423.2.3.9. ROOF VENT INSTALLATIONIf your vent is 8 ft. long or less, you can use a flexible vent 4"x7" x 8 ft long centered by internal support to prevent 4"central exit vent from touching the 7" inlet vent.If the vent is longer than 8 ft. it must be rigid 4" x 6-7/8". Thisfireplace is not approved for a longer flexible vent.Start by determining where the outlet will be on the roof, andcut an opening that fits the fireguard used. Be careful: theopening on the roof will be oval due to the angle of the roof.Build an interior frame 9 x 12.5 in. for a 45° slope) aroundthe opening to allow a minimum clearance of 1 in. fromcombustible materials. It is best to set the opening betweenthe beams to minimize the work.In attics, you may use an insulating shield for attic as well asan insulating sleeve. However, use of the fireguard isrequired when the vent goes through combustible materials.For a vertical vent outlet, you must cut roof covering on a radius of 18 inches around the opening. Thenfix the roof support to the roof with screws provided for this purpose. (Figure 3.2.3.8.c)Figure 3.2.3.8.CFigure 3.2.3.8.aFigure 3.2.3.8.b
