Abstract

Windows play a significant role in achieving quality of life and comfort in buildings. As a part of the building envelope, a window is a filter of conditions between inside and outside. Although they are exposed to same effects as walls they are expected to fullfil requirements such as controlling both heat and sound as a filtering material, suplying air circulation, resisting to water leakeage and above all, transmit light without a glare. Whereas traditional windows have lower resistance to heat flow and to sound transmission, to improve the effect of thermal insulation, a number of the materials and layers has been developed with varying benefits. The first possibility to improve the heat transfer coefficient, the so called U-value, is to increase the number of layers of glass or films. Therefore, the most promising materials for thermal conversion systems are windows with fillings of honeycomb or capillary materials. In a temperate climate, the situation changes with time. Sometimes overheating must be prevented, at other times one wants to gain as much solar radiation as possible to reduce space heating demands. A more elegant solution is choromogenic materials. Their optical properties change during a day or a season. In this rewievly paper, thermal and optical properties of constant and changable transparent insulating materials have been evaluated.