Glass Glossary of Terms


Annealed glass:
Standard float (plate) glass.

Awning window:
Has a top hinge and swings outward from the bottom for ventilation.

Argon gas:
An inert, nontoxic gas used to fill insulating units for improved thermal performance.

Balance system:
The use of springs or weights to hold a vertical sash in any desired position.

Bay window:
An arrangement of three or more individual window units attached to each other. In a typical three-unit bay, a center section usually remains fixed while the two on either side act as individual casements.

Bent glass:
A glass curved through a special process.

The process by which an edge of glass is finished to an angle so that the edge is not perpendicular to either face of the glass.

A piece of neoprene, silicone, or other suitable material used to position glass in a frame.

Bow window:
A bow window can be arranged with three or more equal width units. They can be fixed or operable or mixed in any combination. They are usually mulled together with a small angle such as 13 degrees.

A synthetic rubber that can be used both as a sealant and architectural glazing tape.

A piece that connects with the keeper mechanism to keep the window sashes together when locked.

Casement window:
A window unit in which the single sash cranks outward to the right or left.

A putty-like compound used to block exterior air or moisture leaks where two surfaces meet and have minimum movement. Large cracks can be stuffed with mineral wood and weather sealed with caulking.

Condensation resistance factor:
A measure of the effectiveness of a window to reduce condensation. A higher number means better efficiency.

Curtain wall:
An exterior building wall which carries no roof or floor loads. It consists entirely of metal, or a combination of metal, glass and other surfacing materials supported by a metal framework.

A piece of glass with a sash around it.

Double glazing:
Two panes of glass enclosing a hermetically-sealed air space.

Double-hung window:
A window consisting of two sashes of glass operating in a rectangular frame, both the upper and lower halves can be slid up and down and usually use a counter balance mechanism to hold the sash in place.

Dry glazing:
A method of securing glass in a frame by use of a dry, preformed resilient gasket, without the use of a compound.

Egress code:
A law requiring a minimum opening of a window for persons to exit or firefighters to enter.

Patterns or designs cut into glass either by acid etching or needle etching techniques.

Fixed window:
A window which is stationary, also known as a picture window. Can also refer to: the part of a sliding window or door which is non-moveable, also known as inactive.

Float glass:
Glass which has its bottom surfaces formed by floating on molten metal, the top surface being gravity formed, producing a high optical quality of glass with parallel surfaces and, without polishing and grinding, the fire-finished brilliance of the finest sheet glass. Float is replacing plate glass.

Flush glazing:
A method of glazing wherein the surfaces of the glass retaining members (stops or beads) are in the same plane normal to the glass as the side faces of the frame members; often achieved by providing pockets in these faces

A deposit of contamination left on the inside surface of the sealed insulating glass unit due to extremes of temperatures. Fogging ultimately resulting in seal failure.

Pre-formed glazing materials used for bedding or securing glass and for separating glass from the frame.

Geometric windows:
Specially designed to create rectangles, triangles, half-rounds, full-rounds, ellipses and more

Buys glass and installs it on a “contractor” basis. Examples: installing the window system in large office buildings, shopping center malls, etc.

The process of installing glass in a frame.

Glazing compound:
A soft dough-like material used for filling and sealing the space between a pane of glass and its surrounding frame.

The horizontal portion at the top of the main window frame.

Head expander:
A u-shaped piece of vinyl placed on the head of a window to be used as filler. This piece will expand or lengthen a unit and fill a gap.

Heat-strengthened glass:
Glass which is reheated, after forming, just below melting point and then cooled. A compressed surface is formed which increases its strength. Used for spandrel glass.

Hermetically sealed unit:
An insulating glass unit made up of two lights of glass, separated by a roll formed aluminum spacer tube (at the full perimeter) which is filled with a moisture absorbing material. The unit is then completely sealed, creating a moisture-free, clean dead air space

Inner pane:
The pane of a double-glazed unit which faces the interior of a building.

Insulating glass:
Insulating glass refers to two pieces of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between. Heat transmission through this type of glass may be as low as half that without such an air space. It is also called double glazing.

Interior glazed:
Glass set from the interior of the building.

Used around the exterior of a window where the siding fits. It extends beyond the window to the outside edges of an adjoining j-channel.

Made up of horizontally mounted louvered glass that abut each other tightly when closed and extended outward when cranked open.

The vertical parts of the frame on both sides of the window.

Kryton gas:
An odorless and colorless gas that replaces air between two or more glass panes. Krypton is denser than air and works better to deter heat transfers.

Laminated glass:
Two or more sheets with an inner layer of transparent plastic to which the glass adheres if broken. Used for overhead, safety glazing, and sound reduction.

Another term for a pane of glass used in a window.

Lock rail:
The horizontal part of a sash where the cam lock is attached.

Low-e glass:
Low-e coatings are generally neutral in appearance and designed to reduce heat loss through the glass from inside the building. The coating reflects long-wave energy and subsequently reduces the u-value of the glass. Low-e coatings may also be incorporated into solar control coatings to provide both benefits of retaining heat in the building and reflecting heat from the sun providing improved energy control.

Main frame:
Includes the head, sill and jambs of a window.

An intermediate-connecting member used as a means to “join” two or more window products together in a single rough opening.

Muntin bar:
A small bar that divides window or door glass.

Obscure glass:
Any type of glass with uneven surfaces which offers light diffusion and privacy.

Outer pane:
The pane of double-glazed unit which faces the exterior of a building.

A light or sheet of glass.

Patterned glass:
Presents uneven surfaces with different impressed patterns.

Picture window:
Stationary and framed so that it is usually, but not always, wider than it is tall to provide a panoramic view.

Plate glass:
Polished plate glass is a rolled, ground and polished product with true flat parallel plane surfaces affording excellent vision. It has less surface polish than sheet glass and is available in thickness varying from 1/4″ to 1-1/4″. Now replaced by float glass.

Refers to a unit that is vertically level.

Adding or replacing items to existing buildings. Typical retrofit products are replacement doors and windows, insulation, storm windows, caulking, weatherstripping and vents landscaping.

Visible light transmittance:
A percentage of light that is transmitted through glass. The higher the number the more light is transmitted through the window.

Safety glass:
Glass which must have passed an impact test and either must not break or must break safely.

Creating designs on the surface of glass by using high-pressure air mixed with sand applied to the surface of glass to carve texture.

The portion of a window which includes the glass and the framing sections which are directly attached to the glass. Not to be confused with the master frame into which the sash sections are fitted.

Narrow fixed units mulled or joined to door units to give a more open appearance.

A polymeric organic compound offering excellent resistance to cold, heat and water.

Single glazing:
The use of single thickness of glass in a window or door.

Single-strength glass:
A term used to describe glass with a defined thickness (2.16-2.57 mm).

Slider window:
A slider window may have one or two movable panes of glass. Whatever the type, the windows slide horizontally in the frame.

Spandrel glass:
The area of glass panels that conceal structural building components such as columns, floor slabs, heating, ventilating and air conditioning (hvac) systems, electrical wiring and more.

The vertical parts of a sash.

Tempered glass:
Tempered glass is two or more times stronger than annealed glass. When broken, it shatters into many small fragments, thus preventing major injuries. Also known as “toughened glass.”

Triple glazing:
Three panes of glass enclosing two hermetically-sealed air spaces.

Transom window:
A window located directly above a door opening.

Refers to how much heat passes through the glass. The lower the u-value, the better the insulating quality.

UV block:
A measure of the percentage of ultraviolet rays blocked from being transmitted through the glass. A higher uv block indicates that fewer rays are transmitted through the window.

Vinyl glazing:
Holding glass in place with extruded vinyl channels or roll-in type.

Wet glazing:
Uses a silicone-based substance to secure and seal glass to a sash.

Weep holes:
Small openings on the exterior sill designed to allow water that might otherwise accumulate in a window’s sill to escape.

Weep flaps:
Weep holes covered with vinyl to let water escape while keeping bugs out.

Wind load:
The pressure acting on an external surface of a building caused by the direct action of the wind.

Window wall:
A metal curtain wall of the commercial type, in which windows are the most prominent element. Also refers to smallest fixed lights used with wall systems.

Wire glass:
Polished or clear glass that is 1/4″ thick. Wire mesh is embedded within the glass such that the glass will not shatter when broken. The wire pattern is available in many types. It is frequently used in skylights, overhead glazing and locations where a fire-retardant glass is required.

Paul Rabinowitz Glass is a commercial glass installation, maintenance and repair business, located in Philadelphia, PA.


What We Do

  • Storefronts, curtain walls and interior glass partitions
  • Aluminum, glass and hollow metal entrances
  • Revolver Door installation and service
  • Solar and decorative window Films
  • Same Day Glass Replacement
  • Same Day Door Repairs
  • 24/7 Emergency Service

Smoke Baffles a.k.a. Draft Curtains

A smoke baffle is a substantial, noncombustible curtain that is hung tightly against a ceiling. Smoke baffles cordon off sections of a large ceiling for fire prevention purposes. A smoke baffle acts as a partition and “corrals” heat and smoke in the event of a fire within the curtained area. The depth of the heat and smoke contained within the curtained area can affect how quickly sprinklers are activated.

Research has shown that smoke baffles may have an adverse effect on sprinkler activation. In fact, a study published in the February 2008 edition of Journal of Fire Protection Engineering found that a draft curtain has some effect on sprinkler activation, reducing activation time from 8 percent to 15 percent.

Ideally, smoke baffles work in conjunction with vents in the ceiling that pull the smoke out of the building and prevent the spread of fire. Research has shown that the operation of vents is conversely affected if smoke baffles aren’t present. Such systems are intended to maintain a tenable environment until building occupants are able to evacuate in the case of a fire.

Smoke baffles are also known as “draft stops,” “draft curtains” and “curtain boards.” They are generally required by code where moving stairways, staircases or similar floor openings are unenclosed. Pennsylvania fire codes call for “smoke barrier” construction that can withstand a minimum of 1 hour in fire.

Draft curtains are typically used at stair locations and surround the opening to the level above. The purpose is to limit the spread of smoke during a fire and to allow adequate egress, also known as evacuation, as well.

Paul Rabinowitz Glass, commercial glass company,  installs and maintains smoke baffles in the Philadelphia, NJ and Delaware markets.

The Revolving Door

The first revolving door was invented in 1888 with the goal of preventing wind, snow, rain, dust, or noise from entering buildings. The original patent application was filed by Theophilus Van Kannel of Philadelphia. (He was granted U.S. patent 387,571 for a three-wing “Storm-door structure” on August 7, 1888.)

While Kannel’s design for revolvers featured three wings or chambers that would allow people to pass through, the most often used design is a four-wing revolver. Additionally, revolving doors can feature just two wings or chambers.

Revolving doors provide opportunity for increased traffic while minimizing the ability of people to run into each other. In one hour, a standard four-wing revolving door allows for the movement of up to 4,800 people into and out of a building. Revolving doors are usually seen in large buildings, and it’s these same buildings that account for18.6 percent of America’s total energy costs.

Revolving doors have, over the past two decades, met the security requirements of both Fortune 500 companies and airports.

Revolving doors, or revolvers, have a lot of benefits. Here, we’ll explore some of those benefits, including energy savings, an enhanced user experience, and lobbies that are quieter, cleaner and more beautiful.

Energy Savings

Because revolving doors are both always open and always closed, they provide the least possible amount of air infiltration.Swinging doors exchange eight times more air than revolving doors.

In “Modifying Habits Towards Sustainability: A Study of Revolving Door Usage on the MIT Campus,” MIT researchers considered the effects of revolving doors at several of locations on campus.

Revolving doors are only effective when they are used, and the researchers at MIT found a usage rate of approximately 68 percent. The average daily cost of energy due to air leakage at MIT was $13.10 during the winter, but a 75 percent usage rate of revolving doors drops the cost to $7.66. If the doors saw 100 percent usage, the daily cost of energy would drop to $2.83.

Based on these findings, two revolving doors at one building could save approximately $7,500 per year in natural gas used to heat and cool. That’s a savings of nearly 15 tons of CO2 emissions.

While revolvers have been traditionally considered a cold-climate solution, they’ve become an increasingly popular entryway product in warmer climates, as it’s just as important to keep conditioned air in a building as it is to keep heated air in a building.

More Beautiful, Quiet, Cleaner Lobbies

Revolving doors have other great benefits, including less space usage and better safety. Revolving doors do not require the same kind of space that traditional manual, or “swing,” doors require, and they’re also safer than traditional doors, which can slam closed on users. The chamber style of revolving doors also provide for a cleaner, more quiet lobby since they don’t open directly to wind and street noise.

Increased Safety

Revolvers can be much safer than traditional manual swing doors. Revolving doors that require users to push through max out at approximately 12 revolutions per minute, with canopy- or floor-mounted controls to keep them from spinning out of control. Automatic revolving doors are built with a series of active and passive sensors that keep them safe.

Enhanced User Experience

The ease with which patrons can enter your building when you use revolving doors will make them happy customers. The investment in powered doors demonstrates that your company cares about the patron’s convenience, said Donald Moerbe, president of the American Association of Automatic Door Manufacturers, to These entrances can be especially helpful in positioning your company as a competitor for the business of senior citizens.

The Challenge of Increasing Usage

With as many benefits as revolving doors offer, it’s a no-brainer to install them or retrofit your building with revolvers, but it’s not always such a no-brainer for users to pass through them instead of using a manual or swinging door.

Andrew Shea from Good magazine wrote “How To Hack Big Energy Savings With a Simple Sign and a Revolving Door,” based on his own non-scientific experiments and observations. When there are revolving doors and swinging or manual doors in close proximity, people will follow the flow of traffic unless redirected by someone or something like a sign. Shea observed roughly 28 percent of people using revolvers when most traffic flowed through the swing doors into major buildings in Manhattan. Surely, manual doors are crucial for allowing building access to the disabled and to those bearing large deliveries, but “our country could decrease the $68 billion we spend on heating and cooling every year if the rest of us used revolving doors,” Shea wrote.

Using three different signs, Shea tested the impact of signs on the flow of traffic through revolving doors on Columbia University’s campus. He found that the bigger the sign, and the more closely aligned it is with the building or organization’s branding, the more effective it was. So a two-foot arrow in Columbia’s royal blue that points to the revolving doors and says “Please use revolving doors,” is more effective than a small orange sign with the same script.

Interestingly, the energy savings from using revolvers aren’t linear. You’ll see greater savings when you increase revolving door usage from 50 to 75 percent than you’ll see increasing usage from 25 to 50 percent. And so anything you can do to increase usage of your revolving doors, especially later efforts, will really pay off.