Technical Report

NREL/TP-550-44687

January 2009

Technical Approach for the 

Development of DOE Building 

America Builders Challenge 

Technology Information Packages

D.R. Roberts and R. Anderson
National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401-3393

303-275-3000 • www.nrel.gov

NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency and Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

Contract No. DE-AC36-08-GO28308

Technical Report

NREL/TP-550-44687

January 2009

Technical Approach for the 

Development of DOE Building 

America Builders Challenge 

Technology Information Packages

D.R. Roberts and R. Anderson

Prepared under Task No. BET88001
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iii

Acknowledgments

The authors wish to thank Ron Judkoff and Dane Christensen of NREL for providing 

technical review and comments, and Stefanie Woodward of NREL for providing editorial 

review and revision.
iv

Executive Summary

The U.S. Department of Energy (DOE) has issued a challenge to the homebuilding 

industry to build 220,000 high-performance homes by 2012. The initiative is called 

Builders Challenge. To qualify, homes must meet the requirements of one of three 

compliance paths established by DOE: performance path, prescriptive path, or 

participating in a partner program. The performance path, expected to be the most widely 

used, requires that a home receive a home energy rating and score 70 or better (lower) on 

the EnergySmart Home Scale.

To provide builders with specific design specifications and a prescriptive path to 

compliance, DOE is developing a series of Builders Challenge Technology Information 

Packages (BC-TIPs) — climate-specific lists of energy features that must be installed in a 

home to meet minimum program requirements. 

The National Renewable Energy Laboratory used the BEopt, REM/Rate, and 

EnergyGauge software programs to develop an initial batch of five BC-TIPs. The goal 

was to achieve optimal cost-effective approaches to meeting the 70 EnergySmart Home 

Scale requirement. Additional premium-efficiency packages were developed for each of 

the initial five climates to demonstrate higher levels of cost-effective energy savings. BCTIP marketing materials targeting builders and consumers have been developed for the 

initial set of five climates and are available on the Building America Web site.

This report describes the technical approach used to develop the BC-TIPs.
v

Contents

Executive Summary........................................................................................................... iv

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

Initial Set of Technical Information Packages.....................................................................3

Technical Approach for the Development of Builders Challenge Technical Information 

Packages...............................................................................................................................3

Overview..........................................................................................................................3

Prototype Building Definition..........................................................................................4

Analysis............................................................................................................................5

Finalizing Technology Information Packages.................................................................8

Results..................................................................................................................................9

Technical Information Package Design Limitations..........................................................11

Conclusion .........................................................................................................................11

References..........................................................................................................................12

Appendix A: Example BEopt Input Echo Report – Phoenix, Gas Heating.................... A-1

Appendix B: Example REM/Rate Building File Report – Phoenix, Gas Heating...........B-1

Appendix C: Example EnergyGauge Building Input Report – Phoenix, Gas Heating ...C-1
vi

Figures

Figure 1. Builders Challenge EnergySmart Home Scale.....................................................1

Figure 2. Example Builders Challenge Technology Information Package..........................3

Figure 3. SketchUp rendering of prototype model ..............................................................4

Figure 4. Example Output from BEopt................................................................................6

Figure 5. BEopt economic factors and energy source multipliers used in TIP analysis......7

Figure 6. Analysis flow for developing BC-TIPs................................................................8

Figure 7. Sample package table from BC-TIP document..................................................10

Figure 8. Example energy savings and cost of upgrades from BC-TIP document............10

Tables

Table 1. Cities Selected for Initial Run of BC-TIPs............................................................3

Table 2. Foundation Types Used in the Prototype Models..................................................5

Table 3. Prototype Model Characteristics............................................................................5

Table 4. BEopt Default Statewide Average Fuel Costs Used to Develop TIPs ..................6

Table 5. E-Scale Indices for Prototype Homes....................................................................9
1

Introduction

The U.S. Department of Energy (DOE) has issued a challenge to the homebuilding 

industry to build 220,000 high-performance homes by 2012. The initiative is called 

Builders Challenge. To qualify, homes must meet the requirements of one of three 

compliance paths established by DOE: performance path, prescriptive path, or 

participating in a partner program. In addition to the requirements unique to each path, a 

common set of quality criteria must be verified via third-party inspection.

The performance path, expected to be the most widely used, requires that a home achieve 

a 70 or better (lower) on the EnergySmart Home Scale (E-Scale). The E-Scale (Figure 1)

allows homebuyers to understand at a glance how the performance of a particular home 

compares to that of others. This scale is the same as that used in the home energy rating 

system (HERS) industry as defined by the industry organization, Residential Energy 

Services Network (RESNET).

1 A home that scores 70 on the E-Scale will use 

approximately 70% of the energy as the same home built to meet the minimum 

requirements of the 2004 International Energy Conservation Code (IECC).

Figure 1. Builders Challenge EnergySmart Home Scale

The E-Scale Index is calculated using computer software programs that compare the 

estimated energy use of a proposed home design to the energy use of the same home built 

to meet the minimum requirements of the 2004 IECC. The software user, generally a 

HERS rater, will modify features of the home to achieve the target E-Scale Index, in this 

case 70 or lower. This is commonly referred to as the performance path, because any 

 1 2006 Mortgage Industry National Home Energy Rating System Standards, Residential Energy Services 

Network, Inc., May 19, 2007.
2

combination of design features can be used to meet the overall performance objective for 

the home.

To provide builders with examples of specific design specifications and make the 

Builders Challenge more accessible in markets without a strong HERS presence, DOE 

developed a prescriptive path to meeting the Challenge. To facilitate this path, the

National Renewable Energy Laboratory (NREL) was tasked with creating Builders 

Challenge Technology Information Packages (BC-TIPs).

A BC-TIP provides a list of energy features that must be installed in the home to meet 

minimum program requirements (Figure 2). TIPs offer an alternative to the performancebased approach. Builders who do not have access to HERS raters in their market, or who 

prefer the simplicity of a prescriptive list, can implement the features listed in a TIP for 

their climate region.

TIPs do not offer the full flexibility provided by the performance path and, by definition, 

cannot provide full credit for the performance of specific building characteristics and 

components.

This document outlines NREL’s technical approach in developing the BC-TIPs for 

Builders Challenge.
3

Figure 2. Example Builders Challenge Technology Information Package

Initial Set of Technical Information Packages

An initial set of BC-TIPs has been developed that includes one major metropolitan area 

in each of the five Building America Climate Regions: hot-humid, hot/mixed-dry, cold, 

mixed-humid, and marine. BC-TIPs were developed for all-electric and gas/electric 

homes. Table 1 shows the cities selected to initially represent each climate zone.

Table 1. Cities Selected for Initial Run of BC-TIPs

Climate Zone City

Hot-Humid Houston

Hot/Mixed-Dry Phoenix

Cold Chicago

Mixed-Humid Atlanta

Marine Seattle

Technical Approach for the Development of Builders 

Challenge Technical Information Packages

Overview

To develop the initial batch of BC-TIPs, NREL created energy models of prototypical, 

single-family homes for each of the five Building America Climate Regions. NREL used 
4

BEopt2 energy design optimization software, REM/Rate3 HERS software, and 

EnergyGauge4 HERS software to develop and analyze the models. The BEopt software 

tool was developed at NREL to identify optimal building energy designs aimed at 

minimizing the total of the amortized cost of improvements and the cost of energy.

REM/Rate and EnergyGauge are two widely used HERS software programs accredited 

by RESNET5

Prototype Building Definition

that produce the E-Scale Index. BEopt, REM/Rate, and EnergyGauge all 

utilize energy simulation engines that have passed the HERS building energy simulation 

test (Judkoff and Neymark, 1995).

BEopt was used to identify least-cost approaches to meeting two performance goals, each 

presented in the TIP documents: (1) minimum requirements for the Builders Challenge, 

and (2) a Building America package designed to achieve maximum cost-effective energy 

savings. The REM/Rate and EnergyGauge software were used to ensure the Builders

Challenge-level recommendations are consistent with performance-based approaches to 

reaching the 70 E-Scale threshold.

The prototype building used to develop the TIPs is a 2,500-ft2, 2-story, single-family 

home (Figure 3), sitting on a climate-appropriate foundation – slab, crawlspace, or

conditioned basement as shown in Table 2. The home has a 1.3:1 aspect ratio, with the

front (a long side) facing west. The home has total (frame and glass) window area equal 

to 18% of the conditioned floor area distributed equally on all four sides of the home.

Detailed prototype model characteristics are shown in Table 3.

Figure 3. SketchUp rendering of prototype model

 2 v0.8.7, National Renewable Energy Laboratory

3 v12.6, Architectural Energy Corporation

4 v2.8.00, Florida Solar Energy Center 5 National Registry of Accredited Rating Software Programs, Residential Energy Services Network, Inc.
5

Table 2. Foundation Types Used in the Prototype Models

City Foundation Type

Houston Slab

Phoenix Slab

Chicago Conditioned Basement

Atlanta Crawlspace

Seattle Crawlspace

Table 3. Prototype Model Characteristics

Conditioned floor area 2,500 ft2, 3,750 ft2 w/basement

Conditioned volume 22,500 ft3, 33,750 ft

3 w/basement

Number of stories 2

Number of bedrooms 3

Gross above-grade wall area 2,574 ft2

Window area 450 ft2, 500 ft2 w/basement

Window orientation Equally distributed, 4 cardinal directions

Door area 40 ft2

Setpoint temperatures 68 heating, 78 cooling

Mechanical ventilation Exhaust only, ASHRAE 62.2 levels

Internal gains Building America Benchmark (Hendron, 2008)

Lighting/appliance/plug schedules Building America Benchmark

In developing the prototype building design, small studies were undertaken to examine 

the sensitivity of the E-Scale Index to window orientation and house size. Both studies 

involved changing HERS software prototype models to represent extreme cases:

• Window orientation was changed from equally distributed to 50% west-facing, 

25% east-facing, and 12.5% north- and south-facing. This change increased the EScale Index for the 10 prototype models (five climates, gas & electric space 

heating) an average of 0.78 points.

• House size was reduced by removing the second floor from the prototype, 

resulting in 1,250-ft2 homes without the basement and 2,500-ft2 homes with the 

conditioned basement. This change increased the E-Scale Index by an average of 

6.3 points for the 10 prototype models.

Analysis

BEopt was used in conjunction with the prototype building definition to develop the BCTIPs. It produces building designs that minimize combined construction and energy costs

by using the DOE-2.2 and TRNSYS energy simulation programs to automate a sequential 

search technique for locating least-cost solutions on a path toward net zero energy. The 

software and underlying methodology are described in detail by Christensen et al. (2005, 

2006) and Horowitz et al. (2008).

Figure 4 shows typical output from BEopt. Each point of the graph indicates a unique

combination of energy design features. The dark line at the bottom of the points indicates 
6

the least-cost solution to achieving the source energy savings indicated on the X axis. An 

approximation of the Builders Challenge target is indicated on the graph. Although the 

actual Builders Challenge threshold is 70 or better on the E-Scale, source energy savings 

relative to the 2006 IECC were typically 18%–25% for the climates and heating fuels 

analyzed. Building configurations in this area were examined and analyzed as potential 

Builders Challenge-level packages. Additionally, premium-efficiency packages were 

selected from points at or near the minimum cost point. An example BEopt input file is 

included in Appendix A. Mortgage + Utilities ($/yr)

 

Source Energy Savings (%)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50 60 70 80 90 100

2006 IECC

Builders Challenge Range (70 E-Scale)

Minimum Cost Point

Premium Efficiency Range

Mortgage + Utilities ($/yr)

 

Source Energy Savings (%)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50 60 70 80 90 100

2006 IECC

Builders Challenge Range (70 E-Scale)

Minimum Cost Point

Premium Efficiency Range

Figure 4. Example Output from BEopt

BEopt analysis was performed for each climate listed in Table 1. Standard BEopt default

values were used in the analysis: statewide average utility rates (Table 4), economic 

factors, and source energy multipliers (Figure 5).

Table 4. BEopt Default (EIA 2006) Statewide Average Fuel Costs Used to Develop TIPs

City $/kWh $/Therm

Houston 0.1142 1.1544

Phoenix 0.0763 1.4376

Chicago 0.0685 1.0754

Atlanta 0.0792 1.7789

Seattle 0.0608 1.2786
7

Figure 5. BEopt economic factors and energy source multipliers used in TIP analysis

To the extent possible, the 2006 IECC Standard Reference was used for the BEopt 

analysis so the resulting energy cost savings would be relative to current code. This 

reference is not built in to BEopt, and was hand-configured in the software. There are two 

aspects of the IECC Standard Reference as described in Section 404 of the 2006 IECC 

that could not be precisely configured: Distributions System Efficiency value of 0.8, and 

window U-value and SHGC. In these cases the closest possible approximations were 

used − code-level ducts and windows that most closely matched the code requirements. 

This reference is the point from which the cost of energy efficiency improvements and 

energy cost savings reported in the BC-TIPs are calculated. Because these results are not 

critical − reflecting typical, not actual performance − a close approximation of this 

“current code” suffices in the analysis.

Potential Builders Challenge-level prescriptive packages identified using BEopt were

further analyzed using RESNET-accredited HERS software. It is important that the BCTIPs be checked to ensure they achieve an E-Scale Index of 70 or lower (analogous to a 

70 on the HERS Scale).

Analogous prototype models were created in the REM/Rate and EnergyGauge HERS

software programs. The HERS software prototype models were configured to reflect 

energy efficiency features from BEopt associated with a specific point on the BEopt 

minimum-cost curve. If the E-Scale Index from the software was higher than 70, a point 

further along the savings curve was selected from BEopt, and the HERS prototypes 

reconfigured and reevaluated. Figure 6 shows the iterative process that was followed until 

a least-cost solution resulting in a HERS (E-Scale) Index below 70 was identified for 

each prototype home.
8

E-Scale 

< 70 ?

Mortgage + Utilities ($/yr)

 

Source Energy Savings (%)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50 60 70 80 90 100

Energy 

Feature 

List

Yes

No E-Scale 

< 70 ?

Mortgage + Utilities ($/yr)

 

Source Energy Savings (%)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50 60 70 80 90 100

Energy 

Feature 

List

Yes

No

Figure 6. Analysis flow for developing BC-TIPs

The data presented in Figure 4 demonstrate that there are many solutions near the

minimum cost point on the curve, and that source energy savings as high as 35% relative 

to 2006 IECC can be reached without deviating significantly from minimum cost. The 

cost for the 35% savings point is far below the annual cost point for a 2006 IECCcompliant home, which is the baseline for the data shown in Figure 4. To highlight the

benefit of efficiency levels beyond the E-Scale criterion of 70, a second, higher

performance package is included in the TIP documents. These packages generally 

produce greater cost savings for the homeowner, and in all cases produce greater source 

energy savings with positive cash flow.

Finalizing Technology Information Packages

Once potential Builders Challenge-level packages were identified for each climate and 

fuel type, they were vetted with the Builders Challenge Technical Working Group and 

adjusted slightly for consistency, flexibility, and practicality. For example, the Group 

requested 100% fluorescent lighting be reduced to 90% to provide some flexibility. The 

Group also decided that minimum seasonal energy efficiency ratio (SEER) values for air

conditioners and heat pumps should be 14.0, that the minimum furnace efficiency should 

be 82.0 annual fuel utilization efficiency (AFUE), and that required window solar heat 
9

gain coefficient (SHGC) values should be no lower than 0.356

Results

to accommodate product 

availability. These changes were made to the prototype models in the HERS software, 

and the HERS indices were reevaluated.

Table 5 shows the E-Scale Indices for the Builders Challenge performance level for each

prototype model developed for this analysis.

Table 5. E-Scale Indices for Prototype Homes at Builders Challenge Performance Level

City/Heating Fuel REM/Rate EnergyGauge

Houston/Gas 68 64

Houston/Electric 68 65

Phoenix/Gas 67 63

Phoenix/Electric 67 64

Chicago/Gas 62 64

Chicago/Electric 68 69

Atlanta/Gas 66 63

Atlanta/Electric 68 65

Seattle/Gas 66 69

Seattle/Electric 67 70

Figure 7 shows a typical BC-TIP energy package, clipped from the builder-targeted

marketing flyer. In addition to the energy packages, the estimated costs and savings 

associated with each package are also listed in the BC-TIP marketing flyer (Figure 8). As 

discussed earlier, these savings and construction costs are calculated by BEopt, relative to 

the hand-configured 2006 IECC Standard Reference. The complete TIP document and 

other BC-TIPs are available on the Building America Web site.

 6 The 2009 IECC will require SHGC values lower than 0.35 in warm climates, and the 2010 ENERGY

STAR® window specification is expected to be even more stringent.
10

Figure 7. Sample package table from BC-TIP document

Figure 8. Example energy savings and cost of upgrades from BC-TIP document
11

Technical Information Package Design Limitations

Because of the TIP prototype building definition, builders who use TIPs will not be able 

to take advantage of performance tradeoffs based on window area, window location, 

building orientation, reduced infiltration, etc. Builders interested in receiving full credit 

for specific building designs and performance features are encouraged to use the 

performance path. A home that has a window area greater than 18% of conditioned floor 

area is required to use the performance path.

Conclusion

NREL used the BEopt, REM/Rate, and EnergyGauge software programs to develop an 

initial batch of five TIPs for DOE’s Builder Challenge. The goal was to achieve optimal 

cost-effective approaches to meeting the 70 E-Scale requirement of the Challenge.

Premium-efficiency packages were also developed for each of the initial five climates to 

demonstrate higher levels of cost-effective energy savings.

TIPs quickly and effectively communicate the technical specifications required to meet 

the Builders Challenge. TIPs do not provide the full design flexibility of the performance 

path.

BC-TIP marketing materials targeting builders and consumers have been developed for 

the initial set of five climates and are available on the Building America Web site.
12

References

Christensen, C.; Horowitz, S.; Givler, T.; Courtney, A.; Barker, G. (2005). BEopt: 

Software for Identifying Optimal Building Designs on the Path to Zero Net Energy.

NREL/CP-550-37733. Golden, CO: National Renewable Energy Laboratory.

Christensen, C.; Anderson, R.; Horowitz, S.; Courtney, A.; Spencer, J. (2006). 

BEopt(TM) Software for Building Energy Optimization: Features and Capabilities.

NREL/TP-550-39929. Golden, CO: National Renewable Energy Laboratory. 

Hendron, R. (2008). Building America Research Benchmark Definition: Updated 

December 20, 2007. NREL Report No. TP-550-42662. Golden, CO: National Renewable 

Energy Laboratory. 

Horowitz, S.; Christensen, C.; Brandemuehl, M.; Krarti, M. (2008). Enhanced Sequential 

Search Methodology for Identifying Cost-Optimal Building Pathways. NREL/CP-550-

43238. Golden, CO: National Renewable Energy Laboratory. 

Judkoff, R.; Neymark, J. (1995). Home Energy Rating System Building Energy 

Simulation Test (HERS BESTEST). NREL/TP-472-7332a. Golden, CO: National 

Renewable Energy Laboratory.

International Code Council, Inc. (2006). 2006 International Energy Conservation Code.

ISBN-13: 978-1-58001-270-6.
A-1

Appendix A: Example BEopt Input Echo Report – Phoenix, 

Gas Heating
A-2

GROUP INPUT VARIABLE VALUE UNITS

Location USA_AZ_Phoenix_TMY2

Geometry Total Finished Floor Area (Above Grade) 2500 ft 2

# Floors (Above Grade) 2

Ceiling Height 9 ft

Garage Two Car

Garage Protrusion: 50 %

Garage Position: Left

Roof Gable

Roof Pitch: 0.5

Number of Bedrooms 3

Number of Bathrooms 2

Economics Elec. Marginal 0.0763 $/kWh

Elec. Fixed 8 $/month

Elec. Average 0.0815 $/kWh

Elec. Excess Sellback Rate 0.0763 $/kWh

Gas Marginal 1.4376 $/therm

Gas Fixed 8 $/month

Gas Average 1.684 $/therm

Mortgage Period 30 years

Mortgage Interest Rate (Nominal) 7 %

Marginal Income Tax Rate 28 %

Project Analysis Period 30 years

Inflation Rate 3 %

Discount Rate (Nominal) 5 %

Electric Source/Site Ratio 3.365

Gas Source/Site Ratio 1.092

Gas Carbon Factor 14.74

Electric Carbon Factor 1.67

Efficiency Cost Multiplier 1

Photovoltaics PV Module Generic

Installed Cost 7.5 $/W DC

Derate Factor 15 %
A-3
A-4
A-5
A-6
A-7
A-8
A-9
B-1

Appendix B: Example REM/Rate Building File Report –

Phoenix, Gas Heating
B-2
B-3
B-4
B-5
B-6
B-7
B-8
B-9
B-10
C-1

Appendix C: Example EnergyGauge Building Input Report –

Phoenix, Gas Heating
C-2
C-3
C-4
C-5
F1147-E(10/2008)

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14. ABSTRACT (Maximum 200 Words)

The U.S. Department of Energy has issued a challenge to the homebuilding industry to build 220,000 highperformance homes by 2012. The initiative is called Builders Challenge. To qualify, homes must meet the 

requirements of one of three compliance paths established by DOE: performance path, prescriptive path, or 

participating in a partner program.

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builders challenge; building america; performance path; prescriptive path

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