[modmonster]

the natural convection will be even more improved by having the rads away from the window. on one side of the room the hot air will be moving up from the radiator, on the other side the room cold air will be moving down from the window. the two flows will be working together mixing the air in the entire room in a circular motion.

if you have the radiator under the window the falling cold air and the rising hot air will have to fight each other thus slowing the speed of the resulting air flow and reducing the mixing. also the other parts of the room will be dead zones because they are too far from any source of heat or cold. cirtians will trap the rising air flow and make the mixing even worse.

i think the conventional wisdom is wrong on this one.