The heat load calculator applies the five-component method from ASHRAE Handbook — Refrigeration 2022, Chapter 24: (1) transmission load through walls, floor, ceiling, and doors using the entered panel U-values; (2) infiltration load via the Gosney & Olama (1975) empirical ACH model adjusted for door width, height, and protection factor; (3) product pull-down load from entered commodity, initial temperature, and pull-down period; (4) internal gains from lighting, motors, and occupants; (5) a 10% safety factor. Ambient design temperatures for major U.S. metros use ASHRAE 0.4% design dry-bulb values. Panel U-values are calculated from entered thickness and λ = 0.022 W/m·K (ASTM C518 declared aged value for Foster's foamed-in-place polyurethane panel). Results are validated within ±20% of Heatcraft NROES, Copeland AE-103, Danfoss Coolselector®2, and Bitzer Software for typical commercial walk-in geometries.
References: ASHRAE Refrigeration Handbook 2022 Ch. 24; Gosney & Olama (1975) Int. J. Refrigeration; ASTM C518; IEC 60335-2-89:2019.
Size a walk-in by calculating its total heat load in BTU/hr and matching a refrigeration system to it. The load has five parts under the ASHRAE method: heat conducted through the walls, ceiling and floor; air infiltration each time the door opens; heat pulled from the product as it cools; internal loads from people, lights and fans; plus a safety factor. This calculator adds all five for your dimensions, panel thickness, product and local design temperature, then reports the required capacity in BTU/hr and horsepower.
Most single-location restaurants use a walk-in between 6x6 ft and 8x10 ft, which needs roughly 6,000 to 12,000 BTU/hr of cooling depending on door traffic and ambient heat. Rather than guess, enter your planned dimensions and menu volume here and the calculator returns the exact load; a larger operation or one with heavy door use will need proportionally more capacity.
A rough industry rule is about 40 to 60 BTU/hr per cubic foot for a cooler above freezing and more for a freezer, but that is only a starting point. Actual load depends on insulation R-value, door openings, product pull-down, and local ambient temperature, which is why a component-by-component ASHRAE calculation like this one is more accurate than a per-square-foot rule of thumb.
Yes. Thicker foamed-in-place panels have a higher R-value, so less heat conducts into the box and the refrigeration system can be smaller. Stepping from a 3-inch to a 4- or 5-inch panel measurably lowers the wall/ceiling load, especially for freezers and hot ambients; the calculator lets you compare panel thicknesses directly.