Converting a shipping container into cold storage is one of the smartest ways to create affordable, durable refrigeration for farms, markets, and restaurants. With a little planning, insulation, and modern cooling tech, you can turn a standard 40-foot container into a multi-zone walk-in cooler that keeps everything from fresh greens to root vegetables at the right temperature.

Planning the Project

Start by deciding how you’ll use the space. A common setup divides a 40-foot container into three temperature zones: a rear cold room around 38°F, a middle cool room near 48°F, and a front staging area around 60°F for sorting and loading. Sketch the layout, mark where each air-conditioning unit will go, and note where doors and partitions will sit.

Before any construction, clean and prep the container thoroughly. Remove any old refrigeration equipment, treat rust, and make sure the floor and structure are sound. You’ll also need to plan your electrical setup with a licensed electrician, adding dedicated outlets for each A/C unit and safe condensate drainage.

Building the Structure

Frame two insulated partition walls using standard 2×4 studs to separate the zones. Anchor the framing to the steel walls and floor, then add an insulated exterior door at the front. Cutting openings for your A/C units can be intimidating, but a simple metal-cutting blade will do the job. Frame each opening so the A/C exhausts to the warmer section or outside the container.

Insulation is where your cooler succeeds or fails. Aim for at least R-20 using rigid foam board such as polyisocyanurate or XPS. Avoid fiberglass – moisture will ruin it. Fit the boards tightly between studs and run an unbroken layer of foam across the interior to eliminate heat bridges. Seal every gap with spray foam and foil tape until the space is completely airtight.

Once insulated, install a vapor barrier, then finish the walls with washable panels like FRP or sealed plywood. Add durable corner trim and caulk all seams to stop moisture leaks. Hang the door so it swings inward and install strip curtains between each zone to minimize temperature loss when the door opens.

Electrical Supply

Generally, a sub-panel with 220 volt power supply is needed to run a 40-foot refrigerated container. Locally, companies such as One Call Electric here in Spartanburg does a great job in getting electrical systems run for these.

Installing the Cooling System

The magic of this design lies in the CoolBot-style controller paired with a 24,000 BTU air conditioner.

Each temperature zone gets its own window A/C unit – typically a 24,000 BTU model – and a controller that “tricks” the A/C into running colder than its normal limit. Pricing on this runs about $1,200 per unit and CoolBot controller combo, giving you Complete cooling for around $3,000 to $4,000.

One sensor sits on the coil fins, another measures room air, and a third attaches to the A/C’s built-in thermostat. The result is commercial-grade cooling without a commercial-grade price tag.

For the coldest room, set the controller to about 38°F. The middle zone can be adjusted to around 48°F, perfect for produce like tomatoes or potatoes. The front staging area runs on a standard A/C unit without a controller, staying near 60°F–65°F – comfortable for sorting and loading.

If you want a commercial cooling unites, we have great refrigeration supply companies here in Spartanburg such as Refrigeration Wholesale Inc and United Refrigeration. These cooling systems can raise the refrigeration price to around $8,000 – but talk to them for accurate pricing.

Fine-Tuning and Finishing Touches

Once everything’s sealed and powered, run the system for 48 hours to stabilize temperatures. Check for air leaks with a smoke stick and seal any drafts you find. Install shelving and leave a few inches of space behind racks to allow good airflow. A small fan in each section helps prevent temperature layering.

Keep the space clean, inspect door seals often, and log daily temperatures. Replace strip-curtain panels as they wear out, and clean A/C coils monthly. If a unit fails, simply swap it for a spare – it’s that easy.

A Simple, Scalable Solution

With careful planning and quality insulation, this project turns an ordinary container into a powerful walk-in cooler for a fraction of commercial costs. Farmers gain extra days of shelf life, restaurants store local produce safely, and small businesses gain reliable cold storage they can maintain themselves. Whether you’re feeding a farmers’ market or stocking a kitchen, container coolers make local food systems stronger from the ground up.