Definition: Measure of heat transfer through an insulated structure (wall, ceiling, door). Measured in W/(m²·K). Lower U-value = better insulation.
Calculation: U = 1 ÷ (R₁ + R₂ + R₃ + …) where R is thermal resistance of each layer
Typical Values:
- Well-insulated refrigerated truck body: 0.30-0.40 W/(m²·K)
- Cold room wall (100mm PU foam): 0.20-0.25 W/(m²·K)
- Standard building wall: 1.0-2.0 W/(m²·K) (poor for cold chain)
Why It Matters: U-value directly affects transmission heat load and operating cost. Lower U-value = less heat gain = lower fuel/electricity consumption.
Related Terms: R-Value, Insulation, Thermal Conductivity, Heat Load