Winter creates many hardships, the worst of which can be frozen water and/or sewer lines. I have seen times when wind blowing through a small crack can freeze a pipe 3 feet from the wall in a warm house. Preparation is the key to worry free living.
STANDARD HOUSING: Crawlspace or Basement: Seal all cracks and openings to the outside. Be sure to close, seal and insulate all vents. It never hurts to insulate the wall of a crawlspace with foam board. In most circumstances you should never insulate the floor above the crawlspace as this keeps heat from reaching the crawler and your plumbing.
OUTSIDE: Water lines: Should be buried 6 feet deep. In vacation homes the septic tank should be buried deeper than normal and/or insulated. Remember – dry ground is a good insulator. To keep things from freezing keep the water away. — David Nequette