CIRCADIAN LIGHT EVALUATION OF A SPACE EQUIPPED WITH CLEAR GLASS WINDOW AND OPTIMIZED SHADE VERSUS LOW-E GLASS WINDOW WITHOUT SHADE

Abstract

The aim of this research was investigating the effect of (i) Low-E glazing window and (ii) clear glass window equipped with optimized shade on the circadian light distribution across an interior space. To that end, computer simulations were conducted in the Grasshopper® for Rhino® plugins to evaluate the circadian light of a simulated office space located in Topeka, KS. For this purpose, five cases were studied: a clear glass window (89% visible light transmittance (VT)) with optimized shade (the baseline case), three different low-E glass windows (65%, 53%, and 39% VTs) all without shade (test cases), and a clear glass window (89% VT) without shade (the reference case). The simulations were conducted on four different days (March 20, June 21, September 20, and December 21) at three times per day (10 a.m., 1 p.m., and 5 p.m.) for four orientations (south, east, north, and west) and under two sky conditions. The circadian light data were converted to the circadian stimulus (CS) and evaluated based on the total and Useful Circadian Light Frequency (UCLF). In contrast to total circadian light, the UCLF evaluation indicated that, on average, the optimized shade cases contributed to higher UCLF than Low-E glazing window cases at north and west orientations under clear sky condition (49.9% and 41.5.1% of maximum 66%) and south and north orientations under overcast sky condition (39.3% and 39.1% of maximum 65%) respectively. In conclusion, this study supports the favorable design of optimized shades for the clear glass window in both south and north orientations for their contributions to the interior circadian light in comparison with the Low-E glazing windows with VTs below 65%.