In order to analyse the impact of the surfaces reflectance, daylight factors were monitored from 10.00 to 17.00 under overcast sky in two different cases. The relative difference between daylight factors observed in the test module and in a first scale model (cf. Figure 1.a), showing larger differences of surfaces reflectance (cf. Table 1, Scale model 1), were used to assess this impact. A subsequent improvement of the scale model by the way of a closer match of the surfaces reflectance (cf. Table 1, Scale model 2) was used in an attempt to reduce the divergence between the two kinds of daylight factors. To avoid any bias due to the sky luminance distribution, all models were placed next to the test module (cf. Figure 1.b); measurements in the model and the test room were carried out simultaneously.

Scale Model Location

The scale model location was considered as one possible main source of error, through the impact of different sky view factors and external reflected components : it was carefully analyzed by placing scale models close to the test module, but at different distance from the later (cf. Figure1.b). Work plane illuminances were monitored from 14.00 to 16.00 under clear sky, enhancing the contribution of the external reflected component, their relative divergence being compared. The scale model was placed first in another module, located only a few meters away from the test module, the corresponding window plane
being fully coplanar; the model was moved next to the test module in order to make it benefit from identical sky view factor and external reflected component. Scale model 2 was used in this case, to avoid any bias due to the surface reflectance; measurements in the model and the test room were carried out simultaneously.