Insulation Blankets: Water Heater, Pipe and Equipment Blankets Explained

An insulation blanket is a flexible, wraparound layer of insulation used to cut heat loss from something hot (or heat gain into something cold). In homes, the term usually means a water heater blanket. In industry, it means removable insulation blankets that wrap valves, pumps, pipes and exhaust parts so they can be taken off for service. And builders also use "blanket insulation" for fiberglass or mineral wool batts and rolls. This guide covers all three.

Water heater blankets

A water heater blanket is a fiberglass or foil-faced jacket wrapped around a storage water heater tank. The U.S. Department of Energy's Energy Saver guide estimates that insulating a tank that's warm to the touch saves about 7 to 16 percent a year on water heating costs. Tanks that are already well insulated gain little.

When it pays off:

• The tank feels warm to the touch.
• It's an older model, or the label shows little built-in insulation.
• The heater sits in an unheated garage or basement.

When to skip it:

• Newer tanks often have enough insulation built in, and some manufacturers say a blanket voids the warranty. Check the label and manual first.
• Heat pump water heaters pull heat from the surrounding air; don't wrap them.

Safety rules when you install one:

• Gas and oil heaters: keep the blanket off the top of the tank, away from the burner compartment and air inlet, and away from the thermostat and flue.
• Electric heaters: don't cover the thermostat and element access panels.
• Keep labels, the temperature and pressure relief valve and drain valve uncovered.

Insulating the hot water pipes coming off the tank with foam pipe sleeves adds a few percent more, according to the same DOE guide.

Removable insulation blankets for pipes and equipment

Removable blankets (sometimes called insulation jackets) are custom-sewn covers with insulation inside a tough fabric shell, held on with straps, Velcro or lacing hooks. They're used where regular pipe insulation won't work because the part needs to come apart for maintenance:

• Valves, strainers and flanges on hot water and steam lines
• Pump bodies and heat exchangers
• Engine and generator exhaust parts
• Boiler components

Choose the shell fabric and insulation for the temperature: silicone-coated fiberglass for moderate heat, high-temperature cloth and mineral wool or ceramic fiber for exhaust. Removable blankets reduce heat loss, cut burn risk on hot surfaces and lower room temperatures in mechanical rooms.

Blanket insulation (batts and rolls)

Builders call batts and rolls of fiberglass, mineral wool or natural fibers "blanket" insulation. It's the most widely used type for walls, floors and attics between framing. It's sized to stud and joist spacing and rated by R-value. In an attic, keep it out of the soffit vents with baffles so air can still flow; our soffit calculator covers attic intake ventilation.

Choosing the right one

You want to...	Use
Cut standby loss on an old water heater	Water heater blanket kit (R-value on the label)
Insulate a valve or pump you service often	Removable insulation blanket
Insulate walls, floors or an attic	Fiberglass or mineral wool batts and rolls
Insulate straight pipe runs	Foam or fiberglass pipe sleeves