Thickness matters as much as material. Too thin and you get heat loss, condensation and burn risk; too thick and you waste money and space. Thickness is not a matter of instinct — there are clear criteria. Here are the three that determine insulation thickness on industrial sites, and how to apply them in practice.
The three criteria
| 1. Personnel protection (surface temperature) | Keeping the insulation surface below a set temperature to prevent contact burns. Around 60°C or lower is the usual recommendation, and lower still for metal facing. |
| 2. Condensation control (dew point) | On chilled and refrigeration lines the surface must stay above the dew point of the surrounding air. Below it, condensation, corrosion and mould follow. |
| 3. Economic thickness | The thickness at which the additional insulation cost balances the energy saved. Beyond a certain point the marginal benefit falls away sharply. |
✅The rule is to adopt the thickest of the three. If economic thickness suggests 40 mm but the surface temperature criterion requires 50 mm, install 50 mm.
1. Personnel protection — the surface temperature criterion
The aim is to lower the facing surface temperature so that workers near hot pipework and equipment cannot be burned on contact. The hotter the service, the thicker the insulation must be — and for the same target surface temperature, larger-diameter pipe (with less curvature) needs more thickness.
- Recommended surface temperature to prevent contact burns: generally around 60°C or below (lower for metal facing, which conducts quickly)
- Higher service temperature → greater thickness required
- Larger pipe diameter → greater thickness required for the same surface temperature
- Be more conservative in heavily trafficked areas and on pipework beside walkways
2. Condensation control — the dew point criterion (chilled and refrigeration lines)
Chilled, refrigeration and cryogenic pipework has a cold surface on which airborne moisture readily condenses. Condensation is the most common cause of failure: the insulation takes up moisture, performance drops and the pipe corrodes. Set the thickness so the surface stays above the ambient dew point, and always install a vapour barrier alongside.
| The principle | Insulation surface temperature > ambient dew point → no condensation |
| Humid environments | The higher the humidity (and dew point), the thicker the insulation must be |
| Always required | A fully sealed vapour barrier (PE film, ALGC, aluminum tape) — thickness alone is not enough |
| Caution | Condensation concentrates at joints, valves and hangers — continuous insulation is essential |
3. Economic thickness — cost against benefit
Thicker insulation reduces heat loss, but each additional increment saves less energy than the last. Economic thickness is where the additional material and installation cost meets the annual energy saving. The higher the energy price and the longer the running hours, the thicker that point becomes.
- Hot, high energy cost, continuously running plant → greater economic thickness
- Up to an initial thickness, payback is very fast
- Beyond a certain thickness the additional saving is negligible — beware of over-investment
- Also check the minimum thickness required by mandatory energy-saving and ESCO criteria
Thickness by service temperature — a general guide
Exact thickness must be calculated from service temperature, pipe size, environment and material conductivity, but the following are the starting points commonly used on site. Review against your actual conditions before installing.
| Ambient–150°C hot water | Pipe sections or urethane 25–50 mm — on surface temperature and energy saving |
| 150–300°C steam and thermal fluid | Glasswool or mineral wool 50–75 mm — tighter surface temperature criterion |
| 300–600°C hot pipework | Mineral wool or Cerakwool 75–100 mm and above — consider multi-layer installation |
| Above 600°C | Cerakwool 100 mm+ in multiple layers, with staggered joints |
| Chilled and refrigeration (below 0°C) | Dew point thickness plus a vapour barrier — condensation control comes first |
⚠️Complex fittings (elbows, tees, valves, flanges) tend to end up thinner than straight runs, concentrating heat loss and condensation. Use insulation jackets to secure the same thickness as the straight pipe.
In summary — the order of decisions
- 1) Establish service temperature, pipe size and environment (indoor, outdoor, humid)
- 2) Calculate thickness on the surface temperature criterion (hot pipework)
- 3) Calculate thickness on the condensation criterion (chilled and refrigeration lines)
- 4) Review economic thickness (energy cost and running hours)
- 5) Adopt the thickest of these, and check the legal minimum
💡Tell us the service temperature, pipe size, environment (indoor or outdoor, humidity) and your objective (energy saving, burn prevention, condensation control) and we will calculate the right material and thickness and quote for it. Technical advice: +82 10-4266-9745
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