Common Tornado Myth Involves Glass

Other documents that do address storm shelters include FEMA 320 and FEMA 361. The 361 document, for example, includes a section on tested glazing material. Glass-clad polycarbonate and multi-ply laminated glass with a 90-mil PVB interlayer were tested.

The test panels were impacted by a 15-pound 2-by-4 travelling at 100 MPH. Results found that “glass shards propelled at great distances and at speeds considered dangerous to the occupants.” Its recommendation was that “unless glazing can pass the missile impact test, windows are not desirable in tornado safe rooms.”

However, there is still a place for glazing products in these tornado-prone areas. As Block noted, a tornado leveled 95 percent of Greensburg, Kan., in 2007, and rebuilding efforts have included the use of glazing. In fact, she says architects placed no limits on the use of glass–expect a recommendation that it be high-performance.

 

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