A window is an opening in the wall of a building that allows light and air to enter a room and people to see out. At previous times in history they were merely small oval or square holes in the walls. They are usually glass or a strong, transparent plastic. The word was first recorded in the early 13th century, and originally referred to an unglazed hole in a roof. Evidence of glass window panes in Italy dates back nearly 3000 years.
Various types of windows were invented that allowed light but not weather to pass into a building: mullioned glass windows, paper windows, and plates of thinly sliced marble. In England, glass became common in the windows of ordinary homes only in the early 17th century. Modern-style floor-to-ceiling windows became possible only after the industrial glass making process was perfected. Modern windows are customarily large rectangles or squares with glass surfaces. Churches traditionally have stained glass windows.
The term Passive house (Passivhaus in German) refers to the rigorous, voluntary, Passivhaus standard for energy use in buildings. It results in ultra-low energy buildings that require little energy for space heating. A similar standard, MINERGIE-P®, is used in Switzerland. The first Passivhaus buildings were built in Darmstadt, Germany, in 1990, and occupied the following year. In September 1996 the Passivhaus-Institut was founded in Darmstadt to promote and control the standard. Since then more than 6,000 Passivhaus buildings have been constructed in Europe, most of them in Germany and Austria, with others in various countries world-wide.
Despite the name, the standard is not confined only to houses. Several office buildings, schools, kindergartens and a supermarket have also been constructed to the standard. Although it is mostly applied to new buildings, it has also been used for refurbishments.