THE OWNER BUILT HOME & HOMESTEAD
(Page 13 of 15)
January/February 1971
By Ken Kern
The fact that the floor is warm in a ceiling-heated room may at first seem contradictory. But if the entire surface of the ceiling is heated, there is no chance for convected air circulation. This makes for a uniform temperature, with radiant energy transmitted downward and intercepted by the floor surface. Water temperature in ceiling-heated surfaces must be kept at from 125 to 135 degrees.
RELATED CONTENT
There is a long time-lag in radiant floor heating; slow morning heating and slow evening cooling. A sudden change in weather cannot be compensated for soon enough. This is the usual objection to a hot water radiant system. However, a thinner floor slab will hasten the response to temperature change. Dividing water circuits into separate sections—one circuit for the living area, one for the sleeping area, etc.—will also cut down on heating lag. Likewise, a grid system of pipe layout is more efficient than a sinuous pattern.
The hot water radiant ceiling will of course cut down considerably on heat lag. The latest ceiling panel development—that of attaching the heat coils to the top of perforated metal snap-on panels (with acoustic "thermal blanket" insulation)—has proven to be far more efficient in heat response than the conventional plaster-lath installation. Metal is an excellent heat conductor, and becomes heated almost to the same temperature as the water in the pipes. The exposed metal should be of a matte or "flat" surface (aluminum is best); if polished it has no radiating qualities.
Another recent development in "hydronics" (that is, water heating) has come out of experimental work at the University of Illinois. Considerable time and installation expense can be saved by using 1/4 inch to 3/8 inch flexible copper tubing in place of the usual 3/4 inch steel or copper pipe, since the number of fittings can be reduced one-half. The small appliance-sized, automatically-fed boiler has recently appeared on the market. High temperature water heating combined with water heating for domestic use can be supplied at relatively low cost. Levitt has used both the 3/8 inch copper tubing and the combination water heating appliance (York-Shipley, 94,000 BTU/hr.)
A hydronic system known as "baseboard radiation" is another current development. Heat is provided by baseboard radiation units located usually on cold walls. Some convection effects probably occur, but the units are mainly radiant in their action. Forced hot-water baseboard radiation is low in first cost and simple to install.
About fifty years ago the cast iron stove was moved into the basement and became a furnace. As a "gravity" convection heater it sent up hot air (and other gases!) through a grill in the floor. Basically this gravity warm-air heating system has not been improved upon. It is still the cheapest heating system for the small, compact home, and is perhaps found in existing homes more often than any other type. Air enters the system through one or more "cold air" or "return air" registers, and is heated as it passes through the large return duct.
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