In general, its best to benchmark each building separately, even if there are connections between or underneath the buildings, such as underground parking or ground floor retail.
However, if you want 2 seemingly separate buildings to qualify as a "single structure" it must share an actual, physical connection that is complete and indivisible. In other words, the two buildings must share functional space such as underground parking, an atrium, ground floor retail, or a lobby, to be considered a single structure. Walkways between buildings are not considered functional, shared space, even if they are lighted and/or heated. The building's ownership, metering, and shared HVAC system have no impact whether a building is a single structure.
**This determination is not always straightforward, and it may need to be considered by EPA on a case-by-case basis. Send us a question if you are unsure about your building, because your certification eligibility could be affected.
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. If you have a property that cannot qualify as a single structure, and the buildings are not separately metered, you may benchmark it as a single property, but you will not be eligible for ENERGY STAR certification. If you want to be eligible for certification, you will need to install additional meters to separately meter each building.
Here are some examples to help you determine if you can pass the "single structure" test.
Example 1 - Single structure:
- 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. Properties that are vertically stacked liked this, are ALWAYS a single structure because they share an indivisible actual, physical connection.
- Side-by-side buildings that share a wall, are considered separate buildings. These buildings in the photo below would be considered 4 separate buildings because they do not share any functional space (such as a lobby, or underground parking).
Example 2- NOT a single structure
- An office complex that consists of 2 buildings connected by an outdoor (covered) walkway is NOT considered a single structure.
- An office complex that consists of 3 buildings connected by underground walkways that allow workers to move between the buildings without going outside. These 3 buildings are NOT considered a single structure. The energy use from the underground walkway 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 3- Either a single structure or multiple buildings:
- Two office towers and a hotel are built on top of a street level mall. You can walk from one tower to the other through the mall. While the best practice would be to benchmark both towers and hotel separately (and divide the mall proportionally between the 3 properties), because the mall does constitute a seamless connection between buildings, this property could be considered a single structure.
- Two office towers are built on top of an underground parking garage may also be considered a single structure OR (preferably) each tower could be benchmarked individually.