In today's modern homes, windows come in many shapes and sizes - rectangular, square, triangular, octagon or even round. The more unique shaped windows usually don't open, however, but merely serve to let light into the building.
Windows that open to allow ventilation come in five basic styles:
- double or single hung windows
- sliding windows
- casement or rollout windows
- awning or hopper windows
- louvered windows
Double or Single Hung Windows
This style is a traditional design in which the window slides open vertically. A sash is the framework into which panes of glass are set; on a double-hung window, both sashes can slide, allowing you to open the window from the top and the bottom to improve the circulation of air. On a single hung window, only the bottom sash slides upward - the top half of the window is permanently fixed. Screens are usually installed on the outside of the window frame.
Sliding windows feature sashes that move horizontally instead of vertically. Both sashes are movable in a double-sliding window while only one sash slides in a single-sliding window.
Screens can be placed on the exterior or interior of the window unit.
Casement or Rollout Windows
Casement windows are hinged at the sides and open outward. They can be pushed open or cranked open with a handle. Screens are placed on the inside of the window. Virtually the entire casement window area can be opened, but because it sticks out from the house, it can block breezes blowing from the side.
Rollout windows can be described as half of a casement window. They are hinged from one side only and are often found in bathrooms. They usually have a handle that turns to open the window.
Awning or Hopper Windows
Think of a rollout window mounted sideways, and you have an awning window. Awning windows are hinged at the top and open outward, with screens on the interior. When open, the glass protects the opening like an awning would from rain.
Hopper windows are the same design, only hinged at the bottom instead of the top. They open inward and have screens on the outside.
Awning or hopper windows are often found in basements. When placed above doors, they are called transoms.
Louvered windows have several strips of glass that are tilted open to allow ventilation. The glass is maneuvered with a rollout type handle or a lever.
Because air can leak between the movable pieces of glass even when they are closed, louvered windows tend to be energy inefficient. For that reason they usually are found in mild climates. They can also present a security problem, because it is easy to break one glass strip and then remove the rest, one piece at a time, to gain entry through the window.