A Study on the Blind-Type Light Shelf System for Improvement of Indoor Uniformity Ratio of Illuminance

Abstract

Purpose: Light shelf systems can reduce the energy required for lighting by facilitating natural light ingress deep into a building. However, while they reflect a large amount of light into the building, they tend to create a low uniformity ratio of illuminance, and their indoor illuminance is not adjustable. Also, they are seldom used in architectural design due to their aesthetic disadvantages. This study proposes a blind-type light shelf system, consisting of multiple light shelf slats and blind slats, in order to solve the lighting problem of the light shelf system by modifying it with a blind system to reduce the energy required for artificial lighting. Method: Three combinations of blind-type light shelf system (no light shelf, 50 mm slats, and 100 mm slats) were proposed, and their performance was evaluated based on illuminance and uniformity ratios achieved in the indoor environment. Results: Case 2(50 mm slat) slatshowed an improvement, compared to the unmodified window, of up to 3.2 times while Case 3(100 mm slat), showed an improvement in the uniformity ratio of up to 2.8 times. With the installation of a blind-type light shelf system, the uniformity ratio can be ~3.2 times higher in the winter solstice and summer solstice, resulting in more light penetrating deeper into the interior of the building. The blind light shelf system was more effective in Case 2 than in Case 3 because it was better to have more light slats, despite the narrow slat width.