My home has both upper and lower internal return vents in each major room. Any suggestions on when to close one or the other would be appreciated. For example, do I close the top vents in the winter to pull cooler air into the furnace, or do I close the bottom vent to better circulate the heated air in the house? The former makes more sense, but I'd like to hear from someone who knows more than I.

labman

I think the theory is, use the upper vents in the summer to return the hot air from the ceiling to the A/C, and the lower ones in the winter to return cool air at the floor to the furnace.