Some of the system updates or retrofits revealed by the Level-2 audit may need significant investment of funds, personnel, or other limited resources. Before making this investment, the Owner will most likely want a more thorough understanding of the benefits, costs, and performance expectations. This is the objective of the “investment-grade” Level-3 ASHRAE audit. Investment amounts can vary from tens of thousands to tens of millions of dollars. In the majority of cases, since this can’t be clearly decided or estimated ahead of time, the recommendation and scope definition for a Level-3 audit usually is an outcome of the Level-2 procedure.
The ASHRAE Level-3 audit usually focuses on a “whole-building computer simulation”, where some type of computer program is used to very accurately model how a brick-and-mortar building would react to changes in the energy systems, whether those are major HVAC retrofits or architectural modifications to wall space, windows, and roof. The ASHRAE Level-3 audit involves much more detailed information collection over a period of weeks or even months. Data loggers typically are placed temporarily to keep track of the operation of pumps and motors, temperatures of affected spaces, lighting levels, switching behavior, and additional factors. These data are utilized to calibrate the computer model so that the computer design responds to inputs and changes the same way the actual building might be expected to respond. This calibration is checked and validated by simulating a year or more of historical climate conditions to determine if energy and power usage within the model mirrors actual energy and power usage in the building.
Once the computer model is responding like the real building, changes to energy systems could be simulated with very accurate results. Combining that procedure with construction-grade cost estimating facilitates informed investment decisions.