Insulating pipes that run through cold areas is necessary to keep them from freezing; even then you have to run the water occasionally or add some heat. You could leave the tap running a little during the very cold spells; that's how Grandpa kept them from freezing. You can also get thermostat actuated heating cables that you wrap on before the insulation. That will guarantee they won't freeze, as long as you are not in a power black-out. Sudden wind exposure (loss of snow banking for example) can cause pipes to freeze that never froze before.
A better solution is to partially insulate the crawl space on the perimeter and under the floor, slightly raising the temperature of the crawl space. I recommend RSI 4.9 (R-28) batts in the floor and RSI 3.5 (R-20) on the perimeter (2/3rds as much on the perimeter as in the floor). The crawl space will stay well above freezing (about nine degrees Celsius) and your floor will be more comfortable too. (search keyword "crawl space" for the title "HOW DO I INSULATE CRAWL SPACES?")