Demand for radiant heating systems has increased dramatically over the past four years, despite contractors’ initial hesitations to learn and install the new technology. In 1996, 70.6 million feet of radiant tubing was sold in the United States. That number grew to 138.7 million feet by 1999, according to the Radiant Panel Association. These sales represent an estimated 185 million square feet of radiant floor heating installed in 1999, and of this about 75 percent are residential installations in nearly 45,000 homes.
Most of these installations consist of the "slab on grade" variety, consisting of tubing embedded in concrete slabs or below grade level. In 1998, more than 51 percent of installations were of this type. Thin slab or "sandwich" installations, installing radiant tubing on top of subfloors, made up more than 36 percent of installations, with the remainder being staple-up installations, attaching tubing to the underside of wood subfloors.