We begin by looking at why insulation is always needed under a freezer and when you will need to insulate a cooler. Then we’ll go into the methods of insulating a walk-in including; prefabricated floors, recessed floors, insulated slabs and recessed pits along with providing some of the benefits and limitations of each design. Finally, we’ll circle back and talk a little bit about insulating a cooler when it’s on grade and the benefits of doing so.
FREEZER INSULATION
A freezer floor always needs to have insulation, period. This is pretty straight forward and easy to remember. The reason a freezer needs insulation is due to two factors; operating temperature and how an evaporator works. Obviously if we have a freezer we have temperatures below zero and in many cases we are holding a freezer at -10F. That’s pretty cold and the ground beneath the freezer without any insulation will eventually freeze as well.
Now let’s think about how an evaporator works. An evaporator is a heat exchanger that essentially removes heat from a walk-in. The way they remove heat is by removing moisture and they are very efficient pieces of equipment at removing moisture. If we do not have any insulation underneath a freezer, the evaporator will initially suck moisture out of the concrete (this is why in many new buildings you have excessive condensation in a walk-in right after start-up) and will eventually begin to suck moisture up into the concrete from the ground underneath the freezer.
This moisture will freeze upon hitting the frozen concrete and will somewhat thaw during defrost and will repeat this cycle over and over again during the refrigeration cycle. The eventual result is frost heave which is indicated by cracks and bulging in the floor. If this happens, there’s an ice ball underneath the concrete and that ice ball is going to continue to grow until the freezer is shut down and the ice ball is dug out and a properly insulated floor is installed.
In summary: a freezer always needs insulation beneath it.
COOLER INSULATION
So what about insulation in coolers? Since the temperature of a cooler does not go below freezing, cooler typically do not require insulation.
As long as the cooler is on grade; meaning it has concrete and dirt underneath it, we can place the cooler right on the floor. However, if the cooler is on a second floor or above or if there is a garage, mechanical room or some other room or vacant air space underneath it; or if it’s sitting on a wood floor, we want to be sure to insulate the floor. If the floor is not insulated in these cases, the floor materials will get cold enough to trigger the magical dew point where and begin to accumulate condensation underneath it. At this point, it will begin to drip or rain on the area underneath the cooler. If there’s an office underneath the coolers, the people in that office will not appreciate wearing their GoreTex to the office each day. If the cooler is sitting on a wood floor, it will accumulate condensation and eventually rot the wood at which point the second floor cooler will become a first floor cooler.
So the basic rule of thumb is:
Freezer = Insulate always.
Cooler = Insulate if the cooler does not sit on grade.
How much insulation do we use?
The minimum amount of insulation underneath a freezer is determined through the Federal Environmental Independence and Security Act passed by Congress in 2007 and amended for walk-ins in 2009. The law states that the minimum R-value underneath a freezer is 28. So, the thickness of the insulation used will be dependent upon the R-value of the insulating material. See last quarter’s Advisor Newsletter for a complete discussion on R-values.
SURFACE FLOORS, RECESSED FLOORS, AND INSULATED PITS
The question of whether to use a prefabricated floor or an insulated pit or insulated slab is one that where there is no correct answer; rather there are benefits and limitations to each design. Let’s review each of those here.
Surface Floors
This is floor is usually the easiest to install and takes the least amount of coordination between the walk-in manufacturer, installers and construction personnel. This type of floor is prefabricated by the walk-in manufacturer and typically consists of the same panel design and thickness as the wall panels, although the structural characteristics and wear surface will be different. It can be installed on top of any existing flooring and thus is a very viable option when replacing a walk-in in an existing building or restaurant. The design element to think about when using a prefabricated floor is how the end user will enter the walk-in. If the walk-in is sitting on top of a floor, the decision comes down to whether it will be a step-in or will have an internal or external ramp. If a ramp is desired, it’s important to note what the slope of the ramp is and how that may affect pushing fully loaded carts up and down it.
Recessed Floors and Insulated Floors.
Recessed floors and insulated pits are grouped together because they both required a contractor to either cut out an existing slab or to plan for the recess in advance during building construction.
Recessed Floors
A recessed floor is easy to imagine, it’s a prefabricated floor built by the walk-in manufacturer, and installed into a cut-out in the slab, so that the floor inside the walk-in is level with the floor outside. Typically the cut-out or recess is 1” larger in dimensions than the walk-in and should be the same depth as the floor. So a 10’ x 10’ freezer with a 4-1/2” floor should have a recess that is 10’-1” x 10’-1” x 4-1/2” deep. The benefit of this type of installation is that it eliminates the issues with a ramp, is easy to build and requires minimal coordination on the job site. The drawback of this type of floor is that it typically costs more to build and become quite expensive if manual or electric pallet jacks are to be used with heavy loads. Building structural floors will be a topic of a future newsletter.
Insulated Floors
Insulated floors fall into two main categories; insulated slabs and insulated pits. They contain the same items; a vapor barrier on the warm side of the insulating material, insulation and a top slab. The main difference is the sequence of how they are constructed. Here’s the definition: insulated slabs are constructed before the walk-in is built and delivered, the insulated pit is constructed after the walk-in has been shipped and built at the job site.
Insulated Slab
Given that definition, an insulated slab is where the pit is designed and constructed, by the general contractor based on the insulation and floor strength requirements and typically the walk-in manufacturer or KEC is not involved with its construction beyond the design stage.
That said, during design, it’s not a bad idea to have a walk-in manufacturer review the insulated slab design as there are several items that could come into play depending on the geographic location of where the insulated slab will go.
For example, if the project is a public building along the west coast, there will likely be seismic requirements and therefore, engineers will need to run seismic calculations on the walk-ins. A top slab that is only 2 or 3” thick may not provide enough strength to adequately hold the anchors required by the engineer. An additional concern may be the installation of a large 20’ x 40’ freezer where a forklift will be operating, carrying heavy loads. A structural engineer will likely let you know how thick the topping slab should be (which is, thankfully, beyond the scope of those of us building walk-ins) however, a competent walk-in manufacturer will likely inform you that you may want to install vents or heat in the slab in order to keep ice from forming in the center of the walk-in.
In most cases when building an insulated slab, if the KEC is not providing the pit insulation, vapor barrier and thermal breaks, the KEC should confirm the insulated slab dimensions before releasing the walk-in for production. The key here is that if the dimensions are off an inch or two, those dimensional changes are easily accommodated for in the production of the walk-in rather than once the walk-in has been built and delivered.
Insulated Pits
Let’s now explore an installation where the walk-in is built in a pit. What happens in this case is that the recess or pit is built to the dimensions and depth required and then the walk-in is designed and built taking these dimensions into account. This is the type of install where the walk-in walls recess down into the pit and the complete walk-in is built before the vapor barrier and pit insulation and final topping layer of concrete is poured.
The benefit of this type of install is that it’s fairly simple with respect to coordination between the general contractor, walk-in manufacturer and KEC. Most good walk-in installers have experience building these types of walk-ins and all of the products can be shipped from a single supplier (i.e., walk-in panels, doors, pit insulation, etc) which means that the installer receives everything required for the install from a single source and most of the time in a single delivery.
There is a variation to this type of install that should be noted. That is where a prefabricated floor is built and set down into the recess and concrete is poured on top of the floor. This removes the need for pit material and while it typically costs a little more to construct, it eliminates any errors during install with misapplication of the vapor barrier and/or the insulation material. There is something to be said about simplicity.
What are the Pro’s and Con’s
As discussed earlier, there are benefits and limitations with each type of insulated pit. Many of these items were discussed throughout the text but the table below summarizes the main points with each type of installation.
Finally, let’s take a look at whether or not there’s a benefit of putting insulation underneath a walk-in cooler. As we discussed earlier, if a cooler is not on grade, then we do want an insulated pit. But what about when the cooler is on grade, does it make sense to go ahead and insulate the cooler floor similar to what we are doing for the freezer?
Let’s compare two 10’ x 10’ x 8’ coolers that have 4” walls and ceilings (K-factor of .125 and R-value of 32). For the sake of simplicity, we’ll assume that outside ambient temperatures, product loads and infiltration loads are all equal. The first walk-in will be placed on a 6’ concrete slab while the second walk-in will be placed on 4’ of insulation that is then covered with a 4’ topping slab of concrete.
The table below illustrates the difference in R-values between the different products. In our example we will be adding the R-value of the foam stock board and the R-value of the 4h of concrete together in order to run the comparison.
Box 1, the walk-in sitting on the 6” concrete slab, will have an hourly transmission load of 2,090 BTU’s. Box 2, the walk-in with the insulated slab, has an hourly transmission load of 1,150 BTU’s. As we expect, Box 2 has the lower of two hourly loads and we can see that Box 2 requires 940 fewer BTU/h than Box 1. If we assume that the coolers run at 16 hours per day, 365 days per year, then the difference becomes (940 x 16 x 365) 5,489,600 BTU’s per year savings by installing the insulated floor. Let’s convert the BTU’s to kWH ( 1 BTU = 0.00029307107 kilowatt hours) so our insulated floor saves 1609 kWh per year.
So, if we assume the kWh cost for an area is $.10 then our cooler will save the $160 per year. If the lifespan of a walk-in is 10 yrs, the savings in electricity will be $1,600, if the cooler lasts 20 years, the savings in electricity will be $3,200. The ultimate payback will be based on the cost of the material & labor. I don’t have access to all the material costs but for the 4” of pit material (vapor barrier & insulation) plus labor to install it, the cost would be approximately $450. Add to that the cost of the concrete and its installation price and the payback can be calculated.
The bigger question becomes, is it of value to the end user?
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We’ve been working with Little Caesars for some time. Philip Stiefel, of Stiefel Associates, and Imperial Manufacturing sales person Kristy Heatley, work hard to make sure Imperial Manufacturing walk-in coolers and freezers are the answer to Little Caesars franchisee needs. 
Stacey has always been interested in building and construction. Her first involvement in construction was working for a mid-west commercial walk-in cooler manufacturer. She quickly moved into sales and then served for 10 years as a national account manager at the company.
Stacey spent some time at the Imperial headquarters on the plant floor getting a close look at the manufacturing process and the construction of Imperial walk-in coolers and freezers.
Jim has been with ICS (International Cold Storage) for over 20 years working through inside sales, territory sales, national accounts responsibilities before becoming Director of Sales and Marketing in 2004. Jim’s extensive experience in the Walk-In Cooler / Freezer business includes very strong relationships in the dealer community, chain account segment and manufacturers’ reps. He comes highly recommended by our key accounts, reps and competitors.