How (and Why) to Insulate Water Supply Pipes

Insulating a copper water pipe.

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Insulating water supply pipes in exposed areas of your home is a good idea for several reasons. In cold-winter climates, water supply pipes that are exposed to exterior walls or unheated spaces may freeze, burst, and flood your home—a situation that can cause many thousands of dollars in damage. More than one northern family has gone south for a winter vacation, only to return to a months-long cleanup and restoration job when a single water pipe bursts and pours thousands of gallons of water into the home. Insulating pipes is a key element to any efforts to winterize plumbing in the home.

Insulating water pipes can also save money on energy costs by preventing hot water pipes from losing their heat to surrounding air. Insulating the hot water pipes leading out of your water heater, for example, can reduce heat loss and lower the costs of heating the water. Finally, insulating cold water pipes can prevent the pipes from sweating due to moisture condensation, which can reduce humidity levels in the house in the summertime. 

Where to Insulate Water Pipes

Which water pipes you insulate will depend on why you are doing it. If the goal is to prevent frozen pipes, then the critical pipes to insulate are those that run through unheated spaces, such as exterior walls, unheated garages, the floor cavities above unheated crawlspaces, unheated attics, etc. Generally speaking, it's not necessary to insulate pipes that run through interior walls or in basements that are heated. Both hot- and cold-water pipes should be insulated when the goal is preventing freezing.

If the goal is to lower water-heating costs, then it's wise to insulate hot water pipes wherever you have access to them. This will help prevent heat from radiating away from the hot water pipes and may allow you to lower the temperature setting on your water heater.

If the goal of pipe insulation is to eliminate pipe sweating and humidity, then it is the cold water pipes that are in most need of insulation. When exposed cold pipes contact warmer, more humid air, condensation can form on the pipes. This condensation may drip and puddle on floors, or it may contribute to overall high humidity levels, especially in basements. Insulating the cold water pipes can prevent this condensation.

There are several strategies you can use to insulate water pipes.

Pipe-Wrap Insulation

A common way to protect pipes is with the traditional pipe wrap insulation. This type of insulation is available in many different materials, including flexible foam with rubber backing tape, foam-and-foil pipe insulation, bubble-film pipe wrap, foil-backed natural cotton, and rubber pipe insulation tape.

Pipe wrap insulation is easy to install. You simply duct-tape one end to the end of a pipe (if it's not already self-adhesive) and wrap the insulation around the pipe, overlapping it by at least 1/2 inch with each wrap. Completely cover the pipe, taking care to not leave any areas exposed, then tape the end in place. Pipe-wrap insulating is best suited for insulating small lengths of pipe, or sections where there are many bends.

Tubular Sleeve Insulation

Consider tubular sleeve insulation when longer runs of straight pipe need to be covered. Most tubular sleeves are available in 6-foot lengths, so you can cover a lot of ground quickly. The tubular sleeves can be made of either foam or rubber insulation, and both are available in self-sealing styles. Different diameters are available for different pipe sizes—1/2-, 3/4-, and 1-inch. 

Installing tubular sleeve water pipe insulation is very easy. The sides of the tubular sleeves are split, and once the sleeves are placed over the pipe, the seam can be sealed together or taped shut. It is easy to trim the sleeves to the correct length for each pipe. The corners should be cut to fit tight using miter angles and then duct-taped into place for extra protection. It is a good idea to tape the seams even on self-adhesive styles, since these seams may loosen over time.

Outdoor Faucet Covers

A great many burst pipes occur where hose bibbs extend through the walls of the home to the outdoors. When these exterior metal faucets are exposed to frigid winter temperatures, water trapped inside the faucet can expand and burst—causing a split in either the faucet itself or the pipe just inside the walls of the home. If you are lucky, it will be the faucet that bursts and leaks water outside the home, but if you are less fortunate the burst may occur in the pipe inside the home, causing water to pour into your walls or basement.

A variety of insulated faucet covers are available to protect exterior hose spigots. Some types are simple rigid foam covers that fit snuggly over the faucets to prevent heat loss through the metal pipes, while others are more sophisticated locking devices that are intended to also prevent unauthorized use of your hose spigots.

When combined with other insulating methods, faucet covers are good insurance against burst pipes.

Frost-Proof Outdoor Faucets

Although they do not actually insulate, special frost-proof faucets are a good option for homeowners in colder climates. These faucets are designed with a special valve stem that prevents water from being trapped inside the faucet, where it can freeze, expand, and burst the pipe. The design uses a long valve stem that fits against a valve seat located well inside the house, where temperatures are warmer. The faucet is designed so that water drains out of the valve body when the faucet is shut off, rather than being trapped where cold air can freeze it.

Insulating Pipe Gaps

Just as important as insulating the pipes themselves is to seal all air gaps where pipes extend through exterior walls. A significant amount of heat loss occurs in such gaps where pipes or wires penetrate exterior walls, and blocking these gaps is a critical part of any weatherproofing or winterizing scheme.

Closely examine the gaps around water pipes extending through exterior walls, and block these areas with foam caulking rope, loosely packed fiberglass insulation, or expanding foam applied from a pressurized spray can.

Water Pipe Insulation Tips

Water pipe insulation is a good DIY project that can protect your home from water damage, if done correctly and maintained after installation.

  • When selecting water pipe insulation, consider the R-value of the various options. R-value is a measurement that quantifies the resistance to heat flow of a given material. The higher the R-value, the greater the insulating power of that material. The R-value may not be displayed on pipe insulation, so you may need to do a little research. The colder your climate, the higher the R-value you should look for when choosing pipe insulation.
  • Remove any dirt or grease from the pipes before insulating. No matter what type of insulation you are putting on, it’s a good idea to give the pipes a quick once-over to help the insulation stick better. If you use a cleaner or anything damp, make sure the pipes are dry before installing the insulation. Moisture of any kind can cause the insulation to come loose.
  • Check on the pipe insulation yearly to make sure that its still in good condition and that the pipes are completely covered each winter. The duct tape and self-sealing adhesive on the insulation may come loose over time and expose parts of the pipe. If the pipes are not completely covered, reseal those areas before winter temperatures drop.