Balancing daylight, glare, and energy-efficiency goals: An evaluation of exterior coplanar shading systems using complex fenestration modeling tools

Abstract

Exterior shades are the most effective way to control solar load in buildings. Twelve different coplanar shades with different geometry, material properties and cutoff angles were investigated for two California climates: the moderate San Francisco Bay Area climate and a hot and dry Southern California climate. The presented results distinguish themselves from other simulation studies by a newly developed method that combines three research-grade software programs (Radiance, EnergyPlus and Window 7) to calculate heat transfer, daylight, and glare resulting from optically-complex fenestration systems more accurately. Simulations were run for a case with constant electric lighting and a case with daylighting controls for a prototypical, internal load dominated office building. In the case of daylighting controls, the choice of slat angle and solar cutoff angle of a fixed exterior slat shading system is non trivial. An optimum slat angle was identified for the considered cases. Material properties (e.g., solar and visible reflectance) did not affect energy use if constant electric lighting was assumed, but they did have a significant influence on energy use intensity (EUI) when daylighting controls were assumed. Energy use increased substantially when an additional interior shade was used for glare control.

Side-View Atmospheres under Outdoor Midday High Luminance

“…In order to achieve a balance between spatial contrast and light level. So, a balance between outside view, glare probability, spatial contrast, light level and concentration level on tasting and chatting [39].…”

FAST energy and daylight optimization of an office with fixed and movable shading devices

“…Coplanar shading systems have been analysed by Hoffman in Ref. [9] developing a complex fenestration system not only for daylighting analysis but also for distributing the solar loads on the surfaces of internal environments. The authors found that the paradigm of reducing window to wall ratio for reducing cooling loads could be relaxed employing shading devices.…”

Characterization and data-driven modeling of a retro-reflective coating in Radiance

“…in offices. Yet the supply of daylight and a view to the outside are essential performance criteria in facade design since they address energy efficiency targets as well as the comfort and well-being of occupants [2,3].…”