Volume 40,   Issue 3                             March  2005

Re-Wired

Facing Tough Code Changes, Wired Glass Evolves for a New Era
   
by Jerry Razwick

It was 1973 when ABC first brought the Six Million Dollar Man to television. The premise of the show was simple: Steve Austin, an astronaut and test pilot, suffered a terrible accident. His heroic career was over and his life hung in the balance. Then came those opening words: “We can rebuild him. We have the technology.” And suddenly, the man who was all but dead had a new lease on life. He was given new, high-tech body parts that made him better, stronger and faster, and he had a new mission to accomplish.

Wired glass just may be our industry’s equivalent of the six million dollar man. After decades of proven performance, wired glass began to take some heat. As codes were rewritten, it looked like the writing was on the wall and the days of using wired glass might be reaching an end. But manufacturers knew they had the technology to rebuild it. They knew they could stretch the performance capabilities of wired glass and give it a new lease on life. So they invested the time, energy and resources needed to retool the product for the future. 

Evolutions
To really understand what has happened, it is helpful to know the background of the wired glass story. Invented more than a century ago, traditional wired glass was the first glazing material to offer any meaningful protection in a fire. Most glass shatters or melts in high temperatures, and the glass in wired glass is no exception. But the embedded wire mesh supports the cracked and slumping glass long after standard float glass would have vacated the opening. 

That ability to stay in place proved vital for preventing the spread of fire through a building. Because wired glass was the only available glazing that could perform that function, it filled a much-needed role. Without it, fire-rated areas would have been restricted to solid walls, with no visibility.

At the same time, wired glass presented a dilemma. As great as it was in a fire, wired glass could offer little in the way of impact protection. The imposing, secure image presented by the wires was an illusion. Not only could wired glass be broken easily, but the wires themselves created dangerous snags when broken.

The Codes
So code officials were put in the awkward position of determining which safety need was more critical—fire or impact. Many facilities need both. How do you choose a compromise?

In 1977, the U.S. Consumer Product Safety Commission (CPSC) decided fire safety overrode impact concerns. So the CPSC voted to grant wired glass a temporary exemption from meeting its impact requirements. As long as wired glass could satisfy the American National Standards Institute’s ANSI Z97.1, it was allowed. Code officials recognized the value of being able to see a fire on the other side of an opening. Since that time, wired glass has proved its effectiveness in helping contain fire in real world situations.

Just how different are ANSI requirements from CPSC guidelines for safety glass? The tests are performed in the same way for each, but reflect different levels of impact. A 34- by 76-inch piece of glass is mounted in a vertical frame. A punching “speed” bag is filled with lead shot (similar to BBs found in shotgun shells). This very heavy bag is hung from a cable and dropped in pendulum fashion from various heights to impact the glass. The glass either must not break or do so in a safe manner to meet the standards.

The ANSI Z97.1 standard requires a product to have a minimum of 100 feet/pound of impact resistance per square inch. To simulate this, the speed bag is filled with 100 pounds of lead shot and dropped from a height of 12 inches.

The CPSC 16 CFR 1201 is divided into two categories designed to simulate the impact of a human being running into a lite of glass. The Category I test involves dropping the speed bag filled with 150 pounds of lead shot (similar to BBs found in shotgun shells) from a height of 18 inches. This is roughly equivalent to a child running into the glass with the weight of his entire body, or a teen or adult running into it with an arm or leg. Thus, Category I is also known as the “partial body test.” Category II has a much higher threshold at 400 feet/pounds of impact or roughly the force of a teen or adult running directly into a single lite of glass. In this test, the speed bag is filled with 400 pounds of lead shot and dropped from a height of 48 inches. Category II is, therefore, also known as the “full body impact test.”

The difference between the ANSI Z97.1 and the CPSC 16 CFR 1201 Category I proved to be quite significant. Wired glass was cited in numerous cases of injuries. Most of these occurred among older students in middle and high schools, in which serious injuries were obtained when limbs broke through wired glass and became entangled in the wire mesh.

Clearly, something had to be done to address impact safety at the same time as fire.

Emerging Products
It was at this point that other fire-rated glass products began to emerge. These wireless materials offered tremendous advantages over traditional wired glass and expanded the definition of fire-rated glazing. For example, materials were introduced that capitalized on ceramic’s ability to withstand heat, but in a transparent form. These glass ceramics could offer considerably longer fire ratings than wired glass—up to three hours. It also could be specified in sizes up to 23 square feet—more than double the limit for traditional polished wire glass.

What’s more, fire-rated glass ceramics could do something else: In a laminated form, they meet the impact safety standards of CPSC 16 CFR 1201, Category II. Now there was a product that could do it all, without relying on any wire mesh.

Other alternatives also made their way to market. Glass firewalls were tested to the same standards as solid barrier walls and had the ability to block the transfer of heat. 

Code officials began to rethink their position on wired glass. If new products were available that could meet both fire and impact needs, and if wired glass was the cause of significant injuries, then something clearly needed to be done. 

So in 2003, the International Code Council (ICC) modified the impact safety exemption for wired glass. The International Building Code (IBC) was changed to state that glazing installed in all hazardous locations in K-12 schools, daycare centers and athletic facilities must meet CPSC 16 CFR 1201. It was only a matter of time before the exemption was lifted entirely. In 2004, the ICC updated the code once more to say that the standard would apply to all types of construction. These code changes are expected to go into effect nationwide with the adoption of the 2006 International Building Code.

Moving Forward
Until now, a large percentage of wired glass sales has been for use in hazardous locations—doors, sidelites and windows near the floor. Without those applications, would wired glass go the way of other obsolete products? Would the wireless options completely replace “old faithful?”

As attractive as the newer materials are, wired glass still offered one distinct advantage: price. The advanced technology involved in producing the wireless choices in fire-rated glass is an expensive process, which in turn results in a higher initial cost for the end product. And while the old adage is true that you get what you pay for, not all budgets can accommodate the higher end alternatives to wired glass. 

Thinking Differently
Believing there would always be a demand for a more commodity product, wired glass manufacturers and distributors set about rethinking their products. Today, new types of wired glass are available that can be used in hazardous locations.

One wired glass alternative recently introduced is a laminated version. This product carries a Category I impact rating and fire ratings up to 90 minutes in doors. It is made by laminating traditional wired glass with a special interlayer to another layer of clear glass. Once installed, it looks exactly the same as traditional wired glass.

Laminated wired glass comes with a permanent label, enabling code officials to distinguish it from traditional wired glass and identify the appropriate impact safety rating.

Given the highly innovative nature of the fire-rated glazing market, we can expect continued advances in wired glass. As code requirements and market demands evolve, the new wired glass will be ready to offer better levels of performance than ever before. 

The Author:
Jerry Razwick is the president of Technical Glass Products in Kirkland, Wash.


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