Volume 35, Number 4, April 2000
Good Ol Lami
an old product for a new century
by Dez Farnady
Laminated (or lami) glass is an old product capable of solving many new problems. We have been selling laminated glass as a commodity product for decades but we have been slow to realize that lami may become to the glass industry what the microchip is to computing.
Laminated glass is a composite of multiple layers of glass, a plastic or polyvinyl interlayer, and more glass. The built-up layers are sandwiched together with the vinyl interlayer acting as the glue. In normal glazing applications under normal conditions this sandwich will act and load in a manner similar to a single piece of glass of the same thickness to make a highly-efficient piece of multi-purpose glass.
Think of when you go to the local sandwich shop to place your lunch order. If the shop is worth its salt it will start by giving you about a dozen bread options. Then they have five or six meats to choose from, cheese, lettuce, tomato, pickles, sprouts and so on. You have lots of options and with the right combinations you can build just the right sandwich.
The laminated sandwich can start with any one of a dozen different colors of glass. The next portion is the vinyl, which is also available in several colors and in several thicknesses that can be layered to build up the overall thickness or modify the color. There can be additional glass and more vinyl layers added to create hundreds of combinations that can also be added to air space and glass to make laminated insulating units. Variations are innumerable, depending on the performance or the appearance or the flavor the customer wants or circumstances require. Standard uses of laminated glass today include safety glazing, overhead glazing, ultraviolet protection, sound reduction, security and bullet-resistant glazing, storm or hurricane protection, etc.
Safety glazing is the oldest use for lami because a simple vinyl layer of .030 thickness will allow two pieces of glass sandwiched together to meet code-mandated safety-glazing requirements. The addition of extra layers of vinyl can make the window difficult enough to penetrate to allow it to qualify as security glazing to prevent unwanted intrusion by burglars. That same heavy layer may well function as hurricane protection because it can prevent wind-blown debris from penetrating the building envelope. Multiple layers of vinyl and glass can even stop a bullet. The glass that stops a BB may not stop a bazooka, but with enough layers you can have readily available and serviceable products. Some laminated products can even stop high caliber handguns and rifles.
In recent years, the architectural glass market has also discovered what the automobile business has known for years: it is possible to reduce the damage done by ultraviolet light transmitted through glass without reducing the amount of visible light. According to the vinyl manufacturers, the UV light inhibitors they have developed are able to eliminate the transmission of 99-plus percent of the UV light and leave the glass appearing perfectly clear.
And not only will that vinyl keep out the UV, but it also does wonderful things to prevent sound transmission. This may not be a very scientific explanation, but in effect, that vinyl functions like a shock absorber to sound waves. Heavy, multi-layered combinations of glass and vinyl retain the glass clarity but stop sound transmission, sometimes better than the wall does, and nearly always better than the perimeter frame or standard glazing system.
Laminated glass in overhead glazing has provided the safety required to keep broken glass from falling on peoples heads and at the same time provided the desired view and light transmission. The energy performances not possible with acrylic dome skylights are now achieved easily with insulating units composed of performance tinted tempered glass over laminated. These are the same combinations of energy products previously used only in vertical applications.
While this bit of information is not new to most people in the glass business, I hope it reminds some to consider glazing options from a different view. You may save both yourself and your customer time and money if you are aware of all the things laminated glass can do for you.
Dez Farnady is manager of architectural products for ACI Distribution in Santa Clara, CA. His column appears monthly.
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