A facade is, by extension, any exterior wall of a building; Although by default, when speaking of facade, alludes to the front or main, indicating more data otherwise (rear facade, North facade, etc.) The facade is subject of special care in architectural design, as being the only part of the building seen from the outside, many times is virtually the only resource available for express or characterize the construction. The expressive component is so ingrained in the concept of facade, which sometimes refers to as the ‘fifth facade’ cover when it possesses an aesthetic intention. The facade has experienced multitude of transformations throughout history by its condition of support or canvas for the different architectural styles. However, the most profound changes have been due to the evolution of building techniques. The facade has traditionally been at the same time the structure and the closure of the building, and therefore the ability to open holes for illuminate, ventilate, or have views to the outside has been limited. The historical development of the facade has therefore been a technological race for expanding these needed openings. The size and arrangement of the holes has been fundamentally conditioned by two constraints: the ability to open them (evolution of the load-bearing wall), and the ability to protect them (evolution of the glass).

Although the existence of the glass is documented since more than 5000 years ago in Mesopotamia and Egypt, 2 and while the Roman Empire disseminate it throughout Europe already in 300 BC, 3 no one can speak of a relevant use of this material in the building until the 7th century and the Arab expansion. From then on, the possibility of openings openings in facade began to generate a growing interest. In ancient Rome, before the popularization of glass, was used as a glazing lapis specularis; a type of translucent type of the selenite Gypsum Rock.