> Hart&Cooley. SUBMITTER DRAWING install confidence METABOLIZED VAPOR BARRIER FIBERGLASS INSULATION CORE FIBERGLASS SCRIM CORE «Two plies of black polyester film encapsulate a steel wire helix. Rated pressures (UL—181): 12 in. W.C. positive, 3/4 in. W.C. negative & 1/2" W.C. negative «Recommended maximum operating pressures (ADC Test FD 72—R1): 6 In. W.C. positive for 12 in. diameter and under. 4 In. W.C. positive for 14 in. diameter and over. *Rated maximum alr velocity: 5000 FPM.