to this. The Gherkin features triangular windows on the outer skin which skelter up the skyscraper. These windows open according to weather and building data, allowing more or less air to cross flow through the building for ventilation. Technical details The cavity between the two skins may be either naturally or mechanically ventilated. In cool climates the solar gain within the cavity may be circulated to the occupied space to offset heating requirements, while in hot climates the cavity may be vented out of the building to mitigate solar gain and decrease the cooling load. In each case the assumption is that a higher insulative value may be achieved by using this glazing configuration versus a conventional glazing configuration. Recent studies showed that the energy performance of a building connected to a double-skin facade can be improved both in the cold and the warm season or in cold and warm climates by optimizing the ventilation strategy of the facade. Criticisms The advantages of double-skin facades over conventional single skin facades are not clear-cut; similar insulative values may be obtained using conventional high performance, low-e windows. The cavity results in a decrease in usable floor space, and depending on the strategy for ventilating the cavity, it may have problems with condensation, becoming soiled or introducing outside noise. The construction of a second skin may also present a significant increase in materials and design costs. Building energy modelling of double-skin facades is inherently more difficult because of varying heat transfer properties within the cavity, making the modeling of energy performance and the prediction of savings debatable. See also Climate-adaptive building shell Rainscreen References External links Ventilated facades (Wandegar) European Aluminium Association's publications dedicated to Buildings European Commission's portal for efficient facades EN 13830: Curtain Walling - Product Standard> Architectural elements Energy conservation Types of wall Solar architecture