I am getting the parts together to ventilate a 100 ft3 coat closet so I can put my rack in there. I have pretty much decided on a T6 inline duct fan from AC Infinity. I am mounting the fan in the attic above the closet and ducting it into the laundry/mudroom behind it. Just enough ducting to go from the fan to 2 ceiling diffusers. AC's thermal controller looks pretty slick and has lots of programming options so I will use that. The fan is rated for a max 351cfm.

The closet has a standard door undercut of about an inch give or take. I am trying to find out if that will be able to supply enough makeup air to balance the load on the fan. Is there a formula to calculate that? What other factors to I need to consider? I could always install an intake vent in the door or wall near the bottom of the rack, or cut another slice off the bottom of the door. Any help is appreciated. Thanks.