I actually meant to ask about ceiling fans, as I will have two in my very long living room. I would think that a ceiling fan would make this heat rises thing 100% a mute point, correct?
Most ceiling fans have a reverse switch. In the winter you run it in reverse which pulls the hot air along the ceiling down toward the floor. We use one in our Den sometimes while we watch TV. It has a remote control for the fan and works OK supplementing the Heat Pump air flow from the ceiling register.
Ceiling supply and returns make it easier to furnish a room. No worries about blocking supply or return registers.
If your local climate is a "heating" climate (long cold weather seasons), locating supply registers toward the outside wall is not a bad strategy. If your climate is a "cooling" climate (long warm weather seasons), you can locate supply registers along an inside wall and throw the air toward exterior walls/doors/windows.
As beenthere said, round ceiling diffusers (which my new house has) are great for cooling, not so hot for heating. If you are in a heating climate and it's not feasible to locate the supply registers toward the outside walls/windows/doors, you can locate them along an inside wall and throw the air toward the exterior walls/windows/doors, just as you would in a cooling climate.
Manual T and others state that although return air location is not super critical due to the small amount of influence a return air register has on the surrounding air, it does acknowledge that returns for a cooling climate are better located high, heating climate returns located low or in the floor. The main thing is that a supply register should NEVER throw its air toward a return register.
Why should the supply register NEVER thorw its air toward a return register?
If thr supply reg is trowings its air at the return, then thr return will drawing in the the supplies air instead of the room air. Depending on how close they are.
How close is too close depends on air throw of the supply.
Thanks and you are from Lancaster too...I used to live south of there a bit south of Quarryville.
I have two supplies on opposite walls near the floor. They blow air towards each other but are just in front of a floor to ceiling window with french doors(doors with a transom above) The return is on another wall actually down a hallway that opens into this room. I had the air directed into the room but in the direction of the return instead of across the wall with the doors so I was wondering if this was OK or not.