Tips
Window parts and replacement basics
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What’s the difference between a bay vs. a bow window? Should I care about the U-factor? And what’s a “muntin”, anyway?
Your local Infinity by Marvin partner is a window and door expert, so you don’t have to be. Your free, no-hassle consultation will provide all the information you need to make the best decision, and in a way that makes sense for you.
However, windows are an investment in your home so more information is better. Our glossary of terms is a great place to start!
Common window parts
Learn about the different parts of a common window.
Frame
The stationary portion of a window that surrounds either the glass (direct glaze) or the sash (operating or stationary). There are three components to the frame: the header across the top, the jambs down each side, and the sill across the bottom.
Low-E Glass
E stands for emissivity, which is a material’s ability to radiate energy. The number following the “E” indicate the number of metallic layers. Infinity windows and doors have four choices of Low E coatings. The coatings are thin metallic layers designed to reflect heat.
Divided Lites
Divided lites are an option to replicate historical window designs. Windows used to have separate pieces of glass glazed between muntin bars. Infinity offers Simulated Divided Lites (SDLs) and Grilles Between the Glass (GBGs). SDLs get permanently adhered to the outside surface of the glass to give the appearance of divided lites. GBGs appear in between the glass panes for easier cleaning.
Sill
The lower, horizontal piece of a window or exterior door frame that supports the frame.
Sash
The operating and/or stationary portion of the window that holds the glass and is separate from the frame.
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Window Corner
Sash
The part of the window that holds the glass and opens and closes is called the sash. Window sash and frames can be made out of several different kinds of materials including wood, aluminum, fiberglass, composite, and vinyl.
Rails
Rails are the horizontal window components of a sash. The two rails that meet in the middle of double hung and single hung windows are called check rails.
Side jamb
A jamb is the vertical side of a window frame.
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Cam Lock
A cam lock is a lever-operated lock, which is used to prevent intrusion through the sash.
Keeper
A keeper is the stationary half of a cam lock.
Window Opening Control Device (WOCD)
Infinity windows can come with window opening control devices to limit how far a window can open. The device is shown on a double hung window.
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Bottom rail
The lower horizontal part of the bottom sash of a single hung or double hung window.
Bottom sash
The lower part of a single hung or double hung window that slides up and down to open.
Check rail
The two rails that meet in the middle of a single hung and a double hung window is called a check rail.
Sash tilt pin
A sash tilt pin is the mechanism on single hung and double hung windows that allows the sash to tilt into a room for easy cleaning. It can also be called a cam pivot.
Top check rail
The top check rail is the bottom rail of the top sash in a single hung and double hung window.
Top rail
The upper horizontal component of a window sash.
Top sash
A sash is the part of the window that holds the glass. A sash opens and closes. Single hung and double hung windows have a top sash and a bottom sash. Both sashes slide open and close with a double hung window. Only the bottom sash moves with a single hung window.
Stile
A stile is a vertical member of the framework of a sash, door, screen, or other panel assembly.
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Head jamb
The head jamb is the top component of the frame.
Locking handle
The handle or lever operated lock found on a variety of window types is called the locking handle. When pushed closed, locking handles are designed to pull the two sashes tight together for improved security and energy efficiency.
Operating arm
An operating arm is attached to both the window frame and the sash on casement and awning windows. It is the mechanism that works in conjunction with an operating handle to open and close a sash. It also holds a sash in place when open.
Operating handle
The operating handle on a casement or awning window is the device used to open and close the window. Turning the crank in one direction extends the operating arm and opens the window. Turning the crank in the other direction closes the window.
Side jamb
Side jambs are the vertical components of the frame.
Sill
The sill is the bottom component of the frame. The outside edge of the exterior portion of a window sill is tapered down to help shed water.
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Fixed sash
The fixed sash refers to the sash that does not open and close in a slider window.
Head jamb
The head jamb is the top component of the frame.
Locking handle
The handle or lever operated lock found on a variety of window types is called the locking handle. When pushed closed, locking handles are designed to pull the two sashes tight together for improved security and energy efficiency.
Operating sash
The operating sash refers to the portion of a slider window that opens and closes.
Sash pull
A sash pull refers to the handle on a slider window used to open and close the window.
Side jamb
Side jambs are the vertical components of the frame.
Sill
The sill is the bottom component of the frame. The outside edge of the exterior portion of a window sill is tapered down to help shed water.
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Crank handle
The crank handle refers to the device used to open an awning or casement window. The handle rotates to open and close a window.
Head jamb
The head jamb is the top component of the frame.
Keeper
A keeper is the stationary part of a lock on an awning or casement window.
Locking handle
The handle or lever operated lock found on a variety of window types is called the locking handle. When pushed closed, locking handles are designed to pull the two sashes tight together for improved security and energy efficiency.
Roto-gear arms
A term used to describe the steel shaft, gears, and crank device used for opening awning and casement windows.
Side jamb
Side jambs are the vertical components of the frame.
Sill
The sill is the bottom component of the frame. The outside edge of the exterior portion of a window sill is tapered down to help shed water.
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Bay window configurations
Infinity Bay windows can come as casement windows or double hung windows. They can also have all three windows open and close or all three windows can come as picture windows.
Headboard
The head board refers to the top of a bay window unit.
Picture window
A picture window is a fixed or inoperable window that often appears in the middle of a bay window.
Seatboard
The seatboard refers to the bottom portion of a bay window unit. Infinity Bay Windows have insulated seatboards and create a reading nook or additional shelving.
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Casement Windows
Infinity Bow Windows include casement windows as part of a four, five or six-window assembly.
Headboard
The headboard refers to the top portion of a bow window assembly.
Picture windows
Bow windows that have windows that do not open are referred to as picture windows. They can sometimes be called casement picture windows.
Seatboard
The seatboard refers to the lower portion of a bow window assembly. It can be used for seating to enjoy a sunny day.
Simulated Divided Lites
Simulated Divided Lites (SDLs) get permanently adhered to the outside surface of glass to give the appearance of divided lites. Simulated divided lites have a spacer bar between the panes of glass.
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Half round top
A half round top is one of the 20 styles of arch and round top windows Infinity offers.
Head jamb
The horizontal piece forming the top of the frame on a window or door.
Picture mull
Picture mull refers to the construction of a window. A picture window remains stationary and does not open.
Side jamb
The left and right vertical pieces forming the frame on a window or door.
Sill
The lower, horizontal piece of a window or exterior door frame that supports the frame.
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Window terms
Casement window
A casement window is side-hinged window that swings out from the left or right with crank-out hardware.
Condensation
Moisture that forms on a surface. This could be a result of a difference in temperature between the surface and the air, or high humidity in the home.
Daylight Opening (DLO)
The area of the window or door where light passes through; the width and the height of the visible glass.
Double hung window
Infinity double hung windows have two movable sash (top and bottom) which are hung in the window frame and slide/operate vertically.
Frame
The stationary portion of a window that surrounds either the glass (direct glaze) or the sash (operating or stationary). There are three components to the frame: the header across the top, the jambs down each side, and the sill across the bottom.
Hardware
Window hardware includes locks, crank handles, and hinges on windows used to operate and secure them.
Low E glass
Extremely thin coating of special low emissivity (low E) metallic material are applied to glass pane to boost energy efficiency and block out UV rays.
R-Value
The resistance a material has to heat flow is the R-Value. Higher numbers indicate greater insulating capabilities.
Sash
The operating and/or stationary portion of the window that holds the glass and is separate from the frame.
Sill
The lower, horizontal piece of a window or exterior door frame that supports the frame.
Single hung window
A single hung window looks like a double hung, but only the bottom sash moves up and down.
U-Factor
U-factor measures how well a window keeps heat inside your home. A higher number allows more heat to escape; a lower number allows less heat to escape. If you live in a colder climate, you’ll want to look for a low U-factor.
Ultrex®
Ultrex fiberglass is a proprietary fiberglass composite material made of resin and glass fibers with an integrated finish for durability. This superior material is used in Infinity products.
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Argon gas
Argon gas is a colorless and odorless gas that is less dense than air. It is used to fill the air space between glass panes to increase energy efficiency.
Assembly
Two or more window units mulled (attached) together to create one larger grouping.
Bay windows
A series of windows installed in an angled “bay” formation with a head and seat board. Typically, a bay window consists of two smaller operating units flanking a larger fixed center window.
Bow windows
Bow windows are a series of adjoining window units that are configured in a gradual arc.
Check rail
The horizontal portion of a double hung window where the top and bottom sash meet. Simulated check rails use bars to simulate the look of a double hung window in a casement or glider.
Cottage window
A cottage window contains an unequal sash, top and bottom. Bottom sash is larger than top sash.
Divided lites
Decorative bars permanently adhered to glass (Simulated Divided Lites) or between two panes of glass (Grilles Between Glass) to add architectural interest on a window or door.
Full-frame replacement
Existing windows are completely removed down to the studs and the new window is installed in the opening.
Insert replacement
New windows are installed within the existing frame. Only the old sash, hardware, and covers are removed and replaced.
Mull/mulling
Mull: the actual components used to attach two or more windows and/or door units together to form an assembly.
Mulling
The process of attaching two or more window or door units together.
Muntins
Bars that form the decorative grille pattern on a window or door.
Operator
A moving sash, panel, or unit.
Oriel window
An oriel window has an unequal sash, top and bottom. Bottom sash is smaller than the top sash.
Panel
Stationary or operating portion of the door that holds the glass and is separate from the frame.
Picture window
A fixedstationary window to align with the profiles of operating windows. Sash is non-operable and attached directly to the frame. Often available in significantly larger sizes than accompanying operating windows.
Polygon
Polygon windows are direct glazed in various shapes such as triangles, rectangles trapezoids, pentagons, hexagons, and octagons.
Round top
An arched window that is directly glazed to the frame. Add visual interest to a room and natural light.
Sash lock
A locking device that holds a window shut, such as a lock at the check rails of a double hung unit. Larger units utilize two locks.
Single hung round top
Infinity single hung round top windows provide a is an arched top built on a single hung window frame.
Weatherstripping
A strip of resilient material designed to seal the window or door in order to reduce air and water infiltration.
XO
The letters OX or XO identify the operation of window or door units as viewed from the exterior. The letter O stands for stationary, while the letter X stands for operating.
We hope the glossary of window terms is helpful for you. For more, check out our complete glossary. Also be sure to check out our other blog articles, as we compare window materials and share information on how to pick the best windows for your home.
Questions regarding your windows? Schedule a free consultation with a local expert who can answer any questions you may have about windows and window replacement.