A successful application addresses this type of facade not as an isolated subsystem of a building, but as an integral part of the whole building-its construction, its technical equipment, and the overall energy balance. Twin face is best A typology based on the function and construction of the dual-glass facades classifies the various systems and clarifies the different terms used in the design of the multilayered glass skins. Buffer facades have been around for almost 100 years and are still in use. They consist of two layers of single glazing mounted 10 to 30 inches apart. As with insulating glass, the gap between the two layers of glazing is sealed.
Fresh air gets into the building through separate box windows, cut into the two layers of glazing.
This type of facade is useful for buildings in windy and noisy locations or in places with fumes, where fresh air is supplied by the HVAC system because natural ventilation via operable windows is not possible. The warm air from the room heats the inner layer of glass, improving comfort and reducing heat lost through the facade during cold weather. Shading devices may be mounted within the gap, keeping solar gains outside the occupied areas of the building in the summer, where they may be exhausted immediately. In this way, the extract- air facade lightens the cooling load. To supply the necessary air changes mechanically, however, demands energy and prevents occupants from adjusting the temperature of their individual spaces.