How heavy is glass in relation to its thickness?
Glass is a relatively heavy material. Glazing large openings often requires thicker & heavier glass to minimize deflection and withstand the imposed wind loads. A notable exception is channel glass, which can achieve greater spans in relatively lightweight 1/4″ (6 – 7 mm) thickness thanks to its unique U-shape.
Thicker glass may also provide additional aesthetic advantages, including lending a greater sense of depth and body to the wall. Naturally, the thicker the glass, the greater its weight:
|Glass Thickness||Approx. Weight|
|1/8” (3 mm)||1.5 lb/ft² (7.5 kg/m²)|
|5/32″ (4 mm)||2 lb/ft² (10 kg/m²)|
|3/16” (5 mm)||2.5 lb/ft² (12 kg/m²)|
|1/4″ (6 mm)||3 lb/ft² (14.5 kg/m²)|
|9/32” (7 mm)||3.5 lb/ft² (17 kg/m²)|
|5/16″ (8 mm)||4 lb/ft² (19.5 kg/m²)|
|3/8″ (10 mm)||5 lb/ft² (24.5 kg/m²)|
|1/2″ (12 mm)||6.5 lb/ft² (32 kg/m²)|
|3/4″ (19 mm)||10 lb/ft² (49 kg/m²)|
|1” (24 mm)||13 lb/ft² (64 kg/m²)|
What is annealed glass? What is annealing?
Annealing is the controlled cooling of glass during the manufacturing process. It is the first level of architectural glass production. The process prevents residual stress in the glass, allowing it to be easily handled and processed.
Annealed glass is not as strong as tempered or heat-strengthened glass of the same thickness, and breaks into large shards. It is not safety glass.
What is safety glass?
Safety glass is tempered glass (also referred to as “toughened” or “fully tempered” glass) and/or laminated glass that meets the requirements for ANSI Z97.1 and the federal safety standard CPSC 16 CFR Part 1201 (Consumer Product Safety Commission Safety Standard for Architectural Glazing Materials).
Glass is a breakable material. If it breaks into sharp pieces, or shards, it can injure people and pets. Safety glass improves occupant safety and well-being by significantly reducing this risk. In the case of tempered glass, if broken, it exhibits a characteristic “dice” break pattern of many small pieces that minimize the risk of injury. In the case of laminated glass, if broken, it remains in place, held together by the plastic or resin interlayer at its core.
Safety glass is typically identifiable through a permanent marking (a safety seal), generally located in one of the corners of the glass piece. This marking cannot be removed without damaging or breaking the glass.
The US standards for testing and classifying safety glazing materials are:
- ANSI Z97.1 (American National Standards Institute’s Standard for Safety Glazing Materials Used in Buildings)
- CPSC 16CFR, Part 1201 (Consumer Product Safety Commission Safety Standard for Architectural Glazing Materials)
Where should safety glass be used?
The Consumer Products Safety Commission establishes the federal standards and requirements for safety architectural glass. Federal safety glazing law requires the use of safety glass in defined hazardous locations, designated by the Model Building Codes. Generally, these include:
- Bath and shower enclosures
- All doors, including storm doors, sliding doors, and combination doors
- Sidelites, including and any glazing next to a door or an opening for human passage, if the nearest exposed edge is within 24” (0.6 m) of the vertical edge of the door or the bottom exposed edge is less than 60” (1.5 m) above the walking surface
- Areas where the glass is adjacent to walking surfaces and the bottom edge of the glass is within 18” of the floor
- Areas where the top edge of the glass is more than 36” above the floor
- Glazed panels greater than 9 ft.2 (0.8 m2)
Local building code authorities may have additional safety glazing requirements, which can vary by state, county, city, town, or borough. Because each state has either adopted the model federal safety building code, modified it in some sections, or written completely new sections, it is imperative to be guided by the particular state or local building code where the glass is to be installed. For detailed information, please contact your local code officials.
What is laminated glass? Is it safety glass?
Laminated glass is a safety glass that contains two or more glass lites permanently bonded together with one or more PVB, EVA, or liquid resin interlayers. It meets the requirements for ANSI Z97.1 and/or CPSC 16 CFR 1201, and is typically labeled with a “safety” logo identifying the fabricator, glass type, and the standard it meets. Additional benefits of laminated glass can include improved UV and sound control. Various decorative laminates, including virtually unlimited custom color and interlayer options, are available from Bendheim.
What is tempered glass? Is it safety glass?
Tempered glass is also referred to as “toughened” or “fully tempered” glass. It is heat-treated safety glass with a minimum surface compression of 10,000 psi or a minimum edge compression of 9,700 psi. The surface of tempered glass is approximately four times stronger than the surface of regular annealed (non-safety) glass of the same thickness.
When broken, tempered glass shatters into small, relatively harmless pieces. This characteristic “dice” break pattern minimizes the risk of serious injury.
Bendheim tempered glass meets the requirements for ANSI Z97.1 and/or CPSC 16 CFR 1201, and is typically labeled with a “safety” logo identifying the fabricator (Bendheim), glass type, and the standard it meets.
Bendheim’s tempered channel glass is SGCC-certified and has a “safety” logo permanently etched into the glass, in compliance with federal regulations. The Safety Glazing Certification Council (SGCC) is the largest independent third-party that inspects and test tempered glass to confirm the manufacturing process and result. The SGCC is a voluntary organization. Satisfactory participation in the Council allows the glass manufacturer/fabricator to etch the SGCC logo permanently onto the glass, as notification that the glass has been properly produced.
Tempered glass is required as safety glazing in “hazardous” applications, such as floor-to-ceiling partition walls, entrance doors, sidelites, etc.
Glass cannot be further processed (cut, drilled,etc.) after tempering.
What is heat-strengthened glass? Is it safety glass?
Heat-strengthened glass is non-safety glass. It is approximately two times stronger than regular annealed glass of the same thickness. It features a surface compression between 3,500 and 7,500 psi and an edge compression of 5,500 psi or greater. Heat-strengthened glass’ break pattern is similar to annealed glass.
Heat-strengthened glass is available from Bendheim for special applications that do not require the use of safety glass.
What is heat treated glass?
The term “heat treated glass” can be used for both tempered (safety) glass and heat-strengthened (non-safety) glass.