Facade involves window wall , cladding elements and curtain walls which generates the exterior envelope of the building. The curtain wall systems now possess structural importance equivalent to that gained by other structural elements of the building. As it has a higher exposure to exterior atmosphere , it has to be properly designed , installed and maintained keeping in mind the functionality and sustainability.
Functions of Curtain Walls in Buildings
Elimination of Water Penetration
Water penetration is the fundamental function of a facade. Here bringing a completely impermeable sealed curtain panel system is not possible. Hence two stages of prevention are placed. Primary level where complete defense of water is conducted and if that fails a secondary level where a direction to let percolated water to drained out has to be provided.
This function is more of an environment concern to reduce the emission of carbon dioxide due to rate of heat loss or gain within the external and internal environment.
Resistance to wind , thermal and acoustic action
Wind actions are transferred by the cladding system to the building floors which act as a linear support. Building cladding systems formed of large panels are usually one-way spanning. Each floor level therefore supports one level of wind load on a building.
Thermal insulation function which is strictly necessary for a facade in order to reduce energy consumption and CO2 emissions. Insulated materials are provided to both opaque as well as transparent areas.
Acoustic Insulation too is necessary between the inside and the outside environment mainly city centered building. Massive structural elements possess higher acoustic insulation like masonry or concrete structures.
This can be reduced by providing a selective solar control coating on one of the surfaces of the glass. This coating is called selective because solar radiation of different wavelengths is selectively allowed to pass through the coating: visible wavelengths of light are allowed to pass more freely than infrared wavelengths. For example , spaces for exhibitions or displays of materials can undergo degradation due to ultraviolet radiation.
For this a UV-inhibiting film can be applied to the surface of glazing.
Structural Behavior of Curtain Walls
Curtain walls are considered as structural elements of a building. As it acts as a partition between exterior and interior environment of the building , it has a role in transmission of loads acting for structural stability.
It transmits wind induced loads to the primary structure. It also resists the seismic accelerations keeping the occupants comfortable. Other than this it has to resist gravity loads coming over it.
When considering the durability of the building , curtain walls play an efficient role in adapting to different temperature ranges. This is because of the case in high rise building , as the number of floors the temperature seems high and would be a risk factor for the occupants working in those floors. It is also required to have resistance against water penetration and hence stop corrosion.