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This paper presents, beyond the chronological aspects, an exposure that facilitates the awareness of the historical evolution of the XL019 concept applied to the buildings. Indoor comfort is not achieved unilaterally to fulfill certain ergonomic demands but it is inherently followed by economical optimization and increasing of energy efficiency.
Undoubtedly, the evolution of the concern in the energy efficiency of buildings over time has many dimensions and ramifications, but the purpose of this study is only to emphasize the key moments in the evolution of energy efficient buildings. It covers issues that have had an important impact, durability of use and mass adoption. There are many techniques to improve the energy efficiency of the buildings and this study does not aim to present them all, because the evolution of the concepts is intended to be observed globally. This paper tries to identify the degree of impact and of innovation at their time, related to the energy consumption reduction. It also presents the degree of preservation and classicization and how much are found in the exigencies of the present, aiming to find some invariants of design.