Everyone knows how refrigeration works, right? There’s a big white box in our kitchens called a fridge, and it keeps stuff cold. Above the fridge is the freezer, where things are even colder. By the time we’re three, we know one door is for the orange juice, and the other for the ice cream. What’s so complicated?
Of course, we all know there’s more to it than that. But on a basic level, a standard 18 cubic foot refrigerator and a 3,200 cubic foot walk-in freezer (see below) are remarkably similar. They both depend on insulation, compressors, refrigerant and blowers to function. It’s like comparing a Mini Cooper to a tractor trailer: the concepts are the same, but you’ll never see a Mini towing a tanker of fresh milk.
As a farmer who sells his food directly to the public, the importance of reliable refrigeration can hardly be overstated. Food safety requires proper temperatures, but I also need space to receive, organize and pack my products. Just like a restaurant or a supermarket, having a large refrigerated space is crucial for farmers’ markets sales, or for CSA farms keeping product cold in advance of weekly pick ups. The following is a photo-blueprint of how we built our own walk-in from scratch, using standard 2X4 construction, our own labor, and two specialists who helped perfect it.
You gotta start somewhere. Here, we’re building onto our existing freezer shed and loading dock, which house two conventional ‘locking panel’ walk-in freezers. Jim is laying out the footer dimensions with string. Excavation will follow.
Digging the footers. Things rarely go as planned, and I rented a jackhammer to break up some stubborn rocks. The bandana wins me style points.
The footers are poured, the block laid, and next comes 4 inch pipe spaced at 4 foot intervals. This isn’t for drainage; it’s to allow warm air to flow beneath the slab so the penetrating cold (from the freezer above) won’t heave the subsoil and crack the concrete. (In photo #11, you’ll see the breather caps protruding above ground).
Gravel comes next. This IS for drainage, to keep water away from the slab and provide a level area for the insulating foam sub-surface.
The foam underlayer. Made partially of soy, this insulation is blown in a 4 inch thick sheet, and will provide insulation superior to the injected foam panels on my older walk-ins. This is sprayed by a specialist from tanks on a truck.
A closer look at the foam. Once cured (about 2 days at 70 degrees), it becomes VERY firm… not as hard as concrete, but extremely rigid. Take special note that we left plenty of footer exposure along the edges. This will allow us to ‘tie’ this foam to fresh foam later on, after we’ve built the walls and ceilings. In effect, we’ll create a foam box within a wooden box (i.e., the building itself). Make sense?
Next, we pour our concrete slab OVER the foam. Told you the foam was solid! This will be our floor inside the walk-in, and the foam beneath will provide our insulation. This slab is 22×20 feet, and will later be treated with an anti-slip epoxy sealer.
A closer look at the slab and foam. When exposed to sunlight for a few days, the foam turns from green to yellow.
Next, we build on top of the remaining exposed footer. We’re building double walls here, one on the inside slab and one on the outside footer, the studs offset by six inches. This is important because it allows the foam to be sprayed in such a way that there’s no ‘break’ in the insulation. In other words, the foam will serpentine around the offset studs.
Here’s a closer look at the offset double wall studs. Notice how the underlaying foam remains exposed, so we can connect it to the next application of foam and complete our foam ‘box’ without any breaks.
Photo #11, showing the exposed pipe breathers.
The interior sheathing has been installed on the walls and roof, and now the foam is applied to the walls and allowed to expand.
Once the foam expands, an assistant scrapes the 2×4 studs clean with a special knife, so the exterior sheathing will have a flat surface for nailing.
An extra inch or two is added in the attic because we all know that heat rises! This is applied with less attention to aesthetics, as there will be no plywood sheathing here. Again, this foam looks soft but it’s almost rock-hard once cured.
Getting closer. Next, we glue and install glass board (you’ve seen this product in gas station restrooms), doubling as a moisture barrier as well as an easily cleanable surface.
Our second specialists, installing wiring, compressors and evaporators on the outside…
…and the fans and defrost coils on the inside. The freezer will be calibrated to an arresting 0 degrees fahrenheit. All of the interior walls will be sheathed in glass board, and shelves will be erected to store our meat.
The nearly finished product. Still needs some grading and gutters, but no job is ever truly finished! We built it with a 60 inch door to accommodate a pallet jack. If everything goes as planned, it should serve our farm for many decades. The interior is 3,200 feet (19x21x8 interior), and will house thousands of pounds of beef, pork, lamb and chicken. The project cost $45,000 in labor and materials, funded 100% through sales at farmers’ markets.
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Enjoyed reading your book. The forward by Joel Salatin was a nice touch. Will watch for your next publication. Thank you for showing me there is someone else out there that is trying to make a difference. Kathy D.
Nice work documenting this ambitious DIY project, Forrest. Wonder if it might make a good piece for Acres, USA, with just a little tweaking. I’ll bet a lot of other farmers could benefit from it.
Outstanding! THAT is what I call the perfect Asset. It’s going to change your world for sure.
I hope you share any changes you make to it in the future. I would love to see how you use it, and how it functions when all is finished.
your photos are most excellent. really well explained. Want to come over and build a walk-in cooler at our farm next?
I’ll blog you through it 🙂
Well it looks like your ground is similar to ours. We are planning to run more underground water lines etc., and have considered purchasing a backhoe, used. Looks like the one you are using is a reasonable size and yet the ole jack hammer has come to the rescue. If we still have to use a jack hammer at times maybe a smaller backhoe would serve the purpose
I.e. a terramite. Do you think a smaller unit would have worked for you?
Just curious, as I am looking to have a similar project done myself. What is the average temperature at your location and what is the energy consumption per month for said temperature? Thanks!
^ The monthly energy consumption of the walk in freezer that is.
I Where did you get your walk in freezer door, haven’t found where to get one..We are looking to build a smaller version of your freezer. Enjoyed your site.
Will you be running those eight fans all day and night? If so, won’t they use a lot of energy (>.1,000 watts?) and input a lot of heat into the freezer?
Do you have a moisture barrier on the exterior of your walk-in freezer? If not, have you have any problems with condensation rotting the wood? Any suggestions as to where to find the glassboard you used on the interior? We’re an intentional community farm looking to build our own walk-in freezer. Thanks!
the Glass board is called FRP (fiberglass reinforced plastic) avalable at just ebout every home depot in several colors
I would be interested in knowing the energy consumption as well.
I’ll get back to you on energy consumption, this particular meter services multiple power sources. Right now I can say it’s more efficient than running the two walk-ins and 4 chest freezers that we used to employ, because our monthly bill is lower relative to previous bills. However, we also had a cooler summer than normal, so I’ll have to spread this cost into next year to get a better sense.
What is the R value per 1″ thick piece of the insulation you used?
Thanks for asking, Daniel! The foam has an R value of 18, and is 4 inches thick.
Daniel if the foam is Demilec Soya it has a R-Value of 6 per inch based on core sample no skins.
Hi! i am planning to make my own mobile trailer freezer, looking into your project do you think i can do it as you have done and if so how will i construct the floor.
How did you construct your door? Wood with spray foam intterior? Did you make it yourself?
Also, is your spray foam closed cell?
I work for a cooler manufacturer so I may be a bit biased but for the cost to implement this I think you would have been better served purchasing a cooler in panel form. I’ll state my reasoning.
Your cost of 45,000 is about the going rate for a cooler this size if not higher for a finished cooler this size. The R value you state of 18 is what the spray foam starts at and will drop considerably as it draws moisture in. All foam regardless draws moisture. so no way around this unless 100% vacuum sealed… The amount of wood used in the construction causes problems as well allowing for mold, moisture, and swelling to take place all reducing your refrigerant efforts.
I would pick a cooler manufacturer that used gaskete panels, no wood, and formed pre expanded foam less susceptable to moisture. I’m not doing this to promote my business so I’ll not mention it but our R-value never gets below 18 and starts at 28. Spray foam starts usually at 32 but within 8 years under most testing has been reduced to 8.
But you didn’t factor in how much FUN we had building it! 🙂 Really, an enjoyable endeavor.
Richard – We are looking to do something similar. Can you tell me which company you work for? Thank you – Ed McNamara
Richard I also work in the HVAC/R industry and totally agree with your commentary. I get it they had fun and it looks good in the first few years. As you know time is the enemy with this design and others involving wood construction. I’m sure you also have story’s about wood / insulation installed like a house? Condensation over time collected in the ceiling resulting in the loss of capacity to the point temp can’t be maintained. There are many concerns here. This is in reality a thin concrete floor poured over foam (concrete regardless if it’s even 8″ thick it will crack just as quick as a slab that is 3″ thick) without steel reinforced and a strong supportive under “frame”. For those following along: envision a forklift with it’s weight 3500lbs on the back counterweight, wheelbase is “about two feet wide” with the forks holding 1500lbs of beef combined with the remaining weight of the forklift. (9000 lbs is the typical forklift weight) with the basic concrete offered for housing being of the 3000 lb rating per sq ft. Imagine day to day operation with moisture always trying to get into the concrete and 13,000 lbs going back and forth sometimes pounding on that floor?
The panels glued to plywood? Glue / wood / condensation in time this will be a nightmare that I cannot even begin (bacteria) to explain and the ceiling is always the first failure.
I could go on and on, I only suggest that follow-up and information on failures be told to all in this forum so others can learn.
Thanks for this expert input. All I can say is, so far, so good. I have noticed no performance deterioration whatsoever after 5+ years. Only maintenance is fresh paint on the outside each year.
can anyone give me info to build a batch freezer. i make yougert and would like to freeze it fast.
You really don,t state what the foam guys charged you, and I would be comparing that to “SIPs” Seems to me a foil faced 6″SIP is Almost R 40 and deals with the moisture ingress issue and much less R loss over five years. The last time I priced SIPs they were not that much more. You could spend the time saved to build an outer wall of just 2 x 4’s and vapour barrior. That air space makes your R 40 SIP full value and moisture ingress almost non-exsistant. And then since you are building an outer wall anyway, you don’t need full structual SIPs.
Most SIP manufacturers are fairly local (like franchises) and could FRP one side like you did here. I know this is starting to sound a lot like walk-in freezer panels, but what a world of price difference! In my opinion, walk-in manufacturers really do see you coming.
Or maybe they just didn’t see the SIP industry coming.
Well there you go! You should write your own blog!
I have a silo with nice access through the lower barn – I wonder if anyone has ever re-purposed a silo – sure saves on lots of the infrastructure – have to have flexible panels – but the concrete is already pretty thick. I rent freezer space now – but I should like to bring this asset home.
I was thinking about a combination walk in freezer and refrigerator, and I stumbled across your excellent article. I want an inside the house walk in, but on a (perhaps 1/5 of yours) smaller scale.
I was wondering what your thoughts were about such a combo? Do you think it better to build separate cooling constructs for each section (assuming that one has to walk through the refrigerated section to access the freezer section) or perhaps just using a few well-placed ventilation holes in the freezer front to get refrigerator temperatures in the refrigerated section?
In addition to this, I wonder why you erected the walls and then sprayed on the insulating foam, rather than building the walls on the ground and spraying them while they still lay horizontal. Done this way you could have had thicker foam insulation which would be nice and even throughout, and it would not run down the wall as it set. Was it because of weight considerations?
I understand that I am perhaps being thick here and asking a stupid question, but it was just something that occurred to me as I viewed the pictures.
Hi – I just wanted to thank you for taking the time and effort to write this. It’s very helpful as we figure out how we expand!
Wow, building a cool room looks like a ton of work. Renting jackhammers, backhoes, and tractors may be a little too much work. Wouldn’t hiring a company to help build it save a lot of time?
Probably, but that also applies to essentially everything. As a farmer, I’ve always relished new experiences, and never shied away from hard work 😉
Have your breather pipes worked to keep the soil underneath from freezing? As I research the floor requirements for a walk in freezer most places say that vent pipes are not sufficient to keep the subsoil warm. The alternatives seem to be to provide some type of sub-floor heating, or to pour a concrete pit, layer insulation, and then pour the freezer floor on top of that. Both of these options seem much more expensive than providing breather pipes.
Yes, so far as I’ve observed. We had a terribly cold winter here this year (a full week where temps remained between 0F lows and 20F highs), and I saw no signs of problems. Do your own due diligence, however!
Any updates on this project? It’s been 4 years since it’s been done, would you do it the same way again?
Thanks for feedback.
Seems to be working well. I might have gotten the same economy from just buying the pre-fab panels, but it wouldn’t have been as fun or interesting.
Forrest I give you a lot of credit, my thing is more of “others” to understanding refrigeration and the many problems and shortcomings in these designs that were gone through in the 40s to present day.
Your true benchmark will be 8 years and the state your in depends also on efficiency and durability. Texas / Arizona / the Carolinas will have totally different results and that’s why I fear others getting the wrong thought process on these types of endeavors. In Ct where I am this would work against my clients because it wouldn’t be UL rated etc. Energy discounts etc gone, and with electrical costs here that hurts. I have literally been witness to lawsuits because an entire new evaporator was put in as well as a new condenser being the exact same Hp as the original because the owner thought the unit was “old and shot”. Never had anyone really check it out correctly. Long and short of it was there was nothing wrong with the mechanical refrigeration unit rather the ceiling had condensation built up to the point that “gallons as in 70+” was frozen into this freezer and was putting such a load on the refrigeration unit it lost btu capacity to the point it wouldn’t freeze. They had to crush up the box after removing all the new mechanical refrigeration equipment and installed a new box. Time is the enemy with wood and an environment that could be a problem to (insects / moles / termites etc.) Me? Galvanized studs / high density foam correct to the application of food stuffs / sealed gasketed walls. Again I could go on and on. I wish you the best of luck and I’m glad your a “get it done” kinda guy! This is very much missing these days!