Ductwork Insulation: Heat Loss & Savings
Hot flue-gas and process ducts have very large surface areas, so even modest temperatures add up to large continuous losses. Removable insulation panels cover the duct runs, transitions and dampers while allowing access to inspection doors.
Heat loss vs insulated — by surface temperature
| Surface temp | Bare loss | Insulated | Outer surface | Reduction |
|---|---|---|---|---|
| 120 °C | 1,839 W/m² | 99 W/m² | 27 °C | 94.6% |
| 200 °C | 4,012 W/m² | 210 W/m² | 34 °C | 94.8% |
| 300 °C | 8,075 W/m² | 204 W/m² | 34 °C | 97.5% |
| 400 °C | 14,273 W/m² | 321 W/m² | 41 °C | 97.8% |
Per-m² flat-surface flux, ASTM C680 / ISO 12241, 50 mm Lamella (≤220 °C) or 100 mm Wired mat (>220 °C), 20 °C ambient. Multiply by the bare area.
Worked examples (per year, 8,000 h, natural gas)
| Item | Heat saved | Energy/yr | CO₂/yr | € saved/yr |
|---|---|---|---|---|
| A hot flue-gas duct (20 m², 250 °C) | 113.4 kW | 1,067 MWh | 215.5 t | €61,883 |
| A duct transition / damper (6 m², 250 °C) | 34.0 kW | 320 MWh | 64.7 t | €18,565 |
FAQ
How much heat does a bare ductwork lose?
At 20 °C ambient (ASTM C680): a hot flue-gas duct (~20 m², 250 °C) loses about 113.4 kW; a duct transition / damper (~6 m², 250 °C) about 34.0 kW. Insulating a hot flue-gas duct saves ≈1,067 MWh and ≈215.5 t CO₂ per year (8,000 h).
Can you insulate flue-gas ducts and similar?
Yes. Ducts carry dampers, expansion joints and inspection hatches needing access. Removable panels lift off locally and refit cleanly. Inzonex covers flue-gas ducts, process ducting, transitions, dampers and inspection hatches. The outer surface drops to a touch-safe ≤45 °C and the part stays serviceable.
How much does ductwork insulation save?
Each item saves 96–98% of its bare loss. A hot flue-gas duct at 250 °C saves ≈61,883 €/yr of energy (≈1,067 MWh, ≈215.5 t CO₂) at typical gas prices; payback is usually under two years.
What insulation thickness is used?
Up to 220 °C surface: 50 mm mineral-wool (Lamella); above 220 °C: 100 mm (Wired mat), because conductivity rises with temperature. Both keep the outer surface ≤45 °C.