'Tis the season… hurricane season that is. With the beginning of hurricane season, and Katrina and Wilma still in our mind, this is a great time to answer some frequently asked questions about impact-resistant glazing.

Q: Impact-resistant glazing is often referred to as a systematic approach, what does that mean?

A: Traditional glazing or non-impact applications involve a component approach where the glass and framing are viewed as separate items. The systematic approach means the success or failure for hurricane protection depends on the glazing, aluminum framing, anchors and sealant functioning together.

Q: When specifying IG unit configurations, do you put the laminated lite on the interior or exterior of the building?

A: There isn’t a specific correct answer to this question. If you search the notice of acceptance of various manufacturers, you will see some have the laminated lite inside and some have it outside. The one characteristic that carries through all the approved products is that the laminated lite is the lite structurally secured to the frame with tape and/or caulk and the single lite is next to the applied stop. 

Q: What are the system testing protocols?

A: Impact and cycling, which simulates wind with positive and negative pressure, is required for windows and doors. Air, water, and structural testing is required for all products.

TAS protocols are test protocols implemented by the Florida building code and previously known as PA protocols. They are based on ASTM test guidelines. TAS-201 is for impact based on ASTM E1996. TAS-202 is for structural, air, and water based on ASTM-330, E283 and E331/E547. TAS-203 is for cycling and is based on ASTM E1886. 

Q: What is an impact test and what is the difference between large and small missile resistant test?

A: The Miami-Dade building code requires that every exterior opening, residential or commercial, be provided with protection against wind-borne debris caused by hurricanes. Such protection can either be shutters or impact-resistant products. There are two types of impact-resistant products: large-missile resistant and small- missile resistant. 

A large-missile resistant product is exposed to various impacts with a piece of lumber weighing approximately 9 pounds, measuring 2 inches x 4 inches x 9 feet, traveling at a speed of 50 feet per second (34 mph). Then the product is subjected to hurricane loading of 9,000 wind cycles, positive and negative. A product below 30 feet from the ground must be large-missile impact resistant.

A small-missile resistant product is exposed to various impacts with 10 ball bearings traveling at a speed of 80 feet per second (50 mph). The product is then subjected to wind loads for 9,000 cycles. A product located above 30 feet from the ground must be small-missile resistant.

Q: When using laminated glass for impact-resistant glazing applications is heat strengthening required? 

A: No, it is not required to use heat-strengthened glass but using annealed glass decreases the overall strength of the product (lower psf design pressures). On the other hand, stronger, tempered glass will break into extremely small pieces, which will not allow the product to withstand the cycle part of the impact-resistant testing procedure.

Q: What about that very important and sensitive topic the budget? 

A: This is a difficult question to address because every project is somewhat different. Impact systems are going to cost more than traditional storefronts and curtainwalls. Consult an impact system manufacturer; by seeing the total scope of the project, they will be in the best position to assist in budget and design issues. As always, the best way to ensure a solid bid document is to consult with a manufacturer of the systems early in the process. 

Tony Kamber is national architectural manager for Arch Aluminum & Glass, Tamerac, Fla., and a member of the Architects’ Guide to Glass & Metal Editorial Board.

Architects' Guide to Glass & Metal
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