A building window for mounting to a rough opening defined in a stud frame wall. The building window includes at least one sheet of transparent or translucent material set in at least one sash which, in turn, is disposed in a frame. The frame includes a first mounting flange that extends outward from an outer surface of the frame in a direction approximately parallel to the plane of the at least one sheet of transparent or translucent material. The frame also includes a second mounting flange that extends outward from a first side of the frame in a direction approximately perpendicular to the plane of the at least one sheet of transparent or translucent material. The second mounting flange is configured and arranged to be secured to a perimeter edge of the rough opening defined in the stud frame wall.