campbell Scientific data logger, 

modem Long-term monitoring

Short-term test results are detailed in the following sections. Long-term monitoring will be 

detailed in a future report after collecting at least 1 year of monitored data. 

6.2 Infiltration Testing

An intermediate blower door test (shown in Figure 25), performed after drywall installation but 

before trim, floors, and ceiling penetrations were sealed, identified one significant leakage area. 

A short wall built in front of a third-floor knee wall to increase ceiling height created a framed 

cavity, common to the HVAC chase, that resulted in significant leakage from the attic at the 

angled top plate and sloped ceiling. A second intermediate test, conducted after this area was resealed and the house was substantially complete except for the sealing of all ceiling penetrations, 

showed a significant improvement. Final testing measured an additional improvement for the 

completed house as detailed in Table 6. 

 

Figure 25. Blower door test apparatus and duct test using theatrical smoke
24 

Table 6. Characterization Testing: House Leakage

Performance Metric NCTH Units

House Size 4,441 Finished area (ft2

)

4,568 Conditioned area (ft2)

House Volume 41,847 ft3

Infiltration

Test 1a Test 2b Finalc

2,400 1,380 1,335 CFM50

3.4 2.0 1.9 ACH 50

0.17 0.10 0.10 ACH natural

0.53 0.30 0.29 CFM50 a Before trim and sealing of all penetrations but after sheetrock installation

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

Notes: CFM, cubic feet per minute; CFM 50, cubic feet per minute at 50 Pa; ACH 50, air changes per hour at 50 Pa

6.3 Duct Leakage Testing 

Several rough duct leakage tests were conducted before the furnace was installed. The first test 

indicated higher than expected leakage. A second test, using theatrical smoke (shown in Figure 

25), identified leakage areas, and a third test measured the improvement after additional mastic 

was applied. During the rough tests, the house was not ready for a blower door test, so leakage to 

the outdoors could not be measured. After the furnace was installed, the final duct leakage test 

measured an additional 253 cfm compared to the previous rough test. This may be largely 

attributed to the furnace, coil, and air cleaner cabinets. Sealing registers and grilles to finished 

floors and walls during final testing may also allow additional leakage between these surfaces, 

compared to sealing these areas during a rough test. The majority of the ductwork was concealed 

with drywall, so further testing and repair was not practical. 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, was relatively low. Table 

7 summarizes the duct leakage testing results. 

Table 7. Characterization Testing: Duct Leakage 

Performance 

Metric NCTH Units

House Size 4,441 Finished area (ft2

)

4,568 Conditioned area (ft2)

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 CFM25/100 ft2

n/a n/a n/a 43 CFM25 to outdoors a All three rough duct tests were conducted after ducts were sealed using mastic, before the furnace was installed, 

and before the house was ready for a blower door test, so duct leakage to outdoors measurements were not available. b The higher leakage results of Test 2 were due to use of existing tape from Test 1, which may have come loose in 

some areas. Test 2 was performed using theatrical smoke for demonstration purposes. c Test 3 was conducted after additional duct sealing using mastic. d The final test was conducted after the furnace was installed and the house was complete. 
25

6.4 HVAC Equipment Testing (Startup)

The manufacturer’s regional technical representative assisted with the startup of the heating and 

cooling equipment. The gas furnace initially consumed gas at a much higher rate (based on the 

clocking the meter method) than specified by the equipment nameplate. The furnace gas 

manifold pressures were adjusted accordingly per the manufacturer’s specifications. Typically, 

gas furnace installation instructions state that the gas consumption must be measured and burner 

orifices checked as part of a proper startup. As a result, gas valve adjustments are routinely 

required (for any brand). The thermostat was installed on a wall common to the duct chase; this 

makes sealing the hole for the control wiring behind the thermostat—a conventional practice—

more critical because it helps to isolate any potential temperature difference between the chase 

and house. The thermostat required a 2-degree calibration. 

For the cooling system, despite an accurate air flow measurement and refrigerant charge in 

accordance with industry standards, the system was shown to be operating very inefficiently at 

first. The HVAC contractor had accurately weighed in the refrigerant, the measured subcooling 

was within range for this TXV system, and the system appeared to be cooling adequately. 

Despite these factors, based on additional measurements (including superheat) and an accurate 

furnace air flow measurement by Research Center staff using a flow grid, the technical 

representative calculated that the nominal 4-ton system was undercooling by 9,000 Btu/h (3⁄4 of a 

ton), and therefore running considerably longer than necessary. The factory-installed TXV 

sensing bulb was relocated (a relatively simple adjustment), which corrected the problem. 

6.5 HVAC Duct Distribution Testing

Temperature variations by level measured during the cooling season varied by time of day but 

typically ranged from 1°–3°F (see Table 8). The measured results were best when the two 

downstairs dampers were half-closed. Based on temperature measurements and perceived 

comfort, the duct design appeared to be performing very well, particularly considering the fourlevel design of the house. Long-term monitoring of indoor temperatures and relative humidity 

results will be presented in a future report. The effectiveness of the bedroom transfer grilles as a 

low-pressure, return air pathway was not measured because these interior doors had not been 

installed in the model home. 

Table 8. 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.

First Floor at Thermostat 70.6 71.6 72.2

Second-Floor Master 

Bedroom 70.4 71.6 72.1

Third-Floor Bedroom 70.7 72.6 73.5

Basement Recreation Room 69.7 70.9 72.3

6.6 Ventilation Testing

The fresh air ventilation flow, measured using a hot wire anemometer, was less than expected, 

even in the cooling mode (when the fan should be drawing the most air). One subsequent 

measurement in the heating mode showed an unexpected improvement, although the flow was 
26

still less than anticipated. This lower flow required the controls to open the damper for more 

minutes per hour to meet ASHRAE Standard 62.2 recommendations (ASHRAE 2010).

Bath exhaust fan air flows initially tested significantly less than rated. An investigation revealed 

that an unnecessary control that limited air flow had been installed. Removing this control 

improved the air flows considerably, although they were still below the nominal factory ratings. 
27

7 Gaps and Lessons Learned

7.1 Overview

The level of effort invested during the planning stage was considered important to the successful 

design and implementation of the energy features for this research project. The energy efficiency 

features were selected for durability, practical and repeatable installation, and cost effectiveness. 

7.2 Framing

The floor-framing members were individually engineered to accommodate the floor plan, central 

duct chase, and integrated HVAC supply duct. The optimized wall framing improved thermal 

performance. 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. 

The floor framing design resulted in a rigid floor, and the numbered joists and rim boards made 

for efficient installation after a brief learning curve period.

7.3 Air Sealing

The sealant product and method, including being able to inspect the application before 

proceeding, resulted in a high level of air sealing. The installation of house wrap as a secondary 

exterior air barrier was not completely accomplished (sealing the top and bottom of the house 

wrap was not completed), and the ADA was not completely implemented (sealing the faces of 

the bottom plates and rough framing around windows and doors); these details were not included 

in the subsequent three houses. Intermediate house leakage testing to identify the incremental 

effect of both was not possible because the house wrap, sealant, and drywall were installed 

before an intermediate blower door test could be performed. 

7.4 HVAC

Installing the entire heating and cooling system in conditioned space resulted in significant 

estimated energy savings. This, 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 to accommodate the central duct chase. This chase was critical to installing the 

entire system in conditioned space and was also used for plumbing piping. The integrated 

upstairs duct and floor system required significant effort and site coordination at the design 

stage. A different approach to implementing this design could be to cut an opening through the 

engineered rim board at the factory to accommodate the field installation of the duct after 

framing was complete. For an opening required over a window, a conventional header could be 

installed. As an alternative, the integrated duct and floor design could be eliminated by installing

this duct conventionally (below and perpendicular to the floor joist) with a bulkhead if the design 

aligned with the architectural plan. 

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

could communicate with the ducts (e.g., at the rim areas or at the top of the central duct chase). 

Because the leakage to the outdoors was minimal, the energy penalty was not considered 

significant, although the total duct leakage is still a cause for concern. 

Bath exhaust fan air flows that test below the nominal fan ratings may be widespread (not limited 

to this project) and may be partially caused by a lack of manufacturer guidance for duct design.
28

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

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

be improved by using different duct or fittings (e.g., a larger diameter pipe or a less restrictive 

vent hood). The Research Center continues to investigate the cause and solution of this issue. 

Additionally, the effect of a 600-cfm adjustable flow kitchen range exhaust hood on house 

pressure will be measured. 

Lower than expected fresh air ventilation flow may be attributed to the return duct design. The 

return duct was sized to reduce air velocity and associated noise in accordance with ACCA 

Manual D recommendations (ACCA 2009). This, however, resulted in a low-pressure-drop 

design that might indicate a need for a larger diameter fresh air duct. An overly restrictive intake 

hood may have contributed as well. The test results highlighted a need for additional ducting 

considerations for this supply-type ventilation design, in some cases, to ensure sufficient 

ventilation. The Research Center plans to investigate ventilation air flow improvement methods 

and monitor the long-term performance of this system. 

The additional costs of higher efficiency heating and cooling equipment are expected to be more 

than offset by installing one system instead of two, and by using a simplified duct system. The 

startup of the furnace and air-conditioning system, notably the calibration adjustments that both 

required, highlighted how critical a thorough commissioning procedure and written report are to 

ensure the equipment is operating safely and efficiently. 

7.5 Plumbing

There may be an opportunity to further optimize the plumbing piping by identifying routes that 

are more direct and running reduced diameter piping to some fixtures. 

7.6 Energy Simulations and Cost Effectiveness

The Research Center plans to evaluate the effect of builder substitutions in the implemented 

design on the 30% simulated energy savings goal. In addition, working with WHI, the Research 

Center plans to evaluate the cost effectiveness of the energy features presented in this report; 

much of the cost information was not available when the report was written. These simulation 

and cost details will be presented in the next report.

7.7 Quality Assurance

Scheduled design reviews, site reviews, and inspections are still recommended for subsequent 

houses to ensure that all framing, air sealing, insulation, and mechanical systems are designed 

and installed to optimize performance goals. 
29

8 Summary

8.1 Overview

The specific energy efficiency goals established during the planning stage for this NCTH were 

largely achieved. The project may have fallen short of the 30% energy efficiency goal because of 

builder substitutions. All of the permanent features, though, including optimized framing, 

insulation, windows, plumbing piping, and a single HVAC system with interior ducts were 

implemented. The substituted features (e.g., the cooling system condensing unit) may be easily 

changed in future homes. WHI considered all the permanent features to be cost effective, and the 

builder incorporated them into at least three additional houses of similar design as shown in 

Figure 26.

Figure 26. Three additional houses built using the NCTH features

The thermal envelope design successfully incorporated advanced framing techniques and high 

insulation levels. Short-term testing indicated a very tight thermal envelope. The HVAC system 

was successfully installed entirely within conditioned space, and short-term testing indicated that 

the heating and cooling system was operating efficiently and effectively. The completed NCTH 

is shown in Figure 27.
30

 

Figure 27. Completed test house

8.2 Next Steps

The Research Center plans to work with WHI to prepare a cost analysis, investigate open items 

identified in the Gaps and Lessons Learned section, and prepare a long-term monitoring report 

for this NCTH research project. That report will address the long-term goals and research 

questions presented in this report. 
31

References

ACCA (2009). Manual D, Residential Duct Systems. 3rd Edition. Arlington, VA: ACCA.

ACCA. (2006). Manual J, Residential Load Calculations.8th Edition. Arlington, VA: ACCA. 

ACCA (2004). Manual S, Residential Equipment Selection. Arlington, VA: ACCA. 

ACCA (1992). Manual T, Air Distribution Basics for Residential and Small Commercial 

Buildings. Arlington, VA: ACCA. 

American National Standards Institute (ANSI)/ICC 700-2008 (2009) National Green Building 

Standard (NGBS)

ASHRAE (2010). “ANSI/ASHRAE Standard 62.2-2010, Ventilation and Acceptable Indoor Air 

Quality in Low-Rise Residential Buildings.” Atlanta, GA: ASHRAE.

ICC. (2009). 2009 International Energy Conservation Code. Washington, DC: ICC.
32 

Appendix A Energy Simulations

The NCTH as built with both the optional finished basement and third floor was 30% over the 

Building America B10 benchmark excluding any size adjustment factor. The preliminary energy 

simulations included both 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 28 graphically 

depicts the simulation results.

Figure 28. BEopt simulation results

The “swoosh” shape of the graph indicated that the minimum annualized energy cost occurred at 

source energy savings of approximately 24% (indicted by blue dotted lines). Before reaching the 

minimum cost point, 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 were attainable, but the investment needed to 

attain incremental efficiency gains rose sharply. For example, meeting the project goals of 30% 

energy savings required approximately a 10% higher annualized energy cost than would reaching 

27% savings. 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 

and construction methods, along with 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 B10 benchmark, the as-built design (which will serve as a model home and, as such, includes 

nearly 2,000 ft2

 of optional conditioned space) was subject to a size penalty that reduced overall 

projected savings. Because of the additional conditioned space, the Building America Program 

administers a penalty (which is manifested in a source energy reduction for the B10 benchmark 

design). Figure 29 shows source energy use for the B10 benchmark and the final house design. 

The size penalty reduced theoretical source energy savings by about 7%.
33 

Figure 29. Source energy savings for energy efficient design compared to the B10 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. Figure 30 depicts the components of these savings. 

Figure 30. Annualized utility bill comparison for B10 benchmark and energy efficient design 

For a house with the same energy efficiency solution package but without the 700-ft2 abovegrade 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 31 and Figure 32. 
34 

Figure 31. Source energy use for B10 benchmark and energy efficient design 

(For house without finished third-floor and without finished basement) 

Figure 32. Annual utility bills 

(For house without finished third-floor and without finished basement) 
35 

Appendix B Complexity of the Home’s Thermal Boundaries

WHI’s Camberley Homes

Poplar Run Subdivision, Poplar Run Community, Silver Spring, Maryland 

Victorian Model 

Figure 33 through Figure 35 show three different views of the house’s thermal boundary. 

Figure 33. NCTH thermal envelope, Section A-A 
36 

Figure 34. NCTH thermal envelope, Section B-B 

Figure 35. NCTH thermal envelope, Section C-C 
DOE/GO-102011-3572 ▪ October 2012

Printed with a renewable-source ink on paper containing at 

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