Highly efficient diffuse glass for greenhouse coverings

Nowadays, among the several types of horticultural diffuse glasses for greenhouse coverings, glass products having an anti-reflective (AR) permanent coating on both sides of the glass are more and more used in new built greenhouses to maximize the daylight transmittance, hence the crop yield. This article highlights the huge gap of durability between different technical solutions providing AR functionality to the glass surface, mastered by the glass makers. The work reported here has been the support for the development of the Albarino^® range of AR glasses of Saint-Gobain for the greenhouse application. Different ageing test methods have been used, to establish the behaviour of three different AR glass products exposed to either climatic, chemical or mechanical stresses, representative of the greenhouse application. One clear conclusion is the poor durability of the AR acid-etched glass type. The second important result is that two AR sol-gel glasses with similar initial transmission performance may substantially differ from the durability point of view. In particular, it is blatant that differences after ageing are far more important than the differences of the initial performances. Therefore, it can be concluded that durability is a key criterion of choice to be carefully considered in the selection process of the AR glass as covering material of a greenhouse. A long-lasting, very resistant AR glass appears clearly as a great valuable asset for the grower.