Using Radiance to Estimate Transmitted Solar Radiation Energy for Thin Perforated Screens

Abstract

Design of shading systems is essential, since they plays an important role in the modulation of daylight and solar gains. Yet, current simulation tools are not capable of providing accurate results for both daylighting and energy performance simultaneously, especially when complex geometries are present. This work investigates whether shading coefficients (SC) can be applied to evaluate the performance of thin screens, and it compares the results to those obtained through other methods, such as the use of a fixed transmittance value over the whole year. Results showed that hourly SC can take into account the variability of total transmitted solar radiation throughout the year. As a result, the cooling energy reached reductions of up to 22 % in comparison to the use of a fixed transmittance value. SC also enabled the assessment of inter-reflections within the PS-glazing system, especially those resulted from varying the distance between the PS and glazing.

A Comprehensive Evaluation of Perforated Façades for Daylighting and Solar Shading Performance: Effects of Matrix, Thickness and Separation Distance

“…Nevertheless, PS design parameters such as the distance between the glazing system and the inner face of the screen is also a prominent factor to enhance screen performance. A first overview [14] of the mentioned parameter showed that interreflections within the PS-glazing system constituted a large portion of the total irradiation falling on the glazing when a thin PS was placed 60 cm from the glazing. From the previous work, it was also found that inter-reflections within the PS-glazing system accounted from 5% to 16% of the total annual irradiation, so they should not be ignored when analyzing the energy performance of thin screens.…”