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Why EUI? — An Energy Use Intensity Primer
by Thomas Hootman
Energy use intensity (EUI) is one of the most important and useful metrics employed in the design of low energy and net zero energy buildings. EUI is a measure of total annual building energy use, divided by the gross building floor area.
This can be expressed in terms of site energy or source energy. Common EUI units include kBtu/ft2, kWh/ft2, kWh/m2, and MJ/m2. In the United States, kBtu/ft2 is the EUI unit most commonly used.
What makes the EUI metric so useful is that it serves as a way to compare energy performance of buildings, or compare energy performance with established baselines.
EUI is a measure of energy performance, not of overall energy use. A good analogy for EUI is the miles-per-gallon (mpg) fuel efficiency measure for vehicles, except that, with EUI, the lower the number, the better the energy performance for the building.
As a performance metric, EUI has many uses. During the design of a building, an energy performance EUI target can be set and compared to EUI performance baselines. It can also be used to understand and communicate existing building energy performance.
This is particularly beneficial with regard to building energy performance labeling. At the root of the EPA's ENERGY STAR score is the EUI metric. ASHRAE's emerging energy performance label, Building Energy Quotient (Building EQ), likewise uses EUI as the basis for measurement.
As a performance metric, EUI has many uses. During the design of a building, an energy performance EUI target can be set and compared to EUI performance baselines. It can also be used to understand and communicate existing building energy performance. This is particularly beneficial with regard to building energy performance labeling. At the root of the EPA's ENERGY STAR score is the EUI metric. ASHRAE's emerging energy performance label, Building Energy Quotient (Building EQ), likewise uses EUI as the basis for measurement.
EUI is also useful as a planning tool. It can help manage energy performance across multiple building assets or a large commercial building portfolio. In a similar way, EUI has value in master-planning future projects, as a way to quantify projected energy performance and use through a wide set of mixed uses and building types.
An excellent example of implementing EUI in a large-scale planning effort is the Chicago Central Area DeCarbonization Plan, completed by Adrian Smith + Gordon Gill Architecture. This plan for revitalizing Chicago's loop area focuses on assessment, strategies, and investment in a diverse range of urban design metrics, with a primary goal of energy and carbon reductions.
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The Omega Center for Sustainable Living, a ecological laboratory and classroom located in Rhinebeck, New York and designed by BNIM, is a net zero energy building and a certified Living Building.
Photo: Courtesy BNIM/ © Assassi
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The stated goal of the Bullitt Center in Seattle, Washington is to change the way buildings are designed, built, and operated. Upon its completion, the five-story building, designed by the Miller Hull Partnership, will seek to meet the goals of the Living Building Challenge and will include a rooftop photovoltaic array, rainwater collection features, and on-site wastewater treatment.
Image: Courtesy Bullitt Foundation/ Miller Hull/ Point32
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