Some claim placing the tubing under the floor is less efficient, it is usually someone who is selling something.
Over or under has exactly the same efficiency! Stop and think. Where did the heat go to?
To change the efficiency the heat would have to go somewhere. There are only two places you can change the heating efficiency of a house. Either the heat loss through the structure or the loss up the chimney. In other words the efficiency of the heating appliance or the heat loss of the construction methods are the only two ways to change the efficiency of your heating system.
AT 85°F. SURFACE TEMPERATURE THE FLOOR CAN PUT OFF 30 BTU PER FOOT OF FLOOR SURFACE. MOST NEW
CONSTRUCTION REQUIRES UNDER 20 BTU'S PER FOOT EVEN AT -20°F.
NEW ADVANCED CONSTRUCTION METHODS ARE ATTAINING HEAT LOSSES UNDER 10 BTU'S PER SQ. FT.