When winter's cold hits, waterlines can become very vulnerable to damage. If the metal pipes become cold enough, water in the lines can freeze and expand, splitting the pipe or popping joints loose. When the ice thaws, water can pour through the damaged areas, resulting in quite a bit of damage to your home.

Because of the easy access it provides to plumbing fixtures, crawlspaces are a favorite place for plumbing pipes to be located. The colder it gets in your locale, the more vulnerable those pipes are to freezing, so you need to take some precautions to protect your home from potential damage.

The first step is insulation. If the underfloor area of your home is not insulated, it should be--there can be a substantial amount of heat loss through the floor, resulting in lots of wasted energy. But there is a bit of a catch-22 with floor insulation. When you insulate a floor and stop the heat loss into the crawlspace, you make the crawlspace colder and the pipes become that much more vulnerable. So, whenever you have a crawlspace insulated, you need to be certain that all the pipes are thoroughly insulated as well. You also need to be certain that a vapor barrier is installed over the dirt floor of the crawlspace as part of the overall underfloor insulation package.

The next issue to deal with is the foundation vents, and this is a bit controversial. Foundation vents exist as a means for creating a passive airflow through the crawlspace to remove moisture that might otherwise accumulate there. And while it is crucial that they exist for that purpose, a foundation vent that is open in the winter can allow sub-freezing air to enter the crawlspace and cause the pipes to freeze. Here again, it's essential that the pipes be insulated, but that alone is not enough, since it takes only the tiniest gap in the insulation to allow a pipe to freeze.

For that reason--and here's the controversial part--foundation vents need to remain closed during the coldest parts of the winter. How long they remain closed is a region-by-region decision. If you lived in Hawaii, for example, the vents could probably stay open all year, while in parts of Alaska they may need to be closed for six months or more at a time.

In most areas, however, the vents typically need to be closed for anywhere from two to four months, and can remain open the rest of the time. This is more than sufficient to remove accumulated moisture in the crawlspace, especially since the air's ability to hold moisture is at its lowest in the winter months anyway.

The most effective way of closing off most vents is to use foam blocks, which are readily available from any home center or hardware store. Some foundation vents have swinging plastic doors built into them for the purpose of simplifying closing them off, but they typically don't fit very well and still have enough gaps around the edges that cold air can leak in. Go ahead and close the doors, but supplement them with foam blocks.

In older homes with foundation vents that are not a standard size, you're probably stuck with having to make closure blocks of your own. The best method is to purchase a sheet of rigid foam insulation from a home center or lumberyard, and custom cut blocks to fit your vents. Glue the blocks to an oversized piece of plywood, add a handle, and you have convenient foundation vent blocks that can be reused year after year.

Another vulnerable spot is your outside hose bibs and faucets. For convenience and protection, your best bet is to install freeze-proof exterior faucets. These types of faucets have a long stem that extends well back into the wall or under the house; when you shut the faucet off, the water flow is stopped several inches back from the exterior wall, back where the insulation lives and the temperatures are warmer.

If you don't want to change to freeze-proof faucets, your next best bet is to use foam faucet covers. These dome-shaped devices--again available from home centers and hardware stores--have an internal elastic strap that clips over the head or handle of the faucet and holds the dome against the siding, completely covering the faucet and protecting it from freezing. Faucet covers are inexpensive and easy to install, and can be reused each winter.