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Daylighting simulations with BSDFs
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Daylighting simulations with BSDFs
Ocean 2016 R5 brings a new feature, the Igloo Matrix BRDF model, which allows using data from LBNL WINDOW

Ocean 2016 Release 5 has been made available last week. It brings a new feature, the Igloo Matrix BRDF model, which allows using data from the LBNL WINDOW software (IGDB database).

We have tested it on a 3D office model, with a double glazing unit (DGU) window comprising a high performance solar control coating. The sun is in front of the facade, at 44° elevation, and sky conditions are very clear (Hosek-Wilkie model, turbidity 2.0):

Office render with open curtains, in bright sky conditions

Office render with open curtains, in bright sky conditions

By changing the instrument type to “Perspective Irradiance View”, we can visualize the illuminance of the office surfaces in 3D. This includes the direct sunlight filtered by the coated glazing, diffuse light from the blue sky, and all the indirect light resulting from multiple bounces over the office surfaces. The workspace illuminance reaches 40 000 lux, while some areas are at 1000 lux, which makes it highly uncomfortable.

Office daylighting illuminance simulation with open curtains

Office daylighting illuminance simulation with open curtains. Color scale in lux

At that point, the office users will likely close the window curtains. Depending on their opacity, they will find a compromise between direct sun glare and a room too dark by adjusting the curtain height:

Office daylighting illuminance simulation with a half closed curtains

Office daylighting illuminance simulation with a half closed curtains. Color scale in lux

The simulation shows that illuminance levels on the workspace are now around 1000 lux. There are still very bright areas in the room exposed to direct sunlight at 40 000 lux, which may cause glare if they are in the field of vision.

On the next simulation, we opened the curtains again, and applied a sun redirector film on the glazing. These films are made of tiny horizontal prisms which redirect downwards sunlight to the ceiling, providing a more diffuse light in the room:

Office daylighting illuminance simulation with a sun redirector film applied on the glazing

Office daylighting illuminance simulation with a sun redirector film applied on the glazing

The illuminance levels are now much more homogenous : most of the room is between 4000 lux (red) and 10000 lux (orange).

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