Many home buyers cannot equate a slab-on-ground floor with comfortable living, although it has been demonstrated that with proper construction techniques basementless homes can be comfortable and that they offer some economic advantages. One such way to overcome buyer's objections is by installing a plenum floor. The basic arrangement in a plenum floor is that the floor is supported above the slab to leave space below for the heating plenum and utilities. The source of heat is the downflow or counterflow warm-air furnace commonly used to force air into under-slab ductwork. Warm air from ducts is discharged into the underflow plenum rather than directly into the rooms. In the plenum the warm air moves in all directions and loses part of its heat to the flooring above before flowing through registers into the rooms. There are several advantages with this type of system. One is the plenum system gives a smooth heating pattern instead of the usual hot/cold abruptness. Another is the cost of installing the heating system is lower than for any other type of construction. Also, freezing water lines is never a problem. Finally, the use of prefabricated floor joists offers big savings.