There has recently been developed in England, and now first introduced into this country in the British Embassy in Washington, a new type of patented heating system consisting of concealed hot-water pipes placed in the ceiling.2 While originally developed as the result of a desire to eliminate exposed radiators and grills it was subsequently discovered that radically new heating principles were involved offering decided advantages.
The basic arrangement is in all essentials similar to a regular hot water heating system except that, instead of exposed or concealed radiators, coils with welded joints and tested under high pressure are placed in the ceiling just above its lower surface and buried in the plaster, which is of a special type to prevent cracking. Hot water is circulated at a relatively low temperature either by gravity or by pump. By means of these coils the plaster is raised in temperature to a point where the heat radiated from its lower surface is sufficient to warm the room to the desired point. However, as the air cannot be warmed by convection, owing to the location of the source of heat at the top of the room, and as radiant heat does not appreciably warm the air through which it passes, the air in the room is left at a relatively low temperature. The comfort of the occupants does not depend primarily on the warmth of the air but on the heat radiated by the ceiling, in the same way that a person sitting in a protected sunny spot on a cold winter day may be adequately warmed by the radiant heat of the sun although the air may be very cold. The inventors claim that a room heated by the panel system will be entirely comfortable with the air at a temperature of only 620, and further that with the air heated above that point a sensation of serious overheating will be experienced.1 The recent work of the New York State Commission on Ventilation has shown the dangers to health of overheating, and the importance of a matter of even two or three degrees. This commission recommends that the air temperature be maintained as low as is consistent with comfort, and panel heating may provide a means for comfort at a temperature far below that possible with any other system of heating.
1 Adapted from "The Country House," Architectural Record, November, 1930.
2 Richard Crittall & Co., Ltd., of London, control the patents; Wolff & Munier, Inc., 222 East 41st Street, New York, are American agents.
At the present time, however, the development of the system is still in its infancy and there are many questions yet to be answered. For example, just how is such radiant heat to be thermostatically controlled, and how is the temperature of the air to be properly correlated with the amount of radiant heat? How is a desirable air motion to be procured when there are no convection currents?