One of the biggest things I learned working with the Europeans on the net-zero guidebook was that they shut spaces down at night.

They cut the air to the admin wing, they cut the air to the day clinics, they cut the air to the imaging suite, they cut the air to the cafeteria, they cut the air to retail spaces. Really, anything that's not a patient room gets either shut down or turned down at night. 

I've been looking at data from air handlers: comparing 2PM data (which should be higher) to 4AM data (which should be a lot lower).  I think, as a generalization, we're doing a terrible job of shutting down and turning down air systems. Seems to me that any time we’re shutting off lights, we should be shutting down or turning down HVAC (which uses more energy than lights!).