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Solar optical properties of roller shades: modeling approaches, measured results and impact on daylighting and visual comfort.

Number: pap. 3389

Author(s) : CHAN Y-C., TZEMPELIKOS A., PROTZMAN B.

Summary

One of the challenges with dynamic facades is how to balance the need for daylight versus reducing overall energy use while ensuring comfort for the occupants. This requires detailed knowledge of the solar optical properties of fenestration, which affect the transmission of solar gains and daylight. Although there is adequate information, databases and tools for spectral and angular glazing properties, there is less available information on shading systems. Complex fenestration systems, such as venetian blinds, have been studied and characterized using advanced experimental and computational methods such as bi-directional distribution functions. Nevertheless, there are very limited studies on the solar-optical properties of roller shades, which are very common in commercial buildings. In most existing studies and simulation tools, the properties of roller shades are assumed constant and diffuse. The only available semi-empirical model showed that roller shade properties may have strong direct components and angular variation, depending on the openness factor and fabric color (equivalently, direct and diffuse transmittance). These can affect the energy and daylighting performance, as well as their impact on glare. This paper first provides an overview of current approaches for modeling solar optical properties of roller shades, including advantages and limitations. Then, integrating sphere measurements were conducted to determine the detailed solar optical properties of different products. The results are compared to previous findings and provide useful information about direct-direct, direct-diffuse and angular properties of roller shades, depending on openness factor and color. Finally, the impact of detailed solar optical properties on daylight performance and glare is evaluated using annual simulation results for different fabrics. The results show that detailed shading properties should be used for a more realistic evaluation of the impact of shading on daylighting and visual comfort.

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Pages: 14 p.

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Details

  • Original title: Solar optical properties of roller shades: modeling approaches, measured results and impact on daylighting and visual comfort.
  • Record ID : 30013779
  • Languages: English
  • Source: 2014 Purdue Conferences. 3rd International High Performance Buildings Conference at Purdue.
  • Publication date: 2014/07/14

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