Several proposed changes to ICC 500 Standard for the Design and Construction of Storm Shelters could be up for review this fall, including changes that could impact glazing requirements. These proposals were outlined during a webinar hosted by the American Architectural Manufacturers Association (AAMA) titled “ICC 500: Tornado and Hurricane Storm Shelters.” UL building science group principal engineer Dave Stammen led the discussion.

The Current Code

The 2014 edition specifies that the testing missile for tornado shelters be a 15-pound 2×4 and that the missile for a hurricane shelter is a 9-pound 2×4. Tornado missiles tested at 100 mph equal 5,012-foot pounds of impact energy compared to hurricane missiles tested at 34 mph, which are equal to 350-foot pounds.

“That’s a drastic difference,” said Stammen, who added that shelters tested to tornado standards must undergo pressure and missile impact tests while hurricane shelters must undergo pressure, missile impact and cycling tests. Pressure and missile tests are allowed on separate units.

Missile impact testing is done per ASTM E1886-05. Single doors must pass three impacts while double doors must pass three impacts plus one on the center or mullion. For doors with glazing, an impact must be made in the center of the glass if the glass is equal to or less than 12 inches. If larger than 12 inches, the door is treated as a window.

For windows, two impacts must occur on the same lite of glass, one at the center and one at a corner. If the window has interior mullions then two additional impacts must be tested, though this can be done on a separate unit, one on the center mullion and one at the mullion base.

The pass/fail criteria specifies that the missile cannot perforate the interior surface, there can be no dislodgment or disengagement, no spalling and after all impacts, the permanent deformation must be less than 3 inches.

Proposals for 2020

Stammen explained several of the proposals already approved for the public draft. The major proposal that impacts glazing is that any changes to listed impact-protective systems, such as a change of glazing, will require evaluation by the listing agency or retesting of the entire assembly.

“This is important because if you want to put stronger glazing into an approved product it would typically comply, but just because it’s stronger doesn’t mean the product will pass, especially in minimum sizes. The glass could push the energy elsewhere and fail the unit,” said Stammen.

Another proposal would make the length requirements of missiles less stringent. The length of a tornado missile could be between 10 and 15 feet as long as it meets the weight criteria of 15 pounds. Hurricane missiles could be between 6 and 10 feet as long as the 9-pound requirement is met.

One of the proposals addresses what’s involved in the labeling of the products to create more clarity and consistency. Other proposals call for local weather data to be used to establish rainfall rates, clarifies where to place the Kraft paper to test for spalling and to allow for a tolerance radius for impact to be a 2.5-inch radius circle.

Stammen anticipates that a draft of the ICC 500-2020 standard will be available for a 30-day public review in November. He said the goal is to have the 2020 edition published by December 2020 so that it can be included in the 2021 edition of the International Building Code.