Titanium dioxide nanotechnological coatings for preventive envelope maintenance

This paper illustrates the result of a wide experimental campaign focused on the application of titanium dioxide self-cleaning coating for envelope maintenance. Such coatings have proven to be effective with regards to soiling deposition and build-up on façade surfaces over a time span equal to at least three years. Applications considered within the frame of this study span from opaque to transparent and active envelope components, where the consequences of soiling accumulation are likely to affect the overall building performance. Effects of functional materials application are presented through comparison of surface behaviour with respect to soiling accumulation between non treated cladding elements and the corresponding coated samples, that were subjected to the same environmental conditions. This extensive comparative study was useful to quantify actual self-cleaning performance of envelope materials and determine the convenience of coating application according to the specific substrate and exposure context. Thanks to the self-cleaning behaviour, surfaces are enabled to be cleaned under the sole effect of rainfall, without requiring additional manual work. This represents a significant opportunity for sustainable management of the building envelope, saving natural resources as water and limiting the use of detergents and other specific cleaning products. The integration of self-cleaning coatings represents an interesting option for active envelope systems and also complex geometry building skins, where manual and mechanical cleaning operations seldom represent a viable strategy to ensure building performance over time. The integration of such coatings as preventive maintenance strategies brings about consistent advantages related to the assured cleaned appearance of the façade over time, together with medium and long-term savings related to the avoidance of costly cleaning operations on envelope components. This applies especially to existing buildings, where façade access systems are often not present and whose integration is not possible due to structural or architectural constraints.