Illuminazione naturale e benessere indoor: valutazìone ed aggiornamento degli strumenti normativi locali

The present research aims at analyzing the relationship between the project, the natural lighting, and the residential indoor environments. The reasons that lead to this research are to be found in the complex relationship between natural lighting, sunlight, and health in indoor environments and in the oncoming research of project and technological solutions in order to guarantee an adequate level of indoor health while preserving the environment. After describing the physical and hygienic characteristics of the natural lighting, the various laws (in particular the Italian ones) were taken into account according to the definition of the minimal performance and project requirements concerning the natural lighting of the indoor residential environments. The minimal requirements for the Coefficient of Daily Lighting – CDL (illumination levels on horizontal surface inside the room / illumination levels on the same horizontal surface situated outside, closed to the windows) were satisfied on average during the project phase with a lighting ratio (area of the windows hole / floor area) more than 12.5% (1/8) for every habitable rooms. An analysis based on CDL was then performed, since it is able to estimate the level of lighting of different indoor environments for dimensional and geometric aspects, for specific characteristics of each window opening and for the context situation of the building. During the analysis, the CDL of some rooms (42) was taken and analyzed according to the specific features of the indoor environment in order to evaluate the appropriateness of the current laws on the subject, which are too often recognized as only prescriptive. In conclusion, the current laws, considering the complex reciprocity between natural lighting and indoor environments, are not very adequate in orienting the architect towards more innovative quality and performance oriented choices. According to these deficiencies, it was proposed to integrate those laws with more adequate indications for the computation of the windows surface, and to write a document on the project phase in order to support the architect in her architectonic choices. Such instrument, coming from work in depth of analysis and observation of the behaviour of the natural light in order to better understand the factors able to condition its penetration into the indoor environments, could then be used along with the legislative instruments in order to improve those aspects of indoor health related to natural lighting.