Tank Insulation

Storage water heaters and other hot-water storage tanks rarely have an economically optimal level of insulation. The total R-value for any type of hot water storage tank should be R-15 to R-35, depending on the cost of fuel. If possible, the insulation should completely surround the tank. Usually the tank already has some insulation. Standard storage water heaters have a few inches of fiberglass between the tank and outer steel shell, amounting to R-3 to R-6. New standard models use foam insulation for higher R-values.

Technicians commonly use vinyl-faced fiberglass insulation (3 - 6 inches) to insulate storage water heaters. The insulation is often stapled and strapped to the outside of the tank, with the seams in the vinyl covering taped. The tape alone may not hold the insulation's weight permanently, so plastic straps are often used for support. The tops of gas fired storage water heaters should NOT be insulated, since the vinyl facing is combustible and the insulation might interfere with the draft diverter.

The payback on the water heater insulation installation ranges from 1-2 years. A GENERAL rule of thumb is if the water heater is less than 5 years old, don't insulate it. READ the water heater label - some specifically say DO NOT WRAP. Also, when wrapping, leave a flap for instructions on the tank to be read.

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