Rule-of-thumb from the same C680 simplified method as this site's tables: bare loss ≈ 10 W/m² per °C above ambient in still air — a 180 °C tank wall loses ≈1,600 W/m²; 50 mm of stone wool cuts it to ≈115 W/m² (93% less). Tanks and boiler casings are where m² add up fastest; doors, manways and inspection hatches are the components that need removable solutions so the saving survives maintenance.
Compute your own case: free heat-loss calculator · materials library: 12 datasheets · related: How hot can an exposed surface be for worker safety? · Why does new insulation smoke on first heat-up?
