A cold room is a storage volume enclosed with insulated panels and held at a specific temperature by a refrigeration unit. Because it is nearly impossible to change the panel thickness or door type after installation, most decisions are made at the project stage.
Most of the problems we see in the field also come from this stage: a panel chosen too thin, a door in the wrong position, or a unit bought by square meters. Below we explain step by step which choice is made based on what.
What information should be clarified first?
For a correct cold room design, product, temperature and usage information must be clarified first. Panel, door and unit selection are derived from these three pieces of information.
- Storage temperature: Generally 0/+4 °C for fresh meat and dairy, 0/+10 °C for fruit and vegetables depending on the product, and -18/-25 °C for frozen products.
- Daily product intake: How many kilograms of product enter the room each day, and at what temperature? This is often the real load on the unit.
- Door opening frequency: Is it opened a few times a day, or constantly with a forklift?
- Humidity requirement: Fruit and vegetables need high relative humidity; humidity is less critical for packaged products.
- Location: Is the room inside an enclosed building, or under a sun-exposed roof?
How is panel thickness selected?
Panel thickness is selected according to the difference between room temperature and ambient temperature; the larger the difference, the thicker the panel. Cold room panels are generally sandwich panels filled with polyurethane (PUR) or PIR foam, which has better fire behavior.
| Room type | Typical temperature | Common panel thickness |
|---|---|---|
| Positive-temperature storage | 0 / +8 °C | 80-100 mm |
| Low positive temperature (meat, fish) | -2 / +2 °C | 100-120 mm |
| Freezer storage | -18 / -25 °C | 120-150 mm |
| Blast freezing | -30 / -40 °C | 150 mm and above |
These values are a starting point. A sun-exposed roof, walls adjacent to a hot production area, or a high electricity tariff pay back a thicker panel quickly. Locked (cam-lock) panel joints and joints sealed with the right sealing material are as important as thickness.
In freezer rooms, the floor must not be forgotten. On an uninsulated or unventilated floor, the ground freezes over time, the floor heaves and the covering cracks. For this reason, in freezer rooms floor insulation is designed together with an under-floor heating or ventilation solution.
Which door type should be chosen?
The door type is chosen according to opening frequency, passage width and room temperature. The door is the point where a cold room loses the most heat; the wrong door nullifies even the best panel.
- Hinged door: Common in small and medium rooms and where loading is done by hand.
- Sliding door: Preferred in warehouses with forklift and pallet truck traffic that need a wide opening.
- Strip curtain and rapid door: Used in addition to the main door on frequently opened doors; significantly reduces warm air entering.
Freezer rooms must have a heater in the door frame that prevents freezing and a pressure equalization valve that balances the pressure between inside and outside the room. Without this valve, the door is hard to open once it has cooled down and the panels are stressed.
For safety, every cold room door must have an inside release mechanism and an alarm button inside. The risk of being locked inside is a serious hazard, especially in freezer rooms.
How is the capacity of the refrigeration unit calculated?
The capacity of the refrigeration unit is found by dividing the total heat load of the room by the unit's daily running time. This load is not made up only of heat entering through the walls.
- Heat passing through the walls, ceiling and floor
- Product load: Cooling of the product entering the room, plus respiration heat for fruit and vegetables
- Warm, humid air entering when the door is opened
- Internal loads: Lighting, working staff, forklifts, evaporator fans
- Defrost and safety margin
The unit is selected not to run continuously throughout the day but with an allowance for defrost and stops. In practice, the daily running time is generally taken as 16-20 hours. A unit selected by looking only at the room volume cannot hold the temperature on days when product intake is heavy.
Heat load calculation for your cold room project
Based on your product and usage information, let us prepare the panel, door and unit selection in writing.
Monoblock or split unit?
A monoblock unit is a ready-made unit in which the compressor, condenser and evaporator are combined in a single housing, generally mounted on the panel wall or ceiling. In a split unit, the condensing unit is outside and the evaporator is inside the room, with copper piping between them.
In small rooms and where installation is needed quickly, a monoblock is practical. In medium and large rooms, where condenser heat must be rejected outdoors and in environments where quiet operation is wanted, a split unit is a better choice. If there are several rooms, a central compressor rack can also be considered.
Evaporator and defrost selection
The evaporator fin spacing is selected according to temperature; in freezer rooms the fins are kept wider apart because there is more frosting. In positive-temperature rooms, air (fan) defrost is often enough; in freezer rooms electric or hot gas defrost is needed. The evaporator position should be planned so that the airflow goes toward the depth of the room, not toward the door.
Refrigerant choice
Because of the F-gas regulation, the use of refrigerants with high global warming potential is being increasingly restricted. In new projects, the refrigerant should be chosen with refrigerant availability and ease of service over the life of the unit in mind. A suitable alternative is determined with the manufacturer's recommendation according to room size and unit type.
What are the most common installation mistakes?
The most common mistake is calculating capacity from the room volume instead of the product load. This is followed by placing the condenser in a hot, unventilated corner, not heating the drain line in a freezer room, and not checking the door gaskets.
If the condenser re-ingests the hot air it discharges, a high pressure fault in summer is unavoidable. We explained a similar mechanism in detail in our supermarket display cabinet not cooling article. In freezer rooms, frozen drain water can turn the evaporator into a block of ice.
In the first weeks after installation, record the room temperature, the unit's running time and the defrost intervals. These records let you notice a small setting error before it turns into a major fault.
How do we carry out installation and maintenance?
At YOİ Mühendislik, we start cold room projects by collecting product and usage information. We share the heat load calculation in writing and base the panel, door and unit selection on this calculation. The price is prepared according to the dimensions and needs determined at the site survey.
After installation, periodic maintenance covers condenser cleaning, refrigerant pressure and defrost checks, and door gasket and heater checks. For details, see our cold room service page, and if you need continuous product freezing, take a look at our difference between a blast freezer and a cold room article.
Frequently asked questions
How many mm should the cold room panel be?
In positive-temperature rooms, 80-100 mm polyurethane panels are generally used, and in freezer rooms 120-150 mm. The exact thickness is determined by the difference between room and ambient temperature and by the location of the room.
Can a cold room unit be selected by square meters?
No. Unit capacity must be calculated from the total heat load made up of wall losses, daily product intake, door opening frequency and internal loads. A unit selected by volume cannot hold the temperature on busy days.
Why is a heater fitted to the door of a freezer room?
The heater in the door frame prevents the gasket from freezing and sticking and ice forming in the frame. Together with the pressure equalization valve, it lets the door open easily.
Is a monoblock cold room unit or a split unit better?
For small rooms that need to be installed quickly, a monoblock is practical. In medium and large rooms, where quiet operation is wanted or where condenser heat must be rejected outdoors, a split unit is more suitable.