The thermal conductivity of a steel container is about 50 W/(m·K) – 20 times that of red brick and 200 times that of wood. Under direct summer sun, the roof can reach 70°C (158°F), pushing interior temperatures to 50‑60°C (122‑140°F) – like an oven. In winter, heat escapes rapidly, making the inside freezing cold. Poor insulation ruins customer experience and leads to shocking air‑conditioning bills (commercial electricity in California can be $0.25‑0.35/kWh). Therefore, insulation is one of the top three concerns for overseas clients.
Comparison of the Four Main Solutions
| Solution | Material | Thermal Conductivity (W/(m·K)) | Advantages | Best For |
|---|---|---|---|---|
| Spray polyurethane foam (SPF) | Closed‑cell PU | 0.020‑0.024 | Seamless, moisture‑proof, soundproof | Severe cold (US northern states, Canada) |
| Composite sandwich panel | PU/XPS/rock wool | 0.022‑0.035 | Fast installation, good looks, removable | Most commercial cafés |
| Air gap + reflective foil | Aluminum foil + wood furring | Equivalent 0.15‑0.20 | Low cost, lightweight | Mild climates (e.g., Southern California) |
| Vacuum insulation panel (VIP) | Fumed silica | 0.004‑0.008 | Ultra‑thin (10mm = 50mm of conventional foam) | High‑end, space‑limited projects |
