Best Pipe and Water Heater Insulation

Sleeves are sold by pipe inside diameter (1/2 inch and 3/4 inch cover most homes) and by wall thickness (3/8 inch for mild spaces, 1/2 to 1 inch for unheated crawls and attics). Buy self-sealing slit foam and tape every joint and elbow.

Insulate the first 6 feet of hot and cold lines at the water heater at minimum; the whole hot run if it passes through unconditioned space.

An R-8 to R-11 blanket cuts standby loss 25–45% on an older tank and typically pays back in under a year. Modern tanks with factory R-16+ insulation gain much less — check the label before buying.

Never cover the top of a gas water heater, the flue, the burner access panel, the thermostat, the pressure relief valve or the drain. Leave the bottom 6 inches clear so combustion air can reach the burner. Electric tanks can be wrapped fully except the controls and label.

In hard-freeze climates, pipes on exterior walls or in unheated crawls should get insulation plus, where risk is real, self-regulating heat cable installed under the insulation per the manufacturer's directions.