The objective of this research work is to identify the best double reflective window glass which provides adequate daylighting by controlling solar heat gain as per the requirement of summer and winter seasons of composite climatic zone in India. To attain this objective an investigation of spectral characteristics of different reflective glasses such like gold, sapphire blue, opal blue, grey, green and bronze reflective glasses is carried out experimentally using Shimadzu UV 3600 spectrophotometer in the entire solar spectrum wavelength range from 300 nm to 2500 nm based on ASTM E 424 standards.The measured spectral characteristics were used to compute the visible optical properties in the visible zone and solar optical properties in solar spectrum zone by using International standard method with a MATLAB code. The computed optical properties transmittance, reflectance and absorbance are used in the simulation tool for heat gain and daylight calculations for a school room building. As far as both hottest and coolest days are concerned double gold reflective window glass (DGLDRGW) is found to be the best in the South orientation. During hottest day, DGLDRGW gains minimum heat of 2.13 kWh with adequate daylight factor (2.049% at 9 A.M. and 2.025% at 4 P.M.) and also it gains maximum heat of 8.55 kWh with adequate daylight factor (2.729% at 9 A.M. and 2.732% at 4 P.M.) for school room building among six studied double reflective window glasses. © 2018 International Information and Engineering Technology Association. All Rights Reserved.