Jason, here is the code for the vent stack. IRC P3103.5 Location of Plumbing vent terminal. An open vent terminal from a drainage system shall not be located less than 4 feet (1219 mm) directly beneath any door, openable window, or other air intake opening of the building or of an adjacent building, nor shall any such vent terminal be within 10 feet (3048 mm) horizontally of such an opening unless it is at least 2 feet (610 mm) above the top of such opening. The B vent height looks OK, provided it's at least eight feet from the side wall. ( From the Hart & Cooley installation instructions) The 2/3/10 rule does not apply to B vents.