Conference Paper

NREL/CP-550-48588

August 2010

Using DOE Commercial Reference 

Buildings for Simulation Studies

Preprint

Kristin Field, Michael Deru, and Daniel Studer

Presented at SimBuild 2010

New York, New York

August 11–13, 2010
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USING DOE COMMERCIAL REFERENCE BUILDINGS FOR SIMULATION 

STUDIES

Kristin Field1

, Michael Deru1, and Daniel Studer1

1

National Renewable Energy Laboratory, Golden, CO 

The U.S. Department of Energy developed 256 

EnergyPlus models for use in studies that aim to 

characterize about 70% of the U.S. commercial 

building stock. Sixteen building types – including 

restaurants, health care, schools, offices, supermarkets, 

retail, lodging, and warehouses – are modeled across 

16 cities to represent the diversity of U.S. climate 

zones. Weighting factors have been developed to 

combine the models in proportions similar to those of 

the McGraw-Hill Construction Projects Starts 

Database for 2003-2007. This paper reviews the 

development and contents of these models and their

applications in simulation studies.

ABSTRACT

The U.S. Department of Energy (DOE) Building 

Technologies program has set aggressive energy 

efficiency goals for commercial and residential 

buildings. Making substantial progress toward these

goals requires collaboration between the DOE national 

laboratories and the building industry. For such 

collaboration to be effective, projects require common 

points of reference (Deru et al. 2010). 

INTRODUCTION

The purpose of the commercial reference building 

modeling effort has been to develop standard energy 

models for the most common commercial buildings. 

These models can serve as starting points for energy 

efficiency research, as they represent fairly realistic 

buildings and typical construction practices. DOE, the 

National Renewable Energy Laboratory (NREL), 

Pacific Northwest National Laboratory (PNNL), and 

Lawrence Berkeley National Laboratory (LBNL) have 

agreed on 16 commercial building types that represent 

approximately 70% of the commercial building stock

(Deru et al. 2010). 

EnergyPlus and OpenStudio were used to develop the 

reference buildings. This paper discusses the set of 

models intended to represent new construction that is 

compliant with ASHRAE 90.1-2004 (ASHRAE 2004). 

They consist of 16 commercial building types:

• Offices – small, medium, large

• Schools – primary, secondary

• Retail – stand-alone, strip mall

• Supermarket

• Restaurants – quick service, full service

• Hotels – small, large

• Healthcare – hospital, outpatient facility

• Warehouse

• Midrise apartment building

Each building type has been created and simulated in 

each of 16 climate zones that represent the breadth of 

U.S. climates discussed in ASHRAE 90.1-2004. Table 

1 lists the climate zones and the corresponding 

locations used for design days and weather files.

Table 1 Climate Zones and Locations

CLIMATE ZONE LOCATION

1A Miami, FL

2A Houston, TX

2B Phoenix, AZ

3A Atlanta, GA

3B – Coast Los Angeles, CA

3B Las Vegas, NV

3C San Francisco, CA

4A Baltimore, MD

4B Albuquerque, NM

4C Seattle, WA

5A Chicago, IL

5B Boulder, CO

6A Minneapolis, MN

6B Helena, MT

7A Duluth, MN

8A Fairbanks, AK

Each model input was chosen based on referenced 

standard values, collaboration with colleagues in the 

private and public sectors (including between national 

laboratories), reported studies, and engineering 

judgment. The following subsections review the 

SUMMARY OF INPUTS AND 

ASSUMPTIONS

1
inputs and assumptions briefly. For more detailed 

information, refer to Deru et al. (2010). 

Form

Each commercial reference building type has a 

different form or shape. The shape, total area, floor 

height, and thermal zoning of each building were

determined from the 2003 Commercial Buildings 

Energy Consumption Survey (CBECS) dataset (EIA 

2005) and other appropriate resources. For a detailed 

accounting of these resources, refer to Deru et al. 

(2010). 

Table 2 lists the number of floors and gross floor area 

for each building type.

Table 2 Number of Floors and Gross Floor Area

BUILDING TYPE NO. 

FLOORS

GROSS FLOOR 

AREA, FT2 (M2)

Small Office 1 5,500 (511)

Medium Office 3 53,628 (4,982) 

Large Office 12* 498,588 (46,320)

Primary School 1 73,960 (6,871)

Secondary School 2 210,887 (19,592)

Stand-Alone Retail 1 24,962 (2,294)

Strip Mall 1 22,500 (2,090)

Supermarket 1 45,000 (4,181)

Quick-Service 

Restaurant 1 2,500 (232) 

Full-Service Restaurant 1 5,500 (511)

Small Hotel 4 43,200 (4,013)

Large Hotel 6* 122,120 (11,345)

Hospital 5* 241,351 (22,422) 

Outpatient Healthcare 3 40,946 (3,804)

Warehouse 1 52,045 (4,835) 

Midrise Apartment 4 33,740 (3,135)

* Plus basement.

Fabric

The fabrics (the materials comprising the envelope) of 

the buildings vary with building type and climate. 

Fabric elements include the roofs, foundations, exterior 

walls, and exterior windows. No exterior shading or 

window shading elements appear in the reference 

buildings. 

Roofs

Most reference building types have built-up, flat roofs 

with the insulation entirely above the roof deck

(IEAD). Exceptions include the full-service restaurant, 

quick-service restaurant, and small office, which have 

attic roofs, and the warehouse, which has a metal roof. 

In the models with attic roofs, the assembly thermal 

conductance values apply to the attic floor surface. 

ASHRAE 90.1-2004, Section 5 requires the roof type 

and the principal space type to determine the allowable 

thermal conductance of the roof assembly. The

reference building roofs use the “non-residential” 

space type values, except for the large hotel, small 

hotel, and midrise apartment building, which use the 

“residential” values, and the warehouse, which uses the

“semiconditioned” values.

For a given roof type and principal space type, roof 

assembly thermal conductance values vary according 

to climate in the specifications of ASHRAE 90.1-2004, 

Section 5. Table 3 provides the roof type and primary 

space conditioning type for each reference building 

type. 

Table 3 Roof Assembly Types and Primary Space 

Conditioning Typesa

BUILDING TYPE ROOF 

TYPE

SPACE TYPE

Small Office Attic Roof Non-residential

Medium Office IEADb Non-residential

Large Office IEADb Non-residential

Primary School IEADb Non-residential

Secondary School IEADb Non-residential

Stand-Alone Retail IEADb Non-residential

Strip Mall IEADb Non-residential

Supermarket IEADb Non-residential

Quick-Service Restaurant Attic Roof Non-residential 

Full-Service Restaurant Attic Roof Non-residential

Small Hotel IEADb Residential 

Large Hotel IEADb Residential

Hospital IEADb Non-residential

Outpatient Healthcare IEADb Non-residential

Warehouse Metal Roof Semiconditioned 

Midrise Apartment IEADb Residential

a) The roof assembly types and primary space conditioning 

types listed here are, in conjunction with a building’s 

ASHRAE climate zone, for use with ASHRAE 90.1-2004, 

Section 5, in determining the overall roof assembly thermal 

conductance value. 

b) Built-up flat roof with IEAD.

Foundations 

Ground heat transfer is modeled separately with 

EnergyPlus’s auxiliary Slab program, which produces 

average ground temperatures for inclusion in the main 

simulation input file (EnergyPlus 2009). Most of the 

reference buildings include 4-inch (10-cm) 

heavyweight concrete slabs-on-grade. Only the 

warehouse models have a slab-on-grade thickness of 8 

inches (20 cm). The office, school, lodging, and 

apartment building models also have a layer of carpet.

2
Three reference building types – the hospital, the large 

office, and the large hotel – are modeled with a 

basement. In these models, the underground walls are 

given thermal properties per ASHRAE 90.1-2004, 

Section 5.

Exterior Walls

ASHRAE 90.1-2004 differentiates between four types 

of wall systems – steel frame, mass wall, wood frame, 

and metal building wall. Each reference building type 

has a wall system that most accurately reflects the 

findings of the 2003 CBECS dataset (Deru et al. 2010). 

As with roof assemblies, ASHRAE 90.1-2004, Section 

5 requires both the exterior wall type and the space 

type to determine the allowable thermal conductance 

of the exterior wall assembly. All reference building

walls use the “non-residential” values, except the large 

hotel guest room walls, small hotel, and midrise 

apartment building, which use the “residential” values, 

and the warehouse, which uses the “semiconditioned” 

values.

For a given exterior wall type and space type, exterior 

wall assembly thermal conductance values vary 

according to climate in the specifications of ASHRAE 

90.1-2004, Section 5. Table 4 provides the exterior 

wall type and space conditioning type for each of the 

16 reference building types.

Some models contain exterior swinging doors, and the 

warehouse contains exterior overhead doors. The 

thermal conductance of these elements is determined 

by ASHRAE 90.1-2004, Section 5 and is not included 

in the overall thermal conductance of the exterior wall 

assembly.

Exterior Windows 

ASHRAE 90.1-2004 differentiates between two types 

of vertical exterior windows – fixed and operable. 

Engineering judgment was used to determine whether 

the vertical exterior windows in each model are fixed 

or operable. Some models have both types.

As with roof and exterior wall assemblies, ASHRAE 

90.1-2004, Section 5 requires both the vertical exterior 

window type and the space type to determine the 

allowable thermal conductance and solar heat gain 

coefficient (SHGC) of the window assembly. The 

window assembly includes the frame. 

For given window and space types, window assembly 

thermal conductance values and SHGC values vary 

according to climate in the specifications of ASHRAE 

90.1-2004, Section 5. Table 5 provides the vertical 

exterior window type and space conditioning type for 

each reference building type.

Table 4 Exterior Wall Assembly Types and Space 

Conditioning Typesa

BUILDING TYPE WALL TYPE SPACE TYPE

Small Office Mass Non-residential

Medium Office Steel Frame Non-residential 

Large Office Mass Non-residential

Primary School Steel Frame Non-residential 

Secondary School Steel Frame Non-residential

Stand-Alone Retail Mass Non-residential

Strip Mall Steel Frame Non-residential

Supermarket Mass Non-residential

Quick-Service 

Restaurant

Wood Frame Non-residential 

Full-Service 

Restaurant 

Steel Frame Non-residential

Small Hotel Steel Frame Residential

Large Hotel Mass Residential for 

guest room 

walls, nonresidential for 

other walls

Hospital Mass Non-residential 

Outpatient Healthcare Steel Frame Non-residential

Warehouse Metal Building Semiconditioned 

Midrise Apartment Steel Frame Residential

a) The exterior wall assembly types and space conditioning 

types listed here, in conjunction with a building’s ASHRAE 

climate zone, are for use with ASHRAE 90.1-2004, Section 

5, in determining the overall exterior wall assembly thermal 

conductance value. 

Skylights

Skylights appear in only two reference buildings – the 

primary school and secondary school. In both models, 

they comprise 4.5% of the roof area over the 

gymnasium zones. To determine the overall thermal 

conductance and SHGC for these skylights, the 

reference buildings use the values in ASHRAE 90.1-

2004, Section 5, that correspond with plastic skylights 

with curbs for non-residential space types.

Infiltration

Infiltration is modeled identically for all reference 

building types. Although EnergyPlus includes a 

method for modifying infiltration design flow to 

account for changes in outdoor-indoor temperature 

differential and outdoor windspeed, the infiltration 

modeling has been kept simple in the reference 

building models. An attempt to estimate these effects 

would presume a more detailed knowledge of an 

individual building’s conditions than can be afforded 

to a generic prototype.

3
Table 5 Vertical Exterior Window Types and Space 

Conditioning Typesa

BUILDING TYPE WINDOW

TYPE

SPACE TYPE

Small Office Fixed Non-residential

Medium Office Fixed Non-residential 

Large Office Fixed Non-residential

Primary School Fixed Non-residential 

Secondary School Fixed Non-residential

Stand-Alone Retail Fixed Non-residential

Strip Mall Fixed Non-residential

Supermarket Fixed Non-residential

Quick-Service 

Restaurant

Fixed Non-residential 

Full-Service 

Restaurant

Fixed Non-residential

Small Hotel Operable in 

guest rooms, 

others fixed

Residential for 

guest rooms, nonresidential for 

others

Large Hotel Operable in 

guest rooms, 

others fixed

Residential for 

guest rooms, nonresidential for 

others

Hospital Fixed Residential for 

patient rooms, 

non-residential 

for others

Outpatient Healthcare Fixed Non-residential

Warehouse Operable Semi-conditioned

Midrise Apartment Operable Residential

a) The vertical exterior window types and space conditioning 

types listed here, in conjunction with a building’s ASHRAE 

climate zone, are for use with ASHRAE 90.1-2004, Section 

5, in determining the overall window assembly thermal 

conductance and SHGC values. 

The infiltration design flow is calculated based on 

exterior wall area. A flow rate of 0.4 cfm/ft2 (2 

L/s/m2

) of exterior wall area, measured at a pressure 

differential of 0.3 in.w.c. (75 Pa), is the basis for the 

calculation. Because EnergyPlus accepts inputs for 

use at typical pressure differential conditions, a flow 

exponent of 0.65 is used to determine the flow rate at 

0.016 in.w.c. (4 Pa). Equation 1 demonstrates the 

conversion of the flow rate at the higher differential to 

one at a lower differential.

Qinf,1 = Qinf,2·(∆p1/ ∆p2)

n

 (1) 

Qinf,1 = infiltration flow [cfm/ft2] at ∆p1

Qinf,2 = infiltration flow [cfm/ft2

] at ∆p2

∆p1 = reference pressure differential [in.w.c.]

∆p2 = measured pressure differential [in.w.c.]

n = infiltration flow exponent

The resulting infiltration design flow at the reference 

condition of 0.016 in.w.c. (4 Pa) is 0.059 cfm/ft2

(0.302 L/s/m2

). For most reference building models, 

the infiltration flow is assumed to equal 25% of this 

peak flow when the ventilation system is on and 100% 

of the peak flow when the ventilation system is off. 

Any attic zones are exceptions: they are modeled with 

1 ACH infiltration flow for all hours of the year. Refer 

to Deru et al. (2010) for more details.

Internal Loads 

The use of ASHRAE standards as sources for internal 

loads has homogenized the reference building models 

to some degree. However, there is considerable 

variation from one building type to another. Decisions 

about internal load levels have been made and 

reviewed by NREL, PNNL, and LBNL, with 

significant input from ASHRAE technical committees, 

Advanced Energy Design Guide (AEDG) documents

(ASHRAE 2009), industry-specific design guides, and 

user feedback.

Occupancy

A variety of sources inform the occupancy levels for 

the different space types in the reference buildings. 

The 2003 CBECS dataset does include occupancy 

information; however, a close review of the data shows 

a wide range of values, some more representative of a 

“typical” building than others.

The two principal sources of occupancy levels are 

ASHRAE 62-1999 (ASHRAE 1999) (used because 

ASHRAE 90.1-2004 calls for this vintage of the 

standard) and DOE’s AEDG documents. Peak 

occupant densities by space type for all building types 

appear in Deru et al. (2010). 

Lighting

The reference building models include interior and 

exterior lighting.

Most interior lighting power densities (LPDs) come 

from ASHRAE 90.1-2004. Some healthcare space 

types are not represented as well in that standard, so 

the hospital and outpatient facility models took some 

LPDs from GGHC (2007). All interior lighting 

calculations employ the space-by-space method except 

for the office models, which use the building-area 

method (ASHRAE 2004).

Exterior lighting power in the reference building

models includes façade lighting by area, lighting for 

main and other doors, lighting for canopies, and 

lighting for drive-through windows. LPDs for each of 

these surface types derive from ASHRAE 90.1-2004.

4
Plug and Process Loads

ASHRAE 90.1-2004 does not contain requirements for 

plug and process loads, and measured data are scarce. 

The reference buildings draw from a variety of sources 

to obtain reasonable plug and process load levels, or 

equipment power densities (EPDs). Most EPDs 

originate from ASHRAE 90.1-1989 recommendations 

(ASHRAE 1989), work by Huang et al. (1991), and 

DOE’s AEDG series.

Table 6 provides a snapshot of the primary source of 

EPD levels in each reference building model.

Table 6 Plug and Process Load Sources

BUILDING TYPE SOURCE

Small Office Huang et al. 1991

Medium Office Huang et al. 1991

Large Office Huang et al. 1991

Primary School AEDG series

Secondary School AEDG series

Stand-Alone Retail Engineering judgment

Strip Mall Engineering judgment

Supermarket Engineering judgment

Quick-Service Restaurant Multiple, see Commercial 

Reference Buildings Technical 

Report (Deru et al. 2010)

Full-Service Restaurant Multiple, see Deru et al. (2010)

Small Hotel AEDG series

Large Hotel Huang et al. 1991

Hospital AEDG series, GGHC 2007

Outpatient Healthcare AEDG series, GGHC 2007

Warehouse AEDG series

Midrise Apartment Building America Benchmark 

definition (Hendron 2007)

The estimation of certain types of process loads – 

elevators, commercial kitchen equipment, and 

refrigeration – has received special attention. A 

discussion of the determination of these loads appears 

in Deru et al. (2010). 

HVAC Systems

This section provides a summary of the HVAC system 

inputs in the reference buildings. For more detailed 

descriptions and information about the choice of these 

inputs, refer to Deru et al. (2010).

System Types

Although ASHRAE 90.1-2004, Appendix G, might 

seem to be the most logical resource in determining 

which system type belongs in which model, given the 

frequent references mentioned to this ASHRAE 

standard, the system types it calls for do not always 

reflect the systems installed in real buildings of a given 

primary building activity. In an effort to accurately 

represent the system types common to the activities 

included in the reference buildings, we chose the 

system types in accordance with a study of those 

shown in an analysis of the 2003 CBECS dataset 

performed by Winiarski et al. (2006). The ASHRAE 

Standard 90.1 Mechanical Subcommittee has also 

provided important guidance in the selection of system 

types (Deru et al. 2010). 

Table 7 shows the types of heating, cooling, and air 

distribution equipment included in each of the 16 

reference buildings. 

Economizers are operated under the guidelines 

identified in ASHRAE (2004).

Ventilation

Ventilation amounts in most spaces follow the 

guidance of ASHRAE (1999). The 1999 vintage of 

the ASHRAE 62 standard is used because ASHRAE 

90.1-2004 calls for it, instead of for the 2004 vintage 

(ASHRAE 2004). GGHC (2007) gives more specific 

guidance for some healthcare spaces. Therefore, 

ventilation amounts in some spaces in the hospital and 

outpatient facility models deviates from the typical 

ASHRAE 62-1999 resource and follows these 

guidelines. Demand-controlled ventilation does not 

appear in the reference building models.

Equipment Efficiencies

Fan powers, heating efficiencies, and cooling 

efficiencies all coincide with the maximum/minimum 

allowable values presented in ASHRAE (2004). In the 

case of fan power, slight differences may occur 

because of the difference between what the standard 

specifies and what EnergyPlus requires in input files.

Exhaust fans and the fans in unit heaters, packaged 

terminal air conditioner units (PTACs), and fan-coil 

units (FCUs) do not follow the ASHRAE 90.1-2004 

rules for maximum allowable fan power. Instead, the 

reference buildings use the properties shown in Table 8 

for these fan types.

Service Water Heating

Service water heating (SWH) is modeled in most of the 

reference buildings. All SWH systems in the models 

consist of a natural gas-fired storage tank kept at 140°F 

(60°C).

The AEDG series, ASHRAE 90.1-2007 (ASHRAE 

2007), Gowri et al. (2007), and engineering judgment 

were used to calculate the SWH flows by space type 

and the temperature required at the fixtures. Table 9 

provides the SWH peak use rate and fixture 

5
temperature by space type. Peak flows are multiplied 

by fractional schedules to obtain hourly flows in 

EnergyPlus.

Table 7 HVAC Equipment Types

BUILDING 

TYPE

HEATINGa COOLING AIRSIDEb

Small Office Furnace Packaged DX SZ CAV

Medium 

Office

Boiler Packaged DX MZ VAV

Large Office Boiler Chiller, 

water-cooled

MZ VAV

Primary 

School 

Boiler Packaged DX SZ CAV 

and MZ 

CAV

Secondary 

School 

Boiler Chiller, aircooled SZ CAV 

and MZ 

CAV

Stand-Alone 

Retail

Furnace Packaged DX SZ CAV

Strip Mall Furnace Packaged DX SZ CAV

Supermarket Furnace Packaged DX MZ CAV

QuickService 

Restaurant

Furnace Packaged DX SZ CAV

Full-Service 

Restaurant

Furnace Packaged DX SZ CAV

Small Hotel Gas furnace 

and electric 

heating 

Packaged DX 

AC and 

PTAC units

SZ CAV

Large Hotel Boiler Chiller, aircooledMZ VAV 

and FCU

Hospital Boiler Chiller, 

water-cooled 

MZ CAV 

and MZ 

VAV

Outpatient 

Healthcare 

Furnace 

central heat, 

hot water 

reheat from 

natural gas 

boiler

Packaged DX MZ VAV

Warehouse Furnace and 

unit heaters

Packaged DX SZ CAV

Midrise 

Apartment

Furnace Packaged DX 

split system

SZ CAV

a) All heating equipment is fueled by natural gas, unless 

noted otherwise.

b) SZ = single zone, MZ = multi-zone, CAV = constant air 

volume, VAV = variable air volume, FCU = fan-coil unit 

By creating these 256 commercial building models, 

DOE intends to provide a set of common starting 

points for a wide variety of possible simulation studies.

USES AND LIMITATIONS

Table 8 Fan Properties for Fans Not Following 

ASHRAE 90.1-2004

FAN TYPEa PRESSURE RISE, 

IN.W.C. (PA)

TOTAL 

EFFICIENCY

Exhaust 0.5 (125) 22.5%

Unit heater 0.2 (50) 53.6% 

PTAC and FCU 1.33 (330) 52.0%

a) PTAC = packaged terminal air conditioning unit, FCU = 

fan-coil unit

Table 9 Service Hot Water Peak Flows and Fixture 

Temperatures

MODEL/SPACE TYPE PEAK FLOW 

RATE, 

GAL/H (L/H)

FIXTURE 

TEMP., °F 

(°C)

Small office 3.0 (11.4) 110 (43)

Medium office (per floor) 9.9 (37.5) 110 (43)

Large office (per floor) 21.3 (80.6) 110 (43)

Primary school kitchen 100.0 (379.0) 120 (49)

Primary school restrooms 56.5 (214.0) 110 (43)

Secondary school gym 189.5 (717.2) 110 (43)

Secondary school kitchen 133.0 (503.0) 120 (49)

Secondary school 

restrooms

104.4 (395.0) 110 (43)

Supermarket bakery 5.0 (19.0) 120 (49)

Supermarket deli 5.0 (19.0) 120 (49)

Quick service kitchen 40.0 (151.0) 120 (49)

Full-service kitchen 133.0 (503.0) 120 (49)

Small hotel guest room 1.8 (6.6) 110 (43)

Small hotel laundry 67.5 (255.5) 140 (60)

Large hotel guest room 1.3 (4.7) 110 (43)

Large hotel kitchen 133.0 (503.0) 120 (49)

Large hotel laundry 156.6 (592.8) 140 (60)

Hospital ER waiting 1.0 (3.8) 120 (49)

Hospital kitchen 150.0 (568.0) 120 (49)

Hospital lab 2.0 (7.6) 120 (49)

Hospital OR 2.0 (7.6) 120 (49)

Hospital patient room 1.0 (3.8) 120 (49)

Outpatient facility 40.0 (155.0) 110 (43)

Apartment 3.5 (13.2) 110 (43)

The breadth of primary building activity types lends 

itself to sector-wide studies, or studies of one building 

type across many climates. For example, one could 

use only the restaurant models to examine the effect 

nationwide of using more energy-efficient kitchen 

equipment. Another example might involve demandcontrolled ventilation in schools, using the primary 

school and secondary school models.

Alternatively, including all representative U.S. climate 

zones allows for regional simulation studies across 

several building types. Studies of this type could 

compare the effects of an energy design measure 

across several building types for a given region. For 

instance, one could vary cooling efficiencies for 

several building types across the Southeast and 

6
compare the results to varying heating efficiencies in 

those same building types across the Midwest. 

Many other options may be used as applications for the 

reference building models in simulation studies; 

however, these have limitations. The models represent 

prototypical buildings, so not every building design is 

accurately approximated by a reference building. And 

although a breadth of primary building activities is 

covered, not all can fall into one of the 16 categories.

To demonstrate how the commercial reference 

buildings can be useful for simulation studies, this 

section presents a variety of examples of studies 

currently under way.

SAMPLE APPLICATIONS

Evaluation of ASHRAE Standards

ASHRAE Standard 90.1 is updated every three years. 

As this standard is frequently referenced by building 

codes, changes to it present opportunities to save 

energy in commercial building stock. The updates 

usually consist of aggregating comments and changes 

to individual systems without much regard to the effect 

on the final performance of the standard. The 

performance of the standard is determined after and 

not during its development.

For the 2010 version, ASHRAE has set a performance 

goal for Standard 90.1 of 30% improvement over 90.1-

2004. This aggressive goal has forced the use of 

energy simulations to inform the development and 

progress toward the efficiency goal. PNNL has 

conducted studies for the ASHRAE 90.1 standard 

committee to estimate energy savings from 90.1-2004 

to 90.1-2007 to 90.1-2010 (proposed). These studies 

use the reference buildings and aggregate them with 

the weighting factors discussed previously. The 

aggregate results afford the committee a 

straightforward way to understand the impact of each 

subsequent standard, as one percentage savings 

number.

NREL recently conducted a similar analysis, using the 

reference buildings to estimate the aggregate savings 

of ASHRAE Standard 189.1 compared to 90.1-2004 

and 90.1-2007. The ASHRAE subcommittee for 

Standard 189.1 had set a target of 30% energy 

consumption reduction over 90.1-2007. Simulations 

with the reference buildings, plus postprocessing with 

weighting factors, showed the committee that the first 

iteration of the proposed standard would not reach this 

target. Further modifications were made, and the next 

round of simulations resulted in 30% savings.

ASHRAE Standard 100, which aims to improve the 

performance of existing buildings, has also used the 

reference buildings in its development. Building 

performance in this standard is measured against 

existing building data gathered in the 2003 CBECS 

(EIA 2005). Some buildings may not be well

represented in CBECS because of their primary 

building activities, locations, or both. The results of 

the reference building simulations can be used to map 

the consumption of well-represented areas to that of 

poorly represented areas, because the reference 

building results span 16 building types and all 16 

typical U.S. climates.

Pending further analysis, ASHRAE Standard 100 may 

also take the effects of operating hours into account. If 

simulations of the reference buildings yield 

significantly different energy use intensities (EUIs)

when a building’s operating hours are modified, then 

the committee working on Standard 100 will likely use 

the reference buildings to identify EUIs for a variety of 

building operating hours.

For example, in the application of Standard 100 to a 

large office building, the office building in question 

may have double the hours of operation per week than 

the buildings examined in CBECS. Some office 

buildings, because of the nature of their work, employ 

workers on multiple shifts. Their EUIs will naturally 

increase based on their extended operations. To avoid 

penalizing these buildings unnecessarily, simulation 

analysis would be used to calculate a more appropriate

EUI against which to compare the building in question. 

The large office reference building would be 

simulated, in the applicable climate, with hours 

representative of CBECS data and then with hours 

representative of the building’s actual energy use. 

Comparing both simulations would create a multiplier 

indicating the increase in EUI associated with the 

increase in operating hours. This multiplier would 

then be applied to the CBECS EUI, and the office 

building in question would be compared to an EUI 

more appropriate to its use. 

Comparing Building Vintages

In its work with the reference buildings, NREL has 

also created two vintages of existing building models – 

one representing 1980s and 1990s construction and 

one representing construction before 1980. These 

models use the reference buildings described in this 

paper as starting points and vary a few key parameters 

to represent buildings of the appropriate vintage:

• Increased infiltration for leakier construction

• Increased LPDs

7
• Modified HVAC efficiencies

• For some, changed system types

• Decreased envelope thermal resistance

For more details about the selection of existing 

building inputs, see Deru et al. (2010). These models, 

in conjunction with those described in this paper for 

new construction, can be used to predict the impact of 

energy design measures on existing building stock as 

opposed to new designs.

Ice Storage Modeling

Ice Energy is a private sector company with 

considerable experience in the manufacture, testing, 

design, and installation of ice storage systems. In its 

ongoing research and development efforts, it has 

developed in-house software analysis tools to evaluate 

the performance of its products.

The actual performance of an ice storage system 

depends on the load characteristics of the building for 

which it is installed. Ice Energy has used the reference 

buildings to obtain reasonable hourly load profiles for 

a variety of building types in a variety of climates. 

These profiles serve as inputs to Ice Energy’s in-house 

software. Having pregenerated load profiles allows its 

research to focus less on load forecasting and more on 

product enhancements.

Comparison of Natural Gas Furnace Types

The reference buildings can be used to test the impacts 

of equipment efficiency on a variety of building types 

and primary building activities. The Gas Technology 

Institute (GTI) has used them to estimate the effect of 

high-efficiency rooftop unit furnaces compared to 

standard efficiency furnaces. Because initial capital 

cost increases are associated with the high-efficiency 

units, the GTI needs to understand their potential for 

savings to persuade building owners to make this 

investment.

This research has benefited from the use of the 

reference buildings for three reasons:

• Developing full-scale hourly building 

simulations falls outside the scope of GTI 

research projects. Researchers have preferred 

having representative energy models already 

created and vetted so that they could focus on 

the areas more suited to their expertise.

• Being able to model a variety of commercial 

building types means that the results of the 

GTI study will not be limited to one sector of 

their market.

• The results of the GTI research will depend on 

climate. The reference buildings vary 

envelope properties with climate and take into 

account the effects of different loads on the 

equipment efficiencies allowed by ASHRAE 

90.1-2004. The reference buildings cover the 

16 typical U.S. climates, so this research can 

provide results appropriate to different climate 

zones.

The EnergyPlus inputs of the commercial reference 

building models embody a large collection of buildings 

research. The information included therein has been 

vetted by multiple national laboratories, ASHRAE 

technical committees, industry design professionals, 

academics, and other EnergyPlus users. Others are 

encouraged to use this common collection of buildings 

knowledge to avoid duplicating foundational work in 

their simulation studies.

CONCLUSION

The authors would like to acknowledge Kyle Benne, 

Brent Griffith, Dan Macumber, and Nicholas Long at 

NREL for providing technical assistance on the 

reference building models. Bing Liu and Mike 

Rosenberg of PNNL provided essential insights and 

support. This work was supported by the U.S. 

Department of Energy under Contract No. DE-AC36-

08-GO28308 with the National Renewable Energy 

Laboratory.

ACKNOWLEDGMENTS

ASHRAE. (1989). Energy Efficient Design of New 

Buildings Except Low-Rise Residential Buildings. 

ANSI/ASHRAE/IESNA Standard 90.1-1989. 

Atlanta, GA: American Society of Heating, 

Refrigeration, and Air-Conditioning Engineers.

REFERENCES

ASHRAE. (1999). Ventilation for Acceptable Indoor 

Air Quality. ANSI/ASHRAE/IESNA Standard 

62-1999. Atlanta, GA: American Society of 

Heating, Refrigeration, and Air-Conditioning 

Engineers.

ASHRAE. (2004). Energy Efficient Design of New 

Buildings Except Low-Rise Residential Buildings. 

ANSI/ASHRAE/IESNA Standard 90.1-2004. 

Atlanta, GA: American Society of Heating, 

Refrigeration, and Air-Conditioning Engineers.

ASHRAE. (2007). Energy Efficient Design of New 

Buildings Except Low-Rise Residential Buildings. 

ANSI/ASHRAE/IESNA Standard 90.1-2007. 

8
Atlanta, GA: American Society of Heating, 

Refrigeration, and Air-Conditioning Engineers.

ASHRAE. (2009). Advanced Energy Design Guides. 

Atlanta, GA: American Society of Heating, 

Refrigeration, and Air-Conditioning Engineers. 

Available at www.ashrae.org/publications/

page/1604. Last accessed October 2009.

Deru, M.; Field, K.; Studer, D.; Benne, K.; Griffith, B.; 

Torcellini, P.; Halverson, M.; Winiarski, D.; Liu, 

B.; Rosenberg, M.; Huang, J.; Yazdanian, M.; 

Crawley, D. (2010). DOE Commercial Reference 

Building Models for Energy Simulation – 

Technical Report. Golden, CO: National 

Renewable Energy Laboratory.

EIA. (2005). 2003 Commercial Buildings Energy 

Consumption Survey. Washington, DC: EIA. 

Available at www.eia.doe.gov/emeu/cbecs/ 

cbecs2003/introduction.html. Last accessed 

October 2009. 

EISA (2007). Energy Independence and Security Act 

of 2007. Washington, DC: U.S. Congress.

EnergyPlus. (2009). Auxiliary EnergyPlus Programs – 

Extra Programs for EnergyPlus. Washington, 

DC: U.S. Department of Energy.

GGHC. (2007). Green Guide for Health Care: Best 

Practices for Creating High Performance Healing 

Environments. Version 2.2. www.gghc.org. Last 

accessed October 2009.

Gowri, K; Halverson, M.A.; Richman, E.E. (2007). 

Analysis of Energy Saving Impacts of ASHRAE 

90.1-2004 for the State of New York. Richland, 

WA: Pacific Northwest National Laboratory. 

PNNL-16670.

Hendron, R. (2007). Building America Research 

Benchmark Definition, Updated December 20, 

2007. Golden, CO: National Renewable Energy 

Laboratory. NREL/TP-550-42662. Available at 

www.nrel.gov/docs/fy08osti/42662.pdf. Last 

accessed October 2009.

Huang, J.; Akbari, H.; Rainer, L.; Ritshard, R. (1991). 

481 Prototypical Commercial Buildings for 20 

Urban Market Areas. Berkeley, CA: Lawrence 

Berkeley National Laboratory.

Winiarski, D.W.; Jiang, W.; Halverson, M.A. (2006). 

Review of Pre- and Post-1980 Buildings in 

CBECS – HVAC Equipment. Richland, WA: 

Pacific Northwest National Laboratory.

9
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