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6 Daylighting Example

Daylighting is an emerging area of Monte Carlo surface to surface transport that is gaining increased acceptance from the building design community. The essence of daylighting is to use the structure of the building to capture and distribute internally within the building the natural sunlight, in an effort to live in harmony with the environment as opposed to butting heads against it. Daylighting design involves the careful design and placement of windows to capture the sunlight and the implementation of an internal distribution system within the building. Issues which obtain are: (1) effecting the design so as to prevent excessive glare and (2) the degree to which electrical lighting energy is displaced, resulting in reduced energy consumption and cost savings. As we shall indicate, Monte Carlo offers some pronounced advantages over traditional design techniques, due to its ability to simulate accurately the interaction of sunlight with sophisticated building materials

To illustrate the daylighting process, we provide Figure 22, depicting a cross sectional view of a south-facing room of a typical commercial building. A lower view window 3' in height is located 4' above the floor. This view window provides light to about the front one-third of the room. Indeed, the problem with previous daylighting designs is that strategies to get the light into the rear of the building have been woefully ineffective. To address this limitation, our strategy is to use a specular light duct to light the rear two-thirds of the room. The light shelf begins 8' above the floor and is about 2'' thick (a suspended ceiling). The height above the light shelf is 3', making the total height of the room 11'---suitable for running ducts for a heating/cooling system in the space (11' heights are common in commercial construction). Sunlight entering the upper light duct window encounters the aluminized mylar coating the inside of the light duct, is specularly reflected (analogous to the reflection from a mirror) and traverses the light duct until it strikes the tilted diffuse reflector at the rear of the light duct. Normally, this is a white surface, painted with a flat paint to reflect the light diffusely down and forward toward the front of the room. Monte Carlo offers the ability to simulate specular reflections, which provide just such a means to get the light into the rear of the room.

Figure 22: Cross Sectional View of Daylighting Geometry.