The Superior unique, clean burning design provides 99% heating efficiency, allowing you to operate the logs vent-free with the fireplace damper closed. With no venting required, there is no heat loss up the chimney. Plus heating with Superior gas logs means you'll never again be left in the cold with wet logs or without heat during a power outage. Features Model # FVFM27NR. BTU 20,000 39,000. Control Type Millivolt. Fuel Type Natural Gas. View Style Multi-View. Venting Type Vent-Free. Burner Style Multi-View. Log Material Ceramic Fiber. Manifold Pressure 3.5 W.C. Inlet Gas Pressure in. of water Maximum 10.5 W.C., Minimum 5 W.C. Warranty 3 Year Limited Warranty. Specifications Log Size 27 . Minimum Fireplace Dimensions 32 W x 19 D x 17 H .