A Common Definition for
Zero Energy Buildings
September 2015
Prepared for the U.S. Department of Energy by
The National Institute of Building Sciences
NREL Research Support Facility, photo credit: Bill Gillies, NREL
(This page intentionally left blank)
Acknowledgements
The Project Team would like to thank the Subject Matter Experts who were interviewed during the research phase
of the project, as well as the Stakeholders who provided comments during the evaluation phase of the project. They
all were of great assistance to this effort. (See Appendix 2 for a complete list). In addition, more than 65 individuals
and organizations submitted comments during the public comment period. The team greatly appreciated their input,
which was very benecial to the nal outcome of the report.
Project Team
The Project Team consisted of representatives from both the U.S. Department of Energy and the National Institute
of Building Sciences.
The primary authors of the Zero Energy Building denitions, nomenclature and guidelines included:
Kent Peterson P2S Engineering, Consultant for the National Institute of Building Sciences
Paul Torcellini National Renewable Energy Laboratory
Roger Grant National Institute of Building Sciences
Additional members of the Project Team assisting on the project included:
Cody Taylor U.S. Department of Energy, Building Technologies Ofce
Sonia Punjabi U.S. Department of Energy, Building Technologies Ofce (former Fellow)
Richard Diamond Lawrence Berkeley National Laboratory
Ryan Colker National Institute of Building Sciences
Get Moy AECOM, and Chair of the National Institute of Building Sciences High Performance
Building Council
Earle Kennett National Institute of Building Sciences
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Guiding Principles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Zero Energy Building (ZEB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Zero Energy Campus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Zero Energy Portfolio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Zero Energy Community . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Measurement and Implementation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Energy Accounting and Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Source Energy Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Example Calculation for All Electric ZEB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Example Calculation for ZEB with Multiple Delivered Energy Types . . . . . . . . . . . . . . . . . . . . . . . . 9
Example Calculation for ZEB with Combined Heat and Power (CHP) . . . . . . . . . . . . . . . . . . . . . . . 9
Using Renewable Energy Certificates (REC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Renewable Energy Certificate - Zero Energy Building (REC-ZEB) . . . . . . . . . . . . . . . . . . . . . . . . . 10
Using the terms “Zero Energy Building” and “Renewable Energy Certificate Zero Energy Building” . . . . . . . 10
Appendix 1 - Research Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Appendix 2 – Industry Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1
Introduction
In 2014, the U.S. Department of Energy (DOE) Building Technologies Ofce contracted with the National Institute
of Building Sciences (Institute) to establish denitions, associated nomenclature and measurement guidelines
for zero energy buildings, with the goal of achieving widespread adoption and use by the building industry. The
Institute prepared this report, A Common Denition for Zero Energy Buildings, to present the results of that work.
Background
A zero energy building (ZEB) produces enough renewable energy to meet its own annual energy consumption
requirements, thereby reducing the use of non-renewable energy in the building sector. ZEBs use all cost-effective
measures to reduce energy usage through energy efciency and include renewable energy systems that produce
enough energy to meet remaining energy needs. There are a number of long-term advantages of moving toward
ZEBs, including lower environmental impacts, lower operating and maintenance costs, better resiliency to power
outages and natural disasters, and improved energy security.
Reducing building energy consumption in new building construction or renovation can be accomplished through
various means, including integrated design, energy efciency retrots, reduced plug loads and energy conservation
programs. Reduced energy consumption makes it simpler and less expensive to meet the building’s energy needs
with renewable sources of energy.
ZEBs have a tremendous potential to transform the way buildings use energy and there are an increasing number
of building owners who want to meet this target. Private commercial property owners are interested in developing
ZEBs to meet their corporate goals, and some have already constructed buildings designed to be zero energy. In
response to regulatory mandates, federal government agencies and many state and local governments are beginning
to move toward targets for ZEBs. However, denitions differ from region to region and from organization to
organization, leading to confusion and uncertainty around what constitutes a ZEB.
Goals
A broadly accepted denition of ZEB boundaries and metrics is foundational to efforts by governments, utilities
and private entities to recognize or incentivize ZEBs. A commonly accepted denition and corresponding methods
of measurement for ZEBs would also have a signicant impact on the development of design strategies for
buildings and help spur greater market uptake of such projects.
The denition of ZEBs needs to include clear and concise language to be effective and accepted. Metrics and
measurement guidelines are required to allow verication of the achievement of the key elements of the denition.
The denition, nomenclature and measurement guidelines should address how energy consumption is measured
and what energy uses and types to include in its determination.
In practice, actual projects seeking to verify zero energy should work to ensure no harm is done in the process
of achieving zero energy performance across other, non-energy-related considerations, such as water protection,
optimized comfort for low-load buildings, and comprehensive indoor air quality. While these considerations don’t
affect the denition of zero energy, it is important that in practice a design team ensures that other important
building considerations and values are not sacriced in pursuit of zero energy.
Methodology
Creating a broadly agreed upon and supported denition of ZEB should involve participation from the many
organizations that have a stake in the outcome. DOE selected the National Institute of Building Sciences to
facilitate this collaboration. A non-prot, non-governmental organization, the Institute was established by the U.S.
Congress in 1974 to bring together representatives of government, the professions, industry, labor and consumer
interests, and regulatory agencies to focus on the identication and resolution of problems and potential problems
that hamper the construction of safe, affordable, efcient and effective structures throughout the United States.
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
2
The Institute’s High Performance Building Council (HPBC) led the process to develop commonly agreed upon
denitions for ZEBs. Formed in April 2007 in response to Section 914 of the Energy Policy Act, the HPBC has
representatives from most of the major standards writing organizations, industry trade associations, nonprot
organizations and federal government entities involved with the built environment. It includes representation from
all members of the building team, from designers to builders to owners.
Early in 2014, the Institute, with funding and support from the DOE Building Technologies Ofce, began working
through the HPBC to establish a common national ZEB denition. The Institute and DOE formed a Project Team
(see Acknowledgements section for a list of Project Team members). During the research phase of the project, the
Project Team surveyed existing publications (see Appendix 1 for a list of publications researched) and interviewed
subject matter experts (SMEs) working on ZEBs from across the building industry to develop a full list of issues
to be addressed and a draft set of denitions and metrics. The Project Team presented these ndings to industry
stakeholders involved with the creation and advancement of ZEBs, who were invited to participate, contribute their
perspective and provide their input. (See Appendix 2 for a list of SMEs and stakeholders who participated in the
project.)
In response to the comments received from industry stakeholders, the Project Team rened the initial draft
denitions, nomenclature and guidelines. DOE posted the revised material for public comment in the Federal
Register, Docket EERE-2014-BT-BLDG-0050 Denition for Zero Energy Buildings. The comment period
generated more than 65 comments, which the Project Team then evaluated for relevance and used to further update
and rene the denition.
A basic issue that needed to be established is what to call buildings that are designed and operated in such a way
that energy consumption is reduced to a level that it is balanced by renewable energy production over a typical
one-year period. To make the determination, the Project Team reviewed denitions already in use; collected
opinions of SME and Stakeholders; and considered other DOE programs and goals. In addition, a key factor came
from the DOE Zero Energy Ready Homes program which had received feedback that concluded the term “net”
was confusing to consumers. The desire was to have a term that resonated with building owners. The Project Team
considered an idea advanced by some that “net” is necessary to be accurate in accounting for energy usage. The
team reached the conclusion that the word “net” did not add substantive meaning to the name, since the denition
fully describes how to account for delivered and exported energy. Therefore, in striving for simplicity, consistency
and to accentuate the core objective, DOE and NIBS selected the term “Zero Energy Building (ZEB).” However,
it is recognized that the terms Net Zero Energy (NZE) and Zero Net Energy (ZNE) are in wide use and convey the
same meaning as Zero Energy.
During the review process, the Project Team identied the need for additional denitions for related groupings of
buildings. The team included denitions for “Zero Energy Campuses,” “Zero Energy Communities” and “Zero
Energy Portfolios” to expand the reach of the ZEB concept, provide for the collective generation of renewables
and account for different energy needs of buildings. Some building industry representatives expressed a need to
develop a denition for Zero Energy Ready (ZER) buildings. The team did not include this in the ZEB denitions
developed but it could be added in the future.
This document describes a commonly agreed upon denition of ZEBs with supporting nomenclature and
measurement guidelines to facilitate their use, and sets a bar for denoting a ZEB that can be relevant into the
future. DOE is publishing the results for use by government and industry to support a robust market for zero energy
buildings.
3
Guiding Principles
The Project Team used the following guiding principles in developing a zero energy building (ZEB) defnition for
commercial/ industrial/ institutional buildings. The denition should:
• Create a standardized basis for identication of ZEBs for use by industry.
• Be capable of being measured and veried, and should be rigorous and transparent.
• Inuence the design and operation of buildings to substantially reduce building operational energy
consumption.
• Be clear and easy to understand by industry and policy makers.
• Set a long-term goal and be durable for some time into the future.
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
4
Definitions
In addition to establishing a denition for ZEB, shown below, it was clear that denitions were needed to
accommodate the collections of buildings where renewable energy resources were shared. To meet this need, the
team provided variations on the ZEB denition. The bold text represents key terms that are further addressed in the
nomenclature and guidelines.
Zero Energy Building (ZEB)
An energy-efcient building where, on a source energy basis, the actual annual delivered energy is less than or
equal to the on-site renewable exported energy.
Zero Energy Campus
An energy-efcient campus where, on a source energy basis, the actual annual delivered energy is less than or
equal to the on-site renewable exported energy.
Zero Energy Portfolio
An energy-efcient portfolio where, on a source energy basis, the actual annual delivered energy is less than or
equal to the on-site renewable exported energy.
Zero Energy Community
An energy-efcient community where, on a source energy basis, the actual annual delivered energy is less than
or equal to the on-site renewable exported energy.
5
Nomenclature
This section provides denitions of key terms applied to the Zero Energy denitions.
Annual: Covering at least one period of 12 consecutive months for all energy measurements.
Building: A structure wholly or partially enclosed within exterior walls, or within exterior and party walls, and a
roof providing services and affording shelter to persons, animals or property.
Building Site: Building and the area on which a building is located where energy is used and produced.
Building Energy: Energy consumed at the building site as measured at the site boundary. At minimum, this
includes heating, cooling, ventilation, domestic hot water, indoor and outdoor lighting, plug loads, process energy,
elevators and conveying systems, and intra-building transportation systems.
Campus: A group of building sites in a specic locality that contain renewable energy production systems owned
by a given institution.
Community: A group of building sites in a specic locality that contain renewable energy production systems.
Delivered energy: Any type of energy that could be bought or sold for use as building energyddd , including
electricity, steam, hot water or chilled water, natural gas, biogas, landll gas, coal, coke, propane, petroleum and its
derivatives, residual fuel oil, alcohol based fuels, wood, biomass and any other material consumed as fuel.
Energy: The capacity for doing work. Energy takes a number of forms that may be transformed from one into
another, such as thermal (heat), mechanical (work), electrical or chemical. Customary measurement units are
British thermal units (Btu), Joules (J) or kilowatt-hours (kWh).
Exported Energy: On-site renewable energy supplied through the site boundary and used outside the site
boundary.
Geothermal Energy: Deep-earth heat used for either electricity generation or thermal energy.
On-site Renewable Energy: Includes any renewable energy collected and generated within the site boundary
that is used for building energy and the excess renewable energy could be exported outside the site boundary.
The renewable energy certicates (RECs) associated with the renewable energy must be retained or retired by the
building owner/lessee to be claimed as renewable energy.
1
Portfolio: A collection of building sites that contains renewable energy production systems owned/leased by a
single entity.
Renewable energy: Energy resources that are naturally replenishing but ow-limited. They are virtually
inexhaustible in duration but limited in the amount of energy that is available per unit of time. Renewable energy
resources include biomass, hydro, geothermal, solar, wind, ocean thermal, wave action and tidal action. [DOE
Energy Information Administration Glossary]
Renewable Energy Certicate (REC): Represents and conveys the environmental, social and other non-power
qualities of one megawatt-hour of renewable electricity generation and can be sold separately from the underlying
physical electricity associated with a renewable-based generation source.
Site Boundary: Line that marks the limits of the building site(s) across which delivered energy and exported
energy are measured.
Site Energy: Same as building energy.
Source Energy: Site energy plus the energy consumed in the extraction, processing and transport of primary fuels
such as coal, oil and natural gas; energy losses in thermal combustion in power generation plants; and energy losses
in transmission and distribution to the building site.
1
Federal Trade Commission Green Guides (16 C.F.R. § 260.15(d)
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
6
Measurement and Implementation Guidelines
The guidelines that follow identify the methodology for establishing boundary conditions, conducting energy
measurements and achieving energy balances that support applying the Zero Energy Building, Zero Energy
Campus, Zero Energy Portfolio and Zero Energy Community denitions. The guidelines address:
• Measurement boundaries for all denitions
• Energy accounting and measurements
• Source energy calculations
• Using the “Zero Energy Building” designation
• Using Renewable Energy Certicates
Note: Throughout the section, terms dened in the Nomenclature are italicized.
Boundaries
The denitions require the use of a dened site boundary. The site boundary represents a meaningful boundary that
is functionally part of the building(s). For a single building on a single property, the site boundary is typically the
property boundary. The site boundary should include the point of utility interface. Figure 1 shows the site boundary
of energy and how it forms from building energy, on-site renewable energy production, delivered energy and
exported energy.
Figure 1 – Site Boundary of Energy Transfer for Zero Energy Accounting
Notes
DELIVERED ENERGY
(Renewable &
Non-Renewable)
ON-SITE
RENEWABLE ENERGY
EXPORTED ENERGY
(Renewable)
ENERGY USE
BUILDING NEEDS
Heating
Cooling
Ventilation
DHW
Lighting
Plug Loads
Process
BUILDING SYSTEMS
Energy use
and production
System losses
and conversions
Electricity
Heating Energy
Cooling Energy
Fuels
7
The site boundary for a Zero Energy Building (ZEB) could be around the building footprint if the on-site
renewable energy is located within the building footprint, or around the building site if some of the on-site
renewable energy is on-site but not within the building footprint. Delivered energy and exported energy are
measured at the site boundary.
The site boundary for a Zero Energy Campus allows for the building sites on a campus to be aggregated so that the
combined on-site renewable energy could offset the combined building energy from the buildings on the campus.
The site boundary for a Zero Energy Community or Zero Energy Portfolio would allow a group of project sites
at different locations to be aggregated so that the combined on-site renewable energy could offset the combined
building energy from the aggregated project sites. Zero Energy Communities can share the benet of renewable
energy projects in the community that pool investments from multiple building owners and provide power benets
in return.
Energy Accounting and Measurements
A ZEB is typically a grid-connected building that is very energy efcient. The premise is that ZEBs use the electric
grid or other energy networks to transfer any surplus of on-site renewable energy to other users.
ZEB energy accounting would include energy used for heating, cooling, ventilation, domestic hot water (DHW),
indoor and outdoor lighting, plug loads, process energy and transportation within the building. Vehicle charging
energy for transportation inside the building would be included in the energy accounting. On-site renewable energy
may be exported through transmission means other than the electricity grid such as charging of electric vehicles
used outside the building.
Delivered energy to the building includes grid electricity, district heat and cooling, renewable and non-renewable
fuels. A ZEB balances its energy use so that the exported energy to the grid or other energy network (i.e., campus
or facility) is equal to or greater than the delivered energy to the building on an annual basis.
A ZEB may only use on-site renewable energy in offsetting the delivered energy. On-site renewable energy is
energy produced from renewable energy sources within the site boundary. Renewable fuels delivered to the site
boundary are not included in this term, because they are treated as delivered energy to the building, i.e. off-site
renewables. For example, wood chips or biofuel harvested on-site would be considered on-site renewable energy,
while wood or biofuel/biomass delivered to the site would not be considered on-site renewable energy. The ZEB
energy accounting does not allow non-renewable energy that is exported from the site boundary to offset delivered
energy.
On-site renewable energy production systems may supply building energy, thus reducing the need for the delivered
energy to the building, and/or may be directly exported to energy networks. This is taken into account in the net
delivered energy balance. Zero Energy Campuses, Portfolios and Communities can combine the on-site renewable
energy among different sites under an aggregated site boundary to balance the delivered energy.
Source Energy Calculations
Most building managers are familiar with site energy, the amount of energy consumed by a building as measured
by utility meters. Site energy consumption can be useful for understanding the performance of the building and
the building systems, but it does not tell the whole story of impacts from resource consumption and emissions
associated with the energy use. In addition, site energy is not a good comparison metric for buildings that have
different mixes of energy types, buildings with on-site energy generation, such as photovoltaics, or buildings with
cogeneration units. Therefore, to assess the relative efciencies of buildings with varying fuel types, it is necessary
to convert these types of energy into equivalent units of raw fuel consumed in generating one unit of energy
consumed on-site. To achieve this equivalency, the convention of source energy is utilized.
When energy is consumed on-site, the conversion to source energy must account for the energy consumed in the
extraction, processing and transport of primary fuels such as coal, oil and natural gas; energy losses in thermal
combustion in power generation plants; and energy losses in transmission and distribution to the building site. The
Zero Energy Building denition uses national average ratios to accomplish the conversion to source energy because
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
8
the use of national average source-site ratios ensures that no specic building will be credited (or penalized) for the
relative efciency of its energy provider(s).
Source energy is calculated from delivered energy and exported energy for each energy type using source energy
conversion factors. Source energy conversion factors are applied to convert energy delivered and exported on-site
into the total equivalent source energy. The source energy conversion factors utilized are from ASHRAE Standard
105 . While on-site renewable energy is a carbon-free, zero-energy-loss resource, when it is exported to the grid as
electricity, it displaces electricity that would be required from the grid. In ZEB accounting, the exported energy is
given the same source energy conversion factor as the delivered energy to appropriately credit its displacement of
delivered electricity. Table 1 summarizes the national average source energy conversion factors for various energy
types.
Table 1 – National Average Source Energy Conversion Factors
Energy Form
Source Energy
Conversion Factor (r)
Imported Electricity 3.15
Exported Renewable Electricity 3.15
Natural Gas 1.09
Fuel Oil (1,2,4,5,6,Diesel, Kerosene) 1.19
Propane & Liquid Propane 1.15
Steam 1.45
Hot Water 1.35
Chilled Water 1.04
Coal or Other 1.05
Source energy would be calculated using the following formula:
E
source
=
∑
i
(E
del,i
r
del,i
) - ∑
i
(E
exp,i
r
exp,i
)
Where
E
del,i
is the delivered energy for energy type i;
E
exp,i
is the exported on-site renewable energy for energy type i;
r
del,i
is the source energy conversion factor for the delivered energy type i;
r
exp,i
is the source energy conversion factor for the exported energy type i;
9
Example Calculation for All Electric ZEB
A building has the following actual annual delivered energy of 300,000 kBtu electricity. The on-site
renewable exported energy is 320,000 kBtu electricity from photovoltaics. (Note: The equation is using
energy transferred across the site boundary and does not include on-site renewable energy consumed by
the building.)
Using the formula above, the annual source energy balance would be:
E
source
= (300,000kBtu×3.15) - (320,000kBtu×3.15)
= 945,000kBtu - 1,008,000kBtu
= -63,000kBtu
Since E
source
≤ 0, the building would be a Zero Energy Building.
Example Calculation for ZEB with Multiple Delivered Energy Types
A building has the following actual annual delivered energy types: 200,000 kBtu electricity, 60,000 kBtu
natural gas and 100,000 kBtu chilled water. The on-site renewable exported energy is 260,000 kBtu
electricity from photovoltaics.
Using the formula above, the annual source energy balance would be:
E
source
= [(200,000kBtu × 3.15) + (60,000kBtu × 1.09) + (100,000kBtu × 1.04)] - (260,000kBtu×3.15)
= 799,400 kBtu - 819,000kBtu
= -19,600kBtu
Since E
source
≤ 0, the building would be a Zero Energy Building.
Example Calculation for ZEB with Combined Heat and Power (CHP)
A building with CHP has the following actual annual delivered energy types: 120,000 kBtu electricity
and 260,000 kBtu natural gas. The on-site renewable exported energy is 210,000 kBtu electricity from
photovoltaics.
Using the formula above, the annual source energy balance would be:
E
source
= [(120,000 kBtu×3.15)+(260,000 kBtu×1.09)]-(210,000 kBtu×3.15)
= 661,400 kBtu-661,500 kBtu
= -100 kBtu
Since E
source
≤ 0, the building would be a Zero Energy Building.
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
10
Using Renewable Energy Certificates (REC)
Renewable Energy Certicates (RECs) are tradable instruments that can be used to meet voluntary renewable
energy targets. Energy users can meet voluntary renewable energy goals and support the deployment of green
power through the purchase of RECs. RECs are a credible and easy means to keep track of who can claim the
environmental attributes of renewable electricity generation on the grid. Once a buyer makes an environmental
claim based on a REC, the buyer can no longer sell the REC and the REC is considered permanently “retired”.
The ZEB denition and its variations (Campus, Portfolio, Community) require on-site renewable energy to be used
to fully offset the actual annual delivered energy and require the RECs to be retained or retired. The denitions do
not allow renewable electricity purchased through the use of renewable energy certicates (RECs) to be used in the
ZEB energy accounting.
Multi-story buildings that occupy entire lots located in dense urban areas, or buildings, such as hospitals with high
process loads, may not be able to balance annual delivered energy with on-site renewable energy simply because
the site is not large enough to accommodate all the on-site renewable energy required. These building owners may
choose to have off-site renewable electricity utilizing RECs help balance the annual delivered energy since their
built-up area may result in a commensurate energy requirement that is difcult to meet with a small building site.
The following REC-ZEB denition allows RECs to be used to supplement, after on-site renewable energy sources
have been employed, and balance the annual delivered energy to the building.
Renewable Energy Certificate - Zero Energy Building (REC-ZEB)
An energy-efcient building where, on a source energy basis, the actual annual delivered energy is less than or
equal to the on-site renewable exported energy plus acquired Renewable Energy Certicates (RECs).
Using the terms “Zero Energy Building” and “Renewable Energy Certificate
Zero Energy Building”
The designation Zero Energy Building (ZEB) should be used only for buildings that have demonstrated through
actual annual measurements that the delivered energy is less than or equal to the on-site renewable exported energy.
Buildings designed to be zero energy, but that have not had a full year of operation demonstrating that they meet
the requirements, are encouraged to identify their intent to be or return to being a Zero Energy Building.
The designation Renewable Energy Certicate Zero Energy Building (REC-ZEB) should be used only for buildings
that have demonstrated through actual annual measurements that the delivered energy is less than or equal to the
on-site renewable exported energy plus Renewable Energy Certicates.
11
Appendix 1 - Research Materials
Resource Description Author(s) Publisher
Pub.
Date
2014 Getting to Zero
Status Report
The research report is a look at the projects, policies
and programs driving zero net energy performance
in commercial buildings. It examines the numbers,
locations, types, ownership, and policy and program
drivers for ZNE.
Cathy Higgins,
Amy Cortese,
Mark Lyles
New Buildings
Institute
Jan 2014
ANSI/ASHRAE
Standard 105-2014
Standard Methods of Determining, Expressing,
and Comparing Building Energy Performance and
Greenhouse Gas Emissions
ASHRAE ASHRAE Jan 2014
ASHRAE Vision
2020
This document describes the vision held by members
of the American Society of Heating, Refrigerating and
Air-Conditioning Engineers of a future when buildings
will produce as much energy as they use. These are
net zero energy buildings (NZEBs). The ASHRAE
membership believes such buildings can be market-
viable by the year 2030.
ASHRAE 2020 Ad
Hoc Committee
ASHRAE Jan 2008
Clean Energy Trends
2014
Review of developments in clean energy in 2013,
including a section on Net Zero Energy Buildings
Gaining Ground.
Ron Pernick, Clint
Wilder, James
Belcher
Clean Edge Mar 2014
Definition of a
"Zero Net Energy"
Community
This paper begins with a focus solely on buildings
and expands the concept to define a zero-energy
community, applying the ZEB hierarchical renewable
classification system to the concept of community.
Nancy Carlisle,
Otto Van Geet,
Shanti Pless
NREL
Nov
2009
DOE Challenge
Home Why Zero
Energy Ready is
Readily Achievable:
Technical
Specifications for
DOE Challenge
Home
Overview of the U.S. Department of Energy Challenge
Home Program and requirements for creating Zero
Energy Ready Homes.
Jamie Lyons
U.S.
Department of
Energy
Feb 2010
Energy Star
Portfolio Manager
Technical
Reference: Source
Energy
Evaluation of Source vs. Site Energy as a metric for
measuring energy use by a building.
U.S.
Environmental
Protection
Agency
U.S.
Environmental
Protection
Agency
Jul 2013
Getting to Net Zero
The intent of this article is to provide an overview of
the DOE’s eorts toward realizing cost-eective net
zero energy buildings (NZEBs).
Drury Crawley,
Shanti Pless, Paul
Torcellini
NREL/ASHRAE
Journal
Sept
2009
Getting to Zero
Final Report of the Massachusetts Zero Net Energy
Buildings Task Force.
Massachusetts
Zero Net Energy
Buildings Task
Force
Massachusetts
Zero Net Energy
Buildings Task
Force
Mar
2009
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
12
Living Building
Challenge 2.1
Description of the Living Building Challenge program,
including a definition and measurement system for
Net Zero Energy Buildings.
International
Living Futures
Institute
International
Living Futures
Institute
May 2012
Main Street
Net-Zero Energy
Buildings: The Zero
Energy Method
in Concept and
Practice
This presentation discusses ways to achieve large-
scale, replicable NZEB performance. Many passive and
renewable energy strategies are utilized, including
full daylighting, high-performance lighting, natural
ventilation through operable windows, thermal
mass, transpired solar collectors, radiant heating and
cooling, and workstation configurations to maximize
daylighting.
Paul Torcellini,
Shanti Pless,
Chad Lobato,
Tom Hootman
ASME 2010 4th
International
Conference
on Energy
Sustainability
May 2010
Net Zero and Living
Building Challenge
Financial Study: A
Cost Comparison
Report for Buildings
in the District of
Columbia
The purpose of the Net Zero and Living Building
Challenge Financial Study: A Cost Comparison Report
for Buildings in the District of Columbia was twofold:
First, to investigate costs, benefits and approaches
necessary to improve building performance in the
District of Columbia, from LEED Platinum to zero
energy, zero water and Living Building status, and
second, to advise District government on policy
drivers related to deep green buildings and to analyze
the opportunities for the District to oer incentives to
advance most rapidly toward zero energy, zero water
and Living Buildings.
International
Living Futures
Institute
New Buildings
Institute
Skanska
District
Department
of the
Environment
Feb 2014
Net Zero Blueprint
This article presents the process used for delivering
the Research Support Facility as a replicable blueprint
to achieve a large reduction in building energy use and
to adopt a net zero energy approach for large-scale
commercial buildings without increasing cost.
Tom Hootman;
David Okada;
Shanti Pless;
Michael Sheppy;
and Paul
Torcellini
NREL/
ASHRAE High
Performance
Buildings
Journal
Nov 2012
Net Zero Energy
Buildings
Book
Karsten Voss,
Eike Musall
Detail Green
Books
Feb 2013
Net Zero Energy
Buildings
Page on the Whole Building Design Guide portal
with an overview of NZEBs, including links to related
resources and publications - http://www.wbdg.org/
resources/netzeroenergybuildings.php
Steven Winter
Associates
National
Institute of
Building
Sciences Whole
Building Design
Guide
Sept
2013
Net Zero Energy
Buildings White
Paper
White Paper on Sustainability to inspire architects,
engineers, contractors, building owners, developers,
building product manufacturers, environmentalists,
policymakers, government ocials, corporate
executives, oceholders, and the public to foster the
development of net zero energy buildings and homes.
Rob Cassidy,
Editor with
various chapter
authors
Building Design
& Construction
Mar 2011
Net-Zero Energy
Buildings: A
Classification
System Based on
Renewable Energy
Supply Options
A classification system for NZEBs based on the
renewable sources a building uses.
Shanti Pless, Paul
Torcellini
NREL Technical
Report
Jun 2010
13
Pursuit of Net Zero:
The Walgreens
Experience
Webinar on Walgreen's experience with developing
and operating a net zero store in Chicago, Illinois.
Jamie J. Meyers
Energy Center
of Wisconsin
Mar 2014
The Technical
Feasibility of
Zero Net Energy
Buildings in
California
This study is a forward-looking "stress test" of the
Zero Net Energy (ZNE) new construction goals set
forth by California's energy agencies. This study
assesses the potential performance of best-in-class
building designs in 2020 for both residential and
commercial structures.
ARUP. Davis
Energy Group,
Sun Light &
Power, New
Buildings
Institute,
Engineering
350, Sustainable
Design +
Behavior
Pacific Gas
& Electric
Company
Dec 2012
Toward Fully
Functional Net
Zero Buildings:
An Engineering
Perspective
In this article, current concepts of NZEB are analyzed;
an operational definition (OZEB) of “Net-Zero Energy
Commercial Buildings” is proposed; a design approach
toward achieving site-specific OZEBs is presented; and
examples of evidence-based results are reviewed and
analyzed.
Boggarm S. Setty,
James E. Woods
Unpublished,
pending review
Apr 2014
Zero Energy
Buildings: A
Critical Look at the
Definition
This study shows the design impacts of the
definition used for ZEB and the large dierence
between definitions. It also looks at sample utility
rate structures and their impact on the zero energy
scenarios.
Paul Torcellini,
Shanti Pless,
and Michael
Deru, National
Renewable
Energy
Laboratory
Drury Crawley,
U.S. Department
of Energy
NREL
Jun
2006
European
How to define
nearly net zero
energy buildings
nZEB
A technical definition for nearly zero energy
buildings required in the implementation of the
energy performance of buildings directive recast.
It provides an energy calculation framework and
system boundaries associated with the definition to
specify how dierent kinds of energy flow, which
is taken into account in the energy performance
assessment.
Jarek Kurnitski,
Francis Allard,
Derrick Braham,
Guillaume
Goeders, Per
Heiselberg,
Lennart
Jagemar, Risto
Kosonen, Jean
Lebrun, Livio
Mazzarella,
Jorma Railio,
Olli Seppänen,
Michael Schmidt,
Maija Virta
REHVA Journal May 2011
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
14
Nearly-zero, Net
zero and Plus
Energy Buildings
The topic of Zero Energy Buildings (ZEBs) has
received increasing attention in recent years, up to
inclusion in strategic energy policy papers in several
countries. However, despite the emphasis placed on
the goals, the various ZEB definitions applied mostly
remain generic and are not yet standardized.
Karsten Voss,
Igor Sartori,
Roberto Lollini
REHVA Journal Dec 2012
Principles for
Nearly Zero-Energy
Buildings
The study builds on existing concepts and building
standards, analyses the main methodological
challenges and their implications for the nZEB
definition, and compiles a possible set of principles
and assesses their impact on reference buildings.
Subsequently the technological, financial and policy
implications of these results are evaluated. Finally, the
study concludes by providing an outlook on necessary
further steps towards a successful implementation of
nearly Zero-Energy Buildings.
Thomas
Boermans,
Andreas
Hermelink, Sven
Schimschar, Jan
Grözinger, Markus
Oermann,
Kirsten Engelund
Thomsen, Jørgen
Rose, Søren O.
Aggerholm
Building
Performance
Institute Europe
(BPIE)
Nov 2011
Technical definitions
for nearly zero
energy buildings
The Federation of European Heating, Ventilation and
Air Conditioning Associations (REHVA) has revised its
nZEB technical definition, until now the only available
methodology suitable for the implementation in
national building codes for the primary energy
indicator calculation. The 2013 version was prepared
in cooperation with the European Committee for
Standardization (CEN) and it replaces the 2011 version
with the intention to help the experts in the member
states define the nearly zero energy buildings in a
uniform way. The 2013 version is complemented with
specifications for nearby renewable energy and for
the contribution of renewable energy use. A set of
the system boundaries and equations are given for
energy need, energy use, delivered and exported
energy, primary energy and for renewable energy
ratio calculation. With these definitions and energy
calculation framework, primary energy indicator and
renewable energy ratio can be calculated as required
by the directive. Calculation principles are explained
with worked examples in order to assure uniform
understanding of the definitions.
Jarek Kurnitski REHVA Journal May 2013
Towards nearly
zero-energy
buildings:
Definition of
common principles
under the EPBD
The project supports the European Commission in
its activities to: give guidance to member states
on how to interpret requirements for nearly zero
energy buildings; develop a common reporting
format on nearly zero energy buildings to be used
by member states and evaluate the adequacy
of measures and activities reported by member
states in their national plans on nearly zero energy
buildings; link cost optimality and the nearly zero
energy buildings principle in a consistent way and
facilitate their convergence until 2021.
Andreas
Hermelink, Sven
Schimschar,
Thomas
Boermans,
Lorenzo
Pagliano, Paolo
Zangheri,
Roberto Armani,
Karsten Voss,
Eike Musall
Ecofys:
Politecnico di
Milano / eERG:
University of
Wuppertal
Feb 2013
15
Appendix 2 – Industry Participants
The following individuals representing key industry organizations contributed input and comments in the research
and analysis phases of the project. Their responses were used to formulate the initial denitions and supporting
materials and subsequent versions.
Name Organization
Get W. Moy, PE, LEED AP AECOM, Inc., and Chair of the National Institute of
Building Sciences High Performance Building Council
Brian Castelli Alliance to Save Energy
Harry Misuriello American Council for an Energy Ecient Economy
Pamela Sams, AIA, LEED AP BD+C American Institute of Architects
Daniel Lapato American Public Gas Association
Tanzina Islam American Public Power Association
Edward Mazria, FAIA, FRAIC Architecture 2030
Vincent Martinez Architecture 2030
Scott Shell, FAIA, LEED AP BD+C Architecture Interiors Planning Urban Design
Doug Read ASHRAE
Rob Cassidy Building Design & Construction
Nadav Malin Building Green/Green Source/ Environmental Building
News
Ron Burton Building Owners and Managers Association
International
Paul Bertram, FCSI, CDT, LEED AP BD+C, GGP Business Council for Sustainable Energy
Rick Hermans, PE, HFDP Daikin Applied/ASHRAE
Bill Updike District of Columbia Department of the Environment
Daniel White District of Columbia Department of the Environment
Steve Rosenstock, PE Edison Electric Institute
Neil Leslie Gas Technology Institute
Jerry Yudelson, PE, LEED Fellow Green Building Initiative
James Woods, PhD, PE Indoor Environments Consultant
John Andary, PE, LEED AP Integral Group
David Kaneda, PE, FAIA, LEED AP BD+C Integral Group
Je Johnson International Facility Management Association
Brad Liljequist, AICP, LEED AP International Living Futures Institute
Rick Diamond Lawrence Berkeley National Laboratory
Sandy Fazeli National Association of State Energy Ocials
Patrick Hughes National Electrical Manufacturers Association
Ryan Colker, JD National Institute of Building Sciences
Henry Green, Hon. AIA National Institute of Building Sciences
Shanti Pless, LEED AP National Renewable Energy Laboratory
Paul Torcellini National Renewable Energy Laboratory
Jim Edelson New Buildings Institute
Dave Hewitt New Buildings Institute
A COMMON DEFINITION FOR ZERO ENERGY BUILDINGS
16
Cathy Higgins New Buildings Institute
Carolyn Sarno Goldthwaite Northeast Energy Eciency Partnerships
Peter Turnbull Pacific Gas & Electric (PG&E)
Walter Grondzik, PE, LEED AP Passive House Institute US
Peter Rumsey, PE, FASHRAE, CEM, LEED AP Peter Rumsey
Lawrence Miltenberger PNC Bank Corporation
Scott Williams Target Corporation
David Del Rossi, LEED AP BD+C TD Bank Corporation
Kristine Kingery U.S. Army
Kristen Thomas U.S. Army
Cindy Jacobs U.S. Environmental Protection Agency
Kevin Powell U.S. General Services Administration, Oce of Chief
Greening Ocer
Hal Alguire U.S. Army Ft. Carson Colorado
Mark Hunsiker U.S. Army Ft. Carson Colorado
Joe Wyka U.S. Army Ft. Carson Colorado
James McClendon, PE Walmart Stores, Inc.
Kathy Loftus Whole Foods
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DOE/EE-1247 • September 2015
For more information, visit: buildings.energy.gov