Pattern 16: Daylight from Top and Side

One of the perennial challenges in classroom daylighting is providing balanced illumination at the “back” of the classroom, opposite the perimeter glazing. Historically this was accomplished by maintaining shallow section depths (less than 24’-0”) and creating relatively high ceiling heights (greater than 12’-0”) with large window areas. However, many contemporary classrooms have section depths of greater than 30’-0” with ceiling heights at less than 11’-0”. Once an interior section depth exceeds 25’-0” the contrast between perimeter zone and core of the building begins to increase substantially during daylight hours. Since the human eye tends to adjust to the brightest location within a space this can cause the perception of darkness in the interior section, and glare due to the lack of luminous uniformity across the section. To address this condition, a second (or multiple) source of daylight can be added where possible to provide supplemental illumination and to wash the “back wall” with light.

In this case we explore a range of classroom section designs that include: sidelighting only, north-facing transparent roof monitors, south-facing diffuse roof monitors, diffuse horizontal skylights, and increased perimeter glazing. It is important to note the presence of translucent glazing in all top-lighting configurations where direct beam sunlight has the potential to enter the classroom during hours of instruction. For this simulation diffuse glazing is simulated at a 50% visible light transmission.

There are three primary goals for the effective daylighting of classrooms. The first is to control direct sunlight during all occupied hours. The second is to provide balanced luminance on interior surfaces, especially between the perimeter and key interior surfaces within the classroom.  The third is to provide sufficient ambient daylight illumination for visual tasks. Since classrooms are predominately used during daylight hours, they provide an excellent opportunity for lighting power savings from daylight responsive controls.

The case study example is Chartwell School, designed by the EHDD Architecture. The site receives a range of sky cover including coastal fog and heavy cloud cover with periods of clear skies. For this reason we show each design case under both overcast and clear skies. The ambient illumination criterion is shown at 300 lux.