What is a Net Zero Building?

In January 2024, the White House and U.S. Department of Energy (DOE) released the national definition for a building with zero operating emissions. The initial focus on operational emissions may later broaden to include embodied carbon, the impacts of refrigerants and grid-interactive equipment, according to the DOE. Serving as a framework for increased market alignment to move the building sector toward zero emissions, the definition highlights three principles.

“A zero operating emissions building is one that is:

• Highly energy efficient,
• Free of on-site emissions from energy use, and
• Powered solely from clean energy.”

In June 2024, the DOE announced a national definition of a zero emissions building to support public and private sector efforts aimed at decarbonizing the building sector, which accounts for over one-third of the total U.S. greenhouse gas emissions. The DOE's website states the intention is to offer guidance to support new and existing commercial and residential buildings to reach zero emissions, help advance future clean energy solutions, inspire innovation, address the climate crisis and aid workforce growth. 

Notated as Part 1 of the National Definition of a Zero Emissions Building that focuses on the operational emissions from energy use, the DOE quantifies the minimum requirements: 

1. Energy Efficient: Buildings must use energy efficiently.
2. No On-Site Emissions: No emissions should come from on-site energy use.
3. Powered by Clean Energy: The building's sole power source must be clean energy.

The DOE notes that future versions of the definition may address emissions from the production, transportation, installation and disposal of building materials, minimizing the impacts of refrigerants and other considerations.

How Are a Building’s Zero Operating Emissions Calculated?

The DOE’s definition breaks down the principles with measurable criteria.

“Highly energy-efficient" means the existing building’s energy performance is within the top 25% most efficient buildings in the market, among comparable structures as a measure of whole-building energy use. An ENERGY STAR score of 75 or higher or a measured whole building energy use intensity (EUI) at least 35% better than median EUI meets these criteria.  

For a new building, it must have an estimated whole building energy use of at least 10% less than the energy use outlined in the International Energy Conservation Code (IECC) or ASHRAE 90.1 model code and the building is in the top 10% of energy performance among similar buildings. Such efficiency equates to an ENERGY STAR score of 90 or better.

The efficiency goal is connected to the other two principles: zero greenhouse gas (GHG) emissions and powered solely by carbon-free sources, such as on-site generation and off-site renewable sources. Zero GHG emissions means the building’s site has no combustion of fossil fuels, except for testing and backup generators when grid power is inaccessible.

Buildings can achieve clean energy requirements through on- and off-site clean energy use, so long as the emissions total zero. Clean energy procurement must meet the standards of ASHRAE Standard 228 Sections 8.3 to 8.5, the Environmental Protection Agency’s Greenpower Partnership guidelines or Green-e certified and surplus to regulation (if 100% green power product). Carbon offsets, an activity like planting trees to compensate for GHG emissions, do not meet the requirements of clean energy procurement. 

What is Energy Use Intensity (EUI)?

A building’s energy use intensity (EUI) represents a building’s energy use relative to the structure’s size and other factors. ENERGY STAR explains how EUI is calculated by dividing the building’s total energy consumed for a year by the square feet of the building’s floor area. Simply, EUI is energy usage per square foot.

Buildings with low EUI have good energy performance, but some properties require more energy use based upon function. For example, an elementary school runs on less energy compared to a hospital.

Am I Eligible for FEMA’s Net Zero Energy Buildings Funding? 

The Federal Emergency Management Agency (FEMA) issued new regulations for securing assistance funding for net zero buildings. To qualify, the net zero energy project must be related to disaster recovery or mitigation and the project must meet or exceed energy performance thresholds and renewable generation parameters outlined in the zero energy appendices of the 2021 IECC.   
Three requirements must be met to allow FEMA funding for additional costs or other benefits on new building construction and major renovation projects:

1. The project must meet the definition of new construction or total renovations of existing structures for the purpose of salvaging existing core structural components, historical facades, etc. without functional floor area being preserved.
2. The finished structure must meet or exceed the energy performance levels and renewable generation specifications within the zero energy appendices of the 2021 IECC for commercial (CC) or residential (RC). Local code standards equivalent or stricter than the IECC should be reviewed by the project engineer, design professional, or other project expert to ensure standards are up to par with or surpassing standards set by the IECC.
3. The project must achieve the requirements outlined in these IECC appendices or other versions of the zero energy buildings codes specified by FEMA or DOE. 

For existing buildings with a net-zero energy aspect:

1. The project needs to meet the definition of an existing structure eligible for FEMA funding that is being altered, modified or retrofitted.
2. Partial alterations, modifications or retrofits must meet or exceed the requirements of Chapter 7 and Normative Appendix B, where applicable, within the 2021 or most recent version of the International Green Construction Code (IgCC). Such requirements necessitate the installation of high-performance equipment and materials in the building, although the entire building might not meet the energy performance targets outlined in the IECC Zero Energy Appendices.
3. The project needs to obtain renewable energy generation at or above the annual energy consumption of the building’s alteration, modification, or retrofit, based on methods outlined in the IECC Zero Energy Appendices. Coupled with high-performance equipment and materials, these steps set up existing building partial projects to reach net-zero standards.
4. Construction procedures should follow and perform these requirements as outlined in the appendices and the IgCC.