Just put space heater, or even a lamp with the largest wattage bulb you can find, adjacent to the pipe where it goes thru the wall. I use light bulbs on lamps with a plug in temperature controller under the sink cabinets at a cabin on SML every winter. Better luck with them than heat tape that is not very reliable. Some folks have a lake house - we have a cabin. Original cabin had electric baseboard heat that was wired in the 60s - NOT leaving that on when I'm not there.