The jacket does three jobs: weather/mechanical protection, vapour sealing, and — through its emissivity — setting how hot the surface feels and how much it radiates. Choose by environment first, fire case second, emissivity third.
| Jacketing | Emissivity ε (typical) | Best for |
|---|---|---|
| Aluminium jacketing | 0.10 | general outdoor pipe & vessel jacketing under 450 °C surface |
| Stainless-steel jacketing | 0.30 | fire-protection cases, chemical exposure, offshore, food-plant washdown zones |
| Galvanized-steel jacketing | 0.28 | indoor mechanical protection on a budget |
| GRP / composite jacketing | 0.90 | coastal/chemical atmospheres where metal jackets corrode |
| Silicone-coated glass fabric | 0.90 | removable covers on valves, flanges, turbines, pumps — anywhere access is needed |
| PTFE-coated glass fabric | 0.90 | chemical, pharma and food plants with aggressive cleaning regimes |
Emissivity values: typical published figures for new/weathered surfaces — bright metals age upward (oxide layers raise ε).