These data illustrate a typical white louver blind positioned to eliminate direct sun penetration. It reduces the floor area that is above 300 lux from 96% without blinds down to 71% with blinds down. However, it is a reasonable scenario to solve potential glare while admitting as much daylight as possible, given this blind type. It assumes an active user to adjust blinds given sky condition and sun position.

These data illustrate an inverted blind, or a ‘light redirecting’ blind on an overcast day. Due to the overcast sky, the floor area that is above 300 lux decreases from 89% under a sunny sky to just 21% under an overcast sky. Blinds would ideally be raised to increase daylight penetration, however users often leave blinds in the same position regardless of sky condition or sun position.

Light redirecting blinds are often incorporated with automated motorized controls, which would increase the performance to 44% of the floor area above the criteria (See x.2 No Internal Shading – Overcast).

These data illustrate light redirecting blinds in a daylight-enhanced configuration, just like the previous scenario, however interior furniture is included. This represents the as designed case. The automated blind control system aims to keep direct sun out of the spaces while allowing daylight to wash the ceiling from the open blinds at the top of the window. It is notable that simply by adding office furniture, the floor area above 300 lux decreases from 46% to 36%. This is a dramatic reduction, even though the partitions are partially glazed and remain rather low. The effect of different office furniture design is examined in “Pattern x Office Furniture”. Partitions are almost never considered as an integral part of a daylighting design but they play a substantial role in determining the success of a daylighting project.

These data illustrate the same scenario as the previous case, except under an overcast sky condition. With blinds down and closed 0% of the floor area is above 300 lux, completely defeating the daylighting design.

These data illustrate fabric roller blinds with 5% openness factor under an overcast sky condition. The floor area above 300 lux decreases from 36% under a sunny sky condition to 0% under an overcast sky condition, completely defeating the daylighting design.

These data illustrate ‘bottom up’ fabric roller blinds with 5% openness factor. In this case the blinds are drawn 70% of the way up the window to block most of the direct sun. However the direct sun is now positioned deeper within the space. This can be considered a benefit to total daylight penetration however might cause glare deeper within the space than a top down blind. Bottom up blinds are ideal to provide privacy/comfort for perimeter users at the bottom portion while still allowing for daylight performance. They can also work effectively in conjunction with an exterior overhang that shades the top part of the window such that the blind can block direct sun from entering the bottom portion of the window. One benefit of fabric blinds as that when they are closed, some sense of the view is maintained. However, this access to view also provides line of sight to the disc of the sun, which can produce debilitating glare despite the small openness factor of the fabric. Approximately 53% of the floor area is above 300 lux.