Vent question... insulation?

Need to extend the vent pipe horizontally outside the building envelope, have to stop the condensate condensing on the roof overhang & concrete foundation wall.
Need to add about 4 ft, plan on angling it slightly downward to allow any condensate to exit into a safe area.
do I need to insulate the vent at 20F below design temp? It would be possible to angle it downward at 45degrees but that would look like a kluge add on. I do not want to push more condensate back through the septic system, as we only have a small neutralizer. A plugged vent could be right dangerous I fear.