Schönline Windows & Doors

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Window and Door Glossary:

Key Terms to Know

An IGU, or Insulated Glass Unit, is a multi-pane assembly designed to improve energy efficiency and reduce noise. It typically consists of two or more panes of glass separated by a spacer and sealed to create an insulating air or gas-filled space between the panes. IGUs are a key feature in modern windows, providing superior thermal performance and comfort.

A casement is a window that is attached to its frame by one or more hinges on the side. Casement windows open outward or inward, providing excellent ventilation and a clear view when fully open.

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The frame is the structure that surrounds and supports the window or door, holding it in place. It consists of the head, sill, and jambs, and is a critical component in ensuring insulation, security, and durability.
These terms refer to the direction in which a door or window opens. An inswing door or window opens inward, while an outswing opens outward. The choice between these options depends on space, weather exposure, and personal preference.
Tilt & Turn windows offer versatile functionality. They can be tilted inward at the top for ventilation or fully opened by turning the handle, making cleaning and airflow control more convenient. This design is popular in European-style windows.
A chamber refers to the hollow, internal sections within a uPVC or aluminum window frame. These chambers help with insulation and drainage, improving the energy efficiency and strength of the window frame.

Weep holes are small openings in the window frame designed to allow water to drain away from the window. These prevent water from accumulating and help keep your windows weather-resistant, ensuring long-term durability and performance.

Thermoplastic Vulcanizate (TPV) gaskets are sealing components used in windows and doors to ensure an airtight and watertight seal. Known for their durability and flexibility, TPV gaskets offer excellent resistance to weathering, UV light, and temperature extremes.

A double-pane window consists of two layers of glass with a sealed space between them, often filled with air or gas like argon, to improve insulation and reduce noise. Double-pane windows provide significant energy efficiency and are commonly used in modern homes.
A triple-pane window includes three layers of glass, with two insulating spaces between the panes. This design offers superior insulation, energy efficiency, and soundproofing, making it an excellent option for colder climates or where noise reduction is critical.
Reinforcement steel is added to the inside of uPVC window and door frames to provide additional strength and rigidity. This reinforcement ensures that the frames maintain their shape, especially in larger windows and doors, while also enhancing security.
Cladding refers to the protective outer layer applied to windows and doors, made of aluminum. It provides extra durability and protection from weather conditions while also enhancing the appearance. Aluminum cladding, offers a sleek and modern look while adding strength and resistance to wear.
Low-E (Low Emissivity) glass is coated with a thin layer of metal that reflects heat, helping to keep your home warmer in the winter and cooler in the summer. It improves energy efficiency by reducing the amount of heat that passes through the glass.

Argon gas is often used between the panes of double or triple-pane windows to improve insulation. This inert gas has better thermal performance than regular air, helping to minimize heat transfer and increase energy efficiency.

The U-value measures the rate of heat transfer through a window or door. A lower U-value indicates better insulation and greater energy efficiency, making it an important factor to consider when choosing windows for thermal performance.

SHGC is a rating that indicates how much solar heat passes through the glass. A lower SHGC means less heat enters your home, which is important for energy efficiency, especially in warmer climates.

A spacer is the material used to separate the panes of glass in an IGU. It helps to maintain the correct distance between the panes and can be filled with insulating materials like argon gas to improve thermal performance.

A thermal break is a layer of insulating material placed between sections of a window frame to reduce the transfer of heat and cold. This feature is commonly used in aluminum windows to improve energy efficiency.
A ventilation lock allows windows to open partially while remaining securely locked. This feature provides ventilation without compromising security.
This term refers to a window's ability to resist the formation of condensation on its interior surface. Windows with high condensation resistance help to maintain clear glass and prevent moisture buildup inside the home.
This refers to a window’s ability to reduce noise transmission from the outside. Windows with high acoustic performance are ideal for areas with high noise pollution, providing a quieter and more comfortable indoor environment.
Impact-Resistant Glass Impact-resistant glass, often used in storm-prone or security-sensitive areas, is designed to withstand high impacts from debris or forced entry attempts. It includes layers of laminated glass that help prevent shattering.
A spacer bar is a component used within an IGU to maintain the space between the glass panes. It’s often made of materials like aluminum or steel and can be thermally enhanced to improve insulation.
Warm edge spacers are made from materials that have lower thermal conductivity than traditional spacers, reducing heat transfer and improving the window's energy efficiency. They help lower condensation and improve the window's U-value.
Lamination refers to the process of bonding multiple layers of glass with a plastic interlayer. This enhances the glass's strength and safety properties by preventing it from shattering into sharp pieces if broken.
Grilles, also known as muntins, are decorative bars that divide a window into smaller panes or give the appearance of divided panes. They can be installed between or over the panes for added architectural style.
A transom is a horizontal window installed above a door or another window, allowing for additional natural light. These windows can be fixed or operable for ventilation.
A mullion is a vertical or horizontal element that divides adjacent window units, providing structural support. It’s used in multi-window installations, enhancing both aesthetics and functionality.
The glazing bead is a strip that holds the glass pane in place within the window frame. It ensures the glass is secure while also enhancing the window's aesthetic finish.
Tempered glass is a type of safety glass that is heat-treated to increase its strength. When broken, it shatters into small, blunt pieces, making it safer than regular glass. It’s often used in doors, windows near the ground, and areas where safety is a priority.
Triple glazing refers to windows with three panes of glass, separated by insulating spaces. These windows offer superior energy efficiency, better soundproofing, and increased comfort, especially in extreme climates.
An awning window is hinged at the top and opens outward, creating an awning-like effect that allows ventilation even during rain. These windows are often used in combination with other window types for increased airflow.

An egress window is a window large enough to allow for escape or entry during an emergency, such as in a basement or bedroom. Building codes often require specific dimensions for egress windows in certain areas of the home.

A bay window is a window space that projects outward from the main walls of a building, creating a larger interior space. It typically consists of a central fixed window flanked by two operable windows at an angle.
Similar to a bay window, a bow window extends beyond the exterior wall but is curved in shape, consisting of four or more window units. This design adds a more graceful, rounded appearance to a room.
  • A picture window is a large, fixed window that doesn’t open but provides an unobstructed view of the outside. These windows are often used in living rooms or spaces with a scenic view.
The window sill is the horizontal bottom part of the window frame. It serves as the structural base for the window and also helps channel water away from the wall to prevent damage.
Grilles Between the Glass (GBG) are decorative grids placed between the layers of glass in an IGU, giving the appearance of divided panes without the need for individual windowpanes. This design option simplifies cleaning and maintenance.
The R-value measures a window’s resistance to heat flow. The higher the R-value, the better the insulation. It complements the U-value, which measures the rate of heat transfer.