Evaluation of Missed Energy Saving 

Opportunity Based on Illinois Home 

Performance Program Field Data: 

Homeowner Selected Upgrades 

Versus Cost-Optimized Solutions

S. Yee, M. Milby, and J. Baker

Partnership for Advanced Residential Retrofit

June 2014
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iii

Evaluation of Missed Energy Saving Opportunity Based on Illinois 

Home Performance Program Field Data: Homeowner Selected 

Upgrades Versus Cost-Optimized Solutions 

Prepared for: 

Building America

Building Technologies Program

Office of Energy Efficiency and Renewable Energy 

U.S. Department of Energy 

Prepared by: 

S. Yee, M. Milby, and J. Baker 

Partnership for Advanced Residential Retrofit 

Midwest Energy Efficiency Alliance

20 N Wacker Drive, Suite 1301 

Chicago, IL 60606

NREL Technical Monitor: Stacey Rothgeb 

Prepared under Subcontract No. KNDJ-0-40346-04 

June 2014 
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 Background ..............................................................................................................1

1.2 Illinois Home Performance with ENERGY STAR .................................................1

1.3 Preceding Research by PARR .................................................................................2

1.4 Relevance to Building America’s Goals ..................................................................2

1.5 Study Rationale ........................................................................................................3

2 Research Methodology ........................................................................................................4

2.1 Research Questions ..................................................................................................4

2.2 Data Collection and Analysis...................................................................................4

3 Results ..................................................................................................................................6

3.1 Illinois Home Performance Demographic Comparisons .........................................6

3.2 Comparing Illinois Home Performance and BEopt Measure Packages ..................9

3.3 Energy Savings: Illinois Home Performance With ENERGY STAR Versus BEopt 

Modeling ................................................................................................................13

3.4 Residential Energy Efficiency Measure Sensitivity Analysis ...............................15

3.5 Measure Package Cost Analysis ............................................................................16

4 Discussion ..........................................................................................................................18

4.1 Research Questions ................................................................................................18

4.2 General Programmatic Impacts ..............................................................................20

4.3 Illinois Home Performance-Specific Impacts ........................................................20

4.4 Building Science Impacts ......................................................................................21

4.5 Directions for Future Research ..............................................................................22

5 Conclusion .........................................................................................................................24

References................................................................................................................................................. 25

Appendix A: Illinois Home Performance Measures............................................................................... 26

Appendix B: 2012 International Conservation Code with Illinois Amendments ................................ 30
vi 

List of Figures

Figure 1. Photos: CCS housing groups 14, 12, and 7 (right to left)....................................................... 6

Figure 2. Distribution of IHP- and CCS-characterized homes across the 15 CCS housing groups... 7

Figure 3. Top three savings potential housing groups: spatial distribution and clustering of IHP 

participants in Cook County................................................................................................................ 9

Figure 4. Percentage matching analysis, IHP retrofit measures versus BEopt-recommended 

measures............................................................................................................................................. 12

Figure 5. Modeled EUI reduction differences between IHP measures and BEopt-recommended 

measures............................................................................................................................................. 14

Figure 6. Gas and electricity contributions to total IHP home energy savings.................................. 15

Unless otherwise noted, all figures were created by PARR.

List of Tables

Table 1. IHP Versus CCS Housing Group Demographics....................................................................... 7

Table 2. IHP Measure List......................................................................................................................... 10

Table 3. BEopt Recommended Measure Packages by Type ................................................................ 11

Table 4. Post-IHP Retrofit Infiltration Rate ............................................................................................. 12

Table 5. Electricity, Gas, and EUI Savings From Baseline Consumption Levels for BEopt and IHP 

Measures ............................................................................................................................................. 13

Table 6. Sensitivity Analysis of Housing Group 7 Installed Measures................................................ 16

Table 7. Measure Package Payback Period: BEopt Cost-Optimal and IHP Measure Packages 

(years).................................................................................................................................................. 17

Table 8. Measure Package Cost: BEopt Cost-optimal, IHP, and IHP Measures Modeled by BEopt . 17

Table 9. Number of IHP Homes in Each Housing Archetype................................................................ 19

Unless otherwise noted, all tables were created by PARR.
vii 

Definitions

BEoptTM Building Energy Optimization software

CCS Chicagoland Characterization Study

DOE U.S. Department of Energy

EUI Energy use intensity

IHP Illinois Home Performance with ENERGY STAR

PARR Partnership for Advanced Residential Retrofits
viii

Executive Summary

This report builds and expands off of previous research by collecting and evaluating data from 

800 Illinois Home Performance (IHP) retrofits. This study investigates homeowner measure 

package choices in the Illinois Home Performance with ENERGY STAR® (IHP) program 

compared to cost-optimal choices determined through Building Energy Optimization (BEoptTM) 

modeling software. This research was based on evaluating actual retrofit measure selection in 

800 homes, grouping the homes into one of the 12 Chicagoland single-family housing 

archetypes, determining the most cost-optimal measure mix for each housing archetype using 

BEopt. The cost-optimal measures were then compared with actual measure installations for 

each housing archetype using BEopt. The main objectives of this study are to: 

• Model overall gas and electricity savings from the common measures installed in IHP for 

12 of the 15 housing archetypes in Chicago’s building stock. 

• Compare savings and optimal measure packages between actual measures installed and 

recommended measure packages as modeled through BEopt. The study also made 

general observations about houses that received retrofits through IHP compared to the 

average housing stock in Chicago. 

IHP homes are actual homes that have qualified and been through the IHP utility program. As of 

the time of this study, the majority of homes receiving IHP recognition were from the Chicago 

metropolitan area. Individual homes that received IHP recognition were matched with 

corresponding housing group archetypes from the Chicagoland Single-Family Housing 

Characterization study (CCS). The IHP homes used in this study were able to be matched to 12 

out of the original 15 housing groups. 

After grouping the IHP homes, this study identified the type and frequency of common measures 

installed by homeowners through IHP. Using BEopt software, cost-optimal measures were 

identified and IHP common measures were evaluated for each housing group. Comparison 

between the actual measures installed in IHP homes and BEopt recommended cost-optimal

measures indicates that there is a large difference in measure selection; however, default cost 

assumptions were used in BEopt modeling, and differences were discovered between these costs 

and the actual measure cost in northern Illinois. IHP homes follow roughly the same distribution 

across housing groups as the CCS study distribution. Homes that participated in the IHP program

are older than what would be expected and represent roughly the same distribution of brick and 

frame construction as what was found in the CCS. Findings from the study included: 

1. For most housing archetypes in IHP, the homes received more measures than BEoptrecommended cost-optimal measure packages. The exception was in brick homes where 

fewer measures were installed than BEopt-recommended cost-optimal measure packages. 

2. IHP measure packages result in greater EUI reduction in frame homes and older homes 

than in newer homes and brick homes. 
ix

3. Measure packages installed during an IHP retrofit result in significantly more gas savings 

than electricity savings (because the IHP houses are in a heating climate and use gas to 

heat homes), a finding consistent with BEopt modeling. 

The methodology and findings of this study are important because they provide valuable 

feedback for the current IHP program and guidance into how other whole-home retrofit 

programs can utilize large datasets in self-evaluation to improve the overall cost effectiveness of 

installed measure packages. One of the most important conclusions of this study is that linking 

home categorization to standardized retrofit measure packages provides an opportunity to 

streamline the process for single-family home energy retrofits and maximize both energy savings 

and cost effectiveness. This report outlines a methodology that may be useful for similar 

programs to use when evaluating measure selection and cost effectiveness.
1 

1 Introduction

1.1 Background

The five-county Chicagoland region contains more than 3.3 million homes, many of which are 

aging, energy intensive, and costly for homeowners to maintain (Spanier et al. 2012). Substantial 

potential exists to reduce energy use and increase the comfort, safety, and durability of these 

homes. Despite the retrofit industry’s rapid growth in northern Illinois, the scale needed to 

realize this potential is still lacking. Many programs exist in the Chicagoland region to help 

homeowners make energy-saving improvements to their homes. Because these programs have 

different goals, employ different program structures, incorporate homeowner decisions, and 

address a variety of housing types, individual retrofits may differ substantially in the types of 

improvements made and the level of savings achieved. With this in mind, the Partnership for 

Advanced Residential Retrofits (PARR) will evaluate the measure packages installed in homes 

achieving Illinois Home Performance with ENERGY STAR® (IHP) certification on the basis of 

cost optimality and magnitude of energy savings. 

Building Energy Optimization (BEoptTM) software, developed by the U.S. Department of Energy 

(DOE) National Renewable Energy Laboratory, can be used to identify cost-optimal residential 

retrofit measure packages while taking into account a home’s size, construction, occupancy, 

vintage, location, and utility rates (Christensen et al. 2006). BEopt creates models using a 

systems integrated approach and produces recommendations that can involve improvements to a 

home’s thermal envelope, equipment, construction materials, and construction practices 

(Christensen et al. 2006). BEopt has been used extensively in previous PARR research to define 

cost-optimal retrofit measure packages for different housing types in the Chicagoland region 

(Baker et al. 2013; Spanier et al. 2012). This study uses prior PARR research that determined 

savings from cost-optimal measure packages determined by BEopt for different housing 

archetypes and compares to savings from actual measures installed in homes achieving IHP

certification. Many residential retrofit programs are moving toward the Home Performance with 

ENERGY STAR framework, which will be further discussed in this report; thus, it is important 

to scrutinize program outcomes for missed potential and identify potential areas for 

improvement. 

1.2 Illinois Home Performance with ENERGY STAR

Illinois Home Performance with ENERGY STAR, also known as Illinois Home Performance 

(IHP), is Illinois’ version of the national Home Performance with ENERGY STAR program. 

IHP serves as a statewide platform that links new and existing Illinois whole-home retrofit 

programs and awards a common Certificate of Completion to homeowners who complete the 

IHP process. These residential retrofit programs, called Program Providers, offer quality 

assurance support and financial incentives for various energy-saving measures and capture 

household-level data on retrofits. IHP Program Providers include Ameren Illinois ActOnEnergy 

and Warm Neighbors Cool Friends, Energy Impact Illinois, Delta Weatherization Energy 

Efficiency Program, Historic Chicago Bungalow Association Energy Savers Program, and the 

Nicor Gas-ComEd Home Energy Savings Program. 

IHP takes a systems-based approach to home energy upgrades that requires participating 

contractors to first perform a diagnostic energy assessment, then make targeted improvements 

identified during the assessment, and then verify the improvements by retesting performance. All 
2 

work is completed to Building Performance Institute Building Analyst and Envelope 

Professional standards.

Upon completion of an IHP job, the State of Illinois awards homeowners a Certificate of 

Completion at either a Silver or a Gold level. These certificates are recognized by Midwest Real 

Estate Data LLC, the Northern Illinois multiple listing service, and can be uploaded to other 

Illinois multiple listing service systems. The intent of the Certificate of Completion is to capture 

the value of the improvements that have been made—which are often invisible—allowing 

homeowners to recoup some of that value during home sales and attracting homebuyers who are 

interested in purchasing efficient homes. 

IHP offers homeowners and contractors a variety of additional resources, including a building 

science hotline, an online listing of participating contractors, building science trainings, Building 

Performance Institute certification rebates, and an equipment loan program. 

Visit www.illinoishomeperformance.org for more information. IHP is sponsored by the Illinois 

Department of Commerce and Economic Opportunity. 

1.3 Preceding Research by PARR 

PARR’s Chicagoland Single-Family Housing Characterization study (CCS) used property 

assessor data and utility billing history to identify 15 distinct housing groups in the Chicagoland 

region (Spanier et al. 2012). Through the use of BEopt modeling analysis, the study defines 

energy upgrade packages for each group that result in an optimal level of energy savings. Based 

on potential annual site energy savings and the frequency of a particular housing group within 

the housing population, the study identified housing groups with the largest savings potential, 

and made programmatic recommendations. 

PARR’s successive report, Analysis of Illinois Home Performance with ENERGY STAR Measure 

Packages (Baker et al. 2013), compared BEopt-modeled energy savings from 19 homes that had 

recently participated in the then-nascent IHP program to savings from cost-optimal measure 

packages as reported in the CCC report. These homes represented 8 of the 15 previously 

identified housing groups and nearly 35% of the Chicagoland residential building stock. The 

study found that the measures installed during IHP upgrades did not match BEopt-defined 

optimal measure packages. The installed cost of IHP measure packages cost homeowners, in 

some instances, more than twice as much as BEopt-recommended measure packages. The 

authors also identified various behavioral biases, informational deficiencies, and financial 

incentives that may influence homeowners and contractors to install suboptimal measure 

packages in IHP homes.

1.4 Relevance to Building America’s Goals

This project contributes to Building America’s goal of “ensur[ing] the reliability, effectiveness, 

and persistence of energy upgrades when applied to new and existing homes” by analyzing 

missed energy saving opportunities in the fast-growing Illinois residential retrofit market and 

identifying potentially optimal retrofit investment decisions. Additionally, this research can help 

guide program development and ensure that homeowner and program funding is allocated in the 

most effective ways. These research outcomes address the Building America goal of providing 

“technical support for new and existing home market transformation programs.” This project, 

which is based on both field data and model-generated recommendations, may be particularly 
3 

useful for calibrating rebates and other measure incentives, for targeting marketing toward 

retrofit candidates with high savings potential, and for educating contractors and homeowners 

about the differences between cost-optimal and commonly installed measure packages.

This research is specifically relevant to aging housing populations in cold climates; the housing 

stock of Chicagoland comprises nearly all U.S. cold-climate architectural styles and was largely 

constructed without consideration of energy efficiency. The CCS study reports that the three 

most prevalent residential housing types represent a potential savings of more than 100 million 

therms of source energy if all homes of those types were retrofitted according to PARR’s BEoptrecommended measure packages (Spanier et al. 2012). This region is also the recipient of 

substantial investment toward energy efficiency improvements in recent times (Culltar et al.

2012), and is therefore a productive area for research aiming to close the gap between existing 

home performance practices and cost-optimal practices.

1.5 Study Rationale

Illinois Home Performance Case Studies Follow-on builds off of previous work by collecting 

and evaluating data from approximately 800 IHP retrofits (Baker et al., 2013). This study 

investigates homeowner measure package choices and the missed opportunity for cost-effective 

energy savings within a consistent program framework. IHP’s objective is to infuse a level of 

consistency across the residential retrofit programs arena, thereby reducing market confusion and 

promoting retrofits. However, as IHP is a market-based program, homeowners have the final 

decision on which measure package will be installed in their homes, meaning that cost optimality 

may not drive homeowner decisions. The goal of this research is to evaluate the potential missed 

opportunity among the housing characterization archetypes and to determine if IHP field 

installed measures packages may be closer to optimal, based on modeling, for certain housing 

types, and further apart for others. 
4 

2 Research Methodology

This research builds on previous Chicagoland housing characterization work by including the 

first 800 homes that have been through the IHP retrofit program. Data analyzed in this study are 

drawn from actual retrofit measure selection, Chicagoland single-family housing group 

archetype demographics,1 and BEopt modeling software cost optimization (Spanier et al. 2012). 

BEopt version 1.1 was used for all analysis. The methodology described in this section will 

answer the outlined research questions and serve to shed light on how real-world residential 

whole-home retrofit programs compare with cost-optimized whole-home retrofit modeling. 

2.1 Research Questions

• How do modeled optimal energy savings for each housing type compare to the energy 

savings derived from typically installed measure packages for that housing type? 

• How many homes have participated in IHP for each of the 15 housing types? 

• What are the characteristics of retrofits currently occurring under the IHP program 

platform in northern Illinois? 

• What measure packages are commonly installed for each of the 15 housing types?

• What is the missed energy savings opportunity resulting from not installing cost-optimal 

measures?

• How do large datasets help explain homeowner decision-making behavior and energy 

savings objectives? 

• What housing types should existing programs focus on to provide maximum costeffective energy savings?

2.2 Data Collection and Analysis 

2.2.1.1 Data Collection

The first 800 homes to achieve IHP recognition provided the data utilized in this study. Retrofit 

work was completed on these homes between January 2011 and January 2013. The 800 homes 

are all located in Illinois; the majority of the homes are located in the Chicago metropolitan area. 

For the purposes of this study, the Chicago metropolitan area consists of Cook County only. Data 

from the 800 IHP homes were geocoded and each home was assigned to one of the 15 housing 

groups identified by the Chicagoland Characterization Study, which characterized 432,605 

homes in Cook County, representing approximately 30% of the total single-family housing stock 

in the Chicagoland area (Spanier et al. 2012). Geocoding was conducted using ArcGIS’s US 

Streets Geocode Service. Of the 800 homes, 504 (63%) were located in Cook County and also 

characterized as one of the 15 housing groups. Roughly 2% of the total homes were unable to be 

geocoded and were thus excluded from the study. Housing groups 1, 2, and 9 were excluded 

from this study because none contained more than one IHP home. The three excluded housing 

groups represent 8.5% of the Cook County housing stock (Table 2). 

After the IHP homes were assigned to housing groups, the individual measures completed during 

each retrofit were ranked in order of frequency. Common measures were defined as those that 

occurred in at least 15% of IHP homes for each housing group. A frequency of 15% was chosen 

 

1 Housing characterization is based on the CCS study. 
5 

because it excludes rare measures and potentially random occurrences of measures, especially in 

housing groups with small sample size; however, because the frequency of measures after the 

two most common measures (air sealing and attic insulation) drops substantially, a low cutoff 

point—such as 15%—captures measures that are occurring with enough frequency to be 

considered non-random or common. These measures are listed in Appendix A. 

2.2.1.2 BEopt Modeling Methodology

In order to determine the difference between energy savings associated with IHP common 

measures and BEopt-recommended measures, baseline energy consumption was modeled using 

BEopt for an average home in each housing group. All baseline models utilized the existing 

conditions reported by the CCS (Spanier et al. 2012); for example, a pre-retrofit IHP group 4 

home was identical to a pre-retrofit CCS group 4 home. Once baseline models were created for 

all 13 housing groups, two distinct retrofit scenarios were modeled for each housing group: 

Upgrading the baseline using IHP common measures, and upgrading the baseline using BEoptrecommended cost-optimal measures.

The purpose of modeling these two scenarios was to determine the impact that each scenario’s

collection of measures would have on a housing group’s energy use intensity (EUI). EUI is a unit 

of measurement for total energy used per square foot per year and takes into account both 

electricity and gas consumption. In order to accurately compare measures in the two modeled 

scenarios, several measures had to be modified or excluded from the study. Measures were 

excluded from the modeling because of BEopt software limitations or significant housing 

construction differences between the two scenarios.

The following list displays changes or exclusions to the modeling assumptions developed by the 

CCS and used in this study: 

• Crawlspaces were assumed to be 50% uninsulated and serve the same structural role as

basements (housing groups 7, 11, 13, 14, and 15). 

• Rim joist insulation was not modeled (housing groups 4, 6, 7, 13, 14, 15). 

• Weather stripping was not directly modeled; rather, overall air leakage reduction was 

modeled by BEopt (housing groups 7, 14). 

• Furnace cleaning and tuning were not modeled (housing groups 7, 13, 14). 

• Floor insulation was not modeled (housing groups 6, 8, 12). 
6 

3 Results

The results presented below include analysis of both housing group demographics and the impact 

of different measure packages on EUI. In addition to measure package-level impacts, this study 

also analyzed how individual measures impact overall reduction in EUI. 

3.1 Illinois Home Performance Demographic Comparisons 

Figure 1 shows examples of three archetype homes in Chicago. Figure 2 compares the 

distribution of IHP homes and homes categorized in the CCS across the 15 housing groups. 

Overall, IHP homes followed roughly the same distribution across housing groups as the 

distribution reported by the CCS. Drastic exceptions include housing group 7, which is overrepresented by IHP, and housing group 12, which is under-represented by IHP (Figures 2 and 3).

The top three housing groups targeted by the CCS were 14, 12, and 7; 267 of those homes are 

included in this analysis (Figures 1 and 2). 

Figure 1. Photos: CCS housing groups 14, 12, and 7 (right to left)
7 

Figure 2. Distribution of IHP- and CCS-characterized homes across the 15 CCS housing groups

Table 1. IHP Versus CCS Housing Group Demographics 

Group Frame Year Built # Stories IHP # % of 

IHP CCS # % of CCS

1 Brick Post-1978 1–1.5 1 0.2 10,856 2.5

2 Brick Post-1978 Split level 1 0.2 8,417 1.9

3 Brick Post-1978 2 5 1 20,530 4.7

4 Brick 1942–1978 1–1.5 57 11.2 77,435 17.9

5 Brick Pre-1978 Split level 7 1.4 26,445 6.1

6 Brick 1942–1978 2 25 5 20,755 4.8

7 Brick Pre-1942 1–1.5 162 32.2 50,239 11.6

8 Brick Pre-1942 2 20 4 17,629 4.1

9 Frame Post-1978 1–1.5 0 0 7,318 1.7

10 Frame All years Split level 15 3 9,225 2.1

11 Frame Post-1978 2 18 3.6 4,544 1.1

12 Frame 1942–1978 1–1.5 29 5.6 101,957 23.6

13 Frame 1942–1978 2 37 7.4 16,411 3.8

14 Frame Pre-1942 1–1.5 76 15.2 48,365 11.2

15 Frame Pre-1942 2 50 10 12,479 2.9

Total 503 100 432,605 100

There is significant potential for IHP to target housing groups 4 and 12. Homes in housing group 

4 were built between 1942 and 1978, have brick construction, are 1 to 1.5 stories, have an 

average square footage of 1,217, and have an average EUI of 129.6. Housing group 4 represents 

11.2% of the IHP housing population, but 17.9% of the Chicagoland housing stock. Homes in

housing group 12 were built between 1942 and 1978, have frame construction, are 1 to 1.5 

stories, have an average square footage of 1,185, and have an average EUI of 135.3. Housing 

group 12 represents 5.6% of the IHP housing population, but 23.6% of the Chicagoland housing 

stock (Table 1). Overall, IHP homes had less participation in housing groups that the preliminary

study identified as having lesser cost-effective energy savings potential, as well as less 
8 

participation in housing groups that are rare in Cook County, such as groups 1, 2, and 9. These 

observations are important to the IHP program because certain housing groups represent greater 

opportunities for energy savings than others.

While distinguishing between housing groups is useful, looking at all IHP homes in aggregate 

also reveals trends. Compared with the Chicagoland housing stock, IHP homes are older than 

what would be expected from an even sampling of CCS homes. Also, IHP homes represent 

roughly the same distribution of brick and frame construction as the Chicagoland housing stock. 

Because some contractors working with IHP specialize in certain housing types, and incentives 

are offered on a regional basis, aggregating IHP homes in this way is useful because it helps 

control for these differences that may introduce bias into an energy savings analysis. The IHP 

data used in this study reflects six Program Providers, 60 contractors, and six different regional 

rebate structures. 

Figure 3 illustrates the spatial distribution of IHP homes in Cook County (n = 267) that fall into 

the three housing groups that the CCS identified as possessing the greatest cost-effective savings 

potential: Housing groups 14, 12, and 7. The older frame homes in group 14 are primarily 

located within the city of Chicago and the “inner-ring” suburbs of Cook County. The newer 

frame homes in group 12 are primarily located in the suburbs of Cook County, located to the 

south and northwest of Chicago, farther from the city core than group 14 homes. Group 7 homes 

are located within Chicago, and they represent nearly two thirds (n = 162) of the total 268 IHP 

homes in the top three groups. Preliminary analysis did not reveal any abnormal trends in income 

distribution of IHP homes. Spatial distribution of IHP homes within one region such as this does 

not impact energy savings; however, it provides useful insight regarding IHP program 

geographic coverage.
9 

Figure 3. Top three savings potential housing groups: 

spatial distribution and clustering of IHP participants in Cook County

3.2 Comparing Illinois Home Performance and BEopt Measure Packages

One of the goals of this study is to compare the measures that have been implemented in IHP

homes with those recommended as cost-optimal for BEopt. Aggregating field data from homes 

that have participated in the program help define what measures are commonly installed for each 

housing group. For comparison, this study relied on previous research that used BEopt existing 

home retrofit cost-optimization modeling to identify the most cost-effective measures for each 

housing group; BEopt modeled measures using the housing group characteristics and 

assumptions identified in the CCS (Spanier et al. 2012). It should be noted that BEopt’s default 

costs assumptions were used to model cost-optimal measure packages; some potential 

differences between these assumptions and actual measure costs in northern Illinois are discussed 

later in this report.

Due to small samples sizes in three housing groups, IHP measures were evaluated for 12 out of 

the 15 housing groups. Air sealing and attic insulation were installed in IHP homes for all 12 

housing groups. The most commonly installed measures were, in order of frequency, air sealing, 

attic insulation, crawlspace insulation, venting exhaust fans to exterior,

2

 exterior wall insulation, 

programmable thermostat installation, furnace replacement, and sealing ducts. A breakdown of 

all individual housing group measures packages for each housing group can be found in Table 2. 

 

2 This measure does not impact energy efficiency. It is required by the 2012 International Energy Conservation 

Code.
10 

Table 2. IHP Measure List

GroupFrame

Year Built

# Stories 

Air Sealing

Attic 

Insulation

Exterior Wall 

Insulation

Crawlspace 

Insulation

Exhaust Fans 

Vented to 

Exterior

Programmable 

Thermostat 

Installed

Furnace 

Replacement

Ducts Sealed 

Total 

1 Brick Post-1978 1–1.5 – – – – – – – – –

2 Brick Post-1978 Split 

level – – – – – – – – – 

3 Brick Post-1978 2 x x – – – – – – 2

4 Brick 1942–1978 1–1.5 x x – – x 3

5 Brick Pre-1978 Split 

level x x – – – – – – 2 

6 Brick 1942–1978 2 x x – – – – – – 2

7 Brick Pre-1942 1–1.5 x x – x x x x x 7

8 Brick Pre-1942 2 x x – – – – – – 2

9 Frame Post-1978 1–1.5 – – – – – – – – –

10 Frame All years Split 

level x x – x – – – – 3 

11 Frame Post-1978 2 x x – x – – – – 3

12 Frame 1942–1978 1–1.5 x x x – – – – – 3

13 Frame 1942–1978 2 x x x x x – – – 5

14 Frame Pre-1942 1–1.5 x x x x x – – – 5

15 Frame Pre-1942 2 x x x – x – – – 4

12 12 4 5 5 1 1 1

Among the same 12 housing groups, the measures recommended as cost optimal by BEopt, in 

order of frequency, were air sealing (11 of 12), furnace replacement (9 of 12), attic insulation (8 

of 12), and water heater (8 of 12). A breakdown of BEopt-recommended measure packages for 

each housing group is provided in Table 3. 
11 

Table 3. BEopt Recommended Measure Packages by Type 

Group

Frame

Year Built

# Stories 

Air Sealing

Attic 

Insulation

Furnace 

Replacement

Water Heater 

Replacement

Total 

1 Brick Post-1978 1–1.5 – – – – –

2 Brick Post-1978 Split level – – – – –

3 Brick Post-1978 2 x – x – 2

4 Brick 1942–1978 1–1.5 x – x 2

5 Brick Pre-1978 Split level x x x – 3

6 Brick 1942–1978 2 x x x 3

7 Brick Pre-1942 1–1.5 x – x x 3

8 Brick Pre-1942 2 x x x x 4

9 Frame Post-1978 1–1.5 – – – – –

10 Frame All years Split level x x x x 4

11 Frame Post-1978 2 x – – x 2

12 Frame 1942–1978 1–1.5 x x – – 2

13 Frame 1942–1978 2 x x x – 3

14 Frame Pre-1942 1–1.5 x x x x 4

15 Frame Pre-1942 2 x x x x 4

11 8 9 8

There are substantial differences between the measure packages recommended by BEopt and 

those installed in IHP homes. One of the primary differences is that BEopt’s recommendations 

favored the installation of mechanical equipment, while IHP measures were primarily focused 

around the building envelope. Also, although air sealing is the most common measure both 

installed in IHP jobs and recommended by BEopt, the magnitude differs significantly (Table 4). 

For Table 4, the average post-retrofit infiltration level was calculated by averaging blower door 

data from actual IHP homes within each housing type. Comparison between IHP and BEoptrecommended infiltration rates indicates that IHP retrofits overwhelmingly experienced greater 

reductions in infiltration. 
12 

Table 4. Post-IHP Retrofit Infiltration Rate 

Housing Type IHP ACH 50 IHP Infiltration BEopt Infiltration

3 12.0 Typical Tight

4 9.3 Tight Typical

5 9.0 Tight Typical

6 7.0 Tight No change

7 7.8 Tight Leaky

8 8.1 Tight Typical

10 8.1 Tight Leaky

11 8.1 Tight Tight

12 8.0 Tight Typical

13 8.4 Tight Typical

14 8.4 Tight Leaky

15 8.6 Tight Typical

A percentage matching analysis reveals both similarities and differences in measure selection. 

Figure 4 illustrates the measures recommended by BEopt for housing groups 7, 12, and 14—the 

three groups the CCS identified as possessing the greatest cost-effective savings potential—and 

indicates the proportion of IHP retrofits in each housing group that included each particular 

measure. This figure further demonstrates the infrequency of mechanical equipment measures 

among IHP retrofits, a trend found throughout all housing groups. At the same time, for these 

three housing groups, IHP and BEopt match closely on building envelope measures. As stated 

earlier, IHP retrofits focus heavily on the building shell, including insulation in several areas 

beyond the attic. 

Figure 4. Percentage matching analysis, IHP retrofit measures versus 

BEopt-recommended measures
13 

3.3 Energy Savings: Illinois Home Performance With ENERGY STAR Versus

BEopt Modeling

The measure packages installed by the IHP program and the measures recommended as cost

optimal by BEopt were both modeled for their impact on the overall energy savings for each 

housing group. Evaluation of gas and electricity savings for each housing group type, for IHP 

measures and for BEopt-recommended measures, indicates that both IHP and BEopt measure 

packages had a more significant impact on gas savings than electricity savings. With BEopt 

recommended measures, 3 out of the 12 housing groups experienced greater electric savings and 

4 out of 12 housing groups experienced greater gas savings than the IHP measure packages. IHP 

measure packages reduce energy consumption to a greater degree in more housing groups than 

BEopt cost-optimized measure packages. IHP gas savings ranged from 1% in housing group 3 to 

48% in housing group 12 and exceeded BEopt cost-optimal measures in 8 out of 12 housing 

groups. BEopt measure package gas savings ranged from 12% in housing group 4 and 41% in 

housing group 14. IHP electricity savings ranged from –1%3 in housing group 4 to 7% in 

housing group 14 and exceeded BEopt cost-optimal measures in 9 out of 12 housing groups 

(Table 5). BEopt cost-optimal measure’s electricity savings ranged from 0% in housing group 7 

and 6% in housing group 14 (Table 4). Additional details regarding housing group-level savings 

data for both BEopt and IHP measure packages can be found in Table 5. 

Table 5. Electricity, Gas, and EUI Savings From Baseline

Consumption Levels for BEopt and IHP Measures 

Electricity Gas EUI

Group BEopt

(%)

IHP

(%)

Δ

(%)

BEopt

(%)

IHP

(%)

Δ

(%)

BEopt

(%)

IHP

(%)

Δ

(%)

3 1 0 –1 15 1 –14 9 1 –8

4 1 –1 –2 12 15 2 8 8 0

5 1 3 1 15 17 2 9 12 3

6 1 3 1 18 12 –6 11 8 –3

7 0 1 1 24 24 0 15 15 0

8 3 4 1 30 19 –11 20 13 –7

10 2 3 1 29 26 –3 19 17 –2

11 1 2 1 16 32 16 9 18 9

12 3 4 1 17 24 8 11 16 5

13 3 3 –1 17 28 11 11 17 6

14 6 7 1 41 48 7 28 33 5

15 4 5 2 32 43 11 22 30 8

The magnitude of difference between IHP and BEopt cost-optimal measure packages is 

significant and varies by housing group (Figure 4). Housing groups with values greater than zero 

represent homes in which IHP measures resulted in a greater reduction in EUI and housing 

groups with negative values represent homes in which BEopt measure packages resulted in 

greater reduction in EUI. Two out of 12 housing groups experienced equivalent EUI reduction, 

3 out of 12 housing groups experienced greater EUI reduction with BEopt measures, and 6 out of 

12 housing groups experienced greater EUI reduction with IHP measure packages. Figure 4 

 

3 Increased electricity consumption corresponds directly with exhaust fan electricity consumption.
14 

denotes which housing groups contain brick or frame construction, and also the relative age of 

the average home in each housing group. 

Figure 5. Modeled EUI reduction differences between

IHP measures and BEopt-recommended measures

Overall this analysis has shown that IHP measure packages result in greater EUI reduction in 

frame homes and older homes compared to newer homes and brick homes. This is likely because

it is more difficult to insulate the walls in brick homes, and contractors will avoid selecting this 

measure. It is also possible that frame homes and older homes are more susceptible to issues with 

air leakage, an issue that IHP addresses frequently. According to the brick home models under 

the assumptions used, BEopt does not recommend wall insulation as a cost-optimal measure in 

brick homes. 
15 

Figure 6. Gas and electricity contributions to total IHP home energy savings

Overall, the measures packages installed during an IHP retrofit result in significantly more gas 

savings (Figure 4) than electricity savings. In all 12 housing groups analyzed in this study, 

electricity savings represented less than 10% of the overall energy savings (Figure 4).

3.4 Residential Energy Efficiency Measure Sensitivity Analysis

In addition to evaluating overall energy savings and the differences between IHP and BEopt 

cost-optimal measure packages, this study also conducted a sensitivity analysis of individual 

measures to determine the relative magnitude of individual measures on the overall energy 

reduction. Housing group 7 was chosen for this analysis because it had the largest group of 

installed measures. The measures that were assessed in this sensitivity analysis are: reducing 

infiltration, attic insulation, HVAC equipment replacement, crawlspace insulation, mechanical 

ventilation, programmable thermostat, and duct sealing. Individual residential energy efficiency 

measures work as a system; however, individual measures may impact the overall energy savings 

more than others. Measure-level sensitivity analysis demonstrates that the order of impact of 

energy savings from greatest to least is air sealing, HVAC equipment replacement,

programmable thermostat, attic insulation, and then crawlspace insulation (Table 6). The 

sensitivity analysis has also revealed that duct sealing and mechanical ventilation have a negative 

impact on overall energy savings. Mechanical ventilation has a negative impact on energy 

savings because of the electricity required to operate the equipment. This sensitivity analysis

helps shed some light on why energy savings differ between IHP measure packages and BEopt 

measure packages. 
16 

Table 6. Sensitivity Analysis of Housing Group 7 Installed Measures 

Category IHP Today IHP Measure

Savings

Energy Savings Utility Bill 

Savings 

($/year)

Electricity

(kWh)

Gas

(therms)

Infiltration Very Leaky Tight 153 209 180

Unfinished 

Attic

Ceiling R-7 

fiberglass, 

blown-in, vented

Ceiling R-49 

fiberglass, blownin, vented111 37 38 

Furnace/Boiler Gas, 80% 

AFUE* Furnace

Gas, 95% AFUE 

Furnace –247 200 140 

Crawlspace 

Insulation Uninsulated Ceiling R-13, 

vented –26 48 37 

Mechanical 

Ventilation N/A 100% exhaust 

vented to exterior –11 –5 (5)

Programmable 

Thermostat N/A Heating setback 430 73 93 

Ducts Sealed N/A Tight, uninsulated –36 0 (3)

* Annual fuel utilization efficiency

3.5 Measure Package Cost Analysis

Although cost analysis was not a primary objective of this study, the large differences in measure 

selection between IHP retrofits and BEopt cost-optimal recommendations warrant investigation. 

For each housing group, these differences in measure selection strongly influence retrofit cost 

and energy savings. These two components determine the payback period for the homeowner, a 

critical and often deterministic feature of retrofits. This study evaluated differences in payback 

period for the three housing groups with the highest potential for energy savings, groups 7, 12, 

and 14 (Spanier et al. 2012). BEopt cost data were available for these three housing groups only. 

Analysis of payback periods for IHP retrofits did not include rebates that are available to IHP 

homes for individual measures. Table 7 lists the payback period in years for IHP retrofits for 

each housing group and the payback period in years for BEopt measures for the top three 

housing groups. The average payback period for IHP measure packages (across all housing 

groups) was 19 years (10.7 years without an extreme outlier) with a low of 4 years and a high of 

110 years.4

 The average payback period for BEopt cost-optimal measure packages was 8.4 years 

with a low of 7.1 years and a high of 9.8 years (not weighted by housing type or sample size). 

IHP-installed measures had a longer payback period than BEopt-recommended measures in 

housing groups 7 and 12 and a shorter payback period in housing group 14. Initial analysis of 

payback indicates that BEopt-recommended measure packages are more cost effective than IHPinstalled measure packages; however, further analysis is required to fully assess cost 

effectiveness, and future analyses should strive to utilize a more regionally accurate cost library.

 

4 The 110-year pack back period is an outlier from the rest of the housing groups. Exclusion of this housing group 

lowers the average payback to 10.7 years.
17 

Table 7. Measure Package Payback Period: BEopt Cost-Optimal and IHP Measure Packages 

(years)

3 4 5 6 7 8 10 11 12 13 14 15

BEopt 9.8 8.2 7.1

IHP 110.0 22.2 12.9 16.0 11.5 9.3 5.8 13.2 9.5 8.8 4.6 4.0

Table 8 lists the average total retrofit costs for BEopt-recommended cost-optimal measures, prerebate IHP-installed measures, and pre-rebate IHP-installed measures as modeled by BEopt. 

Because BEopt software selects measures that maximize cost effectiveness and will not select 

measures that negatively impact overall cost effectiveness, the fact that actual IHP-installed 

measure costs and BEopt-recommended measure costs are similar indicates that IHP-installed

measure packages cost close to what is deemed to be optimal by BEopt. Using BEopt to model 

actual IHP retrofit measures generated costs that are significantly higher than actual retrofit costs

(Table 8). BEopt costs were drawn from the National Residential Efficiency Measures Database. 

This discrepancy is important because it indicates that BEopt measure cost assumptions are 

different than actual market costs available to IHP participants. However, even knowing that 

these costs could not be exactly compared, this study still examines the magnitude of differences

between housing groups as a way to gain insight into potential trends. Future research should 

examine why these costs differ by such a wide margin, and revision of the cost library used will 

lead to more accurate analyses. Going forward, program administrators using this methodology 

to evaluate cost effectiveness must be sure to carefully identify measure cost information. 

Table 8. Measure Package Cost: BEopt Cost-optimal, IHP, and IHP Measures Modeled by BEopt

(in dollars)

3 4 5 6 7 8 10 11 12 13 14 15

BEopt – – – – 3,160 – – – 2,035 – 4,808 –

IHP 2,492 3,695 3,484 3,668 3,832 3,652 3,160 4,186 3,795 3,440 3,669 3,566

IHP 

via 

BEopt

– – – – 11,433 – – – 9,954 – 12,255 – 
18 

4 Discussion 

There is a significant gap between what is actually being done in the field and what was 

identified as cost optimal through BEopt modeling. These differences have resulted in significant 

modeled energy reduction values between both scenarios. One potential reason involves air 

sealing actions; for each housing group and under the cost assumptions used, BEopt 

recommended to tighten homes one step only, e.g., from very leaky to leaky. Future analysis of 

why this was recommended would be helpful. IHP data show that in the field, air infiltration 

reduction can move several steps. The results of this research have also shed light on how well 

the IHP program has targeted the existing Chicagoland housing stock. The following discussion 

will explore how the results of this research impact utility energy efficiency program applications of building science, whole-home energy efficiency retrofit programs, and the IHP program. 

In the future, modeling cost effectiveness should attempt to incorporate factors that impact cost 

decisions. Previous research touched on this; however, because this study focused on defining a 

methodology for analyzing energy use in housing archetypes, the authors did not take steps to 

identify and input custom cost assumptions. One way that incorporating more regionally accurate

costs into modeling assumptions can benefit future research is that a reduction in measure cost, 

caused by a rebate for example, may affect exactly what is deemed cost effective (see Baker et 

al. [2013] for related discussion). Rebates are available for multiple IHP measures; however, the 

reduction in cost has not been incorporated in the BEopt modeling. Future cost-benefit measureselection analysis should incorporate real-world rebates so that what is modeled as cost optimal 

incorporates measure costs identical to what is found in IHP qualifying homes. 

4.1 Research Questions

How do modeled optimal energy savings for each housing type compare to the energy 

savings derived from typically installed measure packages for that housing type? 

Modeled optimal energy saving for each housing type varies from what is typically installed 

during IHP retrofits. In general, this analysis has shown that IHP measure packages result in 

greater EUI reduction in frame homes and older homes. 

How many homes have participated in IHP for each of the 15 housing types? 

When this study was written, 503 of the first 800 IHP homes were able to be characterized into a 

housing type. Table 6 lists the breakdown of IHP homes into each individual housing group. 
19 

Table 9. Number of IHP Homes in Each Housing Archetype

Housing Type Number of Homes % of Total

1 1 0.2

2 1 0.2

3 5 1

4 57 11.2

5 7 1.4

6 25 5

7 162 32.2

8 20 4

9 0 0

10 15 3

11 18 3.6

12 29 5.6

13 37 7.4

14 76 15.2

15 50 10

What are the characteristics of retrofits currently occurring under the IHP program 

platform in northern Illinois? 

The retrofit characteristics currently occurring under the IHP program differ between each 

housing group; however, the top measures include air sealing, attic insulation, exterior wall 

insulation, crawlspace insulation, and mechanical ventilation. 

What measure packages are commonly installed for each of the 15 housing types? 

The most common measures installed in all housing types are air sealing and attic insulation. 

A detailed list of common measures for each housing group can be found in Table 2. 

What is the missed energy savings opportunity resulting from not installing cost-optimal

measures?

The majority of housing groups did not save more energy when the BEopt-identified costoptimal measures packages were installed. Only four housing groups experienced a greater 

reduction in energy consumption by installing measures identified as cost optimal. Additionally, 

initial analysis of economic payback indicates that BEopt-recommended measure packages are 

more cost effective than IHP-installed measure packages; however, further analysis is required to 

fully assess cost effectiveness.

How do large datasets help explain homeowner decision-making behavior and energy 

savings objectives?

Large datasets are important because they can help identify trends in retrofit measure selection.

Large datasets have allowed this study to identify trends in what measures are typically being 
20 

installed and what opportunities exist to maximize the energy savings across the Chicagoland 

area.

What housing types should existing programs focus on to provide maximum cost-effective 

energy savings? 

Existing programs should focus on housing groups 7, 12, and 14. These programs represent a 

significant portion of the Chicagoland housing stock and a significant opportunity for energy 

savings. 

4.2 General Programmatic Impacts

This study’s findings and evaluation methodology have significant relevance to whole-home 

retrofit programs nationwide. Many of the results presented in this study are relevant only to the 

climactic conditions and home construction practices of northern Illinois, but the decisionmaking and energy savings associated with retrofit measure selection are transferable to other 

climates and whole-home retrofit programs. One of the primary transferable conclusions of this 

study is that home categorization may help reduce some of the time and energy that goes into 

home energy audits. Specifically, development of an optimal portfolio of retrofit measures for 

each house may allow contractors and auditors to draw upon what has been done in the past to 

quickly recommend what should be done for each specific housing group. Establishment of 

minimum recommended measures for each housing type will allow home performance 

contractors to quickly recommend optimal measures. Streamlining the whole-home retrofit 

process will eventually serve to reduce the overall transaction costs between the homeowner and 

the contractor. This study has shown, however, for most housing archetypes, substantial 

differences can exist between modeled cost and savings and actual cost and savings. Because the 

cost assumptions used here were likely not tailored enough to regional differences and available 

rebates, future research should recognize that accurate cost information is critical to proper 

evaluation. Perhaps the best approach is to make programmatic decisions only after both types of 

analysis.

Another transferable lesson is that early evaluation of a whole home program’s sampling and 

individual measure selection can help provide valuable programmatic feedback. Analysis of how 

a program is sampling a geographic location’s housing population can help identify potential 

areas or housing group populations that are being underrepresented or overrepresented. 

Correlating this analysis to housing-group level differences in energy savings potential can also 

help identify opportunities to maximize energy savings potential and programmatic 

effectiveness. Analysis of the individual measures can help verify that the measures actually 

being installed are achieving the optimal level of energy savings. If the analysis finds that 

measures identified as cost-optimal are not being installed the program’s focus can be redirected 

towards what is deemed to be the most cost-optimal measures. The methodology presented in 

this study should be valuable to other whole-home retrofit programs and can help provide 

valuable programmatic feedback to program managers and energy efficiency policy makers. 

4.3 Illinois Home Performance-Specific Impacts

Overall, the distribution of IHP homes across housing groups roughly matches that of the 

Chicagoland housing stock, with housing groups 7 and 12 being exceptions. Although IHP 

welcomes all housing types, locations, and income levels to participate in the program, housing 
21 

group 7 was greatly oversampled due to a productive program partner focusing specifically on 

the traditional Chicago bungalow, which is characterized as housing group 7. This provides a 

good example of how the focus of a retrofit program can drift toward a particular location, 

housing type, income level, or set of measures despite maintaining openness to all of these 

attributes.

Comparing the population distribution of IHP with the total area housing stock assists in 

identifying gaps in IHP participation, areas of program underrepresentation, and potential for 

greater overall energy savings. More specifically, looking at both EUI reduction potential and a 

total housing group population together can identify areas that may yield the greatest overall 

regional energy savings. Using this method, the CCS identified housing groups with the greatest 

potential for energy savings through BEopt-recommended retrofits: Housing groups 7, 12, and 

14 (Spanier et al. 2012). 

Figure 2 clearly shows that IHP is succeeding at retrofitting homes in housing groups 7 and 14; 

however, homes in housing group 12 are in need of more attention from the program. The small 

sample size in this housing group receiving IHP recognition may be due to socioeconomic 

factors such as limiting homeowner incomes or spatial mismatch between homes and program 

marketing. This study has shown that the IHP program can have significant savings in housing 

group 12; therefore, this underrepresented housing group represents significant energy savings 

opportunity. Further investigation into how the program can more consistently reach these homes 

is warranted.

Also interesting is the apparent effectiveness of the measure packages installed in IHP homes 

with frame construction. As discussed above, this is likely a result of numerous building 

envelope measures such as air sealing and insulation. The high levels of EUI reduction due to 

IHP measure packages in frame homes—and lower levels in brick homes—suggest that if the 

program maintains its current focus on envelope improvements, it may want to focus more on 

frame homes in order to maximize the program’s overall impact on energy savings. 

Alternatively, because IHP measure packages in brick homes are underperforming compared to 

BEopt-recommended measure packages, program incentives could be revised to encourage 

measure packages that more closely match BEopt cost-optimal packages.

Also apparent is the large thematic difference between IHP-installed measures and BEoptrecommended measures. In general, BEopt frequently recommends mechanical equipment 

upgrades, while IHP retrofits focus more heavily on envelope improvements. The IHP program 

should further investigate the feasibility of encouraging the upgrade of water heaters and other 

heating systems. In particular, these equipment upgrades may garner more savings in homes with 

brick construction, whereas building envelope improvements face more challenges than with 

frame homes.

4.4 Building Science Impacts 

Analysis of the measures installed in IHP homes and recommend by BEopt cost optimization 

software has revealed important differences in measure selection. This study has found that, in 

the majority of housing groups, the measure packages common to the IHP program result in a 

greater reduction in energy consumption than measures that have been recommended by BEopt. 

Specifically, this study has found that reducing infiltration through air sealing and heat loss 
22 

through attic insulation has a significantly greater impact than BEopt modeled results. This result 

is important because it reinforces the current program framework and incentive packages offered 

by program providers. 

Every effort was made to generate BEopt cost-optimal recommendations and to model actual 

IHP measure packages under the same assumptions; however, there were several assumptions 

and limitations that confound the modeling software’s measure selection. One of the primary 

differences between IHP contractor measure selection and BEopt measure selection is that IHP 

contactors are required to comply with the 2012 International Energy Conservation Code for 

impacted measures (e.g., attic insulation must be brought up to code if the attic insulation is to be 

improved). Exact requirements of the Illinois version of the code are listed in Appendix B. 

Existing energy code impacts both what is installed in IHP homes and what is not recommended 

by BEopt. For instance, during IHP measure selection, contactors may install a measure (attic 

insulation) to a level that goes beyond cost optimal, and during BEopt measure selection, the 

software may install a measure only to the point at which it is deemed cost effective. Future 

applications where in-field measure selection is compared with cost-optimized measure selection 

should incorporate limiting factors such as local building codes and should look at cost 

optimization not only as an optimal point, but also as a series of near neighbors on a curve that 

can be viewed together. Incorporating real-world influences that impact what is actually installed

will refine and strengthen future comparisons between program measure data and cost-optimized 

measure data.

Analysis of payback and relative cost effectiveness of IHP-installed and BEopt-recommended 

measure packages reveals the economic impact of differing residential energy efficiency retrofit 

measure packages. The cost effectiveness results presented in this study are not conclusive, but 

do suggest that the measure packages commonly installed during IHP retrofits in many housing 

groups can be as cost effective as measure packages deemed cost optimal by BEopt. Payback and 

cost effectiveness metrics cannot be used to evaluate overall program efficacy because they are a

function of both absolute energy savings and total retrofit cost; therefore, the magnitude of 

energy savings and of total measure package costs should be viewed independently to satisfy 

programmatic goals other than economic utility. 

Additionally, the use of BEopt modeling software to model cost optimization has revealed that 

BEopt’s cost assumptions generate significantly higher total measure package costs than what 

are being observed during actual retrofits. In order to accurately model cost optimality, 

researchers must use BEopt software in a way that reflects actual market conditions and retrofit 

measure costs. Future research should work to share actual residential energy efficiency retrofit 

measure cost data so that BEopt can ensure that its cost assumptions are accurate. 

4.5 Directions for Future Research

Further research is needed to update the CCS BEopt models to match the International Energy 

Conservation Code insulation levels and air infiltration reduction levels found in the field data 

and consider other common upgrades by Group. Also, further work is needed to examine and 

compare the costs of both BEopt recommended measures and IHP common measures.

Preliminary assessment of BEopt measure package costs and IHP measure package costs reveals 

that there is a significant cost difference between the two measure packages. Specifically, BEopt 

cost-optimal measures cost more than IHP measure packages. If possible, future research should 
23 

incorporate real-world rebate levels, into the building science modelling software, to control for 

the cost differences between what is being modelled and what is actually occurring. In-depth cost 

analysis was not included in this research, but such an analysis would likely yield key lessons for 

both program administrators as well as BEopt users. The results of this study can also be used to 

further refine and improve upon the assumptions that were originally made in the CCS study. 

Refinement of the original characterization assumptions is important because it can help assure 

that the original characterization and recommended measure packages are accurate and depict 

actual housing stock characteristics. 
24 

5 Conclusion

This project compared the energy savings potential of common IHP measure packages and 

BEopt cost-optimized measure packages. This research builds upon previous work by analyzing 

data from the first 800 homes to receive IHP recognition. Evaluation of the IHP measure

packages was based on the actual retrofit measure selection, Chicagoland single-family housing 

group archetype demographics,5 and BEopt modeling software. Comparison between the actual 

measures installed in IHP homes and BEopt recommended measures indicate that for most 

housing groups, there are substantial differences in measure selection. Overall, IHP measure 

packages result in greater EUI reduction in frame homes and older homes. Measure packages 

installed during an IHP retrofit also result in significantly more gas savings than electricity

savings, as compared to measure packages recommended as cost optimal by BEopt. 

The methodology and findings of this study are important in that they provide valuable feedback 

for the current IHP program and guidance for other whole-home retrofit programs seeking to 

self-evaluate using large data sets. This study supports the hypothesis that archetyping can be 

used to link housing type to standardized retrofit measure packages and streamline the process 

for single-family home energy retrofits to maximize both energy savings and cost effectiveness.

 

5 Housing characterization is based on the CCS study. 
25 

References 

Baker, J.; Yee, S.; Brand, L. (2013). Analysis of Illinois Home Performance with ENERGY STAR 

Measure Packages. U.S. Department of Energy: Energy Efficiency & Renewable Energy. 

DOE/GO-102013-4006. 

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

for Building Energy Optimization: Features and Capabilities. Golden, CO: National Renewable 

Energy Laboratory, NREL/TP-550-39929. 

Culltar, K.; Ehrendreich, G.; Ellnecave, I.; Williams, S. (2012). “Energy Efficiency Policies, 

Programs, and Practices: A Resource Guide for Policymakers.” Midwest Energy Efficiency 

Alliance. 

Spanier, J.; Scheu, R.; Brand. L.; Yang, J. (2012). Chicagoland Single Family Housing 

Characterization. U.S. Department of Energy: Energy Efficiency & Renewable Energy. 

DOE/GO-102012-3604. 

USDOE, 2009a. Efficient Solutions for Existing Homes - Comprehensive Energy Retrofit Case 

Study: Habitat for Humanity - Newburgh, NY. 

http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/ba_cs_retrofit_newbu

rgh_habitat.pdf on Nov 2012. United States Department of Energy, Washington DC. 
26 

Appendix A: Illinois Home Performance Measures

Group Category 

TO2 TO3

BEopt Today BEopt 

Upgrade IHP Today IHP Upgrade

3 

Infiltration Typical Tight Leaky Typical

Unfinished Attic

Ceiling R-38 

fiberglass 

batts, vented

No change 

Ceiling R-38 

fiberglass 

batts, vented

Ceiling R-49 

fiberglass batts, 

vented

Furnace/Boiler Gas, AFUE 

80%, furnace No change Gas, AFUE 80%, furnace No change 

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

4 

Infiltration Leaky Typical Leaky Tight

Unfinished Attic

Ceiling R-19 

fiberglass 

blown-in, 

vented

No change 

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE 

78%, furnace No change Gas, AFUE 78%, furnace No change 

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

Mechanical 

Ventilation Spot vent only No change Spot vent only 100% exhaust vented to exterior

5 

Infiltration Leaky Typical Leaky Tight

Unfinished Attic

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-38

fiberglass 

blown-in, 

vented

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE 

78%, furnace

Gas, AFUE 

92.5%, furnace

Gas, AFUE 

78%, furnace No change 

6 

Infiltration Typical No change Typical Tight

Unfinished Attic

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-38 

fiberglass 

blown-in, 

vented

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE 

78%, furnace

Gas, AFUE 

92.5%, furnace

Gas, AFUE 

78%, furnace No change 

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

7 

Infiltration Very leaky Leaky Very leaky Tight

Unfinished Attic

Ceiling R-7 

fiberglass 

blown-in, 

vented

No change 

Ceiling R-7 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE Gas, AFUE Gas, AFUE Gas, AFUE 95%, 
27 

Group Category 

TO2 TO3

BEopt Today BEopt 

Upgrade IHP Today IHP Upgrade

80%, boiler 92.5%, boiler 80%, boiler furnace

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

Crawlspace 

Insulation None None Uninsulated Ceiling R-13, vented

Mechanical 

Ventilation None None None 100% exhaust vented to exterior

Programmable 

Thermostat 

Installed

None None None 

Heating set 70°F 

with setback 

65°F; Cooling set 

72°F

Ducts Sealed None None None Tight, uninsulated

8 

Infiltration Leaky Typical Leaky Tight

Unfinished Attic

Ceiling R-7 

fiberglass 

blown-in, 

vented

Ceiling R-30 

fiberglass 

blown-in, 

vented

Ceiling R-7 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE 

80%, boiler

Gas, AFUE 

95%, boiler

Gas, AFUE 

80%, boiler No change 

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

10 

Infiltration Leaky Leaky Very Leaky Tight

Unfinished Attic

Ceiling R-7 

fiberglass 

blown-in, 

vented

Ceiling R-38 

fiberglass 

blown-in, 

vented

Ceiling R-7 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE 

80%, boiler

Gas, AFUE 

95%, boiler

Gas, AFUE 

80%, boiler No change 

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

Crawlspace 

Insulation None None Uninsulated Ceiling R-14, vented

11 

Infiltration Typical Tight Typical Tighter

Unfinished Attic

Ceiling R-38 

fiberglass 

batts, vented

No change 

Ceiling R-38 

fiberglass 

batts, vented

Ceiling R-49 

fiberglass blownin, vented

Furnace/Boiler Gas, AFUE 

80%, furnace No change Gas, AFUE 80%, furnace No change 

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

Crawlspace 

Insulation None None Uninsulated Ceiling R-14, vented

12 Infiltration Leaky Typical Leaky Tight
28 

Group Category 

TO2 TO3

BEopt Today BEopt 

Upgrade IHP Today IHP Upgrade

Unfinished Attic

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass 

blown-in, 

vented

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE 

78%, furnace No change Gas, AFUE 78%, furnace No change 

Exterior Wall 

Insulation R-7 No change R-7 R-13 

13 

Infiltration Leaky Typical Leaky Tight

Unfinished Attic

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-38 

fiberglass 

blown-in, 

vented

Ceiling R-19 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE 

78%, furnace

Gas, AFUE 

92.5%, furnace

Gas, AFUE 

78%, furnace No change 

Water Heater Gas 0.54 EF No change Gas 0.54 EF No change

Crawlspace None None Uninsulated Ceiling R-14, 

vented

Mechanical 

Ventilation Spot vent only No change Spot vent only 100% exhaust vented to exterior

Exterior Wall 

Insulation R-7 No change R-7 R-13 

14 

Infiltration Very leaky Leaky Very leaky Tight

Unfinished Attic

Floored R-3 

roof insulation 

unvented 

Ceiling R-38 

fiberglass 

blown-in, 

vented

Floored R-3 

roof 

insulation

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE 

80%, furnace

Gas, AFUE 

95%, furnace

Gas, AFUE 

80%, furnace No change 

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

Crawlspace None None Uninsulated Ceiling R-14, 

vented

Mechanical 

Ventilation Spot vent only No change Spot vent only 100% exhaust vented to exterior

Exterior Wall 

Insulation Uninsulated Uninsulated Uninsulated R-13 

15 

Infiltration Leaky Typical Leaky Tight

Unfinished Attic

Ceiling R-7 

fiberglass 

blown-in, 

vented

Ceiling R-38 

fiberglass 

blown-in, 

vented

Ceiling R-7 

fiberglass 

blown-in, 

vented

Ceiling R-49 

fiberglass blownin, vented 

Furnace/Boiler Gas, AFUE Gas, AFUE Gas, AFUE No change
29 

Group Category 

TO2 TO3

BEopt Today BEopt 

Upgrade IHP Today IHP Upgrade

80%, boiler 95%, boiler 80%, boiler

Water Heater Gas 0.54 EF Gas premium 

0.67 EF Gas 0.54 EF No change 

Crawlspace None None Uninsulated Ceiling R-14, 

vented

Mechanical 

Ventilation Spot vent only No change Spot vent only 100% exhaust vented to exterior

Exterior Wall 

Insulation Uninsulated Uninsulated Uninsulated R-13 
30 

Appendix B: 2012 International Conservation Code with Illinois 

Amendments

Requirements by Component 2012 Illinois Code

Fenestration U-Factor 0.32

Skylight U-Factor 0.55

Glazed Fenestration SHGC NR

Ceiling R-Value R-49

Wood Frame Wall R-Value 20 or 13 + 5

Mechanical Ventilation ASHRAE 62.2

Basement/Crawlspace R-Value 15/19, insulation down 4 ft

Thermal Envelope Testing Requires blower door test < 5 ACH50

Floor R-Value R-30

Eave Baffle Requirement

Wood-Burning Fireplace Tight-fitting flue dampers

Duct Insulation R-6, in attic 4-8

Duct Leakage Requirements 4 cfm25/100 ft2

Building Cavities Not use as ducts or plenums

Mechanical System Piping Insulation R-3

Hot Water Piping Insulation R-3

Equipment Sizing ACCA Manuals S and J

Lighting Equipment Minimum 75% high efficiency
DOE/GO-102014-4425 ▪ June 2014

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