A laboratory test procedure and a guarded hot box facility used to determine the thermal transmission coefficient of skylights are described. Skylights can be tested at an angle of inclination that can be varied from 20° to 90° off the horizontal. The experimental procedure, to determine the skylight R-value, is based on a correlation for the convective heat transfer on the warm side and the weather side of the test specimen. This correlation is obtained from calibration measurements using a calibrated transfer standard (CTS) in the inclined position. The results show that the convective heat transfer along an inclined CTS is substantially different from that along a vertical CTS. Three-dimensional simulations of the conductive heat transfer within the CTS assembly are found to be in good agreement with the experimental results. A complete uncertainty analysis for the calibration experiments and for skylight testing is presented. It is found that the experimental relative uncertainty associated with the thermal transmission coefficient of the test specimen without the frame is of the order of ±6%.

Units: SI