Cold room heat load calculator

How is the heat load of a cold room calculated?

The heat load adds up all the heat that enters the cold room in one day. The refrigeration unit must remove it in 16 to 18 hours of running time, leaving time for defrosting and a reserve for the hottest hours. The calculation has seven parts:

1. Walls, ceiling and floor: Q = U × A × ΔT, where U depends on the panel thickness, A is the surface area and ΔT the difference between outside and inside. In the sun, walls and roof get hotter.
2. Air infiltration: every time the door opens, warm, humid air comes in and has to be cooled. In hot, humid countries it is often one of the largest loads.
3. Products: Q = m × c × ΔT, the heat to remove to bring incoming products down to room temperature, plus the freezing heat if they are frozen.
4. Respiration of fruit and vegetables, which keep giving off heat during storage.
5. Lighting and staff working in the room.
6. Evaporator fans and defrosting.
7. A 10% safety margin.

Example: a 30 m³ cold room for fruit and vegetables

Chilled room at +2 °C, 4 × 3 × 2.5 m, inside a building, with 38 °C outside, 100 mm panels and an insulated floor. It receives 1,000 kg of fruit per day entering at 25 °C, with normal door opening.

That is 64 kWh per day to remove in 18 hours: a cooling capacity of about 3.6 kW (between 3.2 and 3.9 kW). Products and air infiltration make up more than 60% of the load: here, pre-cooling the fruit and keeping the door open for less time reduce the capacity more than thicker insulation would.

Typical cold room capacities

Capacities calculated with the tool for 38 °C outside, a room inside a building, an insulated floor and normal door opening. Chilled room at +2 °C: 100 mm panels, 25 kg of fruit and vegetables per m³ per day entering at 20 °C. Frozen room at −20 °C: 150 mm panels, 15 kg of frozen meat per m³ per day entering at −15 °C.

Per cubic metre, the capacity falls as the room gets bigger: about 140 W/m³ for a small 10 m³ room, 60 W/m³ (chilled) and 33 W/m³ (frozen) for 300 m³. Here the chilled room needs more than the frozen one because it receives warm products to cool every day, while the frozen room receives products that are already frozen. These figures only apply to these assumptions: run the calculation with your own values.

Which panel thickness?

• Chilled room (0 to +12 °C): 80 mm when it is up to about 32 °C around the room, 100 mm above that, which is the most common case in Tunisia, Algeria and West Africa.
• Frozen room (−18 to −25 °C): 150 mm, with an insulated floor, heated under the insulation in large rooms so that the ground does not freeze.

Thicker panels reduce losses further, but the walls often account for a quarter of the load or less: products and air infiltration matter more. See our insulated panels and our cold rooms.

Frequently asked questions

How many kW does a 20 m³ cold room need?

With the assumptions in the table above, about 2.2 kW for a chilled room and 1.9 kW for a frozen room. The result varies a lot with the quantity of products brought in each day and their temperature: run the calculation with your own values.

What is the difference between a chilled and a frozen cold room?

A chilled room keeps products cool, between 0 and +12 °C: fruit and vegetables, dairy products, fresh meat, beverages. A frozen room stores frozen products, between −18 and −25 °C: it needs thicker panels, an insulated floor and evaporator defrosting.

Why is the result a range?

The calculation uses average values: number of door openings, product heat, unit efficiency. The ±10% range is a reminder that this is an estimate. Our design office refines the calculation with the exact data of your project.

Can fresh products be frozen in a frozen storage room?

In small quantities, but slowly: a frozen room is designed for storage. To freeze fresh products every day, a blast freezing tunnel is faster and better preserves their quality.

Does the calculator replace a design study?

No. It gives an order of magnitude to prepare your project. Before any quote, our design office checks the heat load, selects the refrigeration unit, evaporators and controls, and takes your site into account.