September 18, 2025
Thermo-optical Properties
In this video, Francesco Fiorito, from the Polytechnic University of Bari, explains how glass interacts with solar radiation. When sunlight hits a window, some energy is transmitted inside, some is reflected, and some is absorbed. Two key values define a glass's performance: the Solar Factor (or g-value), which measures total heat gain, and the Visible Light Transmittance (VLT), which measures how much light passes through. While clear glass has high values for both, it can cause overheating. Tinted glass reduces heat gain but also makes interiors darker. Selective glass uses special coatings to block heat (a low g-value) while still allowing plenty of light (a high VLT). Other coatings, like low-emissivity (low-e), help with thermal insulation. The video concludes that selecting the right glass is essential for energy efficiency and comfort in buildings. The video was produced by the Open GLASSroom project. Special thanks to Francesco Fiorito for contributing to the Open GLASSroom OER collection. The creation of these resources has been (partially) funded by the ERASMUS+ grant program of the European Union under grant no. 2022-1-DE01-KA220-HED-000089750. Neither the European Commission nor the project's national funding agency DAAD are responsible for the content or liable for any losses or damage resulting of the use of these resources.