Durability test designed for double glazing units with interjacent light-deflecting system

For double glazing units with a light-deflecting system in the cavity between the glass panes, a service life of at least 20 years should be expected. The durability of such a unit depends on the resistance of the glass itself, the unit's edge sealing system and the light-deflecting system against the environmental loads acting upon the glazing unit, when installed as a translucent roof element in the building. To verify the durability of the edge seal and of the solar reflectivity of the light-deflecting system factory-made samples of the glazing units, mostly with original dimensions, were exposed to alternating and constant hygrothermal loads. This included different ambient temperatures and humidity conditions on both sides of the units as well as exposure to artifical sunlight. For the evaluation of the test results the experience with standard tests on insulating glazing systems served as a basis. Thermal transmittance, total energy transmittance, light transmission, adhesion of the sealants and diffusion resistance of the sealants used at the glass edge, gas content and dew point temperatures of the gas in the gap between the glass panes, moisture content of the drying agent in the spacer, temperature resistance of the light deflection system, linear expansion of the deflection system and thickness changes of the gap between the panes were considered. The knowledge gained from these tests led to the optimization of the manufacturing process, the edge sealing and the glazing unit