These awnings are operated by an electric motor, generally hidden inside the roller bar of the awning. The arms open and close the awning at the touch of a wireless remote control or a wall-mounted switch. Modern awnings may be constructed with covers of various types of fabrics, aluminium, corrugated fibreglass, corrugated polycarbonate or other materials. High winds can cause damage to an extended awning, and newer designs incorporate a wind sensor for automatic retraction in certain conditions. Modern awnings are rated for wind tolerance based on width, length, number of supporting arms, and material. Modern awning design incorporates urethane compression joints, steel support structures, and wind sensors. Such designs are currently in use at the White House, Grand Central Station, and the Kremlin. Aluminium awnings have long been popular in residential applications throughout the world. They are available in many colors and are usually painted with a baked-on enamel paint. Among the many benefits of these awnings are cooler temperatures inside the home, shade for your patio, extending the life of furniture and window treatments. Possibly the most beneficial feature of the awnings are the fact that they have a usable life of well over 40 years. Some aluminum awnings are designed to be folded down and fastened to protect windows in case of storms such as hurricanes. Retractable awnings are now becoming very popular with homeowners in the United States. They have been popular in Europe for many years, due to higher energy costs and lack of air conditioning. Some retractable awnings can include photovoltaic cells or rollable solar panels to generate electricity. Retractable awnings can include the following types:  Retractable patio cover systems are the latest "entry" in to the retractable market. Most of these systems are water-proof as compared to water-resistant (lateral arm awnings) and therefore allow no water penetration through the fabric "roof" section. These systems meet Beaufort scale wind loads up to Beaufort 10 (55 - 63 mph) depending on model and size. Another advantage of retractable patio cover systems is that they can be enclosed on the front and sides using solar shade screens. This allows for an "outdoor room" that can be heated in the winter and air conditioned in the summer. These are a modern version of the old storefront crank-up awnings of the last century. The two, three or four tension arms (width dependent) and a top tube are supported by a torsion bar.