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Solar Daylighting in Schools

A study was conducted to compare the performance of three designs for daylighting in classrooms.  The three systems included:

1.    16” wide shelf—a prototype light shelf (Fig. 1) was built using box aluminum channels with a reflective mylar film (2 mm thick, 90% reflectance). 

2.    24” wide shelf—a similar prototype constructed of box aluminum frame and reflective mylar film.

3.    LightLouver System—A unit of angled, reflective blades similar to a fixed venetian blind.  The patented, passive optical design redirects daylight deep into a room while eliminating all direct sunlight penetration onto work surfaces. The angled blades reportedly reflect up to 76% of direct sunlight into a room, and on overcast days they are said to throw around 54% of the available light inside.

Image of light shelves inside the classroom. The reflective top surface of the shelves is visible.

Figure 1. 16” light shelf

The first two systems were fabricated locally, while the third system was purchased directly from the manufacturer.  All three systems were installed in adjacent rooms, with a fourth room used as a control. A grid of light measurements were taken in the fall and early winter on cloudy and sunny days, during the morning, midday, and afternoon (Fig. 2). The light levels were analyzed to determine which system provided the most light gain.  The conclusion of this study was that the 16” light shelf provided the most light gain through these windows. 

Color contour plots comparing light distribution provided by the 16" and 24" light shelves to that of the Light Louver system and to a control room without light shelf. The 16" light shelf bounced light the deepest into the room.

 Figure 2. Average light distribution in rooms.

 

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