Perimeter-Loop Warm-Air Heating Systems
The perimeter-loop warm-air heating system (Figure 6-1) was originally designed for use in residences built on a concrete slab rather than over a basement. The proven success of this duct arrangement in providing efficient and economical heating has resulted in its installation in all types of construction. This is rapidly becoming one of the most popular forms of warm-air heating.
In the perimeter-loop system, round ducts are embedded in the concrete slab or suspended beneath the floor. The air is heated in a warm-air furnace equipped with a blower and is forced through the ducts leading from the furnace to a continuous duct extending around the outer perimeter of the structure. The registers (diffusers) through which the heated air enters the various rooms and spaces
are located along this outer perimeter duct. The most efficient operation can be achieved by placing these warm-air outlets on the floor next to the wall and beneath a window (Figure 6-7). By placing the warm-air outlets here, window drafts are eliminated and the colder outside walls are kept warmed. Research shows that up to 80 percent of the heat loss from a structure can occur at these locations.
The Air Conditioning Contractors of America’s publication Manual 4—Installing Techniques for Perimeter Heating and Cooling is the most authoritative and useful source of information about this subject. (Ask for the most recent edition, because the manual has undergone a number of revisions.)