When does the Performance Period Start?

There is no set time for the beginning of the performance period - each project determines that moment individually. The most useful way to think about when to begin your performance period is probably as the point at which the building is operating the way you intend it to operate from a sustainability standpoint. This would mean that all your policies are in place and implemented, any new equipment is installed and working properly, tracking systems are working, and your data is being generated appropriately. Basically you do everything you need to to 'green' the building, and then you begin your performance period to document the X months of operating green.