Transmittance through five types of commercially sold plate glass (5 mm thick) was measured over the wavelength range from 250 nm to 2500 nm. The results show that while the clear glasses transmit all wavelengths above 350 nm well, the three types of heat-absorbing glass had a lower transmittance level than clear glass in the near-infrared region.
Based on these transmittance spectra, solar transmittance measurement software was used to calculate solar transmittance and visible light transmittance values. The results indicated that the heat-absorbing glasses with relatively low transmittance for both visible and near-infrared regions had the lowest solar transmittance values. A formula similar to the formula on the previous page was used to calculate visible light transmittance in the range of 380 nm to 780 nm, which is regulated along with solar transmittance by JIS R 3106 Testing method on transmittance, reflectance and emittance of flat glasses and evaluation of solar heat gain coefficient. Visible light transmittance values indicate a transmittance level that takes into consideration the human eye’s sensitivity to light.
|Sample Name||Solar Transmittance (τe)||Visible Light Transmittance (τν)|
|Clear Glass 1||81.412||88.733|
|Clear Glass 2||89.612||91.339|
|Heat Absorbing Glass 1||47.428||75.051|
|Heat Absorbing Glass 2||44.367||43.323|
|Heat Absorbing Glass 3||52.023||50.029|
Solar transmittance measurement software* is used to calculate solar transmittance (or reflectance) values from transmittance (or reflectance) spectra according to the specified formula.
|*||This software can only be used to calculate values for single panes of glass and cannot be used for multiple panes of glass.|