Advanced Evaluation of the Performance of Reflective Air Spaces

D. Yarbrough and H. Saber
Reflective Insulation Manufacturers Association,
United States

Keywords: enclosed air space, building materials, heat transfer


Enclosed air spaces with one or more low-emittance surfaces (reflective insulations) have been discussed in the heat transfer literature for more than a century. The use of reflective insulation in the building envelope was given a boost in the 1950s by a battery of hot-box tests and subsequent analysis from the U.S. National Bureau of Standards. Thermal resistances (R-values) based on the NBS data have been published in handbooks and texts for one-dimensional steady-state heat transfer between planar surfaces and used for many years to evaluate thermal performance of reflective insulations. The capability to model and simulate heat transfer by all mechanisms including convection now provides detailed information about heat flow across enclosed air spaces including non-parallel surfaces, leaky enclosures, and subdivision of an enclosure to provide reflective airspaces in series. Results from this advanced capability will be discussed.