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

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Contract No. DE-AC36-08GO28308

High-Efficiency Retrofit Lessons 

for Retail from a SuperTarget

Preprint

Rois Langner, Michael Deru, and Adam Hirsch

National Renewable Energy Laboratory

Scott Williams

Target

Presented at the ASHRAE 2013 Winter Conference

Dallas, Texas

January 26-30, 2013

Conference Paper

NREL/CP-5500-56325 

February 2013
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Rois Langner is a mechanical engineer and Michael Deru and Adam Hirsch are senior engineers with the Commercial Buildings Research 

Group at the National Renewable Energy Laboratory, Golden, CO. Scott Williams is the group manager of mechanical engineering at Target, 

Minneapolis, MN. 

1 

High-Efficiency Retrofit Lessons for Retail 

from a SuperTarget

Rois Langner

Associate Member ASHRAE

Michael Deru, PhD

Member ASHRAE

Scott Williams

Member ASHRAE

Adam Hirsch, PhD

Associate Member ASHRAE

ABSTRACT

Retail buildings are responsible for approximately 18% of energy consumed by commercial buildings in the United States (EIA 2008). 

They offer a great opportunity for energy savings because retail stores have many similarities, and because large companies can implement successful 

energy efficiency strategies across their portfolios. Recognizing this potential, the U.S. Department of Energy (DOE) formed the Commercial 

Building Partnership (CBP) program to work with select companies in retail and commercial real estate to reduce energy consumption by 30% in 

existing buildings and 50% in new construction versus ANSI/ASHRAE/IESNA Standard 90.1-2004 (ASHRAE 2004a). The 

National Renewable Energy Laboratory partnered with Target under the CBP program to design and implement a retrofit of a SuperTarget in 

Thornton, Colorado. The result was a retrofit design that predicted 37% energy savings over ASHRAE Standard 90.1-2004, and 29% 

compared to existing (pre-retrofit) store consumption. Energy simulations of each efficiency measure played a key role in determining a mix of 

solutions that would provide the best value and yield the highest savings. The largest savings came from energy-efficient lighting and cooling 

systems, improved refrigeration, and better control of plug loads. The results of this effort will be carried forward to inform the retrofit of other 

stores across the nation. Other companies will also be able to use these results to achieve DOE’s energy efficiency goals.

INTRODUCTION

Over the past few years, Target and the National Renewable Energy Laboratory (NREL) have collaborated as part of 

the U.S. Department of Energy (DOE)-sponsored Commercial Building Partnership (CBP) program to reduce energy use 

in new and existing buildings by 30% and 50%, respectively, compared to ASHRAE Standard 90.1-2004 requirements. The 

existing Thornton, Colorado store was chosen as a pilot project with the aim to design and implement a retrofit that met or 

exceeded CBP program goals. 
2 

Since the 1990s, Target has had an in-house engineering team that regularly tracks energy use and examines energy 

efficiency measures (EEMs) to implement in its stores. EEMs that show significant savings and make economic sense are 

incorporated into prototypical store designs, reducing energy consumption across the portfolio. For instance, the company

has aggressively lowered its lighting power density throughout many of its stores by retrofitting lamps, ballasts, and 

reflectors in sales floor fixtures. Another example is the company’s unique ventilation strategy. Using ASHRAE Standard 

62.1 (ASHRAE 2004b) performance-based compliance path, the company conducted research to determine a strategy that, 

by understanding and reducing sources of air contaminants, greatly reduces the amount of ventilation air that needs to be

brought into the space during occupied hours, while maintaining good indoor air quality. Further, the company centrally 

monitors and manages its stores’ energy use from its headquarters. In this management structure, the company can track 

individual stores and corporate energy use in real time and identify areas where energy can be saved. 

EEMs that show significant savings and reliable performance are incorporated into retrofit projects in older stores; a 

typical retrofit project currently tracks at 27-28% lower than consumption defined by Standard 90.1-2004. To meet the 30% 

energy reduction goal of the CBP program, Target and NREL worked together to determine the best mix of solutions to 

achieve even higher savings. The team used energy simulation software (DOE 2011a) to evaluate EEMs, and found a 

solution that exceeded the CBP program goals, predicting 37% energy savings. 

The project, completed in fall 2011, is now being submetered to determine if the predicted energy savings match the 

store’s actual energy savings. If successful, the store will save more than 2 million kWh of electricity and more than 7,000 

therms (703 MMBtu) of natural gas annually. This equates to approximately 3.1 million pounds (1.4 million kilograms) of 

carbon dioxide emissions avoided each year. 

Consistent with the intent of the CBP program, the company plans to incorporate EEMs considered in this pilot into 

multiple upcoming retrofit projects. Lessons learned will be shared with other members of the commercial retail building 

sector to encourage a wider adoption of energy efficiency solutions.

BUILDING DESCRIPTION

The store in Thornton, Colorado was built in 2001. It is a single-story, 173,000 ft2 (16,072 m2) store, and like other 

super stores, it sells general merchandise and features a full grocery selection that includes fresh produce, a bakery, and a 

deli. The building is normally occupied from 8:00 a.m. to 10:00 p.m., Monday through Saturday, and 8:00 a.m. to 9:00 p.m. 

on Sundays. Figure 1 shows the floor plan and thermal zoning used in the energy simulation model.

Figure 1: Thermal zoning of the Thornton store. (The letters V, R, and FS stand for vestibule, restroom, and food service, respectively.) 
3 

Table 1 and Table 2 describe baseline building characteristics of the store before renovation. These characteristics 

were used as baseline model inputs, which served as a starting point for the energy studies presented in this paper. 

Table 1: Building Description

Building Component Baseline Building Model

Area 173,474 ft2 (16,116 m2)

Floors 1

Fenestration type Standard 90.1-2004 windows 

Wall construction Precast concrete

Wall insulation 13 + 3.8 ci ft2·h·F/Btu (2.29 + 0.67 ci m2·C/W)

Roof construction Flat built-up roof

Roof insulation 15 ci ft2·h·F/Btu (2.64 ci m2·C/W)

Temperature set points 68°F (20°C) heating; 74°F (23°C) cooling – set back when 

unoccupied to 59°F (15°C) heating; 81°F (27°C) cooling

HVAC Packaged single zone system with direct expansion airconditioning (11.6 EER/3.4 COP) and natural gas heating 

Table 2: Baseline Building Zone and Internal Load Characteristics

Zone Area

ft2 (m2)

Volume

ft3 (m3)

Lights

W/ft2 (W/m2)

Electric Equipment

W/ft2 (W/m2)

Gas Equipment

W/ft2 (W/m2)

General Merchandise 1 722,847

(6,768)

1,651,209

(46,757)

1.42

(15.28)

0.28

(3.05)

-

General Merchandise 2 24,960

(2,319)

565,765

(16,021)

1.03

(11.09)

0.03

(0.34)

-

Grocery 26,520

(2,464)

601,126

(17,022)

1.13

(12.16)

0.02

(0.19)

-

Stockroom 19,834 

(1,843)

449,576

(12,730)

1.30

(13.99)

0.25

(2.69)

-

Checkout 7,493

(696)

169,849

(4,810)

1.42

(15.25)

- -

Pharmacy 3,320

(308)

75,254

(2,131)

0.58

(6.24)

0.48

(5.18)

-

West Vestibule 2,000

(186)

45,334

(1,284)

1.24

(13.35)

2.86

(30.82)

-

Office 7,700

(715)

174,535

(4,942)

2.43

(26.16)

1.14

(12.24)

-

Restroom 880

(82)

19,947

(565)

1.38

(14.85)

- -

Food Service 1,840

(171)

41,707

(1,181)

1.43

(15.39)

58.86

(633.58)

-

East Vestibule 2,000

(186)

45,334

(1,284)

1.24

(13.35)

1.35

(14.57)

-

Bakery/Deli 4,080

(379)

92,481

(2,619)

0.85

(9.15)

33.40

(359.57)

31.39

(337.86)

Total 173,474

(16,116)

3,932,116

(111,344)

228,401 W 290,231 W 128,059 W
4 

ENERGY SIMULATION

The team used EnergyPlus energy simulation software (DOE 2011a) to evaluate EEMs. A baseline model used

original as-built drawings to represent actual energy use before the retrofit. The model was calibrated to measured utility 

data from the Thornton store and submetered data from another store of the same vintage in a similar climate zone. 

A second baseline model for the store represented compliance with ASHRAE Standard 90.1-2004 (ASHRAE 2004a). 

The ASHRAE model was used to benchmark energy performance for the CBP program; the calibrated model was used to 

validate modeling assumptions and to understand the actual effects of EEMs on energy use. 

Once the baseline models were developed, NREL worked with the company to determine a list of potential EEMs to 

save energy. The calibrated energy model showed 8% savings compared to the ASHRAE baseline, identifying a large 

potential for whole-building energy improvement. The current retrofit prototype already incorporates a number of EEMs 

into the design, estimating 27-28% energy savings over ASHRAE standards. NREL used the typical retrofit package as a 

starting point and determined additional measures to further increase energy savings cost effectively. The EEMs considered 

in this project are listed in Table 3 and Table 4. 

Table 3: Recommended Envelope, Lighting, and Kitchen Energy Efficiency Measures for the Thornton 

Store. EEMs that are new additions to the retrofit package are noted with an asterisk (*).

EEM

Implemented 

in Thornton

Store?

Will Consider 

for Future 

Projects?

Climate 

Dependent?

Envelope

Increase roof insulation to R-25 ft2·h·F/Btu (4.4 m2·C/W) No Yes Yes

Reduce infiltration in cart vestibule area No Yes Yes

Lighting 

*Upgrade 114-Watt sales floor fixtures to 59-Watt fixtures Yes Yes No

Remove neon decorative lights throughout sales area Yes Yes No

Remove all backlighting from panels in the electronics section Yes Yes No

Upgrade display and vendor lighting to light-emitting diode 

(LED) or higher efficacy fluorescent lamp/ballast 

combinations

Partial Yes No 

Upgrade valence (concealed) accent lighting to lower wattage, 

higher efficacy linear fluorescent lamps on the sales floor Yes Yes No 

*Upgrade lights in walk-in coolers and freezers to LEDs Yes Yes No

*Upgrade from 32-Watt T8 lamps to 25-Watt T8 lamps in 

offices and storage areas Yes Yes No 

Use daylight sensors to dim electric lighting in vestibules No Yes No

Reduce the number of auxiliary lighting fixtures, such as those 

installed above refrigerated cases Partial Yes No 

Improve distribution and reduce the number of fixtures in the 

back of house and office area No Yes No 

Manage lighting schedules on the sales floor by turning off all 

lights during unoccupied hours Yes Yes No 

Kitchen

Use high-efficiency kitchen equipment No Yes No

Consider close proximity exhaust hood designs and temperature 

and particulate-driven control strategies to lower exhaust 

flow rates

No Yes No 
5 

Table 4: Recommended HVAC, Refrigeration, and Plug Load Energy Efficiency Measures for the 

Thornton Store. EEMs that are new additions to the retrofit package are noted with an asterisk (*).

EEM

Implemented 

in Thornton

Store?

Will Consider 

for Future 

Projects?

Climate 

Dependent?

HVAC

Use performance-based ventilation strategy - continuous rate of 

0.08 cfm/ft2 (0.00041 [m3/s]/m2) Yes Yes No 

*Increase HVAC fan efficiency and control by changing from 

constant air volume to variable air volume Yes Yes No 

Widen temperature dead band set points throughout store Yes Yes No

*Add energy recovery ventilators to the rooftop units that bring 

outside air into the building in the main sales, checkout, and 

grocery areas

Yes Yes Yes

*Add evaporative condensing to the HVAC system Yes Yes Yes

Operate the grocery section at the traditional 53°F (11.7°C) dew 

point temperature and the rest of the store at 55°F (12.8°C) 

to 57°F (13.9°C) dew point temperature

Yes Yes Yes

Indirect evaporative condenser and/or ventilation air precooling No Yes Yes

Refrigeration

*Add evaporative condensing to the refrigeration system Yes Yes Yes

Add LED fixtures to all low- and medium-temperature 

refrigerated cases and walk-in freezers Yes Yes No 

Replace all evaporator fan motors in cases with electronically 

commutated motors Yes Yes No 

*Include strip curtains on all walk-in cooler and stocking doors Yes Yes No

Add night curtains to open produce cases No Yes No

Add doors to open medium-temperature cases. Add variable 

frequency drives to condensers No Yes No 

Add microchannel condensers No No No

Capture waste heat from refrigeration system for air and service 

water heating Yes Yes No 

Use anti-sweat control strategies Yes Yes No

Allow suction temperature to float in response to ambient and 

store conditions No Yes No 

Allow condensing temperature to float in response to ambient 

and store conditions Yes Yes No 

Plug Loads

Set all computers to standby mode when not in use Yes Yes No

*Use a load managing device on drink machines and turn them 

off at night No Yes No 

Eliminate personal printers, copiers, fax machines, and scanners; 

replace with two multifunction print stations No No No 

Replace desktop computers with laptop computers No No No

Identify energy efficiency strategies for stockroom charging 

stations No No No 

Choose checkout stands and registers with standby mode and 

turn off cash registers and checkout stands during 

unoccupied hours

Yes Yes No 

Turn off electronics products during unoccupied hours Yes Yes No

Replace all 32 cathode ray tube monitors in the store with liquid 

crystal display monitors Yes Yes No 
6 

EEMs were modeled and evaluated individually to estimate each measure’s energy savings. The results were provided 

to the company’s management, who then determined the net present value (NPV) and payback period, and considered 

other financial factors such as tax incentives, utility rebates, capital costs, installation costs, operation and maintenance

costs, and energy costs. In general, EEMs with a positive NPV were retained for further consideration; however, measures 

that pay back within five years and emerging technologies with large savings potential were also considered. 

Once determined to be economically feasible, the best mix of EEMs were combined into two “proposed design” 

models, developed to estimate total energy savings. Savings from individual EEMs are not additive; interactions between 

the measures play a key role in final energy savings estimates. The two proposed design models reflect EEMs that were 

implemented in the store (Proposed Design 1), and measures that were implemented in the store plus additional measures 

that the company hopes to consider in the future (Proposed Design 2). The additional measures in the Proposed Design 2 

model include new technologies in the marketplace that have not yet been fully adopted, or are measures that the company

would like to incorporate into remodel designs, but could not determine market, economic, and/or operational feasibility at 

this time.

MODELING RESULTS

Whole-building energy use was estimated for the baseline and proposed design models. A side-by-side comparison of 

these results shows significant energy savings of the proposed design models compared to the ASHRAE 90.1-2004-

compliant baseline. The Proposed Design 1 model shows 37% energy savings, exceeding the energy savings goal of the 

CBP program. Going a step further, the Proposed Design 2 model estimates even greater savings, reaching 49% compared 

to the ASHRAE baseline. These savings can be attributed to a more aggressive lighting power reduction, plug load 

reductions, highest efficiency kitchen equipment, doors on all medium-temperature refrigeration cases (except produce), 

night curtains on produce cases, and HVAC equipment designed to meet the specifications of the DOE High Performance 

Rooftop Unit Challenge (DOE 2011b). Figure 2 compares energy use intensity and energy savings for each building 

model. Table 5 compares energy use and percent savings by end use between the models. 

Figure 2: Estimated energy use intensity of the ASHRAE-compliant baseline, existing store, and two proposed design models. 

0

20

40

60

80

100

120

140

ASHRAE

90.1-2004

Current

Design

Proposed

Design 1

Proposed

Design 2

kBtu/ft2 

Estimated Energy Use Intensity

Savings

Cooling

Heating [gas]

Refrigeration

Fans

Interior Equipment (gas)

Interior Equipment (elec)

Interior Lighting

8%

37% 49%
7 

Table 5: Annual Energy Use and Percent Savings by End Use

End Use 

Category

90.1-2004 Current Design Proposed Design 1 Proposed Design 2

Annual EUI

kBtu/ft2

(kWh/m2)

Annual EUI

kBtu/ft2

(kWh/m2)

Percent 

Savings Over 

90.1-2004

Annual EUI

kBtu/ft2

(kWh/m2)

Percent 

Savings Over 

90.1-2004

Annual EUI

kBtu/ft2

(kWh/m2)

Percent 

Savings Over 

90.1-2004

Heating

(gas) 28(88) 28 (88) 0% 24 (76) 12% 19 (60) 32% 

Cooling 

(electric) 7 (22) 5 (16) 28% 2 (6) 67% 2 (6) 73% 

Lighting 

(electric) 30 (95) 24 (76) 20% 12 (38) 61% 11 (35) 65% 

Equipment 

(electric) 16 (50) 16 (50) 0% 10 (32) 40% 10 (32) 41% 

Equipment 

(gas) 3 (10) 3 (10) 0% 2 (6) 24% 0.3 (1) 89% 

Fans 

(electric) 13 (41) 12 (38) 4% 10 (32) 20% 6 (19) 54% 

Refrigeration 

(electric) 27 (85) 26 (82) 5% 18 (57) 35% 16 (50) 42% 

Total 124 (391) 115 (363) 8% 79 (249) 37% 63 (199) 49% 

The Thornton store was extensively submetered. These data are currently being collected and will be compared to 

modeling results to confirm actual energy savings. If successful, the store will save more than 2 million kWh of electricity 

and more than 7,000 therms (703 MMBtu) of natural gas annually. The greatest electricity savings can be attributed to 

lighting power reduction; refrigeration, electric equipment, cooling, and fan power reductions show significant savings as 

well. Natural gas savings are associated with reductions in heating energy. Table 6 and Table 7 show a breakout of energy 

savings by end use. The savings equate to approximately 3.1 million pounds (1.4 million kilograms) of carbon dioxide 

emissions avoided each year. 

Table 6: Electricity Savings by End Use

Electricity

End Use Category

Energy Savings 

kWh

Refrigeration 484,748

Interior Lighting 926,519

Fans 128,265

Electric Equipment 329,692

Cooling 251,974

Electricity Total 2,327,302

Table 7: Natural Gas Savings by End Use

Natural Gas 

End Use Category

Energy Savings 

Therms (MMBtu)

Heating 5,772 (577)

Service Hot Water N/A

Equipment 1,262 (126)

Natural Gas Total 7,034 (703)
8 

IMPLEMENTATION AND APPLICATION TO THE COMMERCIAL BUILDING SECTOR

The CBP program has acted as a platform for testing innovative buildings-related research. The results of this research 

have been—and will continue to be—formulated into recommendations and lessons learned, checklists, best practices, 

webinars, and other useful tools that can be shared with the rest of the commercial building sector, supporting those who

do not have direct support from national laboratory staff. The goal of this outreach is to encourage other members of the 

commercial building sector to implement similar cost-effective efficiency measures into store designs, aiming for 

widespread adoption and replication.

CONCLUSION

NREL partnered with Target under the CBP program to design and implement a retrofit of a SuperTarget in 

Thornton, Colorado. EnergyPlus was used to evaluate many EEMs and determine energy savings. After determining the 

best mix of energy efficiency solutions, the team was able to develop a retrofit design that predicted 37% energy savings 

over ASHRAE 90.1-2004 (ASHRAE 2004a), surpassing the CBP program goal of 30% savings for a retrofit project. 

The final retrofit design was determined to be the best value that achieved the highest energy savings. Energy savings 

were attributed to a reduction in interior lighting power, followed by refrigeration system EEMs, reductions in plug load 

equipment power, and high-efficiency HVAC strategies. 

Results from this study will be shared with the greater commercial building sector in an effort to encourage a wider 

adoption of EEMs. By communicating the success of the company’s participation in the CBP program, we hope to expand 

the adoption of these cost-effective measures and reduce the energy consumed by the commercial retail building sector.

ACKNOWLEDGMENTS

We would like to acknowledge the entire Target in-house design and engineering team for their dedicated efforts to 

energy conservation. In particular, we would like to thank Scott Williams for his leadership and enthusiasm throughout the 

CBP program. We would like to also thank NREL staff for their support, in particular Eric Bonnema and Brent Griffith. 

Lastly, we would like to thank the U.S. Department of Energy for sponsorship of the CBP program. 

REFERENCES

ASHRAE. 2004a. ANSI/ASHRAE/IESNA Standard 90.1-2004, Energy Standard for Buildings except Low-Rise Residential 

Buildings. Atlanta: American Society of Heating, Refrigeration and Air-Conditioning Engineers.

ASHRAE. 2004b. ANSI/ASHRAE Standard 62.1-2004, Ventilation for Acceptable Indoor Air Quality. Atlanta: American 

Society of Heating, Refrigerating and Air-Conditioning Engineers.

DOE. 2011a. EnergyPlus energy simulation software. www.eere.energy.gov/buildings/energyplus/. U.S. Department of 

Energy, Washington, D.C.

DOE. 2011b. High Performance Rooftop Unit Challenge. www1.eere.energy.gov/buildings/alliances/

rooftop_specification.html. U.S. Department of Energy, Washington, D.C.

EIA. 2008. 2003 Commercial Buildings Energy Consumption Survey. U.S. Energy Information Administration, 

Washington, DC.