The two quantities solar material protection factor (SMPF) and solar skin protection factor (SSPF) are introduced in order to measure and calculate the capability of glass to protect indoor materials and human skin from degradation caused by the solar radiation. Comparison of the SMPF and SSPF values for different glass fabrications enables one to select the most, appropriate glass material for the specific buildings. Numerical examples are shown with measurements and calculations carried out on various glass materials, including two electrochromic window (ECW) devices, and several two- and three-layer window pane combinations. Visibility levels at various protection degrees are also given. (c) 2006 Elsevier B.V. All rights reserved.