Interesting points there. However in my experience, ceiling registers do not move the heat to the floor, or even close. Most diffusers spread the patern across the cieling, and that is where the heat stays. By using low wall registers and returns, you are getting a circulation across the cold floor. And trying to keep the warmth where the people are. I am not a scientist by any means, I just know what my customers seem to like best.
[Edited by Christheheatingdude on 12-27-2005 at 08:57 PM]