June 10th 2024

Building energy modeling crucial to delivering US Department of Energy’s national definition of a zero emissions building

Building energy modeling crucial to delivering US Department of Energy’s national definition of a zero emissions building

Following the release of the U.S. Department of Energy’s National Definition of a Zero Emissions Building, we highlight the crucial role of building energy modeling in delivering the energy-efficient, net-zero buildings of the future.

In a move designed to advance public and private sector efforts to decarbonize the buildings sector, the U.S. Department of Energy (DOE) has released its much anticipated National Definition of a Zero Emissions Building. The definition is intended to provide industry guidance to support new and existing buildings to move towards zero emissions, helping to advance next-generation clean energy solutions, drive innovation, and tackle the climate crisis.

With nearly 130 million existing buildings in the United States - collectively costing over $400 billion a year to heat, cool, light, and power - the buildings sector is currently responsible for more than one-third of total U.S. greenhouse gas emissions. And with 40 million new homes and 60 billion square feet of commercial floorspace expected to be constructed between now and 2050, there is considerable work to be done to retrofit the existing building stock, while ensuring these new buildings are designed, constructed and operated to meet net-zero standards.

Part 1 of the DOE definition, which focuses on operational emissions, states that a building that achieves zero operational emissions from energy use must, at a minimum, be: energy efficient, free of on-site emissions from energy use, and powered solely from clean energy. The definition is not a substitute for the many green building and energy efficiency standards and certifications already in use across the sector. However, eight major green building certification programs in the U.S. have already confirmed that they will embed, align or exceed the zero emissions definition within their certification. 

While standardized definitions are important in knowing what constitutes a net-zero building, a deeper level of understanding is required to know how they can actually be achieved. This is where building energy modeling can play a crucial role in navigating the route to zero emissions buildings, by enabling detailed analysis, comparison and verification of various low impact energy systems and strategies.

Building Energy Modeling for Net-Zero

Building energy modeling is an essential tool for predicting a building’s energy consumption, CO2 emissions, peak demands, energy costs, and renewable energy production. By leveraging the whole-building energy simulation analysis capabilities of the IES Virtual Environment (IESVE), users can undertake comprehensive assessment of a building’s energy efficiency, while also factoring in considerations such as comfort, ventilation, HVAC performance, and optimization.

To support the drive towards net-zero energy buildings, IESVE supports a range of sustainable design strategies focused on electrification and decarbonization of the built environment. These include:

Passive Design

Implement solar shading, site orientation, natural ventilation, and passive solar heating to minimize energy use.

Energy Conservation

Use high-performance constructions, reduce infiltration, install efficient lighting, harvest daylight, and use ceiling fans to conserve energy.

Energy Efficiency

Integrate energy-recovery ventilators, demand-controlled ventilation, combined heat and power (CHP) systems, air and water economizers, and variable speed drive (VSD) fans and pumps to enhance energy efficiency.


Employ heat pumps (air, water, geothermal), heat-recovery chillers, heat pump water heaters (HPWH), and low-temperature radiant heating to transition to electric energy sources.

Renewable Energy Technology

Utilize solar photovoltaics (PV), wind turbines, solar hot-water pre-heating, and geothermal heat exchange to harness renewable energy.

Energy Storage

Incorporate electric battery storage with time-of-use (TOU) control or demand response, and thermal energy storage to manage energy use effectively.

All these capabilities are powered by our market-leading APACHE simulation engine, to provide accurate and reliable analysis across a range of building performance metrics.

While designing our buildings to meet high performance standards is only the first part of the challenge, our capability also extends to supporting robust monitoring and verification (M&V) strategies to ensure that your building’s net-zero design intent carries through into operation. With our newly launched cloud-based platform, IES Live, we can even provide energy and facilities teams with actionable insights to keep your building running optimally and on track towards energy efficiency and net-zero goals.

With the release of this standardized, verifiable basis for defining a zero emissions building, we stand ready with the tools to facilitate the transition towards a more sustainable built environment.

Explore our Building Energy Modeling page for more information and examples of our net-zero energy success stories, or contact our team to learn more.