Glass architecture: is it sustainable?

Sustainable and ecological are becoming fashionable words for advertising products: ecological car, ecological food, ecological bag, even ecological fuel. To claim that a product is sustainable or ecological helps to sell it. This trend applies also to buildings, and sustainable architecture and sustainable design is becoming a fashionable wording. Sustainable architecture has been, for decades, a small cultural niche ignored, sometimes ridiculed, by the official architectural culture, with very few exceptions. Nowadays, instead, also many famous architects, authors of the highest examples of modern architecture, start to include the word sustainable in the description of the main features of their projects. This is a very important and positive trend, since it is the most effective and powerful drive for, eventually, let sustainable architecture get out from the niche in which has been compelled up to now. The examples of sustainable architecture, published on the most important architectural journals and on large diffusion magazines, are the best mean to diffuse culture of sustainability and induce a replication process also in the far wider field of everyday architecture, the one represented by thousand of more or less obscure professional that are the real actors of the development of the building stock. In the last century, and especially in the last few decades, the architectural language has given more and more emphasis to the lightness and the transparency of buildings, pushing towards fully glazed envelopes. A brief history of the irresistible rise of glass envelopes in architecture is recalled for putting the problem in its appropriate cultural framework. The question then posed is: to which extent fully glazed buildings, especially those designed by famous architects claiming themselves as environment concerned, are actually sustainable? This is not a minor question, given their role of model examples of the rising new culture of sustainable building design. The effectiveness of envelope technologies largely used such as all glazed curtain wall and double skin is discussed, taking into account luminous, thermal and acoustic comfort with its connection to energy use, on the basis of the most recent findings available in specialised literature.