Tempered Laminated Glass Specifications

Laminated glass is strenghened to hold together when other types of glass might shatter

Tempered laminated glass is a variety of safety glass that holds together more reliably when it is shattered. Laminated glass contains an inter-layer, typically of high strength polyvinyl butyral (PVB), that is located between its layers and keeps the layers bonded even when broken. An impact that is insufficient to brake the laminated glass into small pieces will create a recognizable "spider web" cracking pattern. Tempered means it is strengthened by the process of heating. Laminated glass can be manufactured with variable properties of visible light transmittance, solar transmittance, visible light reflectance and solar reflectance.

Visible Light Transmittance

Visible light transmittance is the percentage of visible light (with a wavelength from 380 nm to 780 nm) that is permitted to be transmitted through the laminated glass. For instance, Viracons VH1 1-75 permits 82 percent of visible light to be transmitted through the glass, while the VH1 1-50 allows 50 percent of visible light to pass through. Other models in Viracons range permit much lower levels of visible light passage, such as the VH1 3-50, which permits 27 percent, and the VH1 3-40, which permits 20 percent.

Solar Transmittance

Solar transmittance is the percentage of visible, ultraviolet and near infrared energy (with wavelengths between 300 nm and 3000 nm) that is transmitted through the laminated glass. This value scales with the figure for visible light, so VH1 1-75 permits 48 percent of solar rays and VH1 1-50 permits 33 percent, while VH1 3-50 permits 18 percent and VH1 3-40 permits 12 percent.

Visible Light Reflectance

The visible light reflectance is the amount of visible light that is reflected from the laminated glass's surface. Visible light is both reflected inward (Vis-In) and outwards (Vis-Out). For instance, VH1 1-75 has a Vis-In value of 9 percent and a Vis-Out value of 9 percent. VH1 1-50 has a Vis-In value of 8 percent and a Vis-Out value of 14 percent. On the other hand, VH3 3-50 has a Vis-In value of 5 percent and Vis-Out value of 14 percent, while VH1 3-40 has a Vis-In value of 7 percent and a Vis-Out value of 14 percent.

Solar Heat Gain Coefficient (SHGC)

The solar heat gain coefficient (SHGC) is the amount of directly transmitted and absorbed solar energy that enters into the building's interior through the laminated glass. A higher value of SHGC indicates a higher heat gain. The VH1 1-75 has a SHGC value of 0.58, while the VH1 1-50 has a value of 0.48. The VH1 3-50 and VH1 3-40 possess lower levels of SHGC and thus a lower heat gain, with values of 0.38 and 0.32 respectively.

References

• Glass Solutions: PVB Laminated Glass
• Viracon: Laminated Glass