Page 183 - AGC_EN_iBook

183
OPTIMIZaTION OF VISUaL COMFORT aND DayLIGhT aVaILaBILITy
A rst on-site test was carried out with 16 mm thick glass louvres. These were covered with opaque 17 mm wide stripes leaving
15 mm wide transparent bands between them.This test showed that:
–This geometry allows circumsolar light to pass between the opaque stripes when the louvres are at right angles to the direct solar radiation (see the bright lines on the table in Figure 2). –The value of the maximal luminance (sky part of the window) is not acceptable and should be divided by four.
In a second test, conducted at the Peutz laboratories in Mook in May-June 2013, two elements were modi ed:
– the ratio between the opaque and transparent stripes was changed from 17/15 to 19/13;
– an inside blind (‘Verosol Metallized Fabric Silverscreen EB02’) was added.
The new test showed that the bright lines (circumsolar light) on the table had disappeared.The solar factor was 0.203 ± 0.02 (without the inside blind), in line with the previous on-site measurements. The test with the inside blind showed that the luminance was now acceptable from a glare perspective and that the solar factor had dropped to an acceptable value, 0.148 ± 0.02.
Dr Filip Descamps, engineer
Fig. 3. Second test, 4 June 2013 (right image) incident solar radiation 752 W/m2 illuminance on a horizontal outside plane: 8,8814 lux, illuminance on a horizontal inside plane (middle of the table): 865 lux. Sky luminance (left) 2,020 cd/m2 (inside blind version 1), sky luminance (right)
768 cd/m2 (inside blind variant 2, nal selection: Verosol metallised Fabric Silverscreen eB02), luminance of the table 275 cd/m2.