When designing walk-in cold storage, freezers or environmental rooms, a number of design questions must be answered to meet installation requirements.

Walk-in coolers can be constructed with any number of compartments to accomodate process-specific requirements.
Used to cool or freeze products as diverse as hamburger patties and testing samples, walk-in coolers and freezers are important process components. Understanding your options when specifying the unit will help you select one that meets all your needs.

In the early days of walk-in cooler/freezer manufacturing, the rails around the panel's perimeter were made of wood. This became the panel's structure as well as the member into which the panel lock and pin could be installed. The wood rails were either flat or, in some cases, routed out to form a tongue-and-groove connection. Inside the wood rail perimeter, the panel was filled with fiberglass, slab styrene or urethane.

As the years passed, wood rail construction evolved into a wood rail foamed-in-place panel. The wood rail panel was placed in a flat fixture press that held the panel in place during the foaming and curing process. Finally, construction methods evolved to the all-foam panel commonly manufactured today.

When considering walk-in panels, look for a 4" thickness filled with a CFC-free foam urethane that has a minimum insulation value of R-30. Panels should be NSF approved and Underwriters Laboratories (UL) or Factory Mutual (FM) listed as flame spread 25 approved (ASTM E84).

A Look at Design Features

Doors. The door is the most important part of a walk-in cooler or freezer, and it can be equipped with a range of accessories to enhance its operation. They include:

  • Door closers.
  • Kick plates.
  • Viewport windows.
  • Electric opening with push button or automatic eye.

Walk-in cooler or freezer door sizes can range from a single swing, manual door in widths from 24 to 60" to sliding-type doors as large as 10 x 10' high. Larger doors may be required to allow pallet jack lifts or motorized lift trucks access to the unit. The doors should be approved by UL for electrical.

Floors. Your walk-in unit can be specified as floorless or with an insulated floor. Flooring decisions should be made after considering the following:

  • If you are going to operate your walk-in at temperatures of 32°F (0°C) and lower, you must have an insulated floor. This can be provided from the walk-in manufacturer as floor panels or be part of the insulated slab in the case of a floorless walk-in.
  • On larger, low temperature walk-ins, it may be necessary to include subfloor venting or a heating system under the insulated floor area to prevent the subfloor from freezing, which can cause the floor to heave. Work closely with the walk-in manufacturer for recommendations on these types of applications.
  • On floorless walk-ins, choose either a vinyl sealer or foam floor screed. The vinyl sealer should include a NSF approved cove as part of its design.
  • For floorless applications, you also may choose a flat or female bottom wall panel. In this case, as with the foam floor screed, coving must be added to the wall-floor juncture to meet NSF requirements.
  • If heavy cart or forklift traffic will be used inside the walk-in, adequate floor strength is required. This can be best achieved with a floorless walk-in and concrete wearing floor. If the walk-in is supplied with a floor, add a minimum of 2" reinforced concrete floor to the top of the walk-in floor for adequate strength.

Ceiling Panels. Ceiling panels can be provided as free-spanning in lengths up to 16'. With ceiling panels of this length, walk-ins can be constructed with any number of compartments and in unlimited widths. When both dimensions of the walk-in exceed 16', ceiling panels can be manufactured to lock end-to-end as well as side-to-side. The result of this construction is unlimited size and shape in both directions.

Ceiling Support Systems. In cases where the ceiling panels lock to each other in the end-to-end fashion, the ceiling is no longer free-spanning. End-to-end junctions require some type of support system. In the case of indoor walk-ins, the most common method of support is a suspended ceiling system. With this setup, a steel angle is connected to the top side of the walk-in ceiling panels using hanger brackets and fasteners. Then, the walk-in's ceiling is suspended from the customer's building ceiling with hangers provided in the field. Hangers can vary based on installer's preference (threaded rod, steel bar, chain, etc.).

In installations where suspension from the customer's building ceiling is not possible, a self-support system can be specified. The self-support system works on the same principal as the suspended ceiling support, except that the steel angle is replaced with a C-channel that connects to a bearing angle at each end. Bearing angles are located directly over the wall panels at each end. During installation, the interior ceiling will require temporary support until the self-support system can be installed.

The final ceiling support method is a post-and-beam system. This type of support is used for outdoor installations or for indoor installations that cannot use one of the other methods. The manufacturer should design the post-and-beam system to minimize the number of posts in the interior space. On some large outdoor installations, the interior support may require structural steel - which not only supports the ceiling panels but also ties into the wall panels - to satisfy wind load requirements.

A pallet rack system also can be specified to meet the storage needs and the ceiling and wall load requirements for indoor or outdoor installations.

Outdoor Roof Systems. The most common method of weatherproofing the ceiling of an outdoor walk-in is to install a rubber or membrane roof system. Material should be a minimum of 0.035" (35 mil) thickness, and white is preferred to reflect heat load. Most of these systems are flat, but they can be provided with a tapered insulated board that creates a slope when installed under the membrane. The standard slope is 0.125 to 0.25" per ft.

These are only a few of the design factors to consider when determining your walk-in cooler or freezer needs. Work closely with the manufacturer to ensure that the walk-in you select satisfies your process requirements.