Angular dependent optical and thermal properties of advanced architectural glazing

Contact: Dr Andreas Schüler

Physical properties of insulating glazing play an important role in energy management. Precise data allows a better prediction of overheating risks and thermal losses. Manufacturers usually only provide calculated data for normal incidence angle, which is not the most relevant in common situations.
Using the window test bench originally developed at University of Basel (Steiner, 2005) and now installed at EPFL/LESO-PB in Lausanne, we are able to measure transmittance and reflectance at angles of incidence from 0° to 75°. These values are used to determine the coefficient of solar direct energy transmission Te and visible light transmission Tv according to the EN 410 standard (EN410).
The solar gain factor (g-value or total energy transmittance) can also be determined via an additional experiment using the method developed by Reber et al. (Reber, 2005).

The properties of a large number of glasses are accessible through the, a database built by University of Basel and now hosted by EPFL.

glassdbase in an independent and comprehensive database for building glass. It is the place to find data on commercial insulating glasses determined at the Institute of Physics at the University of Basel and EPFL. glassdbase is focused on sun protection glasses.

The database reveals among others the following angular dependent data on insulating glasses:
– spectral transmittance T, spectral reflectance R, and spectral absorptance A
– solar direct transmittance Te, solar direct reflectance Re, and solar direct absorptance Ae
– light transmittance Tv, and light reflectance Rv
– total solar energy transmittance g (g-factor)
– detailed color information on the transmitted and reflected daylight
– general color rendering index Ra


O. Bouvard, S. Vanzo, A. Schüler, 2015, Experimental determination of optical and thermal properties of semi-transparent photovoltaic modules based on dye-sensitized solar cells, Energy Procedia, Proceedings of 6th International Building Physics Conference, IBPC 2015, Torino, 14-17 June 2015 

Steiner R. et al., 2005. Experimental determination of spectral and angular dependent optical properties of insulating glasses. Proc. of CISBAT, EPFL.

Reber G. et al., 2005. Angular Dependent Solar Gain for Insulating Glasses from Experimental Optical and Thermal Data. Proc. of CISBAT, EPFL.

NF EN 410, Glass in building, Determination of luminous and solar characteristics of glazing. 2011. AFNOR