Experimental analysis of marble building envelope degradation caused by acid rain: optic characteristics and color change

Marble envelopes represent a relatively common architectural solution both in the past and nowadays, characterizing numerous buildings’ façades. At the same time, considering white marbles, these envelopes are able to mitigate Urban Heat Island phenomenon and to reduce solar heat gains, thus improving indoor thermal comfort for occupants. This advantage is made possible thanks to their intrinsic optic characteristic of high solar reflectance. However, current rates of environmental pollution cause a faster degradation of the marble elements, implying different consequences: i) changes in optic characteristics; ii) changes in color and, therefore, iii) aesthetical modifications to the initial appearance of the façade. Not only could the appearance of the marble façade be modified, but also its reflectance characteristic, which is linked to the energy efficiency of the solution. These deterioration issues need to be further investigated in order to predict both aesthetical and energy performance of such facades when degradation occurs. Therefore, in this research, surface modifications of marble materials are experimentally analyzed by mean of in lab accelerated weathering and consequent surface examination in terms of color and optic characteristics change. Results quantify the extent of such degradation caused by acid rain on considered marble surfaces, in order to provide useful information both for building designers and for producers of marble panels for building envelope applications, and to quantify their optic-energy performance during the course of the years.