Guide to glass codes: How glass becomes spaghetti
For many years, plain old annealed glass in a variety of thicknesses was sold as a commodity. Today, however, the glass market has evolved to include a range of value-added products that fills many purposes, including hurricane-impact resistance. With seemingly endless options available, the glass market looks like a plate of spaghetti—a twisted, tangled pile of value-added options atop the plain glass plate. This confusion can make marketing and selling value-added products challenging for the glass industry. However, by examining the glass mélange from the consumer perspective, the industry can straighten out its spaghetti and make value-added products much more palatable to buyers.
The ingredients: raw materials
Flat glass sold to fabricators constitutes the most basic raw material; everything else gets piled upon this plate. The fabricators then bring in that stretchy stuff known as interlayers. Like pasta, they come in a variety of shapes, types, colors and sizes. Then come sealants, desiccants, metal targets, paint, spacers and gas. The fabricators cut, coat, paint, laminate, temper, insulate and finally label the glass products to create the variety of impact-resistant products available on the market today.
Labeling has emerged as an area of increased importance. Municipal code officials need to know exactly what window systems are being used because the number of glass options and performance requirements has increased significantly. Last spring in Charleston, S.C., for example, code officials made one contractor pull windows out of a building and made another purchase shutters because the labels did not prove that the windows provided sufficient protection in a hurricane-impact zone. The glass fabricator who understands the importance of clear and concise labels can do his or her part in helping to keep window manufacturers and installers out of trouble with building inspectors.
As if there were not enough choices available, glass also is paired with framing systems, another pile of pasta mixed in with the spaghetti. Depending upon factors such as thermal properties needed, area to be spanned, the estimated wind load and the type of building, an appropriate framing system must be selected. Aluminum framing systems currently dominate the hurricane-impact market because of their strength, durability and versatility. Aluminum has an estimated 65 percent market share of approvals in Miami-Dade County, Fla., in 2005. However, depending upon the project requirements and building locations, wood, steel, polyvinyl chloride and other framing materials also are used. Together, the glass, frame, attachments and anchoring make up the window system, that has to be tested.
The impact-resistant testing process adds another set of tangles to the spaghetti plate. When it comes to hurricane-impact glazing—especially for windows that must meet the requirements set forth by Miami-Dade County—the fabricator and frame manufacturer collaborate and discuss proposed designs with county building officials before the testing process begins. When the design has been agreed upon and certified samples built, testing begins.
In hurricane-prone regions, building codes and test standards have been adopted to ensure the integrity of the building envelope during a hurricane. Systems are tested as a unit, not as separate parts, to ensure that the entire system will function as designed. Code officials recognize four basic regulations for windborne debris: ASTM International’s ASTM E 1886 and 1996, included in the International Code Council’s codes; the Florida Building Code High Velocity Wind Zone standard, in force in Dade County; the Texas Department of Insurance Program 1-98; and the Southern Building Code Congress International’s SBCCI 12-97 Wind-borne Debris Standard.
The first step is to identify where the window or door system will be used; this will determine the test criteria. If a system passes impact- and cyclical-load tests, it is laboratory certified as missile-resistant and can then be submitted for further county or state certification.
Finally, after a system is approved, it can be purchased as a glazed system, or a glazing contractor can purchase lineals, glass and other glazing supplies to construct and install the unit. All components, including the glass, frame, sealant, gaskets, setting blocks and any other parts the glazing contractor uses, must be identical to and installed in the same manner as those tested.
Straightening the spaghetti
As the number of hurricane-impact products grow, the potential for market growth makes it well worthwhile for industry participants to try to straighten out the spaghetti for all involved. When bringing an impact-resistant product to market, use the following 10-step recipe:
1. Determine the target market. Do you want customers in the Florida High Velocity Wind Zone, Florida without the HVWZ, or other markets that require fenestration products that have passed large-missile-impact tests or small-missile-impact tests for residential or commercial fenestration and so forth? This selection will determine what test protocols and products need to be analyzed before proceeding.
2. Select test procedures. Based on your choice of market, review the test procedures applicable to that area. Maybe only small-missile tests are needed, or perhaps Dade County qualification is not necessary. This decision will have tremendous cost impacts on the system and qualification process as many elements need to be changed, depending on the test methods.
3. Determine the largest system. Consider the cost of testing versus the market potential for that product. A company may spend $50,000 to $60,000 trying to qualify its glazing to the largest size unit it sells on a national basis, but that unit may be less than 1 percent of annual sales. On the other hand, if executives size the system to its most common size to gain entry, the costs of qualification will be reduced significantly to possibly $10,000 to $15,000. Of course, if architects and specifiers need the largest size system to sell the package, company officials must make the testing investment.
4. Determine structural requirements. Once market and unit sizes are selected, determine the structural capability of the frame and the glass. Manufacturers should not automatically assume annealed glass will get them through the qualifications they need for the market. Just because annealed glass will pass impact and cycling tests does not mean it will be acceptable according to the building codes that reference ASTM E 1300, the glass strength standard.
5. Select and design frames. Once the structural requirement is known, the frame must be selected or designed to perform during test and in-field use. Some critical elements include the capability to handle the design pressure, a glass pocket wide enough to hold laminated glass or an insulating laminated glass unit with the proper air space and glazing, a minimum 1⁄2-inch glass bite and interior glazing. The lamination should always be placed toward the interior of an insulating unit.
6. Select components. Again, depending upon previous choices, manufacturers will know whether they need to have products with a Notice of Acceptance or simply a qualified, certified and tested system. Component choice should be made on the basis of
• Listed NOA components, if applicable
• Unit size
• Test method: ASTM International or Dade County criteria, large- or small-missile testing and so forth
• Frame rigidity
• Anchoring system.
7. Construct the units with approved components. Units must be constructed exactly as they will be manufactured with all components documented, including NOAs, if applicable. Limited substitutions are allowed. Instructions for installation must be provided and units must be supplied to the test lab in an installation mock-up buck, a frame to put the window or glazing into for testing.
8. Perform lab testing for certification. Select an independent and certified laboratory for the market being sought, such as a Dade County-certified lab, SBCCI-certified lab, Florida certified lab and so forth. Ship three fully cured, assembled and bucked systems to the lab for testing with selected protocol. The lab will schedule and inform the manufacturer of the test date. On-site witnessing can and should be done. If all units pass, the system will be certified by the lab with the proper documentation.
9. Produce documentation as tested. Both laboratories and certifying agencies will require CAD drawings of the systems, including component specification for the samples as tested. The lab also will remove a section of the tested specimens to determine if all three units are exactly the same and if they conform to the submitted documentation. If all is in agreement, the lab will issue a certified test report to be used for sales and further certification.
10. Submit documentation for approval. The certified test report is submitted to the governing body for acceptance. In the case of Dade County, this process takes four to six months if there are no negative issues or missing requirements. Use a General Submission Checklist or appropriate system checklist for a window, door, curtain wall or skylight and component supplier NOAs for Dade County. For more information, visit www.buildingcodeonline.com.
Then, with their spaghetti straightened, manufacturers can sit back and wait for the hungry hordes to descend on the company’s delicious offerings.