WASHINGTON, Jan. 23In work that has major implications for improving the performance of building insulation, scientists at the University of Namur in Belgium and the University of Hassan I in Morocco have calculated that hairs that reflect infrared light may contribute significant insulating power to the exceptionally warm winter coats of polar bears and other animals. The research was published today in The Optical Society's (OSA) open-access journal, Optics Express.
Biophotonics expert Priscilla Simonis, a researcher at the University of Namur and lead author of the Optics Express paper, was intrigued by the ability of polar bears to insulate their bodies to temperatures of 37 degrees Celsius (98.6 F) even during long, cold winters when outside temperatures are a frigid -40 C (-40 F). The feat was especially impressive given that the bears have a layer of fur that is only 5 centimeters thick.
The insulating power of the animals' coats made Simonis wonder why thermal insulation in buildings doesn't work as well. "Why do we need at least 60 cm of rockwool or glasswool" common types of building insulation made from minerals or glass fibers "to get a temperature of 20 degrees Celsius inside from about -5 degrees Celsius outside?" she asked. "Why is the polar bear fur much more efficient than what we can develop for our housing?"
Simonis and her team tackled the question by re-examining two of the different ways heat can travel: radiation, which transfers thermal energy through electromagnetic waves, and conduction, which transfers thermal energy through the vibrations of neighboring atoms and molecules. Most people assume that fur and feathers keep animals warm primarily by trapping a layer of air that slows thermal conduction, says Simonis. But she and her colleagues suspected that radiation might play a bigger role.
The scientists performed some
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The Optical Society