Window Types

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When selecting windows, there are a number of operating types to consider. Traditional operable window types like the projected or hinged types such as casement, awning, and hopper, and the sliding types such as double and single-hung and horizontal sliding. Also, the current window market consists of storm windows, sliding and swinging patio doors, skylights and roof-mounted (i.e., sloping) windows, and window systems that can be installed to create bay or bow windows, miniature greenhouses, or full sun rooms.

Awning windows have hinges at the top and open outward. Hinged windows such as awnings typically have lower air leakage rates than sliding windows from the same manufacturer because the sash closes by pressing against the frame. Screens are placed on the interior of the window unit. Similar to casements, the entire window area can be opened, while sliders are limited to less than half of the window area.

Casement windows are side hinged. Hinged windows such as casements generally have lower air leakage rates than sliding windows from the same manufacturer because the sash closes by pressing against the frame. Casement windows project outward, providing significantly better ventilation than sliders of equal size. Because the sash protrudes from the plane of the wall, it can be controlled to catch passing breezes, but screens must be placed on the interior side. Virtually the entire casement window area can be opened, while sliders are limited to less than half of the window area.

Hopper windows are hinged at the bottom and open inward. Hinged windows such as hoppers generally have lower air leakage rates than sliding windows from the same manufacturer because the sash closes by pressing against the frame. Screens are placed on the exterior of the window unit. Similar to casements, the entire window area can be opened, while sliders are limited to less than half of the window area.

In double-hung units, both sashes slide vertically. Only the bottom sash slides upward in a single-hung window. Ventilation area can vary from a small crack to an opening of one-half the total glass area. Screens can be placed on the exterior or interior of the window unit. Sliding windows, such as single or double-hung units generally have higher air leakage rates than projecting or hinged windows.

Both sashes slide horizontally in a double-sliding window. Only one sash slides in a single-sliding window. Ventilation area can vary from a small crack to an opening of one-half the total glass area. Screens can be placed on the exterior or interior of the window unit. Horizontally sliding windows generally have higher air leakage rates than projecting or hinged windows.