Use the best window types for your project!
Architects and engineers, take this course for PDH credit here.
First let’s start with a couple of charts that show window types organized by category, with architectural symbols for these window products:
The simplest type of window is a fixed window. It has no moving parts and does not open. It usually consists of a single frame, within which glass is installed. Residential fixed windows are sometimes called picture windows.
Single and Double Hung Windows
Here in the U.S., common window types are single and double hung windows. They are named “hung” because the original design involved having the operable sash hung from ropes or chains which then were placed over a pulley at the top of each jamb. The rope or chain then was attached to a counterweight concealed in the jamb, allowing the sash to be easily raised and to stay at the height to which it was raised.
These days, numerous styles of balances are available, but they usually involve springs rather than counterweights. Double hung windows have the top and bottom sash operable. Single hung windows only operate the bottom sash. The horizontal rail where the upper and lower sash meet is called the meeting rail.
Because the sash of hung windows slide in the frame, sweep-type weatherstripping is typically used.
Sliding Windows and Doors
Other common window types are sliding windows and doors. These utilize wheels or rollers at the bottom of the operable portion, known as the sash. The sash travels horizontally in tracks at the top and bottom of the master frame. Usually only one of the sash operate, however when both sash operate, the window is called a “double slide.”
Due to the presence of a track at the sill of a sliding window or door, water can accumulate in the track. These products must have provisions to “weep” the water to the exterior. This poses a design challenge because weep holes can conduct air infiltration to the interior.
Because the sash of sliding windows and doors slide in the frame, sweep-type weatherstripping is typically used.
Projected Windows and Doors
This family of window types includes project-out awning windows, project-in hopper windows, inswing casement windows, outswing casement windows, balcony doors, top hung inswing windows, tilt turn windows, pivoted windows and jalousie windows. In architectural drawings, operation of all windows and doors that swing (as opposed to slide) is indicated by dotted lines that converge at an edge of the window, forming a V shape. The point of this V is the theoretical hinge location. I use the term “theoretical’ because the actual hinge is not always positioned at this location. Example: the project-out window has the V pointing to the top, at the theoretical hinge location. If butt-hinges were used, that would also be the exact location. Instead, scissors hinges are used at the sides. These are far preferable because they hold the sash open in any position.
Image above shows a project-out awning window (center). At left is the scissors hinge that is installed in the jambs (sides), yet at right, the convention for indicating operation with dotted lines formed into a V, point at the theoretical hinge location at the top, as if the hinges were butt hinges as used on a typical door.
Project-out awning and project-in hopper windows compress their weatherstripping when they are closed, so they use compression-type weatherstripping, sometimes called gaskets. These window types are often combined with a fixed window above or below. A common design in high-rise construction is to place these near the floor.
This European window type involves a sash that operates in two directions: as an inswing casement (typically for cleaning) and as a project-in hopper (for ventilation). Both functions can be controlled by a single handle. These windows have not really gained a foothold in the US for reasons of cost. Other impediments to their widespread acceptance include having the ventilation near the ceiling, interference with window treatments, and widespread use of window washers who can work from the outside efficiently without needing to gain entry into the living units.
This window type involves multiple project-out sash, usually comprised of single-thickness (monolithic) glass. They are gang-operated and frequently not weatherstripped. This is a product that is designed for a tropical environment or sunrooms that are only used in summer.
Every year hundreds of people, especially children, die and are injured because they either fell from windows or were injured by windows or broken glass, or any combinations of the above. Design professionals cannot be too careful when designing around this serious set of issues.
Care must be taken to limit the opening of any windows near the floor (preferably ALL windows) to a maximum of 4”.
All glass at or near walking surfaces, and in or near doors and bathtubs/showers must be safety glass.
Be sure to check all of the prevailing codes, including local building codes, local amendments to the code, local property maintenance codes, local ordinances and any industry specific guidelines (such as for hotels, hospitals, etc.) to ensure compliance.
Do not be deterred if, for example, window limits are not mandated in any of the codes. Check with the fire department and life-safety codes to ensure proper egress, and then limit those windows and use safety glass if a danger of accidental impact exists.
Glazing and Sash – Definitions
Installing and sealing glass into a surrounding frame is called glazing the glass into the frame. The term glazing also refers to the glass or whatever other material (sheet plastic or metal panels, for example) that may be glazed into a frame or sash.
A sash is the operable frame that resides within the outer frame, called the master frame. In the aluminum window industry, only operable windows have sash. Sash in projected windows are also called vents.
In the wood or wood-clad window industry, both fixed and operable window types often consist of an inner and outer frame, and so the frame immediately adjacent to the glass is sometimes called a fixed sash.
More about window types: Window Weatherstrips and Gaskets
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