| Load Component | Watts | BTU/h | % of Total |
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How to Use the Cold Room Load Calculator
Enter room length, width and height, the target room temperature, and the design ambient temperature. The default of 32°C is a conservative summer value, so replace it with your local design temperature. The wall U-value default of 0.033 W/m²K matches typical 100mm PIR or PU insulated panel construction, so adjust it for your actual panel thickness.
Door opening frequency drives infiltration load, so high-traffic grocery receiving areas need a higher opens per hour than back-of-house storage. Lighting and evaporator fan wattage are direct heat sources inside the conditioned space.
For each stored product, add its expected inventory weight and size for the maximum simultaneous inventory, not the average. Respiration rates vary widely by product: 12 W/tonne for onions and 25 for apples, versus 500 to 750 W/tonne for asparagus, broccoli and strawberries at 2°C. Cross-check the full result against the general refrigeration load calculator.
The default 10% safety margin and 18 hrs/day run time convert peak load to required equipment capacity, accounting for defrost time and cycling. Produce rooms should also use a smaller evaporator TD (3 to 5°C, not the 6 to 8°C typical of freezers) to maintain 90 to 95% RH. See the evaporator sizing calculator and defrost calculator.
Cold room design for Canadian produce, dairy, and floral storage
Cold rooms for living products like fresh produce and flowers carry a load that generic walk-in calculators leave out: respiration heat. Fruits, vegetables, and cut flowers stay metabolically active after harvest. They consume oxygen and give off carbon dioxide, water vapour, and heat at a rate that depends on species and temperature. Get this number wrong and the evaporator runs continuously but never pulls the room down to setpoint during busy receiving periods.
Canadian cold room applications cover a wide range: grocery store produce rooms, farm-gate coolers in the Ontario and BC fruit belts, cut flower storage at Vancouver florists, cheese aging rooms in Quebec, and pharmaceutical storage in urban distribution centres, where Health Canada's GUI-0069 guidelines for storing and transporting drug products call for mapped, monitored and alarmed storage areas. Each has its own product load, humidity requirement, and regulatory framework, whether provincial food safety or Health Canada.
Respiration heat by product category
Respiration rates at 2°C in this calculator run from 12 W/tonne for onions and 25 for apples up to 500 W/tonne for asparagus, 700 for broccoli and 750 for strawberries, which is why a strawberry room often needs a larger evaporator than its size suggests. Rates rise steeply with temperature, so a load worked out at 2°C understates a room held warmer. In the built-in example (400 kg of lettuce, 200 kg of broccoli, 300 kg of apples and 100 kg of strawberries), respiration adds 303 W, about 19% of the 1,613 W design load. For precise design, take respiration data for your exact product and temperature from the ASHRAE Refrigeration Handbook, and check each commodity's recommended storage temperature and freezing point in USDA Agriculture Handbook 66.
Humidity control in produce cold rooms
Produce cold rooms target 90 to 95% relative humidity to prevent moisture loss and wilting. That means the evaporator coil must run with a small temperature difference (TD) between coil surface and room air, typically 3 to 5°C instead of the 6 to 8°C common in freezer applications. A smaller TD keeps the coil warmer, which reduces moisture condensing out of the room air. It also changes coil selection, because the same duty at a lower TD needs more coil face area. Use the evaporator sizing calculator with a TD of 3 to 4°C when specifying produce room coils, and check the defrost calculator to confirm off-cycle defrost is enough, since active defrost adds unwanted heat and moisture. If a coil still ices up between defrosts, the evaporator freeze calculator is a good place to start diagnosing why.
Equipment duty, pull-down and running cost
Design load is the peak heat the room must lose. Equipment duty scales it by 24 divided by the compressor run hours, so the default 18 hours turns 1,613 W into 2,151 W in the built-in example. Pull-down treats every kilogram entered as arriving each day at its entry temperature and cooling to setpoint, which makes it the largest term in that example at 700 W, or 43%. Because the same mass also drives respiration, the pull-down term is conservative for a room where only part of the stock turns over daily. The annual cost figure assumes a COP of 2.8, which works out to about 5,047 kWh and $656 a year at $0.13 per kWh for the example. Use the annual energy cost calculator to compare that estimate against your own utility rate structure.
Frequently Asked Questions
Add each product as its own row, and the calculator sums respiration heat from every product stored at the same time. Most produce rooms hold a mix, for example 500 kilograms of lettuce, 300 kilograms of broccoli and 200 kilograms of apples together, and that mix adds about 315 watts of respiration heat at 2 degrees Celsius. The key design question is the largest inventory the room will ever hold at once, so size for that worst case rather than the average. In Canadian grocery distribution centres where stock turns over quickly, daily receiving can push inventory well above average, and the system must carry the combined pull-down and respiration load during those peaks. Cross-check the result against the general refrigeration load calculator to confirm the respiration component is being captured.
Yes. Pharmaceutical cold rooms are usually held at 2 to 8 degrees Celsius, the common refrigerated label condition, so the temperature window is tighter and excursions matter more than in a produce room. Health Canada's GUI-0069 guidelines expect storage areas to be temperature mapped with sensors in the worst-case locations, monitored with calibrated devices and alarms, and backed by retained records. In practice that means redundant sensors, round-the-clock monitoring with alarm notification, and backup power or redundant refrigeration. The refrigeration load is similar to a produce room, and pharmaceutical products carry no respiration heat in this calculator, but the equipment specification is stricter: no short-cycling, even airflow distribution, and a defrost strategy that does not push the room above 8 degrees Celsius.
Most fresh fruit and vegetables need 85 to 95 percent relative humidity and store best at 0 to 4 degrees Celsius. High humidity prevents wilting and moisture loss, while the low temperature slows respiration and microbial growth. Herbs and leafy greens do best at 0 to 2 degrees Celsius and about 95 percent relative humidity. Keep ethylene-sensitive produce such as leafy greens and broccoli apart from ethylene producers such as apples and bananas, which matters for multi-room design. Some produce is chilling-sensitive, and bananas and many tropical fruits are damaged below roughly 10 to 13 degrees Celsius. Packaged dairy is typically held at 2 to 4 degrees Celsius and is less sensitive to room humidity than loose produce.
Wall transmission load scales directly with U-value, so halving the U-value roughly halves the wall's contribution to total load. Standard 100 millimetre insulated panel construction gives a U-value around 0.033 watts per square metre kelvin, and 150 millimetre panels can drop that to around 0.022. In the built-in 6 by 4 by 3 metre example that change cuts transmission from 105 watts to 70 watts, which trims the design load by about 38 watts out of 1,613. Larger rooms with high wall-to-volume ratios gain more. For smaller rooms with frequent door openings or heavy respiration loads, transmission is often a small fraction of the total, so the payback on extra insulation depends on the application, not just room size.