by Brian Stokes
As one of the most powerful forces produced by nature, hurricanes cause more than $2 billion in damages annually. Ongoing debates in the construction industry concerning which materials provide the best hurricane protection have caused manufacturers to provide newer and better products every year. One such introduction has been impact-resistant glass and hurricane-resistant glazing.
Impact-resistant glass is derived from laminated glass, which is a plastic interlayer material sandwiched between two lites of glass. The primary function of impact-resistant glass is to prevent flying debris from penetrating the building envelope. Its secondary purpose is to keep the shards of glass intact, in the event the unit is broken.
Published research results have triggered many arguments between manufacturers of PET films and laminates as to the best hurricane-resistant glazing to use for the protection of buildings and lives. But, one point we all seem to agree on is that the glass needs to remain in the frame for any type of protection to work. There is no point in holding the glass together if the whole glazing lite comes out of the frame during a hurricane. If the glazing lite comes out, the large piece of glass could be a lethal threat to whatever or whoever it hits, leaving the building vulnerable to the full force of the storm.
These debates have led to the use of laminated glass that is mechanically fixed to the frame. Hurricane-resistant glazing consists of a three-ply interlayer, the middle layer a heavy-duty PET (polyethylene tetraphthalate) film, cushioned on both sides by a plastic interlayer. The PET film is longer than the glass size and held into the glazing frame mechanically. Under the extreme conditions of a hurricane, hurricane-resistant glazing that had edge delamination or was impacted and broken, would not be removed from the frame.
The invention of this glazing method has changed the glazing industry in several ways. Prior to its inception, many manufacturers of windows and doors had to consider alternate methods of glazing. This was mainly due to the fact that smaller sizes of glass were required to meet tougher impact standards. Because natural lighting is such an integral part of building design, more stringent building codes were not widely welcomed. Since hurricane-resistant glazing was invented, daylight openings have become larger and more versatile.
It has been nearly seven years since Hurricane Andrew devastated South Florida. Since that time, stricter codes have become more acceptable, buildings safer and the increased costs we once saw are now declining. Recently, Hawaii and Texas have adopted similar standards (within coastal regions) and the state of Florida is expected to do so by the year 2001. There has also been much debate regarding these issues in the Carolinas in the wake of Hurricane Fran. The adoption of hurricane-resistant glazing, like any new technology, has been a slow and progressive process. However, with increased acceptance, mankind increases its chances of surviving mother nature.
Brian Stokes is the business development manager for Glasslam NGI Inc., based in Pompano Beach, FL.
Industry Responds to First-Draft of Floridas Statewide
To many industry professionals, hundreds of local codes in Florida are cause for confusion. So, many breathed a sigh of relief in June 1998 when Governor Lawton Chiles signed the Statewide Uniform Building Code into law. When it takes effect in 2001, the statewide code will integrate building code licensing, education and enforcement duties of 14 state agencies and more than 450 independent jurisdictions. But now that a draft of the code expected for completion in 2001, is circulating, some are unhappy with some of its provisions.
One of the most controversial changes is the Florida Building Commissions elimination of wind-load requirements from the first draft. The response to this from a representative of an association of leading shutter manufacturers was, without the wind-load requirements, the draft building code takes us back 20 years in terms of hurricane protection and it totally ignores the hard lessons we learned from Hurricane Andrew.
Others in the industry are not as concerned with what appears in the first draft. I dont think it [wind load requirements] will be weakened in the final code, said Brian Stokes of Glasslam NGI of Pompano Beach, FL. There are so many factors involved and wind-load plays too large a role for it to be eliminated.
Windstorm Center Collects Valuable Hurricane Data
The Idaho National Engineering and Environmental Laboratorys (INEEL) Windstorm Center in Idaho Falls, ID, houses technology that will aid architects and builders in the construction of hurricane-resistant homes. The experimental data collected from the test results will help scientists as they finish designs and begin construction of the larger pilot windstorm center, The Homesaver facility, planned to open in 2003.
According to representatives at INEEL, the windstorm center simulates a natural storm by using a bank of 18 fans in three layers that run at different speeds and different times, creating turbulence and 90 mph winds. Traditional wind tunnels have a uniform flow of air, with one speed and one direction. The bank of fans in the Center produce wind, which is funneled down to increase intensity and directed by louvers and speed changes to produce wind gusts. The wind field created in the Center is equal to a category one hurricane.
The test results will be able to benefit everyone, said project manager Cheryl OBrien. According to OBrien, customers will be able to test windows, shutters or tie-down products for their ability to withstand high winds.
The Scale Windstorm Center is one-fourth the size of the Homesaver facility, which will eventually test full size homes and buildings by exposing them to severe, turbulent wind. The Center will provide scientists with experimental data on performance of the model, such as controllability of the blowers, air flow generation, and characterization of wind turbulence.
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