Determine the energy model’s scope. In general, to simulate the performance of building systems an energy model has to include all spaces served by a common HVAC system. However, central HVAC systems often extend beyond the scope of CI projects. For example, if the project scope is a single floor fit-out in a four story building, it’s likely that the building HVAC systems will serve all four floors. The model will simulate the energy use of all four floors, but the CI project can account for only a portion (25% in this case) of the energy use and energy savings from efficiency upgrades.