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Building Energy Use and Emissions

Buildings and facilities rely on mechanical systems and electrical systems to operate fixtures, equipment and controls; deliver a thermally comfortable space; and maintain a high level of indoor environmental quality for occupants. Building operations consume approximately 40% of the energy and 74% of the electricity produced annually in the United States, according to the U.S. Department of Energy. Any energy and electricity used in buildings that was generated through the combustion of fossil fuels also produces greenhouse gas (GHG) emissions. These GHG emissions directly contribute to air pollution and climate change. Climate change mitigation requires the reduction of GHG emissions through strategies such as building decarbonization.

Net Zero Energy

Net Zero Concept

Net Zero Emissions is a term that refers to the reduction of GHG emissions generated from resource consumption to as close to zero as possible and the concept is applicable to all resource use, including energy.

Net Zero Energy means consuming no more energy than is produced from renewable sources. Achieving a Net Zero Energy Building requires reducing energy use, increasing energy efficiency with which energy is used‚ replacing energy generated from fossil fuels with energy generated from zero-emission sources‚ and understanding the effects of energy technologies on the climate. For guidance on reducing energy consumption, see:

For additional guidance on managing energy consumption, see SFTool's Energy Management Systems page.

Graphic showing five components that add together to equal Net Zero Emissions. 1 - Low Embodied Carbon Materials. Buy Clean, low embodied materials. 2 - Deep Energy Retrofits. 40% deep energy retrofits and ultra-low energy. 3 - Building electrification. Convert buildings from onsite fossil fuel to electric. 4 - Grid Integration + Storage. Deploy grid-interactive efficient buildings with energy storage to match the clean grid. 5 - Carbon Pollution Free Electricity. Achieve 100% use of carbon free electricity.
Aiming for Net Zero Emissions

Related Topics

Air Conditioning

Air Conditioning generally refers to the process for cooling air in a space. It is most often achieved through a mechanical system that uses the refrigeration cycle to produce chilled air or water. The newly chilled air or water is then used for cooling a space.

Air Handling Unit (AHU)

An air handling unit uses blowers to circulate conditioned air and accepts returned air to be conditioned again. In addition to blowers, AHUs contain heat exchangers, which transfer heat between cool and warm materials. For example, when a space needs air conditioning, warm air from the space is returned to the AHU. This warm air is cooled by circulating a chilled liquid into the heat exchanger. This newly cooled air can then be blown back into the space.


ASHRAE (formerly, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers) is the governing body which creates and releases the standards regarding indoor air quality, thermal comfort, and energy efficiency.

ASHRAE.orgnon government site opens in new window

ASHRAE Standard 90.1

ASHRAE Standard 90.1 provides the minimum requirements for energy-efficient design of most buildings, except low-rise residential buildings, in the United States. It offers the minimum energy-efficient requirements for design and construction of new buildings and their systems, new portions of buildings and their systems, and new systems and equipment in existing buildings, as well as criteria for determining compliance with these requirements.  See Legal Requirements for applicability to Federal buildings.


Boilers are fuel-burning appliances that produce either hot water or steam. The resulting steam or hot water is circulated through piping for heating or process uses. Proper maintenance and operation of boiler systems is important to ensure efficiency and reliability. The source of heat for a boiler is typically the combustion of fuels such as natural gas, coal, oil, or wood.

DOE EERE FEMP | Purchasing Energy-Efficiency Commercial Boilersopens in new window

Building Automation System

A building automation system (BAS) is used to monitor and control building components and systems. BAS can integrate the operation of fans, pumps, heating/cooling equipment, dampers, mixing boxes, thermostats, and other devices. Monitoring and optimizing temperature, pressure, humidity, and flow rates are key functions of modern building automation systems.

FEMP Training - Building Automation Systems for Existing Federal Facilitiesopens in new window

Building Commissioning

The process that focuses on verifying and documenting that the facility and all of its systems and assemblies are planned, designed, installed, tested, operated, and maintained to meet the Owner's Project Requirements. This means testing all systems (HVAC, lighting controls, domestic hot water systems, etc.) to ensure they function as intended. Proper commissioning saves energy, reduces risk, and creates value for building operators. It also serves as a quality assurance process for enhancing the delivery of the project.

DOE EERE | Commissioning for Federal Facilitiesopens in new window

Building Commissioning Associationnon government site opens in new window

Building Operating Plan

The building operating plan is a document that describes conditions representing good building performance. These conditions should reflect the needs of building management and occupants. This document also describes the installed building equipment, how it should operate, and the environmental requirements it should meet.

Building Performance Rating Method

ASHRAE Standard 90.1 is often used as a baseline to rate proposed new buildings or retrofitted buildings that are designed to be “better than code” by some margin. Examples include green building programs (e.g. LEED), utility financial incentive programs for energy efficiency, and EPAct 2005 requirements that Federal buildings are designed to achieve energy consumption levels at least 30 percent below the ASHRAE 90.1 reference standard. The Building Performance Rating Method in Appendix G of the Standard outlines procedures for modeling buildings to meet the needs of these programs. This is a more comprehensive flexible method than those used for demonstrating code compliance (see Energy Cost Budget Method), as it provides credit for additional deign measures and practices (e.g. favorable building orientation).

Carbon Footprint

A Carbon Footprint is the amount of greenhouse gas emissions (in units equivalent to carbon dioxide emissions) emitted by an entity, be it a person, building, company, or country.


A chiller is a machine that removes heat from a liquid using a refrigerant in a vapor-compression or absorption refrigeration cycle. This liquid can then be circulated through a heat exchanger to cool air or other equipment as required. Chillers are typically powered by electricity, steam or natural gas.

DOE EERE FEMP | Purchasing Energy-Efficiency Air-Cooled Electric Chillersopens in new window

DOE EERE FEMP | Purchasing Energy-Efficiency Water-Cooled Electric Chillersopens in new window

Chlorofluorocarbon (CFC)

At one time, CFCs were commonly used as refrigerants. However, since they deplete ozone in the stratosphere, their production has long been banned in many countries. They will be phased out entirely, worldwide, by 2030.

EPA | Hazardous Air Pollutantsopens in new window

Climate Change

Changes in average weather conditions that persist over multiple decades or longer. Climate change encompasses both increases and decreases in temperature, as well as shifts in precipitation, changing risk of certain types of severe weather events, and changes to other features of the climate system.

Source: GlobalChange.gov | Climate and Health Assessment, A5 Glossary and Acronyms opens in new window

Learn more: Climate Terms and Tools


Cooling is the process of keeping a building at a comfortably cool temperature during hot times. It can be done naturally, through ventilation and shading or by using refrigerants in chillers to remove heat.


In the context of buildings, electricity is the flowing of electron-powered energy used to power machines and other devices. Traditional electricity is created in coal-fired plants. More sustainable, renewable electricity can be generated through solar panels, wind farms, and other means.


Emissions are the discharge of a substance. In the building’s context, emissions usually refer to greenhouse gas emissions into the atmosphere (e.g., the release of carbon dioxide during fuel combustion).

Energy & Atmosphere

Buildings and facilities rely on the operation of mechanical systems and electrical systems to maintain a high level of indoor environmental quality for occupants. Building operations consume approximately 40% of the energy and 74% of the electricity produced annually in the United States, according to the U.S. Department of Energy.

Learn more about Energy & Atmosphere.

Energy Cost Budget Method

There are several methods for demonstrating compliance with ASHRAE Standard 90.1, one of which is the Energy Cost Budget (ECB) Method described in section 11 of the Standard. The ECB Method is a comparative modeling approach in which a proposed building design is modeled and compared to the prescriptive minimum requirements for code compliance, called the ECB design.  Modeling must demonstrate that the design energy cost does not exceed the energy cost budget to comply. The ECB Method is focused on minimum code compliance and less flexible than the Building Performance Rating Method.

Energy Efficiency

Energy efficiency is a comparison of the amount of energy used compared to the amount of output produced. In the built environment, this means using the least amount of energy (electricity, natural gas, etc.) to operate a facility appropriately. Steps that can help a building run efficiently include: ensuring there are no air leaks, using sensors or timers to ensure the building isn’t operating when vacant, and using energy-efficient equipment.

Energy Harvesting

Energy harvesting captures ambient energy from sources such as the sun, wind, water, and from heat in the ground. That energy can then be stored or used for devices large and small. 

Energy Performance

Assessing a building’s energy performance involves comparing its energy use to that of peers or a standard. The ENERGY STAR program provides recognized benchmarks for assessing a building’s energy performance.

Energy Recovery

Energy recovery involves recapturing what would be waste energy for reuse. For example, waste heat from operating mechanical equipment can be stored and used to heat building air when needed.

Energy Simulation Model/Energy Model

Energy modeling is a computer based tool that predicts the amount of energy that a building will consume. It is a helpful way to identify potentially inefficient systems and compare a building’s energy use to a baseline performance case.

DOE NREL | Building Technologies Analysisopens in new window

DOE EERE | EnergyPlus Energy Simulation Softwareopens in new window


ENERGY STAR is a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy that helps businesses and individuals save energy and fight climate change through energy efficient products, homes, and buildings. Products with an ENERGY STAR label are independently certified to have met the energy efficiency requirements set forth in ENERGY STAR.  Over 70 different product categories have ENERGY STAR certified products including various building products, electronics, office equipment, lighting and fans, appliances, water heaters, battery chargers, and heating and cooling products. For buildings, the EPA provides ENERGY STAR Portfolio Manager®, an online tool to measure and track energy and water consumption, as well as greenhouse gas emissions. The EPA also offers ENERGY STAR certification for top performing commercial buildings and industrial plants. To be eligible for ENERGY STAR certification, a building must earn an ENERGY STAR score of 75 or higher, indicating that it performs better than at least 75 percent of similar buildings nationwide.

http://www.energystar.gov/opens in new window

Fossil Fuel

A hydrocarbon deposit that is used for fuel, such as petroleum, coal, or natural gas, derived of living matter from a previous geologic time. The supply of these fuels is not renewable, meaning that they cannot be replaced quickly enough and in sufficient amounts to keep pace with current usage. The burning of fossil fuels for fuel energy also contributes to pollution and releases greenhouse gasses into the atmosphere.

FEMPopens in new window

Global Warming Potential (GWP)

A measure of the ratio of the warming caused by a substance to the warming caused by a similar mass of carbon dioxide. Values are typically expressed over a 100-year time horizon. Carbon dioxide's GWP is defined as 1.0. The larger the GWP, the more warming the gas causes. For example, methane's 100-year GWP is 28, which means that methane will cause 28 times as much warming as an equivalent mass of carbon dioxide over the same time period.

EPA | Greenhouse Gas (GHG) Emissionsopens in new window

Greenhouse Gases

Gases that trap heat in the earth’s atmosphere are called greenhouse gases. Examples of greenhouse gases include carbon dioxidenon government site opens in new window, methane, and chlorofluorocarbons. The primary source of carbon dioxide emissions is the combustion of fossil fuels for energy.

EPA | Greenhouse Gas (GHG) Emissionsopens in new window

FEMP | Annual Greenhouse Gas and Sustainability Data Reportopens in new window

Guiding Principles for Sustainable Federal Buildings

The Guiding Principles for Sustainable Federal Buildings and Associated Instructions are a set of sustainable principles for integrated design, energy performance, water conservation, indoor environmental quality, materials, and resilience aimed at helping Federal agencies and organizations:

  • Reduce the total ownership cost of facilities
  • Improve energy efficiency and water conservation
  • Provide safe, healthy, and productive built environments
  • Promote sustainable environmental stewardship

Guiding Principles for Sustainable Federal Buildings and Associated Instructions

Heat Exchanger

A heat exchanger transfers heat from one medium to another. They are commonly used in space heating, refrigeration, and air conditioning.


Heating usually refers to the mechanical system used to heat air inside a building. There are many types of standard heating systems. Central heating is often used in cold climates to heat private houses and public buildings. Those systems contain a boiler, furnace, or heat pump to heat water, steam, or air. The heating equipment is usually located in a central location such as a furnace room in a home or a mechanical room in a large building.

Heating, Ventilating and Air Conditioning (HVAC)

Heating, ventilation, and air conditioning systems are designed to work together to maintain occupant comfort. From residential to commercial settings, HVAC systems help to keep people comfortable and healthy by maintaining good indoor air quality and comfortable temperatures.

Whole Building Design Guide | High-Performance HVACnon government site opens in new window

Measurement and Verification Plan (M&V Plan)

A Measurement and Verification (M&V) Plan describes the process to determine the energy savings from energy conservation measures. A comprehensive plan helps building management keep track of energy use and identify problems. M&V plans also help identify systems which use energy, monitor electricity metering, track the success of energy-savings plans, and identify the party responsible for keeping up with the execution of the M&V plan.  A discussion of measurement and verification plans may be found in the International Performance Measurement and Verification Protocol (IPMVP) from the Efficiency Valuation Organization (EVO).

Efficiency Valuation Organization (EVO)non government site opens in new window

DOE | M&V Guidelines: Measurement and Verifciation for Performance-Based Contracts (version 4.0)opens in new window


To know how a building is performing, it is necessary to monitor its system performance and energy use. This is often done through sensors and energy metering for each energy-using system in a facility (electricity, natural gas, hot water, etc.). Monitoring of the building’s systems is also important to ensure that equipment is functioning correctly and safely, and to find and repair problems before they become hazards.

Montreal Protocol

The Montreal Protocol is an international treaty ratified in 1987 which requires that the production and consumption of refrigerants that deplete ozone by phased out by 2020 in the U.S. and other more developed countries and by 2030 in developing countries. Refrigeration equipment lasts for decades, so decisions made now will impact building compliance well past 2020.

EPA | Significant New Alternatives Policy (SNAP) Programopens in new window

Ozone Depletion Potential (ODP)

A measure of the amount of degradation a chemical compound will have on the stratospheric ozone layer. Both the ODP and global warming potential (GWP) are important considerations for refrigerants, since some refrigerants that are identified as better alternatives in terms of ODP have high GWPs.


Recommissioning is the process through which buildings are commissioned again at some time after their initial completion, occupancy, and commissioning. Recommissioning is a check to ensure that building systems are still functioning as originally planned, constructed, and delivered, and to identify where periodic operating procedure changes or drifts in control calibrations have affected building mechanical system performance in a previously commissioned building.

DOE EERE | Commissioning for Federal Facilitiesopens in new window

Building Commissioning Associationnon government site opens in new window


A refrigerant is a substance used to provide cooling in the refrigeration cycle. The most common refrigerants being produced today are a variety of hydrofluorocarbons and non-halogenated hydrocarbons. Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are being phased out due to their ozone depletion and global warming effects.

EPA | Hazardous Air Pollutantsopens in new window

EPA | Significant New Alternatives Policy (SNAP) Programopens in new window

Renewable Energy

Renewable energy comes from sources that are either inexhaustible or can be replaced very rapidly through natural processes. Examples include the sun, wind, geothermal energy, small (river-turbine) hydropower, and other hydrokinetic energy (waves and tides). Using renewable energy reduces a building's carbon footprint. There are various options for providing renewable energy to buildings, the most common being solar photovoltaic (PV) panels. Buildings can also purchase renewable energy from offsite sources.

EPA | Renewable Energyopens in new window

DOE | Office of Energy Efficiency and Renewable Energyopens in new window

Resource Metering

Metering is the measurement of fuel (such as electricity, natural gas, and steam) and water used in facilities. Meters are useful for determining compliance with building operating plans and other monitoring activities.

See U.S. Department of Energy guidance for Federal Agencies.opens in new window  


Retro-commissioning is commissioning of a building that has never been or was not fully commissioned at its completion. It includes developing a building operation plan that identifies current operating requirements and needs, conducting tests to determine whether building systems are performing optimally in accordance with the plan, and making any necessary repairs or changes.

DOE EERE | Commissioning for Federal Facilitiesopens in new window

Building Commissioning Associationnon government site opens in new window


Submetering or system-level metering is used to determine the proportion of energy use within a building attributable to specific end uses or subsystems (e.g., the ventilation system of an HVAC system). This energy use information can be used to support energy management and identify opportunities for additional energy saving improvements.

SFTool's Submetering Wizard

See U.S. Department of Energy guidance for Federal Agencies.opens in new window  


Ventilating is the process of "changing" or replacing air in any space to replenish oxygen, control temperature, and remove moisture, odors, smoke, heat, dust, airborne bacteria, and carbon dioxide. Ventilation includes both the exchange of air to the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality in a building.

Share non government site opens in new window

Did You Know?

Plug loads can average approximately 30% of electricity use in office settings, much of which can be attributed to parasitic loads (power draw of a plug-load that is not performing useful work). Source: Plug Load Research Review Summaryopens in new window; GSA Office of Federal High-Performance Green Buildings (2013).. Reduce your plug load costs with SFTool  

Case Study

Spatial Equity

Open Workspaces

Organizations today are less hierarchical and work is more team based, more mobile, and more cross functional. A key to spatial equity is that space layout and workstation standards are based on new ways of working and specific work tasks and business needs rather than organizational hierarchy.

View Case Study