Walk-in coolers and freezers are staples of restaurants, hotels, supermarkets, and any other place that needs to store fresh, frozen, or pre-cooled food products. These walk-ins are enclosed, refrigerated storage spaces that have footprints generally smaller than 3000 square feet and can be used for things such as storing perishable food items or packaging food. Walk-ins are often used as medium-term cold storage—with standard refrigerators acting as short-term storage and refrigerated warehouses acting as long-term storage. Just like any refrigeration system, walk-ins use an evaporator inside the unit and a condenser outside the unit to move heat outside, thus cooling the inside.
From a broad perspective, there are three kinds of walk-ins: self-contained, remote condensing, and multiplex condensing. Self-contained walk-ins, as the name implies, are cold storage rooms where the refrigeration system is a complete package with the evaporator and condenser in one unit, similar to a window A/C unit. Self-contained walk-ins are typically built outside of buildings which they serve. Remote condensing unit walk-ins have the condenser unit somewhere other than directly adjacent to the room and not packaged with the evaporator, such as on the roof of the building. Remote condensing unit walk-ins are typically built into the buildings they will serve and may have multiple evaporators. Multiplex walk-ins use a centralized system with multiple condensing units and evaporators. Multiplex walk-ins are always built directly into the buildings they serve.
To help walk-ins operate efficiently, their walls are constructed with insulated walls, floors, and ceilings. The insulation material, typically some variety of foam, is sandwiched between thin walls, usually ones made from steel or aluminum. Insulating the walk-in keeps the temperatures inside and out separated, requiring less work from the evaporators and condensers to maintain the temperature and conserving electricity. In addition to being insulated, walk-in floors should also be reinforced to support any equipment and product they will hold.
Another way to increase efficiency is to install curtains at the doors. Whenever an employee enters or exits the cooler or freezer, heat from the outside comes into the cold room. This in turn requires the system to use more energy to bring the temperature back down. Curtains help reduce temperature fluctuations inside the walk-in. There are typically two kinds of curtains: strip and air. Strip curtains are made up of thick plastic sheets cut into strips while an air curtain is made up of a wall of air, blasted at a high velocity from directly above the door. Both designs help keep the temperature of walk-in coolers and freezers low and efficiency high.
Complete Materials and Components List for Building a Walk-In Cold Room
Building a walk-in cold room requires more than the refrigeration unit alone. A complete system includes structural insulation, refrigeration components, doors and seals, electrical and control components, and proper sealing to help maintain stable temperature, reduce energy loss, and protect stored products.
The exact bill of materials depends on the room size, target temperature, application, refrigerant, local codes, and whether the system is self-contained, remote condensing, or connected to a centralized refrigeration system.
| Category | Materials and components | Function |
|---|---|---|
| Structural enclosure | Insulated wall panels, ceiling panels, floor panels, panel joints, structural supports | Creates the insulated room envelope and separates the cold space from the surrounding environment. |
| Flooring | Insulated floor, floor finish, floor protection, drainage where required | Helps reduce heat gain from below and supports safe operation, cleaning, and product handling. |
| Refrigeration system | Condensing unit, compressor, condenser, evaporator or unit cooler, expansion valve, refrigerant pipes, refrigerant | Removes heat from the cold room and maintains the required storage temperature. |
| Refrigeration line components | Solenoid valve, filter drier, sight glass, shut-off valves, check valves, pressure switches, service valves | Supports refrigerant control, system protection, service access, and reliable operation. |
| Doors and access | Insulated door, door frame, hinges, handles, door closer, safety release, threshold | Provides safe access while limiting warm air infiltration. |
| Sealing and insulation details | Door gaskets, vapor barrier, panel sealant, joint sealing, pipe penetration sealing | Reduces air leakage, moisture ingress, and ice formation risk. |
| Controls and monitoring | Cold room controller, temperature sensors, defrost control, alarms, monitoring devices | Manages temperature, defrost, alarms, fans, and system operation. |
| Electrical components | Control panel, power supply, wiring, protection devices, lighting, switches | Powers and protects the refrigeration system, controls, and room equipment. |
| Airflow and defrost | Evaporator fans, defrost heaters or defrost control, drain pan, drain line heater where required | Maintains airflow across the evaporator and helps prevent ice build-up. |
| Safety and compliance | Emergency release, alarms, signage, refrigerant safety measures where required | Supports safe use, service access, and compliance with applicable regulations. |
Key refrigeration components in a walk-in cold room
A typical walk-in cold room refrigeration system includes:
- Condensing unit to compress and circulate refrigerant
- Compressor to raise refrigerant pressure and move heat through the system
- Condenser to reject heat outside the cold room
- Evaporator or unit cooler to remove heat from inside the room
- Expansion valve to regulate refrigerant flow into the evaporator
- Solenoid valve to control refrigerant flow in the refrigeration circuit
- Filter drier to protect the system from moisture, acid, and particles
- Cold room controller to manage temperature, defrost, fans, alarms, and system protection
- Temperature sensors and pressure controls to support stable and safe operation
- Refrigerant piping and insulation to connect the indoor and outdoor parts of the system
Danfoss components used in walk-in cold room systems
Danfoss supports walk-in cold room systems with components for refrigeration control, system protection, refrigerant flow, and efficient operation.
| System need | Danfoss product area |
|---|---|
| Packaged refrigeration solution | Optyma™ condensing units |
| Temperature, defrost, alarm, and system control | Optyma™ Control and cold room controllers |
| Refrigerant flow into the evaporator | Thermostatic expansion valves and electronic expansion valves |
| Refrigerant circuit control | Solenoid valves |
| Moisture and particle protection | Filter driers |
| System monitoring and protection | Sensors, pressure switches, and controls |
| Low-GWP refrigerant transition | A2L-ready, CO₂-ready, and low-GWP compatible component options |
However they are built, walk-in coolers and freezers are important parts of many different businesses across a multitude of industries.
Join us next time for our detailed look at which components are the best to choose for your walk-in.
Part 2 - Walk-in coolers: compressors and heat exchangers
Part 3 - Walk-in coolers: filter driers and sight glasses
Part 4 - Walk-in coolers: pressure switches, ball valves, and fan speed controllers
Part 5 - Walk-in coolers: thermostatic expansion valves and solenoid valves
Part 6 - Walk-in coolers: temperature controls
Part 7 - Walk-in coolers: a summary
1) https://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/safe-food-handling/keep-food-safe-food-safety-basics/
2)http://www.shaverinc.com/soft-wall-solutions/pvc-strip-doors-curtains/
3)http://www.mckeedoor.com/air-curtains/