Evaluation of indoor thermal environmental, energy and daylighting performance of thermotropic windows

Improving the energy performance of building envelope is a key to promote building energy efficiency. As a part of building envelope, Windows are recognized as the weakness of building envelope in reducing building energy consumption and thus should be as more energy efficient as possible. Currently available window products, such as double-glazed windows and tinted double-glazed windows, have their limits in balancing the performance of indoor thermal environment, energy and daylight. However, thermotropic materials, which change their light transmission behavior reversibly, have a great potential in achieving an excellent comprehensive performance. Therefore, this paper carried out energy, daylight and indoor thermal environment simulations to investigate the performance of a developed novel kind of thermotropic material for energy-efficient windows using the building simulation software DeST. Results show that thermotropic double-glazed windows can reduce 70% and 53% of highly uncomfortable indoor thermal environmental conditions in west-facing room, respectively, compared with double-glazed windows and tinted double-glazed windows. Moreover, they can reduce 19% of cooling electricity requirements in west-facing rooms compared with double-glazed windows, and provide an appropriate indoor illumination condition.

► Thermotropic windows were investigated by using building simulations.
► They can balance the performance of indoor thermal environment, energy and daylight.
► They can be widely used in energy-efficient buildings.