The second field of interest in the scanning sky simulator applications concerns the assessment of a specific daylighting system designed for buildings at the design stage.

The analysis is aimed at determining the most suitable solution in order to maximise the entrance of diffused skylight and meeting the daylight factor standard requirements, while screening at the same time direct component of solar light, so as to control overheating and glare phenomena. Forthis kind ofstudies, quantitative and qualitative data are collected for a larger number of conditions with the aim of reproducing to a greater extent daylight variations during the year, within an indoor environment. Consequently, the analysis protocol is based on the simulation of different sky condition (clear, overcast, intermediate), periods of the year (December, March and June) and hours of a single day (from sunrise to sunset), in order to appraise the environmental variations for a minimum and a maximum availability of external natural light, for different weather conditions and periods of the year.

These aims were at the basis of the study carried out for the daylighting design of the new Faculty of Maths, Natural Science and Physics library in Alessandria, which is presently at a design stage. The daylighting system conceived forthe library is a large south-oriented glazed surface equipped with a mobile micro-perforated aluminium louvershade. Quantitative and qualitative analysis were carried out for different louver tilt angles, in order to verify both the effectiveness of the screening effect and the internal availability of daylight during different periods of the year.

A similar procedure was used to assess the aluminium louvered shading system designed for the sky-light for of the new SACMI headquarter in Bologna. In this case, the screen was supposed to be fixed, so different louver tilt angles were tested so as to determine a suitable position representing a fair compromise forthe entire year between screening of direct sun-light and letting diffuse skylight in.

1. Conclusions

The paperdescribes the potential applications ofthe use ofscaled models and artificial scanning sky in the fields of daylighting design and research.

In particulartwo different categories ofapplications are highlighted: the comparison of environmental performances ofdifferent daylighting systems and the optimisation, during the design stage, of a specific daylighting system.

For the first category an exhaustive example, concerning the comparison of lighting environmental performances ofdifferent traditional shading devices, is presented. The systems, designed to ensure an equal energy performance (similar SF for both summer and winter period) were applied to the model of a sample classroom and tested under the artificial sky and sun. Results obtained through the simulations ofdifferent sky conditions and Sun paths showthe differences in the lighting performances, emphasising in particular best results for the horizontal fins and the external light shelf (considering daylight quantity, daylight penetration and uniformity over the cross section as evaluation criteria).

The quantitative and qualitative effect of different shading finishing was also assessed. Specularand semispecularfinishing used for internal light-shelves always produced higher illuminances and contributed to increase daylight penetration towards the rear part ofthe room. Nevertheless such finishing, and in particularthe specularone, created, when reached by direct sun light, high luminance areas on the ceiling, which can be a potential cause of discomfort glare.

For the optimisation of daylighting systems during the design stage, the use of a scanning sky simulatorallowed evaluation ofdesigned systems and comparison ofdifferent solutions: for instance the most effective tilt angle forfixed louvers of a shading device designed fora building skylight could be determined.

In conclusion, from the experiences carried out at the Daylighting Laboratory in Turin it comes out that the use ofscale models under artificial sky and sun is a useful tool for both daylighting design and daylighting research as it allows an accurate simulation ofdifferent daylight conditions (both standard or experimental), a quantitative and qualitative evaluation oflighting environmental performances and definition ofdaylighting systems’ geometric and photometric characteristics.