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R-49 is the common target for the roof or ceiling in cold and mixed climates. That is about 20 inches of blown fibreglass, 15 inches of blown cellulose, 16 inches of fibreglass batt or about 8 inches of closed-cell spray foam. Air seal the ceiling plane before adding any of it.
A blanket on an older tank pays for itself in a season. Enter your tank size for blanket dimensions, cost and expected savings.
With these inputs:
| Result | Value |
|---|---|
| Blanket size needed | 5.2 ft × 5 ft |
| Surface area | 26 sq ft |
| Recommended R-value | R-10 |
| Estimated annual savings | $19 |
| Typical blanket cost | $38 |
| Payback period | 2 years |
Blanket width = π × tank diameter · Surface area = circumference × tank height · Savings ≈ water heating share of the bill × 3–5%
Yes, but never cover the top, the burner access, the thermostat, the pressure relief valve or the flue. Electric tanks can be wrapped everywhere except the controls.
Usually not — anything made in the last decade already has R-16 or better foam. Touch the side of the tank: if it feels warm, a blanket helps.
On an older tank that feels warm to the touch, yes — that warmth is standby loss you are paying for continuously. On a modern well-insulated tank the gain is much smaller, because the manufacturer already did most of it. Touch the side of the tank: if it is noticeably warm, a blanket has something to work with.
With real care, and some manufacturers prohibit it outright. A gas heater draws combustion air at the bottom and vents at the top, and covering either is genuinely dangerous. The top, the burner access, the thermostat, the pressure relief valve and the drain must all stay clear. If in doubt on a gas unit, do not.
Yes — the first few feet of hot outlet pipe carries heat away continuously through convection, and it is cheap to cover. Doing the tank and leaving bare pipe out of the top is a common half-job that gives up a meaningful share of the benefit.
Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.