Degradation of Historical Façades Exposed to Wind-Driven Rain: Laboratory Simulation and Protective Measures

Abstract

Wind-driven rain constitutes one of the most significant sources of moisture in buildings [1, 2]. Specific research evidence concerning the influence of wind-driven rain penetration on the durability of historic materials and on the degradation of decorated surfaces, still needs to be comprehensively investigated and fully evaluated. This paper outlines the results from an experimental investigation carried in the climatic wind tunnel. It is composed of three main parts: (1) field-work consisting in a detailed survey of damage to decorated, historical façades; (2) laboratory work concerning the simulation of wind-driven rain, its assessment and validation through comparison to natural weather data; (3) experimental evaluation of protective panels as a temporary protective measure for façades with heritage values. The rain simulation data show good correlation with the Dingle and Lee model [3] while slightly diverging from the raindrop size distribution provided by Best [4] due to the inability of the sprinkler system to generate larger drop sizes for high pressures and the side walls effect in the tunnel. The experimental analysis shows that protective panels consisting of single-ply plastic net with 1x1cm grid fixed to a timber frame, provide a simple and cheap solution for the partial protection of the façades from wind-driven rain. Such panels provide good visibility, water permeability (avoiding wind blocking effects) and at the same time adequate catching of raindrops in order to reduce degradation of the historical façades beneath them. Future work is suggested in order to deepen experimental validation of rain simulation and to evaluate the protective panels in re-al life applications.