DAYLIGHT VS SUNLIGHT: TECHNOLOGICAL DESIGN STRATEGIES

Solar radiation control, in its two light and thermal components, through the transparent envelope is one of the most complex design elements, especially in the Mediterranean countries. The sun-building relationship is conflicting and needs to be studied in detail; the considerations related to natural lighting and its effects on energy requirements for lighting and visual comfort anyway cannot be done ignoring the ability of the building in order to use the socalled “solar gain”, which is one of the relevant principles of bioclimatic architecture, not only to optimize energy benefits in the winter, but also to save consumption in the summer.
The transparent component plays the role to manage the complexity of such a relationship, implementing a mediation among conflicting needs (fig. 01). Thus it becomes more and more a multifunctional element that plays a strategic role in evaluating the energy quality of a building. In the summer, in climatic conditions such as those ones existing in the Mediterranean area, solar inputs can represent even 70-80% of overall energy requirements, and in this period of the year, transparent components represent the most critical point of the building envelope. The lack of control on these supplies is translated not only into high primary energy consumption for air conditioning in the summer, but it also affects comfort conditions negatively [1].
In this context, it is necessary to individualize appropriate design control parameters for the transparent envelope, in order to optimize the relationship among building, thermal radiation and light.