Researchers at the Wind Engineering Research Center at Texas University, in conjunction with the Portland Cement Association, compared the impact resistance of ICF walls to conventional wood frame walls. Testers used a compressed air cannon to shoot a 2x4 wood stud traveling at 100 mph straight at the walls. This is equivalent to the weight and speed of debris generated during a tornado with 250 mph winds. The missile easily passed through the wood wall of an old-style house, not slowing in speed and no damaging the 2x4 missile. However, when shot at the ICF wall, the missile not only failed to penetrate the wall, it completely shattered and did no damage to the concrete.