Glazing - Types
Glazing and framing systems can be unforgiving, inherently the weakest thermal component of the building envelope. On the other hand, when managed properly, they provide endless architectural opportunities and high-performance outcomes via daylight access, views and control of the building envelope performance.
Glazing and framing are highly diverse in their application and design intent, from safety and sound to comfort, thermal performance and advanced optical considerations.
Annealed Glazing
Annealed glazing is the most commonly used architectural glazing. Because it is not heat-treated and therefore not subject to distortion typically produced during glazing tempering, it has good surface flatness.
On the downside, annealed glazing breaks into sharp, dangerous shards. Heat-strengthened and fully-tempered glazing are heat-treated glazing products, heated and quenched in such a way as to create residual surface compression in the glazing. The surface compression gives the glazing generally higher resistance to breakage than annealed glazing.
Heat-Strengthened Glazing
Heat-strengthened glazing has at least twice the strength and resistance to breakage from wind loads or thermal stresses as annealed glazing. The necessary heat treatment generally results in some distortion compared to annealed glazing. Like annealed glazing, heat-strengthened glazing can break into large shards.
Toughened Glazing
Fully tempered glazing provides at least four times the strength of annealed glazing, which gives it superior resistance to glazing breakage. Similar to heat-strengthened glazing, the heat treatment generally results in some distortion. If it breaks, fully tempered glazing breaks into many small fragments, which makes it suitable as safety glazing under certain conditions.
Laminated Glazing
Laminated glazing consists of two or more lites of glazing adhered together with a plastic interlayer. Because it can prevent the fall-out of dangerous glazing shards following fracture, it is often used as safety glazing and overhead glazing in skylights. The plastic interlayer also protects from ultraviolet rays and attenuates vibration, which gives laminated glazing good acoustical characteristics. Because laminated glazing has good energy absorption characteristics, it is also a critical component of protective glazings, such as blast and bullet-resistant glazing assemblies.
Low Iron Glazing
Low-iron glazing is a type of high-clarity glass made from silica with very low amounts of iron. This low iron level removes the greenish-blue tint that can be seen, especially on larger and thicker glazing sizes, making it ideal for aquariums, shopfronts and other applications where clarity is a priority.
Manufacturers create low-iron glass by reducing the amount of iron in the molten glass formula. By modifying the iron content, we can increase light transmittance by 5 – 6%, reducing solar reflectance.
Double-glazed
Double-glazed units consist of two or more lites of glazing with a continuous spacer that encloses a sealed air space. The spacer typically contains a desiccant that dehydrates the sealed air space. The air space reduces heat gain and loss, as well as sound transmission, which gives the double-glazed unit superior thermal performance and acoustical characteristics compared to single glazing. Most commercial windows, curtain walls, and skylights contain double-glazed. The service life is typically determined by the quality of the hermetic sealants installed between the glazing and the spacers and the desiccant quality.
Triple-glazed
Triple-glazed units consist of two or more lites of glazing with a continuous spacer that encloses a sealed air space. The spacer typically contains a desiccant that dehydrates the sealed air space. The air space reduces heat gain and loss, as well as sound transmission, which gives the triple-glazed units superior thermal performance and acoustical characteristics compared to double-glazing.
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