Insulating Plumbing Pipes

Insulating water pipes can save energy by minimizing heat loss through the piping. Insulating pipes will reduce the risk of condensation forming on the pipes, which can lead to mold and moisture damage. Pipe insulation can protect the pipes from freezing and cracking in the winter, which can cause considerable damage in the walls of the home and result in significant home repair bills for the homeowner. Studies by DOE’s Building America program have shown that distribution heat loss in uninsulated hot water pipes can range from 16% to 23% depending on the climate. Adding 3/4 inch pipe insulation can cut overall water heating energy use by 4% to 5% annually (Backman and Hoeschele 2013).

The best practice for builders and designers is to avoid running water pipes in exterior walls or through unheated attics. It is preferable to design the home so that plumbing fixtures align with interior walls. If pipes must be run in exterior walls, the pipes should be insulated. To further protect the pipes from heat loss, the wall cavity containing the pipes should be air sealed by caulking or foaming all seams between the back wall of the cavity and the framing and by sealing any holes through the framing for the piping. In addition, cavity insulation should be installed behind the pipes, between the pipes and the exterior wall.

If a house has a hydronic (steam or hot water) heating system, heat loss can be reduced by as much as 90% by insulating the steam distribution and return pipes (DOE 2006). In a retrofit of a 19-unit multifamily housing building in Chicago with a central boiler, all of the accessible hot water heating pipes were insulated. (See Figure 1 and Figure 2.) Insulating the pipes with 1 inch of jacketed fiberglass cost $4,720 but the building owners estimated energy cost savings of nearly $2,300 per year, for a 2.1-year payback (Farley and Ruch 2013).

Pipe insulation is available in several forms: tubular pipe sleeves, spiral insulation wrap, and fiberglass batts that can be taped around the pipes. If properly installed, all three can be effective.

Tubular pipe sleeves are made from flexible closed-cell polyethylene or neoprene foam and come pre-cut with a lengthwise seam for easy installation. Some pipe coverings come with adhesive strips already adhered to both sides of the slit. Just peel off the plastic coverings and press together. There are different diameters of sleeves available to accommodate the varying sizes of pipes, so measure pipes before purchasing and match the pipe’s outside diameter to the pipe sleeve’s inside diameter to ensure a snug fit.

Spiral insulation wrap can be made of fiberglass, foil, or polyethylene foam. Simply unroll the material and wrap it around the hot and cold water pipes. Pipes can also be wrapped with fiberglass insulation. The fiberglass may come with a vapor barrier facing on one side or the plastic can be purchased and wrapped around the pipes after the fiberglass insulation is installed. Be sure to wear gloves, goggles, and a dust mask when installing fiberglass.

How to Insulate Pipes Using Tubular Foam Sleeves

1. Cut the pipe sleeve to length and wrap it around the pipe, with the slit facing down, making sure there are no gaps between sleeves. To cover bends in the pipe, make a joint at the elbow and angle the ends of the foam to form a mitered corner that fits the angle of the pipe.
2. Remove the paper strips covering the self-sealing, pre-glued seam and press the edges together.
3. Tape over the seams and joints with acrylic or aluminum foil tape to increase durability.
4. Use wire, tape, a plastic tie, or metal clamp to secure the insulation (and plastic covering) to the pipe every 1 to 2 feet.
5. Use caulk or foam to seal any holes where the pipes penetrate walls, floors, ceilings, or framing.
6. If pipes run through exterior wall cavities, insulate the wall cavity just as you would the other cavities if using blown cellulose, fiberglass, or spray foam, which will easily fill in the space behind the pipes. If using fiberglass or mineral wool batts, split the batt lengthwise. Slide half the batt behind the pipes and fit into the cavity. Fit the remainder of the batt in front of the pipes to fill the cavity. Alternatively, cut a piece of rigid foam to fit the wall cavity dimensions. Run a bead of foam adhesive around the back of the foam, slide it behind the pipe and press it into place to seal it to the back wall of the cavity. Use caulk or canned foam to air seal the edges to the framing of the cavity. Lay a split batt over the front of the pipes.

How to Insulate Pipes Using Spiral Wrap or Fiberglass Batts

1. Secure the end of the spiral wrap or fiberglass batt on the pipe with tape.
2. Wrap the insulation around the pipe in a spiral fashion, overlapping each successive layer by a ½-inch for tape or half the width of the batt insulation. Wrap batts as loosely as possible, because compressing them will reduce their R-value.
3. If using fiberglass insulation without a moisture barrier, wrap plastic around the insulated pipe and seal with tape to keep the insulation from getting wet.
4. Use wire, tape, a plastic tie, or metal clamp to secure the insulation (and plastic covering) to the pipe every 1 to 2 feet to keep the insulation from sliding.
5. Use caulk or foam to seal any holes where the pipes penetrate walls, floors, ceilings, or framing.
6. If pipes run through exterior wall cavities, insulate the wall cavity just as you would the other cavities if using blown cellulose, fiberglass, or spray foam, which will easily fill in the space behind the pipes. If using fiberglass or mineral wool batts, split the batt lengthwise. Slide half the batt behind the pipes and fit into the cavity. Fit the remainder of the batt in front of the pipes to fill the cavity. Alternatively, cut a piece of rigid foam to fit the wall cavity dimensions. Run a bead of foam adhesive around the back of the foam, slide it behind the pipe and press it into place to seal it to the back wall of the cavity. Use caulk or canned foam to air seal the edges to the framing of the cavity. Lay a split batt over the front of the pipes.

How to Insulate Steam Pipes

1. Measure the length of the pipe you are insulating and cut the fiberglass sleeve to match. Any surface over 120°F should be insulated, including boiler surfaces, steam and condensate return piping, and fittings. Use 1-inch-thick, heavy-density, resin-bonded fiberglass sleeves approved for steam or hot water heating systems, since other forms of insulation can melt.
2. Open the pre-cut fiberglass sleeve by pulling on the release strip.
3. Fit the sleeve around the pipe and align the self-sealing lap over the sleeve.
4. Seal by rubbing firmly on the adhesive strip to seal the lap to the sleeve.
5. Wrap high-temperature tape around the pipe where two sleeves meet.
6. Install removable insulation jackets on elbows, tees, and other pipe fittings.
7. Use caulk or foam to seal any holes where the pipes penetrate walls, floors, ceilings, or framing.

8. If pipes run through exterior wall cavities, insulate the wall cavity just as you would the other cavities if using blown cellulose, fiberglass, or spray foam, which will easily fill in the space behind the pipes. If using fiberglass or mineral wool batts, split the batt lengthwise. Slide half the batt behind the pipes and fit into the cavity. Fit the remainder of the batt in front of the pipes to fill the cavity. Alternatively, cut a piece of rigid foam to fit the wall cavity dimensions. Run a bead of foam adhesive around the back of the foam, slide it behind the pipe and press it into place to seal it to the back wall of the cavity. Use caulk or canned foam to air seal the edges to the framing of the cavity. Lay a split batt over the front of the pipes.