Transparent insulation of building facades—Steps from research to commercial applications

Abstract Transparent insulation materials (TIM) represent a class of new materials for application in solar thermal conversion systems. A U -value below 1 W/(m 2 K) and an energy transmittance greater than 70% characterize TI materials. With these physical properties TI materials outperform all conventional glazing systems and further increase the efficiency of thermal conversion of solar radiation. In winter, low elevation solar irradiance on vertical surfaces can be used effectively. Experiments, simulation calculations and results from demonstration projects have shown the space heating potential of transparently insulated walls. A properly built passive TI element on a sun-facing massive building facade can save heating energy by up to 200 kWh/(m 2 yr) each annual heating period. The paper describes the transparent insulation of building facades from the basic idea to the satisfying results of demonstration projects. Fundamental considerations for TIM and wall parameters, a list of projects, exact descriptions of TI wall constructions, the reduction of space heating demand and future developments from part of this paper. It is a summary of the work done in this specific field in the past 10 years giving examples of the dynamic developments in solar energy from the basic ideas to commercial systems. A Self-Sufficient Solar House, which is almost totally heated with transparently insulated walls, is an outstanding culmination of TI research and TI application.