Thin film angular selective glazing

Angular selective glazing based on special obliquely deposited thin films, has considerable potential for optimizing the overall performance of a window in temperate to hot climates. In contrast to most currently used glazings for these environments it has the ability to control solar heat gain and glare while providing a clear view through the window and considerable but not excessive light gain. Various deposition techniques and film materials will be discussed and the spectral and integrated optical performance of single and double-layered systems presented for various directions of incidence. Full optical characterisation requires measurements for incidence directions over half a hemisphere. Some of this is presented but most data is confined to planes of incidence where angular selectivity is greatest as determined by deposition geometry. Two layer systems are designed to provide a low emittance and better solar control than the single layer systems while retaining good visible angular selectivity. The single layers are primarily to provide angular selective control of the visual radiation since they have moderately high transmittance in the near infrared and a high emittance. Theoretical models used to extract structural information and model the complex optical properties are introduced and their predictions assessed. Preliminary results on simulation of the performance of full size angular selective windows in comparison to other types of solar control glazing such as low e heavily tinted windows are discussed in terms of their relative impact on cooling load, lighting contribution, glare control and total energy savings.

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