Volume 37, Issue 6, June 2002
It’s Not Just Florida Anymore!
by Robert Foster and John L. Feininger Jr.
An impact-resistant 1600 Wall System® with Sentry glass was used on North Miami Public Safety Building. The architect for the project was Spillis Candela & Partners Inc. of Coral Gables, Fla., and the glazing contractor was Custom Glass Co. of Fort Lauderdale, Fla.
Ask a few people what comes to mind when you mention the words “impact resistance” and you will probably hear the words “hurricanes” or “Florida.” Yet an increasing number of states and counties are approving building codes and protocols that protect against the damage inflicted throughout the United States by heavy storms and the “mini-tornadoes” that form rapidly within them. In addition, building owners are recognizing the value of the protection that impact-resistant building products provide.
From New York to the Carolinas and Texas, wind-borne debris regions have been delineated and covered by new building codes. The problems are not only coastal or hurricane-related. Stories are being told from Minneapolis to Nashville. Have you heard the one about the wind-borne debris that punctured the sliding doors and destroyed contents of a condominium building, except for the few owners who had the foresight to install impact-resistant sliders? Or the entire curtainwall that detached from the side of a building and had to be replaced with a higher performance product from another manufacturer?
These stories may sound dramatic, but there can be no doubt that the relatively small additional expense for impact-resistant products is a sound investment for building owners and architects not only for protection of life and property, but also for security reasons. More important, they demonstrate that severe weather damage is not “just Florida anymore” and can happen to almost any owner, anywhere.
Insurance companies in many states are also driving changes in building codes by offering price breaks to building owners for updating with impact-resistant products. These not only protect against wind-borne debris penetration during violent weather, but also provide added security against vandalism and break-ins.
Multiplying Effects of Building Envelope Penetration
Consider what happens during a severe storm or hurricane. A major cause of damage is penetration of the building envelope by wind-borne debris, which can smash vulnerable points such as glass in doors, storefronts, curtainwall and windows. When loose wreckage forces its way inside buildings, the openings cause significant increases in internal air pressure that typically exceed the design capabilities of exterior building components. These “mini-tornadoes” can cause windows, roofs and walls to blow out and expose contents to secondary wind and water damage while the storm rages.
Preserving the integrity of these points of entry can mean the difference between virtually no damage and complete devastation. It also provides increased security both against the looting that can follow severe weather and throughout the year.
Large missile impact tests are required for products such as entrances and storefronts installed up to 30 feet above grade. The tests simulate large wind-borne debris, such as tree limbs and other large objects. Small missile impact tests simulate smaller wind-borne debris, such as roof gravel, and are required for products installed more than 30 feet above grade, such as curtainwall, sliding doors and windows. The first phase of test requirements call for entire systems–glass, frames, sealants, locks and fasteners–to resist wind-borne debris penetration. The second phase of the test involves severe pressure cycling tests that imitate the dangerous pressure changes that occur as storms and hurricanes pass.
Large missile impact-tested products closer to ground level are typically silicone glazed, while small missile impact tested products are usually dry glazed. The silicone glazing that typically is required for large missile tested products is needed primarily due to both of the impact glass plies breaking upon impact. This allows the glass to rotate in the framing system during pressure cycle testing. Usually the small missile impact test does not break both glass plies. Therefore, the glass is more rigid and does not rotate as much during the pressure cycle testing. Thus, a typical dry glazing approach is usually sufficient.
Currently, there are four basic codes that incorporate impact standards: South Florida Building Code (SFBC), Standard Building Code (SBCCI), Florida Building Code (FBC) and the International Building Code (IBC). Each of these codes reference specific impact and pressure cycle testing: SFBC – Dade County Protocols 201, 202 and 203; SBCCI – SSTD 12; FBC – Testing Applications Standards TAS 201, 202 and 203; and IBC – ASTM E 1886 and E 1996. Effective March 1, 2002, the SFBC has been replaced with the new FBC.
Some codes borrow portions from others and adjust them for local conditions. All basically require wind-borne debris protection of glazed openings for areas within delineated high miles-per-hour wind-borne debris regions. All codes require approved, independent testing to comply with ASTM, AAMA and impact-cycle standards. Local governments or code enforcement offices establish specific wind speed/wind-borne debris region lines, using physical landmarks, such as roads, rivers, etc.
Testing for products outside these areas do not have such restrictive requirements. It is important to check with your local code official for advice and to ensure that you have the applicable code for the project you are working on. There are minor differences in testing procedures within the different standards. It is important to remember that a Miami-Dade County (BCCO) Notice of Acceptance (NOA) is still valid and recognized by the State of Florida. The BCCO NOA product approval process is a viable evaluation entity. Typically, a Miami-Dade Country NOA is accepted as complying with all of the various code requirements.
The FBC mentions specifically the necessity of applying standards and rational analysis of sizes when project configurations do not completely conform with codes. While Miami-Dade County is at the forefront of performance standards, several minor deviations may affect your job. One standard might not meet another. Once again, it is important to ask the correct questions and go to the local code official for advice. Codes change frequently within counties and sometimes there are different interpretations within the same county. The glazing contractor who knows the local information and interpretations holds trump cards in selling his expertise when talking to an architect or building owner.
Manufacturers who provide single-source responsibility provide glazing contractors with an advantage. Purchasing the complete envelope of impact-tested entrances, storefront framing, curtainwall and windows from one manufacturer simplifies the job and gives glazing contractors valuable time to concentrate on other critical needs. For complex impact-resistant projects, technical assistance, engineering and field support from your manufacturer ensures an easier journey through the installation and code compliance process.
It is worth mentioning a caution regarding the use of shuttered application options for architectural aluminum products. Shutters require installation and removal time, change aesthetics and require storage when not in use. For these reasons, the commercial-construction industry standard is the use of impact-resistant glass products.
New glass technology has enabled the introduction of several new infill options and costs have been reduced substantially. Glass has evolved from a special exposed laminate to glass-clad polycarbonate and now standard use of 0.090 PVB (Polyvinyl Butyral) for large-missile applications. Your project may not require such high design pressures. This can affect the system chosen, the hardware choices and the overall-installed cost.
Sliding glass doors, swing doors, storefront framing, fixed windows, window wall and curtainwall need no longer be considered the vulnerable areas on commercial buildings where penetration starts the chain of destruction in violent storm conditions. Building owners in East Coast cities from New York to Texas and inland cities such as Nashville and Minneapolis, are considering impact-resistant options for these products. Government buildings, schools, hospitals, universities and banks are increasingly realizing the wisdom of impact resistance for safety of life and property in violent weather as well as year-round security. Impact resistance is no longer “just Florida anymore.”
Florida Building Code
Southern Building Code
National Hurricane Center
Kawneer Company Inc.
Robert Foster has 38 years of sales and marketing experience with Kawneer Co. He currently serves as senior marketing manager at the company’s Norcross, Ga., corporate office. John L. Feininger Jr. is marketing manager for entrances and framing systems at Kawneer.
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