Antireflection treatment of low-emitting glazings for energy efficient windows with high visible transmittance

The objective of this study is to increase the visible transmittance of a low-emittance (low-e) glazing as much as possible by antireflection treatment. This has been carried out by depositing thin porous films of silicon dioxide, SiO2, on both sides of a commercial glazing with a pyrolytic low-e tin oxide-based coating. SiO2 was chosen because its refractive index makes it suitable for antireflection treatment of both the uncoated glass side and the side of the tin oxide coating. The deposition of the antireflective films was performed with a dip-coating method, where the substrate was dipped in a sol–gel of silica. Two different silica sol–gels were used, one was manufactured in the laboratory and the other one was a commercial solution with a higher porosity. An increase of the integrated visible transmittance (Tvis) by 9.8% points up to 0.915 was achieved for a coating produced with the commercial solution. Calculations of U value, g value and Tvis for window configurations were also performed.