Thermoflex Inc., a Miami, Fla. precast producer, has introduced a residential concrete building system that utilizes fiber-reinforced, light-weight, cellular concrete panels. The panels can be used for both interior and exterior walls and for the roof. The panels are made using a slurry of Type I portland cement, polypropylene fibers (1% by volume), and a proprietary foaming agent. According to Thermoflex technical engineer Eugene Berger, the main advantages are thermal efficiency, light weight, impenetrability, fire resistance, and the strength to withstand hurricane-force winds. Tests according to ASTM C 236 for surfaced skim-coat plastered panels resulted in an R value of about 16. The panels were also tested by shooting a 9-pound piece of 2x4 lumber into the panel at a velocity of 55 mph, and steel jacketed bullets from firearms of a variety of calibers. The walls withstood all projectiles with minimal damage. The wall panels were also subjected to fire testing, according to ASTM 136, and wind loads exceeding 300 mph, both with minimal damage. Although panel costs are slightly higher than conventional masonry, savings are realized in field labor costs, which offset the higher material costs.