A more environmentally conscious design of passive solar buildings: the role of acoustical insulation with reference to traffic noise.

ln the past, passive solar buildings were specifically designed with respect to energy and thermal comfort requirements. Within this framework a fa9ade able to collect solar energy and bring indoor suitable conditions for occupants was thought of as an optimal building device. On the contrary, little attention was paid to their acoustic behaviour. In general, a high value of the overall thermal trasmittance is applied to a solar wall; if, particularly, this feature is combined with high values of surface density, with the aim of guaranteeing appreciable delays of heat transfer (like in storage walls), the wall generally assures a high level of noise insulation as well. Nowadays technicians are becoming more and more interested in this feature in order to increase the spreading of the use of solar buildings in urban areas: a storage wall, in fact, besides capturing great amounts of solar energy, can also reduce the rising level of external noise (particularly due to the traffic of transportation systems) that enter dwellings causing annoyance to people. Nevertheless, it should be noted that if storage walls are combined with large glazed surfaces, they reduce their acoustic properties greatly. Moreover, if the passive element is totally represented by a glazed surface, such as a greenhouse, the high value of its transmittance is combined with a low value of its surface density, obtaining fast heat transfer, but poor sound insulation. . This evidence makes it necessary to describe the physical behaviour of a passive element both from a thermal and an acoustic point of view. Of course, such a description should be effected for every building module. In fact, due to the little attention paid to the comprehensive problem in the original design, buildings greatly modified to overcome acoustic problems are becoming widespread in urban areas. In this paper some guidelines will be proposed for a method which is able to evaluate the above-cited characteristics in passive solar buildings, compared to conventional buildings, in order to maintain indoor comfort conditions. It would represent an effective procedure for a more environmentally conscious design of solar buildings within urban areas.