[Zeke]

A note on interior doors and central heating/AC: A typical room register (vent) will be 12 x 6, or 72 sq. in. It's probably fed by a 6" duct which is 28 Sq. in; 7" = 38.

If your doors are cut 1" above the finish floor or carpet the average 30" door yields 30 sq inches of under door flow. If you want your system to perform at all, you must see to this if you want to close doors off and still have conditioned rooms.

There are many other dynamics involved, of course.