Industry Reference
Glazing Glossary
Definitions of common terms used in commercial and residential glazing, glass installation, and building code compliance.
A
- Annealed Glass
- Standard float glass that has not been heat-treated. It breaks into large, sharp shards and is the starting point for tempered and laminated glass production.
- Argon Gas Fill
- An inert gas injected between panes of an insulated glass unit (IGU) to reduce heat transfer. Argon is denser than air and improves the U-factor of the window system.
B
- Butt-Joint Glazing
- A frameless glazing technique where two glass panels meet edge-to-edge with only a sealant joint between them, creating a seamless, modern appearance.
C
- Captured Glazing
- A glazing method where the glass is held in place by pressure plates or snap-on trim covers attached to the framing system, allowing exterior access for glass replacement.
- Curtain Wall
- A non-structural exterior wall system, typically aluminum-framed glass, that hangs from the building structure like a curtain. It carries no floor or roof loads and is designed to resist air and water infiltration, wind forces, and seismic movement.
D
- Dry Glazing
- A method of securing glass in a frame using pre-formed gaskets rather than wet sealants. Common in storefront and curtain wall systems for easier field replacement.
F
- Fire-Rated Glass
- Glass that has been tested and certified to resist fire, smoke, and radiant heat for a specified duration (20, 45, 60, 90, or 120 minutes). Required near exits, stairwells, and property lines per building codes.
- Float Glass
- Glass manufactured by floating molten glass on a bed of molten tin, producing perfectly flat, uniform sheets. This is the base product for nearly all architectural glass.
G
- Gasket
- A pre-formed rubber or silicone seal used to secure glass within an aluminum frame and prevent air and water infiltration. Gaskets degrade over time and are a common maintenance item.
- Glazing
- The process of installing glass into a building frame or opening. Also used as a general term for the glass and framing system itself. A "glazier" is the tradesperson who performs this work.
H
- Heat-Strengthened Glass
- Glass that has been heated and cooled more slowly than tempered glass, making it about twice as strong as annealed glass. It breaks into larger pieces than tempered glass and is often used in laminated assemblies.
I
- IGU (Insulated Glass Unit)
- A sealed assembly of two or three glass panes separated by a spacer and air or gas-filled gap. IGUs are the standard for energy-efficient commercial and residential windows, providing thermal insulation and noise reduction.
L
- Laminated Glass
- Two or more glass layers bonded together with a plastic interlayer (PVB or SGP). When broken, the interlayer holds the fragments in place, providing safety, security, and sound attenuation. Required in overhead glazing and certain safety applications.
- Low-E Glass (Low-Emissivity)
- Glass with a microscopically thin metallic coating that reflects infrared heat while allowing visible light to pass through. Low-E coatings are essential for meeting California Title 24 and Arizona energy code requirements.
M
- Mullion
- A vertical or horizontal structural member that divides and supports adjacent panels of glass in a curtain wall or storefront system.
P
- Point-Supported Glazing
- A structural glazing system where glass panels are supported by metal fittings (spiders or patch plates) at specific points rather than continuous framing, creating a frameless appearance.
S
- SHGC (Solar Heat Gain Coefficient)
- A rating from 0 to 1 that measures how much solar radiation passes through a window as heat. Lower values mean less heat gain. Title 24 sets maximum SHGC limits for different climate zones in California.
- Silicone Structural Glazing (SSG)
- A method of bonding glass to an aluminum frame using structural silicone sealant instead of mechanical captures. This creates a flush exterior appearance with no visible framing on one or more sides.
- Skylight
- A glazed opening in a roof that allows natural light into the space below. Commercial skylights must meet specific thermal, structural, and waterproofing requirements per building codes.
- Spandrel Glass
- Opaque or translucent glass used to conceal structural elements, floor slabs, and mechanical systems between vision glass areas on a building facade. Typically uses ceramic frit, opacifier, or shadow boxes.
- STC (Sound Transmission Class)
- A rating that measures how effectively a window or wall assembly blocks sound transmission. Higher STC values mean better noise reduction. Laminated glass and wider airspaces in IGUs improve STC performance.
- Storefront System
- A non-structural aluminum framing system designed for ground-floor commercial applications such as retail storefronts, office entries, and lobbies. Lighter duty than curtain wall, with frames typically visible on both interior and exterior.
T
- Tempered Glass
- Glass that has been heated to approximately 1,150 degrees F and rapidly cooled, making it 4-5 times stronger than annealed glass. When broken, it shatters into small, relatively harmless granular pieces. Required by building codes in hazardous locations.
- Thermal Break
- An insulating barrier built into an aluminum frame to reduce heat transfer between the interior and exterior. Thermally broken frames are required for energy code compliance in most commercial applications.
- Tinted Glass
- Glass with color added during manufacturing (bronze, gray, green, or blue) to reduce solar heat gain and visible light transmission. Often combined with Low-E coatings for optimal performance.
- Title 24
- California's Building Energy Efficiency Standards (Part 6 of the California Building Code). Title 24 sets mandatory requirements for glazing U-factor, SHGC, and visible transmittance based on climate zone, orientation, and window-to-wall ratio.
U
- U-Factor
- A rating that measures the rate of heat transfer through a window assembly. Lower U-factor values indicate better insulating performance. U-factor accounts for the entire assembly including glass, frame, and spacer.
V
- Vision Glass
- The transparent portions of a building facade intended for occupants to see through, as opposed to spandrel areas which are opaque.
- VLT (Visible Light Transmittance)
- A rating from 0 to 1 that measures the percentage of visible light that passes through glass. Higher VLT means more natural daylight enters the building. Important for retail storefronts and daylighting strategies.
W
- Weep Hole
- Small drainage openings at the bottom of a storefront or curtain wall frame that allow water to drain from the glazing pocket to the exterior. Clogged weep holes are a common cause of water infiltration in commercial buildings.
- Wet Glazing
- A method of sealing glass in a frame using liquid sealants (typically silicone) that cure in place. Provides excellent weather sealing but is more labor-intensive than dry glazing methods.
- Wire Glass
- Glass with an embedded wire mesh that holds the glass together when broken. Historically used as fire-rated glass, it is being replaced by modern fire-rated ceramics and tempered products in many applications.
32 terms defined
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