Princeton researchers have uncovered a significant error in the method used for decades to measure radiant heating and cooling in buildings.
The research team of Forrest Meggers, assistant professor of architecture and the Andlinger Center for Energy and the Environment says the error rests with a standard sensing instrument, called a globe thermometer, and associated formulas used to calculate comfort, which do not properly account for a type of air flow known as free convection. They said the findings could mean that engineers and designers have relied on inaccurate measurements for decades when evaluating thermal comfort systems.
Although air conditioning is still the primary solution for cooling in the United States and other places, radiant heat exchange has been identified as an energy-efficient alternative to keep people cool. But radiant systems have not always been seen as standalone solutions. The researchers say this historic oversight could help to explain why and enable architects to make better use of radiant cooling systems by incorporating large surfaces and choosing materials that promote transmission of thermal radiation (and minimize the need to condition the air).
For example, Meggers’ team has shown that letting the air warm up by five degrees while cooling surfaces can lower energy demand by up to 40% and maintain occupant comfort.