Pipes are vulnerable any time they're in a location where they're exposed to low-enough temperatures for long-enough periods that the water inside them can freeze. Once the freezing occurs, the water expands, rupturing the pipe, splitting the seam between the pipe and a fitting, or damaging components such as cartridges inside faucets. Once the pipes warm up and the ice melts again, the damage becomes evident -- often in the form of a flood inside the house!
Although a frozen pipe can occur just about anywhere, pipes in unheated attics and underfloor basements and crawl spaces are at the most risk. And ironically, the better you insulate the ceiling and the floor, the more you put pipes in those areas at risk. Heat that had been escaping from the house into those areas used to be keeping the pipes warm, so when you add insulation and stop heat loss from the house, the attic, basement and crawl space become colder, and pipes are more vulnerable.
Keep the water pipes insulated
Any water pipes that are not buried in your underfloor, wall or attic insulation need to be insulated. The easiest method for the do-it-yourselfer is to use a foam sleeve, which is pretty much like slipping a bun over a hot dog. The sleeves are actually long foam tubes, and are available with different interior diameters to fit different pipe sizes. The tubes are slit along one side, so installation is simply a matter of opening up the slit and fitting the tube over the pipe.
At each elbow or other fitting in the pipe, cut out a wedge from one side of the tube so that it will bend around the joint in the pipe. Cutting can be done with scissors or a sharp utility knife. After you bend the tube around the fitting and snap it over the next pipe, it should stay in place on its own, and the seams and elbows don't require any sealing. If you do need to seal any odd joints or patch in any small pieces, you can hold things together with utility tape from the home center or hardware store where you purchased the foam sleeves.
The pipes can also be wrapped using scraps of fiberglass insulation. This is less expensive than the foam sleeves, but a little more time consuming if you're not used to the process. Typically, fiberglass batt insulation is cut into strips. It's then wrapped around the pipes, either in a spiral fashion or by folding it lengthwise over the pipe. As the insulation is installed, it's held in place with a spiral wrapping of very fine copper wire, which is available on spools from any hardware store or home center.
Close foundation vents and look for air leaks
Now for a small bit of controversy, which is almost sure to generate a letter or two: Close off your foundation vents! Use foam blocks or other insulation, and seal the vents to prevent cold air from entering. The vents are there to allow air to circulate under the house and remove unwanted moisture, and they should remain open during whatever part of the year that temperatures remain above freezing. But during the winter, when humidity levels are low and the risk of a frozen pipe outweighs the need for ventilation, be sure they get closed off.
Attic vents are a different story. Due to their location and the year-round need for attic ventilation to prevent ice damming, they should not be closed off. You should, however, carefully examine the area around each vent to be certain that no pipes are exposed to the air coming in from the vent.
If you find a pipe that is adjacent to a vent, double up the amount of insulation that's on the pipe, and permanently close off that portion of the vent that's directly exposed to the pipe.
Another thing that can greatly increase the chance of a pipe freezing is to expose it to outside air. This often happens when the pipe is installed near a foundation vent or an attic vent, or in an exterior wall in which holes were drilled for plumbing or wiring.
In any open walls, use expandable foam sealant to close off any holes and gaps in the framing. In colder climates, pipes should never be installed in exterior walls, and pipes should never be run in exposed soffits or other uninsulated framing areas.
Exterior faucets are another potential freeze problem. When installing a new exterior faucet, your best bet is to use a freeze-proof type (freeze-proof faucets are required by code in some areas), which has a long stem that extends back into the insulated portion of the house, so it shuts the water off at a spot where it's not exposed to freezing outside air.
If your house is not equipped with freeze-proof faucets, you can insulate them quickly and easily by installing an insulated dome over them. The dome is simply a large foam shell that fits over the faucet, and is held in place with a strap or a long hook.
All of the materials you need for pipe insulation, including faucet domes, pipe wraps, wire and other material, can be found at any home center or plumbing supply retailer, as well as hardware stores, discount stores and most lumber yards.
By Paul Bianchina for Inman News January 8, 2010
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