Pattern 10: Toplighting

Toplighting is a term used to describe introducing daylight from above, usually through the roof. This is often accomplished with skylights or roof monitors and is sometimes in combination with clerestory windows. The term skylight to floor area ratio (SFAR) is often used to describe the amount of skylight area installed relative to the floor area it is meant to provide daylight for. In this pattern we explore combinations of skylights, roof monitors and clerestories so we use the term glass to floor area ratio (GFAR) instead. The main advantage of toplighting is that it provides access to the brightest part of the sky, the zenith, and has more hours of solar exposure than any other glazing orientation. That means that a substantial amount of daylight is available for long durations and can be delivered in a uniform manner. However it does not usually come with substantial view access to the outdoors. When designing toplighting, it is important to consider the size and placement of the apertures, their proximity to adjacent reflective surfaces, line of slight to the apertures so as to avoid glare potential and the role of ceiling height.

This pattern analysis explores the effect of different combinations and amounts of skylights, monitors and clerestories. The case study used to examine these design alternatives is a hypothetical warehouse space of the same dimensions as Yesler Community Center in Seattle, WA, designed by Mithun.

This pattern sequence explores toplighting design under overcast sky conditions during September at noon with workplane illumination data represented in lux. The overcast sky was selected because it represents a worst case scenario that must be considered in most US climate regions. Warehouse spaces with racks require additional attention be paid to daylighting the vertical surfaces of the storage racks and these spaces often have rather low ambient lighting design criteria. In this pattern, we selected 150 lux of horizontal illumination as one of the daylighting design criterion. The percentage of floor area above this value is presented for each permutation.