4.1. Blind optimization

As explained in Section 3, the lighting problems that bother LESO-SEB occupants the most are due to daylight overprovision. It is therefore necessary to take a close look at the glare protection devices installed within the ADS-equipped office rooms, to identify their weak spots and to find ways to optimize them. Figure 2(left) shows the faqade of the LESO-SEB. Each office room is equipped with two grey fabric blinds which can be controlled via four control switches inside the office (one “up” and one “down” switch for each blind). The upper blinds cover the actual ADS and are regularly used to reduce the illuminance levels when the users feel that there is too much daylight in the office or that the office seems too bright, and they are also used for glare protection (i. e. to block out direct sunlight). The lower blinds are used less frequently by most users and serve mainly for glare protection. However, the interviews carried out during this study have revealed one important weak spot of this blind configuration: For technical reasons, small gaps occur

between the blinds of the different offices (see Figures 2(left) and 2(right a)) ). At some moments of the day, these gaps can lead to glare problems in an office even though its respective blinds are lowered. These glare problems get even worse when the blinds of a neighbouring office are left open (e. g. due to occupant absence in this office). Figure 2(right b)) visualizes one potential way to deal with these problems: Instead of installing all blinds at the same distance from the facade (as illustrated in Figure 2(right a)) ), every second blind could be shifted away a small distance from the facade. Like this, the gaps could be closed. On the other hand, such a modification might lead to shading of offices by their neighbouring offices’ blinds and therefore to conflicts between the building occupants.

Figure 2: Left: The LESO-SEB’s anidolic facade with upper blinds, lower blinds and gaps between the blinds. Right: Schematic view of existing and optimized blind configuration.

Another possibility to deal with the above mentioned problems related to gaps between the different external blinds would be to improve an internal, manual curtain system made out of numerous long fabric curtain elements (see Figure 3( left) ) already installed within the offices. The occupants can manually open and close these curtains and also tilt the curtain elements around their vertical axes. However, these curtains do not seem to be frequently used and were described as “quite annoying” by some interviewed occupants. It might be indicated to think about installing a more adapted blind system here. Another weak spot pointed out by some occupants are the small lateral windows that exist between some of the different LESO-SEB offices (see Figure 3(right)). These lateral windows can sometimes cause glare to the occupants when the external blinds of their neighbouring office are open. The resulting annoyances could easily be avoided by installing an additional small blind at this point of each office.