To help mix the warmer air in the winter between upper and lower stories.

wrote in message
ups.com...

Jeff wrote:
Assuming the door is open I doubt it would make much difference in the
summer. Sucking air from the room would draw air mostly from the hallway
and not the incoming duct. Main problem is incoming duct is too small or
blocked.

If having returns isn't important for cooling, why bother having them
upstairs at all?