Duct and Pipe Insulation


Ducts running through an unfinished or partially finished basement that gets even just occasional use should be insulated to keep the area warmer. Duct insulation is available in 1 and 2-inch thicknesses. If your ducts are rectangular opt for the thicker of the two. This can help cut heat losses down by one-third more than the 1-inch.

Insulating the ducts will increase the temperature of air at registers. Therefore, if your ducts don’t already have dampers, add some before insulating them. And then fine-tune the air system for more uniform heat/cool air distribution throughout the various areas of your home.

Ducts between joists can be wrapped with cut blankets stapled to the floor. Joints can be sealed using duct tape. Insulation can be wrapped around all sides of other ducts and sealed with tape; leaving the vapor barrier on the outside.

Extend the insulation beyond the end of ducts, and then cut an insert with a facing flap. Fold the flap and tape it, package style.


Besides insulating pipes in cold climate areas to protect them against freezing, wrapping exposed cold water lines prevents them from sweating and collecting moisture in warmer climates and months. This won’t help conserve energy. But it will prevent drippings and condensation that can cause spots or water damage.

Wrapping both hot and cold water pipes will help to conserve energy. In fact, when contractors compute heating and cooling load needs, they tack on an additional 10 to 20-percent to cover calculated losses associated with inadequately insulated ductwork and pipes.

Types of Pipe Insulation

You have a choice when it comes to pipe insulation type. If you select spongy adhesive-backed insulating tape, make sure and wind the tape around pipes with one layer overlapping the other by about ½-inch.

Flexible foam, slit-sleeve insulation will protect the pipe with a thick jacket. This type insulation is quick and easy to apply. It is also a great choice for longer pipe runs and as additional insulation over adhesive-backed tape for extra cold winter months.

Cut the insulation using a hacksaw or utility knife; use short lengths to fill spaces at pipe ends and corners. At pipe junctions, wrap uncovered areas with spongy insulation tape; peel off the backing and wrap several layers.

Other types of pipe insulation to consider include:

  • Self-sealing fiberglass insulation. It comes with or without an “all-service jacket,” in various thicknesses – ½-inch to 4-inches. Molded and heavy density, it is used primarily by commercial and institutional buildings.
  • Sponge felt insulation comes in straight blocks, as well as preformed shapes for valves and fittings.
  • Wool felt is available in thicknesses of ½-inch to 1-inch. It comes with a canvas jacket, and is formed using matted fibers of wool, fur, or hairs that have been pressure rolled. Wool felt is useful for both cold water service and hot water pipes.
  • Cork pipe covering is comprised of compressed and molded bark from cork trees. It comes with a coating of plastic asphalt. This makes a good choice for all kinds of cold waterlines and low-temperature range pipes.
  • Heating Tape.

A Word about Heating Tape

Heating tape is a great way to insulate water pipes in areas where winter temperatures are extreme. It consists of plastic coated wire to wrap around pipes, and is plugged into an electrical outlet to keep pipes from freezing.

Also known as “heat cable,” heating tape is relatively easy to install. Different types of heating tape have distinct requirements; read and follow instructions carefully, and take necessary precautions. Also make sure to plug the tape into a properly functioning ground-fault circuit interrupter (GFCI), to protect against electrical shock.

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