Energy Use Intensity (EUI) is an indicator for how energy efficient a building’s design and operations are. EUI is not the same thing as energy use, but understanding the types of energy can help us to better understand the EUI metric.
Site Energy vs. Source Energy
There are two ways to classify energy use for a building: site energy and source energy. Both can be used for EUI.
Site energy is the amount of energy a building consumes at the site, as reflected in utility statements. Renewable energy that is generated and used on site is also included in site energy. Renewable energy that is generated on site but exported to the grid is not included as it is not used operationally by the building.
Source energy goes beyond the site footprint and encompasses all raw energy required to operate the building, including site energy, delivery, and production losses.
Since either site energy or source energy can be used to calculate EUI, you need to be mindful of which measure is used if you’re comparing EUI metrics between buildings. Read more about site energy vs. source energy here.
How to Calculate EUI
Calculating the site EUI for a building can be done in 3 simple steps:
- Convert all of the energy types and quantities from the various utilities servicing the building in the past 1 year into kBTU.
- Add all of the kBTU values to determine the total energy (site or source).
- Divide the total energy by the total building area in square feet to get site or source EUI.
Take, for example, a 5,000 SF office building that uses electricity for all of its lighting and plug loads and natural gas for its heating. The electricity use in 1 year is 15,000 kWh. The heating load in the past year was 19,000 CF. Using the list of energy conversion rates from the Department of Energy, 15,000 kWh is equal to 51,180 kBTU and 19,000 CF is equal to 194,940 kBTU. We can then add these together to get a total site energy use of 246,120 kBTU. Dividing this value by the square footage of the building, we get a final site EUI value of 49.
For some more info on EUI, including benchmark values for various building types, check out ENERGY STAR’s page here.
What is TEDI?
TEDI is the Thermal Energy Demand Intensity and measures the annual heating load per floor area for a building. The energy that is included in TEDI, therefore, is also included in EUI.
We can think of EUI like an umbrella that covers TEDI as well as other building energy loads like lighting and appliance/plug loads. What is important to remember is that the TEDI metric alone does not capture the overall building energy consumption as EUI does.
TEDI is primarily influenced by two elements of the building envelope: insulation and air tightness. A building that is highly insulated with an airtight enclosure will achieve a better TEDI value.
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Building Envelope Consulting for Improved Energy Performance
Reducing your building energy use can help to meet the upcoming energy and emissions standards set by several large cities across the US, including Boston’s BERDO 2.0. Here are some things we can do to help:
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Reach out to us today if you’re ready to get started!