A "single structure" is a building where all of its parts share an actual, physical connection that is complete and indivisible. In other words, two buildings must share functional space that cannot be divided among the buildings (such as underground parking, an atrium, or conference space) to be considered a single structure. Hallways or interior walking paths between buildings are not considered functional, shared space, even if they are lighted and/or heated. The building's ownership and shared HVAC system have no impact whether a building is a single structure.
Note - EPA's best practice is to benchmark each building separately because that will isolate potential problems and help you find the most cost-effective improvements. However, we know it’s not always possible. Here are some examples to help you determine if you can pass the "single structure" test.
Example - Single structure:
- An office building that has three stories of common space including an atrium, a cafeteria, and seamless connections between two towers can be considered a single structure, even though it may appear as two above ground towers.
- Single tower with an office on floors 1-8 and a hotel on floors 9-14. Although you may think of the office and hotel as separate and they may even be run by separate companies, this is one single tower and must receive certification at the whole building level, including both the office and hotel.
Example - NOT a single structure
- An office complex that consists of two buildings connected by an outdoor (covered) walkway is NOT considered a single structure, and energy use in these buildings must be separately benchmarked.
- An office complex consists of three buildings connected by underground walkways (“tunnels”) that allow workers to move between the buildings without being exposed to the outside weather. This is NOT considered a single structure, and energy use in these buildings must be separately benchmarked. The energy use from the tunnel in this example (lights/heating cooling) also needs to be included. Since it will most likely be very minimal, it doesn't matter which building you add it to. Or, if the tunnel energy is sub-metered you could divide the energy among the separate buildings.
Example - Either a single structure or multiple buildings:
- Two office towers built on top of an underground parking garage may be considered a single structure OR (preferably) each of the towers may be benchmarked individually (don't include the parking energy), provided they have complete, measured energy data. EPA’s best practice is to benchmark each building separately, but we will accept ENERGY STAR certification in this case as a single property.
If you have a property that cannot qualify as a single structure, but they are not separately metered, you may benchmark it as a single building, but you will not be eligible for ENERGY STAR certification.
If you want to be eligible for certification, you will need to install an additional meter to separately meter each building. Installing separate meters is a best management practice because it will isolate problems and target the most efficient improvement opportunities.