Should the infiltration rate be higher or lower when a space is occupied?

Below are the schedules for a “Closed Office” zone program. The assumption appears to be that the infiltration drops to 25% when the space is occupied, but I would expect the infiltration to be higher when occupied due to a larger difference between indoor and outdoor temperature, as well as the use of exterior doors.

What is the reasoning behind this? (477.1 KB)

This is an assumption for nonresidential buildings, and comes from ASHRAE 90.1. The argument is that the commercial HVAC systems (such as VAV) positively pressurizes the building when it is running (hence, during occupied periods), which should drastically reduce the infiltration rate. This is documented somewhere in the ASHRAE 90.1 user manual.