Measurement of Fenestration Net Energy Performance: Considerations Leading to Development of the Mobile Window Thermal Test (MoWitt) Facility

[+] Author and Article Information
J. H. Klems

Applied Science Division, Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94270

J. Sol. Energy Eng 110(3), 208-216 (Aug 01, 1988) (9 pages) doi:10.1115/1.3268259 History: Received January 01, 1985; Revised February 01, 1988; Online November 11, 2009


We present a detailed consideration of the energy flows entering a building space and the effect of random measurement errors on determining fenestration performance. Estimates of error magnitudes are made for a passive test cell; we show that a more accurate test facility is needed for reliable measurements on fenestration systems with thermal resistance 2–10 times that of single glazing or with shading coefficients less than 0.7. A test facility of this type, built at Lawrence Berkeley Laboratory, is described. The effect of random errors in this facility is discussed and computer calculations of its performance are presented. The discussion shows that, for any measurement facility, random errors are most serious in nighttime measurements, and systematic errors are most important in daytime measurements. It is concluded that, for this facility, errors from both sources should be small.

Copyright © 1988 by ASME
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