Proponents of radiant floor heating systems have long suggested that their method is more effective and more efficient than forced-air systems, though admittedly without any statistical proof. In fact, preliminary results from an NAHB Research Center study would prove the contrary. But according to an article published in THE JOURNAL OF LIGHT CONSTRUCTION, a sister publication of REMODELING, we're back to where we started: knowing nothing definitive.
The study involved a Habitat for Humanity house in Schenectady, N.Y. Both types of heating systems were installed in the house. Alternating heating systems in two-week intervals throughout the 2001-2002 winter, researchers monitored temperature as well as gas and electrical consumption. The preliminary results showed that the radiant system used 22% more fuel per heating degree-day than the forced-air system.
According to the JLC article, John Fantauzzi, technical director for the Radiant Panel Association, sent a letter to the Research Center outlining several objections he had with the study and its findings. Among other issues, Fantauzzi pointed out that when the switch was made from radiant to forced air, heat gradually releasing from the floor aided in heating the room, allowing the forced-air system to expend less energy than if it started from scratch. The radiant system would not have benefited when the switch went the other way.
Additionally, because the radiant system relies on heating the OSB subfloor and having that heat the air, the system would have had to use more energy switching back and forth than if it was in use for the entire winter.
Fantauzzi also thought the center was irresponsible for reporting the preliminary results of the study. "The conclusions in the final report may be very different," he told JLC reporter Jon Vara. "But a lot of people are only going to remember hearing that 'radiant heat is 22% less efficient than hot air.'" Center spokesperson Margo Thompson denied that there was any anti-radiant bias in the report or any ulterior motive in releasing the preliminary version of the report.
The article quoted Thompson as saying that her organization was looking at possible errors or inconsistencies that might have skewed the results. They hope to find out whether the sealed-combustion boiler used by the radiant system performed at maximum efficiency and if the hot-air furnace likewise lived up to its AFUE rating.