Cladding is the process of applying one substance over another to create a sheet or skin. Cladding is used in construction to provide thermal insulation, weather resistance, and to improve the appearance of buildings. Cladding may be made of a number of materials, including timber, metal, stone, vinyl, and composite materials such as aluminium, wood, cement-recycled polystyrene blends, and wheat/rice straw fibres. Rainscreen cladding is a form of weather cladding that provides both protection from the elements and thermal insulation. The cladding does not need to be waterproof; it is merely a control factor that can be used to steer water or wind safely away from the building structure in order to control run-off and prevent it from infiltrating the structure. Cladding may also be used to control noise, whether it's coming in or going out. By nature or substance, cladding may become a fire hazard.