Pipe Heat Loss Calculator & Insulation Savings
Updated 11 June 2026 · ASTM C680 / ISO 12241 method
How much heat does a bare pipe lose — and how much does insulation save? Pick the pipe size (DN), temperature and length and get the bare vs insulated loss in W/m, plus energy, CO₂ and payback from Inzonex removable insulation. Cylindrical ASTM C680 / ISO 12241 method.
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Bare vs insulated pipe heat loss by size (200 °C, per metre)
| Pipe size | Bare loss | Insulated | Outer surface | Reduction |
|---|---|---|---|---|
| DN15 (½") | 268 W/m | 39 W/m | 27 °C | 85.5% |
| DN25 (1") | 421 W/m | 49 W/m | 28 °C | 88.4% |
| DN50 (2") | 760 W/m | 69 W/m | 29 °C | 91.0% |
| DN80 (3") | 1,120 W/m | 89 W/m | 30 °C | 92.1% |
| DN100 (4") | 1,441 W/m | 106 W/m | 31 °C | 92.6% |
| DN150 (6") | 2,121 W/m | 143 W/m | 31 °C | 93.3% |
| DN200 (8") | 2,762 W/m | 177 W/m | 32 °C | 93.6% |
| DN300 (12") | 4,082 W/m | 246 W/m | 32 °C | 94.0% |
Per-metre cylindrical flux, ASTM C680 / ISO 12241, 50 mm mineral-wool removable insulation, 20 °C still-ish air. Multiply by your pipe length.
Same DN100 pipe — loss rises steeply with temperature
| DN100 pipe at | Bare loss | Insulated | Reduction |
|---|---|---|---|
| 120 °C | 660 W/m | 50 W/m | 92.4% |
| 200 °C | 1,441 W/m | 106 W/m | 92.6% |
| 300 °C | 2,900 W/m | 128 W/m | 95.6% |
| 400 °C | 5,125 W/m | 201 W/m | 96.1% |
Pipe insulation — FAQ
How much heat does a bare pipe lose?
A bare steel pipe at 200 °C (20 °C ambient) loses ~268 W/m at DN15, ~760 W/m at DN50, ~1,441 W/m at DN100 and ~2,762 W/m at DN200. Loss rises steeply with temperature — a DN100 line goes from ~660 W/m at 120 °C to ~2,900 W/m at 300 °C.
How much does pipe insulation save?
50 mm of removable insulation on a DN100 pipe at 200 °C cuts the loss from ~1,441 to ~106 W/m (93%). Over 100 m at 8,000 h/yr that's ~133 kW saved, about 1,067 MWh of fuel-equivalent heat per year, and a touch-safe ~31 °C surface.
What pipe insulation thickness do I need?
Here: ≤220 °C → 50 mm mineral-wool (Lamella); >220 °C → 100 mm (Wired mat), because conductivity rises with temperature. Both hold the outer surface ≤45 °C. The calculator sizes it for your pipe.
Why removable insulation on pipes?
Valves, flanges and fittings on a pipe run need regular access; fixed lagging gets cut off and never refitted, leaving hot gaps. Inzonex removable jackets unzip in minutes for inspection and refit with no damage — so the whole line stays insulated, not just the straight runs.