Types of Architectural Glass

01.12.2021

Architectural glass is glass that is used as a building material. 

Glass is an ancient building material, which facilitated penetration of light into buildings.

There are different types of architectural glasses with different appearance and properties, which can be used in buildings: 

  1. Annealed glass
  2. Wired glass 
  3. Heat-strengthened glass
  4. Heat-soaked glass
  5. Toughened glass
  6. Laminated glass 

Annealed (Float) glass 

Annealed (float) glass is the base glass that is form from the float glass process. 

Float glass can be broken easily and when it is broken, the glass shatters into sharp-edged shards. Becasue of that, float glass is not safety glass. Usually, this glass is suited for smaller applications such as cabinet glass doors, basement windows, tabletops, mirrors and more. Float glass is relatively cheap in comparison to other glass types such as Toughened glass.

Heat-treated glass

Briefly, the glass is heated to approximately 1200ºF (650ºC) and then force cooled to create surface and/or edge compression in the glass.
Two type of heat treated glass: 
  • Toughened glass
  • Heat strengthened glass

Toughened (tempered) glass

Tempered glass is also known as Toughened glass. 

Tempered glass is typically used in areas that: 

  • need increased mechanical strength versus annealed and heat-strengthened glass,
  • drilled (prior to tempering) or used in point support systems,
  • are subjected to thermal stress from temperature gradients, and
  • locations requiring safety glazing without glass fall-out concerns,
  • laminated glass applications requiring added glass strength and glass shard retention post breakage.

Heat-strengthened glass

Also known as semi-toughened (semi-tempered) glass, heat strengthened glass is a type of heat-treated glass and similar to toughened glass except that the cooling is done at a much slower pace. Similar to toughened glass, as it also goes through the furnace process. The process is similar to the traditional process of glass tempering. Annealed glass is heated to approximately 650-700 º C, but the cooling process is slower than that for tempered glass. 

Key features of heat-strengthened glass: 

  • The mechanical properties of heat-strengthened glass fall between annealed and fully-toughened glass. It is twice as strong as untreated annealed glass of the same thickness. 
  • Due to the relatively lower rate of cooling during the heat strengthening process, heat strengthened glass develops less stress as compared to fully toughened glass. 
  • Heat-strengthened glass is 3 times more resistant to thermal stress in comparison to normal annealed glass.

Heat-strengthened glass is not a safety glass product as defined by the various code organizations.

Heat-strengthened glass applications: 

  • When additional strength is needed to resist wind pressure, thermal stress or both,
  • Heat-strengthened glass can be selected for applications that do not specifically require a safety glass product, 
  • or when safety break pattern of fully tempered glass is not required.
  • For low optical distortion ( having flatter surface,  results in the facade having less optical distortions.)
  • Avoid the potential of spontaneous breakage,
  • Icreasing mechanical strength versus annealed glass,
  • Laminated glass applications: Heat-strengthened glass allows the internal layer of laminated glass to adhere more evenly because of a flatter finish surface.
  • re subjected to thermal stress from temperature gradients, and laminated glass applications requiring larger break patterns such as hurricane, balcony (undrilled) and blast and glass shard retention post-breakage.

Heat soaked glass

Heat soaking is a process in which toughened (tempered) glass is subjected to a temperature of 290°C for several hours in a heat-soaking oven. This will cause the panel to break if any nickel sulphide inclusions are found.

this method is used to reduce the risk of spontaneous breakage in architectural glazing.

Typically used for:

  • High rise glass facades.
  • Overhead glazing.
  • Balconies and balustrades.
  • Any application where a superior toughened glass is required.

Laminated Glass

Laminated glass is basically a glass sandwich. It is crafted by adhering two pieces of annealed glass together by a vinyl layer (EVA, PVB, or SGP). The vinyl layer holds the glass together if the glass is broken or impaled.

This is far less of a worry with laminated glass, as the glass stays in place when shattered. However, as laminated glass is not as resistant to breakage as tempered glass, accidental impacts, such as a stray ball or other flying object, are more likely to cause the glass to break and therefore need replacing.

 

Safety and security are historically the best-known characteristics of laminated glass as the interlayer tends to retain the broken glass shards and act as a penetration barrier.

toughened or heat strengthened laminates should be considered over annealed laminates,

Chemically Strengthened Glass

Chemically Strengthened Glass is annealed glass which is strengthened by a chemical exchange of ions. 

 

 

Insulating glass units

Insulating glass consists of two or more lites of glass separated by a hermetically sealed space for thermal insulation and condensation control.
The airspace between the glass lites can be filled during the manufacturing process with either dry air or a low-conductivity gas, such as sulfur hexafluoride or argon.

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