Choosing your windows

Avoid risk of injury caused by broken glass with toughened and laminated forms!

Glass can be a dangerous material

When standard glass breaks, it can form dangerous shards and splinters. To avoid risk of injury caused by broken glass, high tech safety glasses are available in toughened and laminated forms – most of which can be used in double glazing window. Wired glass also qualifies as a safety glass. Less effective, it is only awarded the class C level of the British Safety (BS) standards scale.

Usage of safety glass

Safety glass is now mandatory in some areas of the home (see Building regulations), as well as throughout some types of buildings such as schools. Glass used in roofs must also meet safety requirements in case of an object falling on to the double glazing window which could cause fragments falling below.

Standard requirements for safety glass

Safety glass must conform with the BS 6206 standard requirements in order to qualify as safety glass. Three levels of impact resistance exist under the BS specifications – A, B and C - with class A being highest. For glass to be awarded the class A safety standard, it must be able to resist an impact of 45kg without breaking, or break safely. However those with projects for safety glass should be prepared for the more stringent European safety standards that are currently coming into effect for the UK (for more information see Standards)

Laminated glass

Laminated glass is comprised of one or more interlayers, sandwiched between two or more sheets of float (or annealed) glass. The interlayers are composed of a PVB (polyvinyl butyal) laminate, or cast resin.

Cast resin laminated glass is manufactured by pouring liquid resin into the cavity between two glass sheets. This method of laminate is often used where heavily textured or patterned glass is to be used.
PVB laminated glasses tend to have a higher safety performance and are the more commonly used variety. One or more sheets of glass are bonded together with one or more PVB interlayers. If the glass suffers an impact, it may eventually fracture, but the broken fragments will remain bonded to the interlayer.

Other benefits of laminated glass

Safety grade laminates also act as a deterrent against burglary and vandalism. Depending on the composition of the laminate and thickness of the glass, different levels of performance are also possible for acoustic insulation and protection against firearms and explosions. (Also see Security Glass).

Toughened Glass

Toughened, or tempered, glass is four to five times stronger than ordinary float glass. If it is broken relatively harmless fragments, known as ‘dice’, are formed which are unlikely to cause injury. Toughened glass that meets with the highest British Safety Standards, Class A, is suitable for use in structural double glazing window where the glass is to be fixed by bolts or clamps.
Toughened glass is made by heating prepared and processed glass sheets to a temperature of 700°C (just above the softening temperature of glass) The sheets are rapidly cooled by blasts of cold air to both surfaces, resulting in the outer surface contracting and solidifying before the interior of the glass. This process increases the tensile strength of the glass and gives it safe breakage characteristics.

Combinations

Toughened and laminated safety glass can be combined with other double glazing windows such as decorative, easy clean, thermal insulation and solar protection glass within the same double glazing window. (See Which Glass Combinations).






© 2008 - double-glazing-info.com | Contact-us | Legal Notice | Site Map