Essential Parts of Windows: A Clear Guide to Window Types and Components

When choosing new windows, you’re likely to find there are a lot of terms that may be unfamiliar to you. The following are some of the most common window terms and definitions to help you gain a clearer view when shopping for replacement windows!

Types of Windows

There are many types of windows to choose from. Most open differently. Others are configurations of window types. Below are some of the most common types.

Awning Windows

These windows function like their name. They hinge at the top and push out from the bottom to produce an awning. When open, this window protects from rain while allowing for ventilation.

Bay Windows

Traditionally, Bay windows are made from three windows: a large picture window flanked by smaller side windows which may be set at 30°, 45°, 60° or 90° degree angles.

Bow Windows

Bow windows are composed of any number of windows joined together to create a gentle curve. Bow windows can use double hung, casement and/or picture windows. A mullion is a vertical or horizontal structural piece that connects three or more windows together. They are often used in bay or bow windows to provide architectural support and aesthetic appeal.

Casement Windows

Assembled as a complete operating unit, casement windows feature a combination of window frame, sash, weather-stripping, and concealed hinges. Operating casement windows are hinged on one side, or at the top or bottom. They typically have a crank handle for smooth opening and closing.

Double Hung Windows

Double hung windows have two movable sashes, which allow them to slide open vertically. Coil spring blocks and tackle balancing devices keep them up when in the open position.

Gliding Windows

These windows slide open and closed side-to-side like a sliding patio door.

Picture Windows

A picture window may also be called a fixed window or a direct glazed or non-operable window. It is a large window that doesn’t open or close. They are called direct glazed because they don’t have a sash, they are glazed directly to the window frame. These windows allow for unobstructed views from your home.

Single Hung Windows

This window looks like a double hung window, but the upper sash is fixed. Only the lower sash moves up and down.

Specialty Shaped and Round Top Windows

Windows come in virtually any geometric shape you can imagine, including octagon, hexagon, trapezoid, pentagon, and triangle. Many shapes are available as operating casement window with either left/right hand opening or tilt-out awning window opening.

Transom Windows

Transom windows are windows that sit above a door or window. They were originally designed to add ventilation to homes while keeping doors locked and the home secure. Today they are primarily used for added light and beauty. Transom windows are available in many shapes and can be stationary or operating depending on preference.

Window Components

Although there are many types of windows, all have the same basic components; the frame, sash, and glass also commonly referred to as glazing.

The Sash

The sash is the operating and/or stationary portion of the window separate from the frame unit.

Check Rails

Check rails are the horizontal components that meet in the middle of a double hung and single hung window.

Daylight Opening

The daylight opening refers to the total amount of glass in a window not including the sash stiles and rails or the window frame.

Glazing Bead

Glazing bead are the pieces of wood, vinyl, or aluminum that hold the glass in position in the sash. Glazing bead on the interior side of the sash is often called sticking.

Lift

The lift is the handle on the sash that allows you to open the window.

Muntin Bars and Grilles

Although the terms muntin bars and grilles are commonly interchanged, they are different. Both result in a decorative grid-like look on window sashes. Muntin bars are dividers used to hold and connect small panes of glass which run rail to rail and stile to stile. Historically, large panes of glass were not available and muntin bars were needed to create large windows for natural light and expansive views. Grilles, on the other hand are decorative pieces used to create grid-like designs on large pieces of glass creating a traditional, historic look.

Rails

The rails are the horizontal components along the top and bottom of the sash.

Sash Lock

A sash lock is a device that holds a window shut and secure. It will not open from the outside. Larger units may use two sash locks.

Stiles

Stiles are the vertical component along the sides of the sash.

 

Window Glass

Window glass can also be referred to as window panes or window glazing. Panes are the glass part of the window sash, and can be single, double, or triple pane. Single-pane windows are one sheet of glass while double pane windows are created from 2 sheets of glass separated by a spacer bar. The resulting airspace is typically filled with inert gas like argon, and is the primary source for energy efficiency in today’s windows. The space between the panes also helps with soundproofing.

Divided Lites

Divided lites create the look of multiple, individual panes of glass in a window or door. They can be built using separate panes of glass or they can be simulated by using a large piece of glass with grilles attached to the interior and exterior surfaces mimicking the look of multiple panes. Divided lites are popular in a wide range of architectural styles, from historic replications to modern farmhouses. 

 

Glass Spacer

A glass spacer (also called a spacer bar) is used to create insulated glass by separating the glass panes and creating an air pocket between the panes.

 

Insulating Glass

Insulating glass consists of two or more sealed glass panes separated by a space between to reduce heat transfer. Insulating glass, which can contain argon for improved thermal insulation, is one of the most impactful window and door features in terms of energy efficiency. 

Obscure Glass

Obscure glass is often used on entry doors and bathroom windows and features a pattern in the pane that provides privacy while maintaining full light transmission.

 

Tempered Glass

Tempered glass is safety glass that is required for large windows and windows that are low to the ground. The glass is heated and then cooled rapidly in a controlled environment for added strength. The tempering process makes the glass safer due to the pebble-like fragments created when shattered.

 

Parts of a Window Frame

The window frame is the stationary, outer structure of the window that encloses the glass or sash and is made up of the following parts…

 

Balances

Window balances are weights that counter-balance sashes on single hung and double hung windows. These allow for easier opening and prevent the window from slamming down.

Brick Mould Casing

The brick mould casing is the exterior molding on a window or door frame that sits against the structure’s exterior material, serving as a decorative boundary for siding, brick or other material.

 

Casing

The casing is the interior trim that surrounds the window or door which covers the gap between the window/door and the drywall, hiding the frame, insulation and caulking.

Cladding

The vinyl, fiberglass or aluminum jacket that covers the wooden core on the exterior side of a window or door is called the cladding. It helps preserve the wood and improve its weather resistance.

Drip Cap

An aluminum or vinyl piece at the top of windows and doors that directs water off the casing of the unit to help prevent water damage and rot.

Head Jamb

The head jamb is the horizontal component along the top of the frame.

Jamb Liner

The jamb liner is the covering over the space between the window frame and the finished interior wall. The jamb liner helps create a tight seal around the sash to reduce drafts and improve energy efficiency.

Jamb Extension

A jamb extension is an addition to a standard-sized jamb to adapt the window unit to a deeper wall thickness.

Sill

The sill is the horizontal component along the bottom of the exterior frame, designed to shed water and prevent it from entering the window. The window sill can also be called the window ledge or the window bottom.

Side Jamb

The side jamb are the vertical components along the sides of the frame that connect the head and the sill.

Screens

Screens are made of close-mesh woven material of metal or fiberglass attached to an aluminum or wood surround, inhibiting the entry of insects while still permitting light, air, and field of view when windows and doors are open.

Weather-stripping

Weather-stripping is the seal that helps improve the energy efficiency of the window, installed around the window frame and sash. Made of felt, foam tape or formed plastic, this strip of resilient material reduces air and water infiltration by sealing the sash and frame.

As always, if you have any questions about windows, doors or what will work best for you project, CONTACT US today. Check out blog on the different parts of a door, A Helpful Guide to Door Parts.