Copyright Goodheart-Willcox Co., Inc. Chapter 12 Radiant Heating Systems 239 represents a forced-air heating system. Notice that there is a large discrepancy between the ideal heating curve and the forced air heating curve. When heating with a forced air system versus a radiant floor heating system, not only are there sizable increases in stratification from floor to ceiling but also the temperatures at floor level are significantly lower, Figure 12-3. Considering the fact that a per- son’s feet will typically lose heat faster than his or her head, one can see that this configuration is less than desirable. 12.1.2 High-Mass versus Low-Mass Radiation The difference between high-mass and low-mass radiation is an important concept to understand because it can significantly affect the best design for a hydronic heating project. The difference between these two types of radiation systems mainly involves their capacities and abilities to store heat energy. Low- mass radiant systems possess a very limited capacity to store heat energy, while high-mass radiant systems have a much higher capacity for energy storage. An example of a low-mass system is finned tube baseboard radiation, Figure 12-4. An example of high-mass radiation is embedding radiant heating tubes in DID YOU KNOW? Radiant Heating—A Brief History Radiant heating dates back to ancient times, when the Romans warmed rooms by running the flues of slave-tended, wood-burning fires under elevated marble floors. This kept the occupants’ toes and togas nice and toasty. Many centuries later in the United States, architect Frank Lloyd Wright em- bedded copper pipes in the concrete floors of his Usonian homes (in Lakeland, Florida) and warmed them with hot water. A few postwar subdivisions, including Levittown, New York, followed suit, but when the copper pipes eventually cor- roded most homeowners abandoned their radiant heating systems rather than jackhammer through their floors to get rid of them. 110°F 100°F 85°F 90°F 90°F 90°F Room Air Temperatures Forced-air heating system Hydronic heating system 80°F 75°F 68°F 60°F 65°F 65°F 60°F 81°F 81°F 81°F 65°F 65°F 60°F 60°F Goodheart-Willcox Publisher Figure 12-3. This illustration shows the effects of temperature stratification using a forced-air heating system.