Fort Benning Indianhead 

Townhome Renovations 

R. Stephenson, S. Roberts, T. Butler, 

and E. Kim

NAHB Research Center

December 2012
NOTICE

This report was prepared as an account of work sponsored by an agency of the 

United States government. Neither the United States government nor any agency 

thereof, nor any of their employees, subcontractors, or affiliated partners makes any 

warranty, express or implied, or assumes any legal liability or responsibility for the 

accuracy, completeness, or usefulness of any information, apparatus, product, or 

process disclosed, or represents that its use would not infringe privately owned rights. 

Reference herein to any specific commercial product, process, or service by trade 

name, trademark, manufacturer, or otherwise does not necessarily constitute or imply 

its endorsement, recommendation, or favoring by the United States government or 

any agency thereof. The views and opinions of authors expressed herein do not 

necessarily state or reflect those of the United States government or any agency 

thereof.

Available electronically at http://www.osti.gov/bridge

Available for a processing fee to U.S. Department of Energy

and its contractors, in paper, from:

U.S. Department of Energy

Office of Scientific and Technical Information

P.O. Box 62

Oak Ridge, TN 37831-0062

phone: 865.576.8401

fax: 865.576.5728

email: mailto:reports@adonis.osti.gov

Available for sale to the public, in paper, from:

U.S. Department of Commerce

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone: 800.553.6847

fax: 703.605.6900

email: orders@ntis.fedworld.gov

online ordering: http://www.ntis.gov/ordering.htm

Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste
iii

Fort Benning Indianhead Townhome Renovations 

Prepared for: 

The National Renewable Energy Laboratory 

On behalf of the U.S. Department of Energy’s Building America Program 

Office of Energy Efficiency and Renewable Energy 

15013 Denver West Parkway 

Golden, CO 80401 

NREL Contract No. DE-AC36-08GO28308 

Prepared by: 

R. Stephenson, S. Roberts, T. Butler, E. Kim

Southface Energy Institute

as part of the NAHB Research Center Industry Partnership 

400 Prince George’s Boulevard

Upper Marlboro, MD 20774 

NREL Technical Monitor: Stacey Rothgeb 

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

December 2012 
iv

[This page left blank]
v 

Contents

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

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

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

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

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

1.1 Background ..........................................................................................................................1

1.2 Overview ..............................................................................................................................2

1.3 Goals 3

2 Energy Efficient Solutions Package ................................................................................................... 4

2.1 Overview ..............................................................................................................................4

2.2 Building Enclosure...............................................................................................................7

2.2.1 Foundation and Framing ..........................................................................................7

2.2.2 Air Sealing ...............................................................................................................8

2.2.3 Insulation..................................................................................................................8

2.2.4 Fenestration ..............................................................................................................8

2.3 Systems ................................................................................................................................9

2.3.1 HVAC ......................................................................................................................9

2.3.2 Domestic Hot Water ..............................................................................................10

2.3.3 Lighting and Appliances ........................................................................................10

2.4 Estimated Cost of Energy Efficiency Solution ..................................................................11

2.5 Measure Interactions ..........................................................................................................13

3 Technical Pathway ............................................................................................................................. 15

3.1 Inputs to Building Energy Optimization Software ............................................................15

3.2 Simulation Results .............................................................................................................15

4 Experiment .......................................................................................................................................... 21

4.1 Test Plan.............................................................................................................................21

4.2 Research Questions ............................................................................................................21

4.3 Technical Approach ...........................................................................................................21

5 Testing ................................................................................................................................................. 23

5.1 Short-Term Characterization Testing ................................................................................23

6 Summary ............................................................................................................................................. 25

Appendix A: Unit Plans ............................................................................................................................ 27

Appendix B: Test Results by Unit Type.................................................................................................. 31
vi 

List of Figures

Figure 1. Fort Benning Indianhead townhomes, pre-renovation ........................................................... 1

Figure 2. Fort Benning Indianhead townhomes, post-renovation ......................................................... 2

Figure 3. Townhome building envelope ................................................................................................... 7

Figure 4. Interior framing at first floor ...................................................................................................... 8

Figure 5. Existing single pane, metal framed windows .......................................................................... 9

Figure 6. New double pane, vinyl framed windows with low-E glazing ................................................ 9

Figure 7. New air handler installation ..................................................................................................... 10

Figure 8. New electric storage water heater........................................................................................... 10

Figure 9. Annualized utility bill comparison for pre- and post-renovation cases.............................. 13

Figure 10. Existing ductwork, mold and moisture damage.................................................................. 13

Figure 11. Existing ductwork, building cavity used as return plenum................................................ 14

Figure 12. Source energy comparison of the pre and post-renovation cases ................................... 15

Figure 13. Source energy savings contribution for individual renovation measures ....................... 16

Figure 14. Average annual source energy use results ......................................................................... 20

Figure 15. HVAC duct tightness (cfm25/unit area).................................................................................. 23

Figure 16. House infiltration rate (ACHnat) .............................................................................................. 24

Figure 17. W4 unit plan (not to scale) ..................................................................................................... 27

Figure 18. W5 unit plan (not to scale) ..................................................................................................... 28

Figure 19. W6 unit plan (not to scale) ..................................................................................................... 29

Figure 20. W7 unit plan, first floor (not to scale) ................................................................................... 30

Unless otherwise noted, all figures were created by Southface.

List of Tables

Table 1. Fort Benning Unit Types.............................................................................................................. 1

Table 2. Fort Benning Indianhead Townhomes Building Specifications .............................................. 4

Table 3. HPwES Prioritization Table.......................................................................................................... 5

Table 4. Georgia Power Incentives............................................................................................................ 6

Table 5. Estimated Costs of Energy Efficiency Options ....................................................................... 11

Table 6. Parallel Path Analysis, Existing Conditions ............................................................................ 17

Table 7. Parallel Path Analysis, Post-Renovation Conditions.............................................................. 18

Table 8. Average Annual Source Energy Use Results.......................................................................... 19

Table 9. Test and Monitoring Parameter Description............................................................................ 22

Table 10. Average Test Results ............................................................................................................... 23

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

Definitions

ACHnat Air changes per hour at natural conditions

AFUE Annual fuel utilization efficiency

BEopt Building Energy Optimization

Btu British thermal unit

CFA Conditioned floor area

cfm25 Air flow (cubic foot per minute) at 25 pascals

DHW Domestic hot water

E Electric

EF Energy factor

ft2 Square foot

G Gas

h Hour

HPwES Home Performance with ENERGY STAR

HSPF Heating seasonal performance factor

in. Inch

kBtu Thousand Btu

kWh Kilowatt-hour

MBtu Million Btu

NREL National Renewable Energy Laboratory

SEER Seasonal energy efficiency ratio

SHGC Solar heat gain coefficient

yr Year
viii 

Executive Summary

As part of the National Association of Home Builders Research Center Partnership for High 

Performance Homes, Southface Energy Institute completed a post-renovation analysis of the Fort

Benning, Georgia, Indianhead townhomes renovation project. Completed by Clark Realty 

Partners in 2010, the project included the rehabilitation of 207 townhome units for base housing 

to Army personnel at Fort Benning. The Building America Program goals for this project 

included determining the projected energy savings over the pre-renovation condition, evaluating 

the quality assurance approach implemented by the project team, and identifying gaps and 

barriers in current Building America simulation tools associated with attached housing. The 

intent of this report is to outline the energy upgrade package implemented in this project and the 

findings of the Southface Energy Institute’s post-renovation analysis.
1 

1 Introduction

1.1 Background

Southface Energy Institute (Southface) conducted a post-renovation evaluation of the Fort

Benning, Georgia, Indianhead Townhomes project as part of the National Association of Home 

Builders Research Center Industry Partnership through the Building America Program. 

Completed in 2010, the project included the renovation of 207 townhome and duplex units by 

Clark Realty for Army personnel housing at Fort Benning. Table 1 shows the four unit types that 

were renovated. 

Table 1. Fort Benning Unit Types 

Unit Type Number of Units Conditioned Area (ft2)

Townhome W4 6 1,440

Townhome W5 28 1,456

Townhome W6 42 1,350

Townhome W7 220 1,536

These existing homes were unoccupied and in a state of disrepair when the renovations began 

(see Figure 1). Previous occupants had complained of high energy bills, interior moisture issues, 

and poor indoor air quality. Appendix A contains plans for each type of unit. 

Figure 2 shows one of the units after renovation. 

Figure 1. Fort Benning Indianhead townhomes, pre-renovation 
2 

Figure 2. Fort Benning Indianhead townhomes, post-renovation 

1.2 Overview

When completed at scale like the Fort Benning Indianhead renovation project, upgrades of 

existing housing offer opportunities to save a significant amount of energy. This project was the 

first Home Performance with ENERGY STAR (HPwES) project in the nation to use sampling 

for quality assurance. In this case, the 207 townhome and duplex units included in the project 

had essentially identical existing conditions given their common history of construction and 

maintenance. They received a standardized upgrade package including improved building 

envelope components and new HVAC and domestic hot water (DHW) systems. Given the 

uniform nature of the project, applying methods from production-scale, new construction, quality 

assurance approaches—specifically sampling methods for pre and post-renovation inspections—

presented an opportunity to meet the project’s energy savings and improvement goals in a costeffective manner. 

Southface initially provided quality assurance and administrative support for this project through 

Clark Realty’s involvement with the HPwES program. The energy upgrade package for the 

project was chosen based on the current Southface HPwES renovation priority list and the energy 

improvement measures incentivized through the Georgia Power energy efficiency rebate 

program. As a result, no simulation modeling was completed during the design phase of the 

project. Southface has completed a post-renovation analysis of the project. This analysis 

compared the selected measures to those recommended by energy modeling tools and was 

designed to determine the energy savings achieved by the project, identify any missed energy 

upgrade opportunities, and evaluate the current structure of the HPwES priority list. Given that 

incentive programs continue to influence homeowner and developer decisions on which energy 

upgrade measures to include in a major renovation project, this post-renovation analysis also 

allows the impact of the rebate program on the chosen measures to be assessed. 

The post-renovation simulation analysis also offered an opportunity to evaluate Building 

America simulation tools and their applicability to attached housing. Current Building America 

simulation tools, namely Building Energy Optimization (BEopt, E+ version 1.1), do not include 
3 

options for evaluating attached housing with adiabatic walls or homes with multiple wall types. 

Alternative approaches include using parallel path analysis to determine a total U-value wall 

input for BEopt or the use of alternative software packages following the Building America 

House Simulation Protocols (Hendron & Engebrecht, Building America House Simulation 

Protocols, 2010). The comparison of the results from these different approaches highlights 

current gaps for modeling attached housing. 

1.3 Goals

Specific goals for the post-renovation analysis for this project included the following: 

• Document and estimate the cost of each energy upgrade measure included in the 

renovation. 

• Determine the projected savings over the pre-renovation condition. 

• Complete statistical analysis of pre- and post-renovation diagnostic testing results to 

determine if sampling serves as a valid quality assurance model for large-scale renovation 

projects of this type. 

• Identify gaps and barriers in current Building America modeling tools. 

• Compare the structure of Southface’s HPwES priority list and the Georgia Power 

incentive program with energy upgrade packages derived from modeling tools. 

The intent of this report is to outline the energy upgrade package implemented in this project and 

the findings of Southface’s post-renovation analysis.
4 

2 Energy Efficient Solutions Package

2.1 Overview

The energy improvement measures implemented as part of this renovation were in large part 

chosen to bring the project up to current energy code standards, International Energy 

Conservation Code 2006.1 Table 2 lists the existing building specifications and chosen energy 

upgrades for the project. 

Table 2. Fort Benning Indianhead Townhomes Building Specifications

Measure Pre-Renovation Post-Renovation

Foundation Slab n/a

Foundation Insulation R-0 n/a

Wall Insulation R-9 R-13

Ceiling Construction Vented attic Vented attic

Ceiling Insulation R-8 R-30

Window Ratings U-1.27, SHGC-0.75 U-0.33, SHGC-0.24 

Average Infiltration 1.31 ACHnat 0.41 ACHnat

Heating Efficiency 80 AFUE 8 HSPF

Cooling Efficiency 10 SEER 13 SEER

Average Duct Leakage 0.69 cfm25/CFA 0.056 cfm25/CFA

Thermostat Analog Programmable

Hot Water Efficiency 0.57 EF, natural gas 0.94 EF, electric

Notes: SHGC, solar heat gain coefficient; ACHnat, air changes per hour at natural conditions; AFUE, annual fuel 

utilization efficiency; HSPF, heating seasonal performance factor; SEER, seasonal energy efficiency ratio; cfm25, 

cfm at 25 Pa; CFA, conditioned floor area, EF, energy factor

The project’s participation in the Southface HPwES program and the availability of energy 

rebates from the local electric power utility, Georgia Power, also drove the decision process 

around specific energy improvement measures. Until 2011, Southface administered Georgia 

Power’s residential demand side management and incentives program, which used the structure 

of the Southface HPwES to award energy upgrade rebates. The program includes training and 

quality assurance requirements for participating contractors (Clark Realty in this case). Projects 

participating in the program undergo a comprehensive whole-house audit to assess existing 

conditions within the homes and establish priorities for energy upgrade measures to be included 

in renovation work. The priority list shown in Table 3 grades existing conditions based on the 

audit results, with an “A” priority representing a high opportunity for improvement, a “B” 

priority representing slightly less of an opportunity, and so on. Southface developed this priority 

list in 2003 based on experience with existing home renovation projects and the feedback of 

industry experts. The existing conditions found for the Fort Benning Indianhead Townhomes are

highlighted in bold in Table 3 (Southface Energy Institute, 2008). 

 

1 Available for purchase from the International Code Council at http://shop.iccsafe.org/2006-international-energyconservation-code-soft-cover.html. 
5 

Table 3. HPwES Prioritization Table

Improvement Existing Condition Priority

Air Sealing ≥0.75 ACHnat A

Air Sealing 0.50–0.74 ACHnat B

Air Sealing 0.4–0.49 ACHnat C 

Improve Ducts ≥25% duct leakage A

Improve Ducts 16.0%–24.9% duct leakage B

Improve Ducts 10.0%–15.9% duct leakage C

Improve Ducts 5.0%– 9.9% duct leakage D

Insulate Attic (Attic Floor Air Sealing 

Must Precede Insulation Work) R-0– R-9 A 

Insulate Attic (Attic Floor Air Sealing 

Must Precede Insulation Work) R-10–R-19 B 

Insulate Attic (Attic Floor Air Sealing 

Must Precede Insulation Work) R-20–R-29 C 

Insulate Attic Kneewalls None A

Insulate Attic Kneewalls Insulated, unsheathed, or 

incomplete sheathing B 

Insulate Attic Kneewalls Insulated: sheathed, but only 

effective R-13 D 

Insulate Walls None C

Insulate Floor None B

Insulate Floor Any C

Insulate Basement/Crawlspace Walls None B

Insulate Basement/Crawlspace Walls Any C

Radiant Barrier No radiant barrier D

Replace Heating System 60–69 AFUE/5 HSPF A

Replace Heating System 70–79 AFUE/6 HSPF C

Replace Heating System 80–89 AFUE/7 HSPF D

Replace Cooling System 6.0–7.9 SEER A

Replace Cooling System 8.0–9.9 SEER B

Replace Cooling System 10 SEER D
6 

Improvement Existing Condition Priority

Replace Water Heater <0.5 gas, <0.85 electric C

Replace Water Heater <0.56 gas, <0.89 electric D

Insulate Water Heater and Pipe electric B

Insulate Water Heater and Pipe gas C

Install/Upgrade Passive Attic Ventilation 

(Confirm Presence of Effective Air 

Barrier Between Attic and Living Space)

Passive ventilation net free area 

does not meet code standard B 

Remove Powered Roof Ventilation And 

Install/Upgrade Passive Attic Ventilation 

(Confirm Presence of Effective Air 

Barrier Between Attic and Living Space)

Powered roof ventilators on roof A 

Improve Windows Jalousie windows A

Improve Windows Metal single pane B

Improve Windows Wood single pane C

Improve Windows Metal single pane with storm C

Improve Windows Wood single pane with storm D

Improve Windows Metal double pane D

The audit and priority list identified infiltration, duct leakage, attic insulation, and window 

replacement as high priorities for energy improvements. Additionally, the HVAC and DHW

systems were in a poor state of repair and required replacement. Georgia Power also provided the 

following incentives to the project for specific upgrade measures, totaling $1,200. 

Table 4. Georgia Power Incentives

Incentive ($) Requirement

250 Air sealing when priority A or B

100 Duct sealing when priority A or B

200 Attic insulation when priority A or B and when air sealing and sealing 

of ducts located in attic performed

550 Wall insulation to R-13

100 Install programmable thermostat (allowable models) only when duct 

sealing and duct insulation performed or not an A or B priority

The incentives offered through the Georgia Power HPwES program and the low cost of 

electricity available to the project through its association with the Army ($0.06/kWh) drove the 

decisions on the chosen energy upgrades and the switch from gas to electric for heating and 

cooking. 
7 

2.2 Building Enclosure

The thermal boundary for these homes includes a slab-on-grade foundation, exterior walls, and 

the attic-floor/second-floor ceiling, as well as adiabatic demising walls that separate units (see 

Figure 3). These homes underwent a gut rehabilitation renovation where the existing structure 

was left in place and all insulation was replaced.

Figure 3. Townhome building envelope

2.2.1 Foundation and Framing

All homes in the project had slab-on-grade foundations, with some homes having small 

foundation retaining walls to account for changes in grade. The first-floor exterior walls of these 

homes were built with 8-in. concrete masonry unit block, with 2 × 4 furred out interior wood 

framing (see Figure 4), and the second floor was built with 2 × 4 wood studs. Traditional framing 

was used for the roof structure to create a vented attic assembly.

Legend

Above-Grade Wall

Adiabatic Wall

Below-Grade Foundation Wall

Attic Floor
8 

Figure 4. Interior framing at first floor

2.2.2 Air Sealing

The pre-renovation inspections identified the following areas as air leakage pathways and 

prioritized air sealing measures in these areas:

• Attic access doors

• Electrical and plumbing penetrations 

• Baths at exterior walls

• Window and door rough openings 

• Floor and ceiling HVAC penetrations 

• Sill plate to slab and subfloor at second floor. 

Small penetrations were sealed with caulk and expanding foam, and for larger holes, sheet goods 

(plywood, oriented strand board, sheet metal, or rigid foam board) were used.

2.2.3 Insulation

Existing insulation (fiberglass batts in exterior walls and at the attic ceiling) was removed and 

replaced with new fiberglass batts that met current energy code insulation requirements of R-13 

fiberglass batts in exterior walls and R-30 blown fiberglass insulation in attic ceilings. 

2.2.4 Fenestration

The single pane metal framed existing windows (see Figure 5)were removed and replaced with 

new vinyl clad low-E glazing units with a low SHGC of –0.24 and a U-value of 0.33 (see Figure 

6). Rough openings were sealed with expanding foam. 
9 

Figure 5. Existing single pane, metal framed windows

Figure 6. New double pane, vinyl framed windows with low-E glazing

2.3 Systems

2.3.1 HVAC

The existing HVAC systems, 10-SEER air-conditioning units and 80-AFUE furnaces, were in 

extreme states of disrepair. In some cases building cavities had been used for air distribution, and 

furnace flues were not correctly functioning. Completely replacing the HVAC systems and duct 

distribution systems in each unit alleviated these problems. Air source heat pumps (13 SEER and 

8 HSPF) replaced the existing furnaces (see Figure 7). The units were placed in sealed closets 

and ductwork was sealed following HPwES protocols. No building cavities were used for air 

distribution with all runs fully ducted. 
10 

Figure 7. New air handler installation

Existing kitchen range hoods and bath exhaust fans were replaced with new models that vented 

to the outside.

2.3.2 Domestic Hot Water

New electric storage water heaters (0.94 EF; see Figure 8) replaced existing gas-fired units. 

Plumbing was replaced or repaired where necessary.

Figure 8. New electric storage water heater

2.3.3 Lighting and Appliances

Kitchens were outfitted with ENERGY STAR refrigerators and dishwashers. Lighting fixtures 

were replaced with standard fixtures with incandescent bulbs. 
11 

2.4 Estimated Cost of Energy Efficiency Solution

Actual cost data were not available for this project, but BEopt’s cost library showed an 

incremental capital cost for the project of $11,230 for the modeled unit. When reduced by the 

$1,200 local utility rebates earned by the project, the incremental capital cost was approximately 

$10,030 (Table 5). The $1,000 annual savings in utility bills shown by the BEopt simulation 

model (Figure 9) gives a simple payback projection for the project of approximately 10 years. 

Given that these are rental homes, however, the utility bill savings will immediately benefit the 

residents. Because the developer is not directly experiencing any benefit from these utility bill 

savings, monetary, marketing, or other drivers are needed to motivate developers to include 

energy efficiency measures in rental housing projects. The Fort Benning Indianhead Townhomes 

renovation project demonstrates the impact of energy efficiency incentives on the developer 

decision-making process, because Clark Realty would not have engaged with the HPwES 

program without the incentives from the Georgia Power rebate program. 

Table 5. Estimated Costs of Energy Efficiency Options

Group Name Category Name

Incremental 

Capital Cost 

($)

Post-Retrofit Existing

Building Orientation 0 East

Neighbors 0 None

Operation

Heating set point 0 71F

Cooling set point 0 76°F

Misc. electric loads 0 1

Misc. gas loads 0 1

Misc. hot water loads 0 Benchmark

Natural ventilation 0 Benchmark

Walls Wood stud 4,483 Fort Benning retrofit 

walls R-13

Fort Benning 

existing walls R-9

Exterior finish 0

Ceilings/

Roofs

Unfinished attic 414 Ceiling R-30 cellulose 

blown-in vented

Fort Benning 

existing attic R-8

Roofing material 0 Asphalt shingles dark

Radiant barrier 0 None

Foundation/

Floors

Slab 0 Uninsulated

Exposed floor 0 20% exposed

Thermal 

Mass

Floor mass 0 Wood surface

Exterior wall mass 46 1⁄2 in. drywall

Partition wall mass 0 1⁄2 in. drywall

Ceiling mass 0 1⁄2 in. ceiling drywall

Windows/

Shading

Window areas 0 Front 70, back 101, left 

0, right 0

Front 110, back 

102, left 0, right 0

Window type 0 U 0.33, SHGC 0.24 U 1.2, SHGC 0.75

Interior shading 0 Benchmark

Eaves 0 2 ft

Overhangs 0 None

Airflow Infiltration 386 0.49 ACHnat 2.14 ACHnat

Mechanical ventilation 0 Spot vent only

Major Refrigerator 780 ENERGY STAR top Standard top 
12 

Group Name Category Name

Incremental 

Capital Cost 

($)

Post-Retrofit Existing

Appliances mount freezer mount freezer

Cooking range 0 Electric conventional Gas conventional

Dishwasher 50 ENERGY STAR Standard

Clothes washer 0 Standard

Clothes dryer 0 Electric

Lighting Lighting 0 B10 benchmark

Space 

Conditioning

Air conditioner 0 None SEER 10

Furnace (1,251) None Gas 80% AFUE

Heat pump 4,511 SEER 13, HSPF 8.1 None

Ducts 1,891 3% leakage, R-8 68% leakage, R-4

Ceiling fans 0 Benchmark

Water 

Heating

Water heater (80) Electric EF 0.94 Natural gas EF 

0.60

Distribution 0 R-0 Trunk branch 

copper

Solar DHW 0 None

Solar DHW azimuth 0 Back roof

Solar DHW tilt 0 Roof pitch

Power 

Generation

Photovoltaic system 0 0 kW

Photovoltaic azimuth 0 Back roof

Photovoltaic tilt 0 Roof pitch

HVAC Sizing Cooling capacity 0 3 tones

Heating capacity 0 80 kBtu/h

First Year 

Total 

Incremental 

Capital Cost

11,230

Energy 

Rebates 1,200

Total 

Incremental 

Capital Cost 

Less Energy 

Rebates

10,030
13 

Notes: G, gas; E, electric

Figure 9. Annualized utility bill comparison for pre- and post-renovation cases 

2.5 Measure Interactions

Many of the energy efficiency measures incorporated into the renovation package had additional 

benefits for occupant health and comfort and mitigated existing moisture, mold, and combustion 

safety risks. Previous occupants had complained of high energy bills, interior moisture issues 

(see Figure 10), and poor indoor air quality. The existing ductwork in these homes was in a high 

state of disrepair and in some cases building cavities had been used as open plenums (see Figure 

11), introducing moisture and contaminants into the air stream and causing pressure imbalances 

in the homes. Complete replacement of the ductwork alleviated these issues. Moisture damage

was also repaired and the resulting mold growth was removed. Replacing gas furnaces, water 

heaters, and ranges with electric units also removed potential combustion safety risks from the 

homes.

Figure 10. Existing ductwork, mold and moisture damage
14 

Figure 11. Existing ductwork, building cavity used as return plenum 
15 

3 Technical Pathway

3.1 Inputs to Building Energy Optimization Software

Through simulation, BEopt produces a comparison of the pre- to post-renovation conditions. The 

comparison includes source energy use and equivalent annual energy cost based on energy costs 

and the costs of the improvement measures, within the limits of the software and cost data. A W4 end unit was chosen as a worst-case unit for simulation modeling because it had the highest 

percentage of exposed wall area and the highest window to floor area ratio. A worst-case 

orientation was also chosen for the simulation modeling with the front of the home facing east 

and the exterior end wall facing south. Optimization studies for the project were not completed 

because this simulation analysis occurred after the renovation. 

3.2 Simulation Results

Energy simulations for the worst case W4 end unit showed a post-renovation source energy 

savings of 43% over existing conditions. The post-renovation energy simulations included source 

energy savings analyses and cost-effectiveness comparison. Figure 11 graphically depicts the 

simulation results.

Figure 12. Source energy comparison of the pre and post-renovation cases 
16 

Figure 13. Source energy savings contribution for individual renovation measures

Additional simulations were run to determine the contribution of the individual measures 

included in the renovation package (refer to Table 2). The largest savings came from improved 

duct and envelope leakage rates, as well as high performance window upgrades. Although the 

switch to an electric water heater saved money because of the low electric rate ($0.06/kWh) 

available through the project’s connection with Fort Benning, a source energy penalty was 

incurred with the switch from natural gas. 

To input these attached housing units into the BEopt software, a parallel path workaround was 

used to calculate an average U-value input for the exterior walls based on the different exterior 

wall types and the adiabatic party walls. Tables 6 and 7 show these calculations for the existing 

and post-renovation conditions. 
17 

Table 6. Parallel Path Analysis, Existing Conditions

W4 Wall U-Value Brick, End Unit W4 Wall U-Value Siding, End Unit

Framing Width (in.) 3.5 Framing width (in.) 3.5

Block Width (in.) 8 Block width (in.) 8

Block Face Thickness (in.) 1.25 Block face thickness (in.) 1.25

Brick Width (in.) 4

Cavity Framing/Rib Cavity Framing

Interior Film 0.68 0.68 Interior film 0.68 0.68

Interior Covering 0.45 0.45 Interior covering 0.45 0.45

Frame/Cavity 9 3.85 Frame/cavity 9 3.85

Sheathing 0.5 0.5 Sheathing 0.5 0.5

Block Face (1.25 in.) 0.125 0.125

Cavity (Air)/Rib 1 0.55

Block Face (1.25 in.) 0.125 0.125

Exterior Insulation 0 0 Exterior insulation 0 0

Exterior Air Space 0.97 0.97 Exterior air space 0 0

Exterior Covering, Brick 0.44 0.44 Exterior covering, siding 0.61 0.61

Exterior Film, Winter Exterior film, winter

Path Thermal Resistance 13.29 7.69 Path thermal resistance 11.24 6.09

% of Clear (Framing) 75% 25% Percentage of clear 75% 25%

% of Clear (Block) 84% 16%

Isothermal Plane 11.9 R-value Isothermal plane 9.0 R-value

0.084 U-value 0.111 U-value

Parallel Path 11.2 R-value Parallel path 9.3 R-value

0.089 U-value 0.108 U-value

Conductivity 1.134 Btu-in./h∙ft2

∙°F Conductivity 0.377 Btuin./h∙ft2

∙°F

Brick Siding Adiabatic

Wall Proportion R-Value 11.24 9.28 100

Wall Proportion U-Value 0.089 0.108 0.010

% of Wall 34.4% 38.6% 27.0%

Average Assembly 

Thickness 8.46 inches

Parallel Path 13.4 R-value

0.075 U-value

Overall Conductivity 0.634 Btuin./h∙ft2

∙°F
18 

Table 7. Parallel Path Analysis, Post-Renovation Conditions 

W4 Wall U-value brick, end unit W4 Wall U-value siding, end unit

Framing Width (in.) 3.5 Framing width (in.) 3.5

Block Width (in.) 8 Block width (in.) 8

Block Face Thickness (in.) 1.25 Block face thickness 

(in.) 1.25

Brick Width (in.) 4

Cavity Framing/Rib Cavity Framing

Interior Film 0.68 0.68 Interior film 0.68 0.68

Interior Covering 0.45 0.45 Interior covering 0.45 0.45

Frame/Cavity 13 3.85 Frame/cavity 13 3.85

Sheathing 0.5 0.5 Sheathing 0.5 0.5

Block Face (1.25 in.) 0.125 0.125

Cavity (Air)/Rib 1 0.55

Block Face (1.25 in.) 0.125 0.125

Exterior Insulation 0 0 Exterior insulation 0 0

Exterior Air Space 0.97 0.97 Exterior air space 0 0

Exterior Covering, Brick 0.44 0.44 Exterior covering, siding 0.61 0.61

Exterior Film, Winter Exterior film, winter

Path Thermal Resistance 17.29 7.69 Path thermal resistance 15.24 6.09

% of Clear (Framing) 75% 25% Percentage of clear 75% 25%

% Of Clear (Block) 84% 16%

Isothermal Plane 14.9 R-value Isothermal plane 10.4 R-value

0.067 U-value 0.096 U-value

Parallel Path 13.2 R-value Parallel path 11.1 R-value

0.076 U-value 0.090 U-value

Conductivity 0.968 Btu-in./h∙ft2

∙°F Conductivity 0.316 Btuin./h∙ft2

∙°F

Brick Siding Adiabatic

Wall Proportion R-Value 13.18 11.08 100

Wall Proportion U-Value 0.076 0.090 0.010

% of Wall 34.4% 38.6% 27.0%

Average Assembly 

Thickness 8.46 in. 

Parallel Path 15.7 R-value

0.064 U-value

Overall Conductivity 0.538 Btuin./h∙ft2

∙°F
19 

To validate this workaround approach, a comparison was conducted between the BEoptE+ v1.1 

simulation results and the results from an alternative hourly energy simulation software, 

EnergyGauge USA v2.8.05. Identical inputs were used for both software packages based on the 

specifications outlined in Table 2. The 2008 Building America House Research Benchmark 

Definition was used for the EnergyGauge USA simulation runs, though, because the software 

package has not been updated with 2010 Building America House Simulation Protocols. Table 8 

shows the average annual source energy consumption results for both the pre- and postrenovation cases from both software packages. 

Table 8. Average Annual Source Energy Use Results

Average Source Energy Use (MBtu/yr)

BEopt 

PreRenovation

EnergyGauge 

PreRenovation

BEopt 

PostRenovation

EnergyGauge 

PostRenovation

Miscellaneous (E) 33.615 29.677 35.919 33.283

Vent Fan (E) 0.252 0.287 0.252 0.276

Large Appliance (E) 19.685 18.422 23.075 24.497

Lights (E) 14.717 14.712 14.717 14.712

HVAC Fan/Pump 

(E) 13.574 19.352 4.713 6.914

Cooling (E) 62.677 80.933 21.838 24.497

Heating (E) 0.000 0.000 14.053 12.323

Heating (G) 87.444 85.176 0.000 0.000

Hot Water (E) 0.000 0.000 30.019 29.447

Hot Water (G) 17.802 16.271 0.000 0.000

Large Appliance (G) 3.178 4.914 0.000 0.000

Miscellaneous (G) 0.767 1.201 0.000 0.000

Total (E) 144.520 163.382 144.586 145.948

Total (G) 109.190 107.562 0.000 0.000

Total MBtu 253.711 270.944 144.586 145.948

The results agree fairly well, with EnergyGauge USA showing a 46% source energy savings 

compared to the 43% source energy savings found using the workaround method in BEopt (see 

Figure 14). The largest discrepancies arise with the miscellaneous electric, HVAC fan/pump, 

cooling, large appliance, and miscellaneous natural gas loads. The discrepancy in cooling load is 

of most concern for this workaround approach. The differences in miscellaneous electric, 

cooling, large appliance, and miscellaneous natural gas loads can be traced to the changes 

between the 2008 and 2010 Building America Benchmark and the differences in the modeling 

software packages used. Based on the outcome of this comparison, the parallel path workaround 

used appears to present a valid simulation approach that can be used until BEopt is updated to 

include attached housing units. 
20 

Figure 14. Average annual source energy use results

0.000

50.000

100.000

150.000

200.000

250.000

300.000

BEopt

Pre-Retrofit

EnergyGauge

Pre-Retrofit

BEopt

Post-Retrofit

EnergyGauge

Post-Retrofit

Avg. Source Energy Use (Mbtu/yr) 

Misc. (G)

Lg. Appl. (G)

Hot Water (G)

Hot Water (E)

Heating (G)

Heating (E)

Cooling (E)

HVAC Fan/Pump (E)

Lights (E)

Lg. Appl. (E)

Vent Fan (E)

Misc. (E)
21 

4 Experiment 

4.1 Test Plan

A detailed testing plan was presented in Southface’s Test Plan outlining simulation comparisons 

and short-term characterization testing completed to answer the research questions outlined in 

the next section (Southface Energy Institute, 2011). The focus of this test plan was on short-term 

testing and analysis. Long-term monitoring is not planned for this project.

4.2 Research Questions

This project answered the following research questions: 

• What gaps and barriers currently exist in BEopt software for attached housing 

applications and do planned software updates adequately address these issues?

• Does sampling serve as a valid quality assurance model for large-scale renovation 

projects of this type? If so, what is the appropriate sampling size? 

• How does the cost effectiveness of the energy upgrade measures chosen for this project 

compare with that of other potential energy upgrades? 

• How does the structure of Southface’s HPwES priority list and Georgia Power incentive 

program compare with energy upgrade packages derived from modeling tools? 

4.3 Technical Approach 

The technical approach for this project called for short-term characterization testing to establish 

pre-renovation conditions and verify the post-renovation whole-house infiltration and duct 

leakage rates. With guidance from the HPwES program, a sampling approach for this testing was 

developed. Requirements included the following: 

• Pre-renovation testing of each unit type (interior and exterior) until the average of testing 

results ±1 standard deviation (SD) was completely within one priority range 

• Post-renovation testing for all units in pre-renovation test sets, as well as 1/7 of remaining 

units.

Table 9 briefly describes the test methods employed and their purposes. 
22 

Table 9. Test and Monitoring Parameter Description

Parameter of 

Interest Test Method Purpose

House Infiltration 

Rate

Blower door test and 

diagnostic evaluation 

• Test-in: Find overall infiltration rate and 

assess primary leakage paths

• Test-out: Find overall infiltration rate and 

locate remaining major leakage paths

HVAC Duct 

tightness Duct leakage test

• Test-in: Assess leakage and opportunities 

for improvement 

• Test-out: Discover duct leakage rate to the 

outside

Short-term test results are detailed in Section 5. 
23 

5 Testing 

5.1 Short-Term Characterization Testing

Testing results showed a drastic improvement in both duct leakage and house infiltration rate 

from the pre- to post-renovation condition. The project achieved the HPwES goal of reducing air 

infiltration by a minimum of 0.40 ACHnat and reducing duct leakage to less than 10% of total 

floor area served in all unit types. In all, 48 units underwent pre-renovation testing and 61 units 

underwent post-renovation testing, which represents 23% and 29% of the total units, 

respectively. Four W5 units types burned following test-in and were not rebuilt. Average test 

results are shown in Table 10, and Appendix B contains test results for each unit type. Average 

duct tightness was measured at 5% of floor area served at test-out and average house infiltration 

was measured at 0.43 ACHnat, with very low SDs for the results of both tests. 

Figures 15 and 16 depict aggregate results from pre- and post-renovation testing for HVAC duct 

tightness and house infiltration rate. The low variation in post-renovation testing demonstrates 

that sampling represents a valid approach for quality assurance for large-scale renovation 

projects of this type. 

Table 10. Average Test Results

HVAC Duct Tightness

(cfm25/unit area)

House Infiltration Rate

(ACHnat) 

Test-In Mean Median SD Mean Median SD

48 Units 

(23% of Total) 68% 70% 0.085 1.54 1.46 0.567 

Test-Out Mean Median SD Mean Median SD

61 Units

(29% of Total) 5% 5% 0.016 0.43 0.42 0.049 

Figure 15. HVAC duct tightness (cfm25/unit area)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Pre-Renovation Post-Renovation

Average

Min

Max
24 

Figure 16. House infiltration rate (ACHnat) 

0

0.5

1

1.5

2

2.5

3

Pre-Renovation Post-Renovation

Average

Min

Max
25 

6 Summary

The renovation approach used in this project proved to be a cost-effective approach for 

implementing energy improvement measures at scale. Implementing a large-scale renovation 

project for homes of similar vintage and condition using a standard upgrade package has the 

potential to achieve significant energy savings, projected at greater than 40% in this case. 

Simulation models showed that the current structure of the Southface HPwES priority list led the 

project to a fairly optimized package of energy upgrade measures. The Fort Benning Indianhead 

townhomes renovation project demonstrated the impact of energy efficiency incentives on the 

developer decision-making process. Clark Realty would not have engaged with the HPwES 

program without the incentives from the Georgia Power rebate program. 

Applying quality assurance methods from production-scale new construction, specifically 

sampling methods for pre- and post-renovation inspections, presents an opportunity to meet the 

project’s energy savings and improvement goals in a cost-effective manner. For this project 23% 

of all units underwent a test-in inspection and 29% underwent test-out. The project met its 

performance goals on all units, reducing infiltration by 0.40 ACHnat and duct leakage to less than 

10% of total floor area served in all unit types. Future research efforts could focus on the 

minimum sampling rate necessary to consistently meet project goals.

The current version of BEopt, BEoptE+ v1.1, does not include options for simulating attached 

housing types. The parallel path workaround implemented in this project, however, appears to be 

valid based on modeling results from alternative hourly energy simulation packages that include 

options for simulating attached housing. Southface plans to further validate the results found 

using the parallel path workaround once an updated version of BEopt that includes options for 

simulating attached housing types is released. 
26 

Bibliography 

Hendron, R. (2008). Building America Research Benchmark Definition. Golden, CO: National 

Renewable Energy Laboratory. 

Hendron, R., & Engebrecht, C. (2010). Building America House Simulation Protocols. Golden, 

CO: National Renewable Energy Laboratory. 

Parker, D., & Cummings, J. (2009). Comparison of ENERGYGAUGE USA and BEopt Building 

Energy Simulation Programs. Cocoa, FL: Florida Solar Energy Center. 

Polly, B., & al, e. (2011). A Method for Determining Optimal Residential Energy Efficiency 

Retrofit Packages. Golden, CO: National Renewable Energy Laboratory. 

Southface Energy Institute. (2008). Georgia Power Home Performance with ENERGY STAR 

Contractor Manual. Atlanta, GA: Southface Energy Institute. 

Southface Energy Institute. (2011). Test Plan: Fort Benning Indianhead Townhome Renovations.

Atlanta, GA.
27 

Appendix A: Unit Plans

Figure 17. W4 unit plan (not to scale) 
28 

Figure 18. W5 unit plan (not to scale) 
29 

Figure 19. W6 unit plan (not to scale) 
30 

Figure 20. W7 unit plan, first floor (not to scale) 
31 

Appendix B: Test Results by Unit Type

W4

Total 

Units 6

% Leakage ACHnat

Test-In Total Average Median SD Average Median SD

Interior 2 66% 66% 0.072 2.03 2.06 0.417

End 4 69% 69% 0.148 2.35 2.35 0.071

All 6 67% 66% 0.087 2.14 2.21 0.365

% 100% 34%

% Leakage ACHnat

Test-Out Total Average Median SD Average Median SD

Interior 2 3% 3% 0.000 0.49 0.50 0.022

End 4 4% 4% 0.007 0.48 0.48 0.064

All 6 3% 3% 0.004 0.49 0.48 0.064

% 100%

W5

Total Units 22(28 total, 6 burned)

% Leakage ACHnat

Test-In Total Average Median SD Average Median SD

Interior 2 58% 58% 0.085 2.13 2.13 0.141

End 6 61% 59% 0.088 2.03 2.12 0.281

All 8 60% 59% 0.081 2.06 2.12 0.247

% 36%

% Leakage ACHnat

Test-Out Total Average Median SD Average Median SD

Interior 0

End 2 6% 6% 0.009 0.45 0.45 0.014

All 2 6% 6% 0.009 0.45 0.45 0.014

% 9%
32 

 

W6

Total Units 42

% Leakage ACHnat

Test-In Total Average Median SD Average Median SD

Interior 7 71% 69% 0.040 1.28 1.23 0.161

End 5 73% 74% 0.043 1.26 1.26 0.197

All 12 72% 74% 0.040 1.27 1.24 0.168

% 29%

% Leakage ACHnat

Test-Out Total Average Median SD Average Median SD

Interior 9 5% 5% 0.011 0.49 0.48 0.037

End 7 5% 5% 0.013 0.41 0.42 0.037

All 16 5% 5% 0.012 0.45 0.45 0.054

% 38%

 

W7

Total Units 137

% Leakage ACHnat

Test-In Total Average Median SD Average Median SD

Interior 12 69% 75% 0.078 1.32 0.94 0.587

End 10 75% 0.75 0.149 1.35 1.01 0.656

All 22 69% 0.75 0.089 1.33 0.95 0.604

% 16%

% Leakage ACHnat

Test-Out Total Average Median SD Average Median SD

Interior 19 5% 5% 0.015 0.41 0.40 0.032

End 18 6% 5% 0.019 0.41 0.40 0.039

All 37 6% 5% 0.016 0.41 0.40 0.037

% 27%
DOE/GO-102012-3575 ▪ December 2012

Printed with a renewable-source ink on paper containing at 

least 50% wastepaper, including 10% post-consumer waste.