Due to the industrialization of the 19th century the economy recovered, which led to population growth in Vienna and had a significant impact on architecture. After dismantling the city¿s fortification walls, the Vienna Ring Road became a famous boulevard, where opulent public and private buildings were erected. One of the first buildings was the Heinrichshof, designed by architect Theophil Hansen. During this time more and more prestigious buildings were built along the ¿Ring¿. Famous architects like Otto Wagner, Ludwig Förster, as well as their students, put a new complexion on the Vienna Ring Road. The way of living changed, the bourgois entrepreneurship required a new hybrid architecture, which combined housing- and workspace. Moreover, a new kind of housing was created the so called ¿Mietzinshäuser¿ where the working class lived in crowded and cramped flats. . An essentialelement of these buildings in terms of structure and design were the windows, which will be covered in detail in this paper. This examination aims to show the factors, which had significant impact on the design of windows in the ¿Gründerzeit¿. The first step was to investigate the constructions of these historical windows, called ¿Kastenfenster¿. Another important criterion is the change of building material, such as reinforced concrete, which affected the size of openings. Furthermore, current housing projects in Vienna shall be analyzed to gain more information about the development of windows since the industrialization. Following this theoretical approach, the second part covers the architecture project ¿ a residential building at the Wienfluss with housing- and workspaces.