GlassCatalogue_LowRes

Glossary Of Terms / T
Toe bead
A bead of material applied at the apex between the glass stop and horizontal frame
member into which the light is set.
Tong marks
Small surface indentations near the edge of vertically toughened or vertically heat
strengthened glass. These are caused by the tongs used to hold the glass during this
method of heat treatment.
Toughened glass
Flat or curved glass that has been heat treated to induce a high surface and /or edge
compression. Toughened glass, if broken, will fracture into many small pieces (dice) which
are more or less cubical. Fully toughened glass is approximately 4 to 5 times stronger than
annealed glass of the same thickness when exposed to uniform static pressure loads. It is
sometimes called ‘Tempered glass’.
Toughened laminated safety glass
Laminated safety glass which has two panels of toughened safety glass in the make-up.
Total energy transmittance or solar factor (SF) or solar heat gain coefficient (SHGC)
This describes the fraction of total incident energy which passes through a glazed area of a
building when compared with the incident energy upon it. The components considered for
this calculation are the direct solar energy transmittance and the indirect thermal energy
heat transfer values.
The calculation sums the fractions of incident direct solar energy and the ambient thermal
energy which passes through the glazed area under specific environmental conditions.The
calculation takes account of the following factors, specified by the regional international
standards:
• The angle of the sun with respect to the façade
• Ambient air temperature differential across the glazed assembly
• Surface heat exchange coefficients for both internal and external surfaces
ASTM E971-11, EN 410 and ISO 9050 are the most commonly applied standards for energy
performance calculation for glazed areas.
These calculations provide standardized values of heating energy arriving inside a building
and is expressed as a number between 0.00 and 1.00. A lower total solar energy number
means less heat penetration inside and a reduction in air-conditioning operating cost.1
implies all radiation travels through the glass, 0 implies no radiation travels through the
glass.
Trace elements
A chemical added to glass in only small amounts to affect the properties of the glass.
Translucent glass
Glass that transmits light with varying degrees of diffusion so that vision is semitransparent.
252 Product Catalogue For Glass Processors & IG Manufacturers