Insulation isn't magic...it can't create heat, it only slows the transfer of heat. If there's no heat there, it won't make any! You may need to put down a good vapor barrier on the ground and carefully seal and insulate the foundation walls and rim joist. This would help trap some of the building's heat, and help prevent it from leaking out. Any air movement from leaks will overcome that heat and allow things to get cold enough to freeze. I'm not a big fan of heat tape, but as a temporary fix, that should help if it is applied properly. Won't help if the power goes out.