A measure of insulation effectiveness quantifying resistance to heat flow, expressed in m²·K/W (SI units) or ft²·°F·hr/BTU (imperial units). Higher R-values indicate better insulation performance – an R-5.0 insulation allows half the heat transfer of R-2.5 insulation for the same temperature difference and surface area. In refrigerated transport, R-value determines the steady-state thermal load the refrigeration system must continuously overcome. However, specified R-values rarely reflect real-world performance due to thermal bridging through metal framing, fasteners, door seals, and body panel penetrations. A vehicle specified with R-4.0 polyurethane insulation might have effective R-value of 2.8-3.2 after accounting for thermal bridges, increasing heat infiltration 25-40% above theoretical calculations. ATP testing standards allow significant thermal bridging, creating gap between compliance specifications and actual operational performance. Professional frozen food transport requires engineering-grade insulation design with thermal bridge management achieving effective R-values 30-40% higher than minimum ATP standards, reducing refrigeration system runtime, fuel consumption, and temperature excursion risk during multi-stop operations.
Engineering Formula: For detailed R-value applications in heat transfer calculations and insulation performance analysis, see Heat Transfer Through Insulation in our Technical Formulas Reference.
Related Terms: Insulation (Thermal), Heat Transfer (Thermal), Energy Efficiency (Cold Chain), Reefer Vehicle