Temperature and Heat Loss Characteristics of Concrete Floors Lain on the Ground

The heat loss, temperature, and moisture-permea tion characteristics of nine types of concrete slab floor construction laid on the ground were investigated in a specially built structure. The room air above the floors was maintained at 70 deg. F. by electrical convection heaters, but there were no heating elements placed in the floors. An extensive thermocouple system was instailed to measure temperatures throughout the floors and air spaces of each compartment. The best overall performance was obtained with a floor construction in which a two-inch thickness of rigid waterproof insulation extended six inches down parallel to the exposed edge of the fioor and two feet back under the concrete slab. The floor surface temperature six inches from the exposed edge for an outside temperature of zero deg. F. was 62 de g. F. for this insulated floor as compared with 45 deg. F. at the same location on the surface of an uninsulated floor of similar construction. The heat loss through the insulated floor was about 70 percent of that through the uninzulated floor. Isotherm patterns drawn for each type of floor construction indicated that beyond a distance of three feet from the exposed edge of the floor, the path of heat flow was essentially straight downward and that the magnitude of heat flow was practically constant. The isoherms for the bordering three feet of the floor section showed the effect of different amounts and placements of insulation. The heat flow was downward through the floor into the ground and then upward to the outside, as well as directly through the exposed edge of the floor to the outside. Moisture permeation tests were being contined as the data and results obtained to date were not considered conclusive. The data available indicated that a vapor barrier may be more, effective in the spring and summer months than in the winter.U.S. Department of Commerce, Office of Technical Service