Hot air rises. Cold air falls. We all know this. Then why do we have diffusers in our ceilings that allow the hottest air (winter) in our rooms to rise up through them into the duct work above our ceilings? When our ac units cool our rooms they also cool our ducts to some degree... wouldn't it be wise to keep that last bit of cool air in the ducts after our circulation fans stop?
The flow of energy in either of these situations could be controlled by creating easily installed "flapper" type diffuser located doors that open with fan generated air flow & close with no fan generated air flow. I believe simple diffuser "flappers" could potentially save folks a substantial amount of money on energy costs. I would love to see if I'm right or wrong.