Glossary of Common Glass Terminology

We believe in educating our customers as a pillar of our customer service. This blog serves as testament of to our word. Compiled below is common terminology that the glazing industry uses when talking about windows. This is meant to supplement our Basic Guide To Glazing.

Glazing Definitions

Argon Gas: Gas that is injected between the layers of a double pane, insulated glass unit (IGU). Argon gas used to be more common in the past than it is now. Modern IGU’ash use UV and insulating coatings that increase the window’s thermal rating.

Awning Window: An awning window is a tilt window that opens from the bottom. The windows are usually open by push or by crank.

Balance: A balance mechanism regulates the placement and force needed to hold up single and double hung windows. Balances are usually hidden inside the window’s sash. Balances vary in terms of design, strength, weight.

Bay Window: a three-sided window that is three-dimensional, protruding from the house.

Bow Window: Is a curved bay window. Generally speaking, a bow window has smaller windows than a bay window.

Casement Window: is a window that is attached to the frame by hinges on one side (similar to a door). Casement windows generally open by cranks.

Casing: decorative trim around interior frame of window.

Compression Jambs: liner in window jamb that can be pushed in, allowing you to tilt the window sash. Assists in maintaining weather-tight seal between window sash and jamb.

Cottage Style Window: is a double hung or single hung window where , the bottom sash is larger than the top sash.

Crank Handle: opening mechanism used for hopper, casement, and awning windows.

Double Hung Window: a window in which both the top and bottom sash move up and down. Double hung windows typically have more balances than single hung windows.

Egress: the size opening a window creates for access.

Fixed/Picture Window: a window with no moving parts or sashes.

Grilles/Muntins: are used for window decoration or home security. These are dividers on the housed of a window that prevent intruders from entering through the window.

Grilles-Between-The-Glass : are grids inserted between two pieces of glass, making the window pane easier to clean.

Head: the horizontal member forming the top of the window frame.

Jamb: vertical members of the window frame.

Jambliner: internal frame part that holds the sash in place.

Keeper: on a double hung window, this is part of the lock system that engages the lock latch for a secure fit.

Low-E: stands for “low emissivity”. Low-E coating on a window pane lets light in, yet reflects heat and keeps harmful UV rays out in the summer and keeps heat inside during the winter. Low-E can be on all sides of the glass, depending on the desired thermal results.

Mulled: the combination of how individual pieces of glass are attached together.

NFRC Rating: National Fenestration Rating Council (NFRC) provides unbiased energy performance ratings for windows, doors and skylights. The NFRC rating is the gold standard when giving opportunity to choose windows.

Rail: horizontal part of a sash.

Rough Opening: the opening in a wall in which a window is to be installed. Rough openings are commonly measured before the window has been installed.

R-Value: marks a window’s resistance to heat loss or gain. The higher the R-value, the better the window reduces heating and cooling bills.

Sash– A window shushes together form the frame that holds the glass in place. Sashes are commonly made from wood, aluminum or vinyl.

Silicone– Silicone sealant is used to fill gaps and keep moisture out of the space. Silicone is an elastic material that is able to expand and contract anywhere from 25%-65%. Silicone can be used in outdoor application because it does not decompose when exposed to Ultra Violet light. A silicons lifespan has a lifespan from 20-60 years.

Sill: the horizontal piece forming the bottom of the window frame.

Simulated True Divided Lites (Grids): grilles attached to the interior and exterior of a window, with a bar between the window panes, to give the appearance of true divided lites.

Single Hung Window: a window with only one sash-usually the lower one-that moves up and down.

Spacer Material: material along the perimeter of the sash, sandwiched between two pieces of glass.

Stile: vertical part of a sash.

Tempered Glass: type of glass that, when broken, shatters into small pieces to protect you from injury.

Thermal Break: part of a window or door that reduces transfer of cold or heat from one surface to another.

Thermal Rating-

Tilt Latch: a locking mechanism that, when released, enables the sash to tilt inward.

Tilt Pins: on a tilt double-hung window, tilt pins rotate the sash when it opens into the home.

True Divided Lites: muntins in a cross-hatch pattern creating one window with several small separate windows within.

Urethane– This is a sealent used in glazing. Its elasticity allows for 25%-50% movement during temperature change. Urethane is used to fill and seal gaps. Urethane is best used indoors or anywhere will light exposure would be limited. Ultra Violet rays decompose urethane. Urethane’s lifespan is typically 5-10 years.

UV (Ultraviolet) Rays: the rays of the sun that can filter through windows and heat up a room. There are UV reflective glass coatings that protect your home from UV rays.
U-Value: the amount of heat entering or escaping through a window. The lower the U-value, the better the insulation value.

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