Building Our Walk-in Cooler

February 24, 2015

In order to keep our produce in great shape this summer, we needed to set up a method of dependable refrigeration on a large scale.  We consdered a variety of options that we could purchase including everything from a couple of standard refrigerators to a ready made walk-in cooler.  However, nothing seemed quite as good as just building a walk-in cooler ourselves.  So like other projects, this one started at the drawing board.  


Now, after about a month of work, we have a finished product that we are quite happy with.  The cooler will have ample space for our first few years of operation and a combination of cooling methods and solar photovoltaic panels will make this walk-in cooler net zero in keeping with our other low impact practices.  


Read on to see how this project came together and feel free to ask questions if you would like to know more about the building process.  It is difficult to find information on this subject so we would be happy to share what we have learned.  



We are in the process of renovating a character home in Riversdale and thankfully the home came with an undeveloped basement, which was the perfect starting point for a walk-in cooler.  Because most of our basement is below grade, the temperature of the concrete walls will remain cool throughout the summer and dramatically reduce our energy demands for the cooler. 


The framing, insulating, and finish work involved familiar tasks for the most part but refrigeration technology was a new realm for us.  Research led us to a product called the CoolBot which is a small controller that overrides the controls of standard window air conditioner to instruct the unit to cool a room to 4 degrees Celsius instead of a more typical room temperature.  The CoolBot was developed for farmers just like us who were looking for an effective alternative to more expensive and maintenance laden commercial refrigeration systems.  After discovering this technology, we had the confidence to proceed with the project so we ordered an air conditioner began the construction of our cooler walls.


At one end of our basement is a nook surrounded by 3 exterior walls.  The space is 10 feet wide and 6 feet deep which is an appropriate size for our cooling needs, and tucking the cooler into this nook meant that only one of the cooler walls would need to be heavily insulated from warm indoor temperatures.  Therefore, choosing this location over other options will reduce our insulation costs up front and save us energy in the long run.


Construction of the cooler began with the levelling and insulating of the floor surface.  Base gravel was first tamped and levelled and then covered with 3 inches of rigid foam.  We used interlocking DriCore panels for the floating floor on top of the insulation.  The concrete walls were insulated with 2 inches of rigid foam screwed directly to the concrete.    
































A layer of OSB was then screwed to the wall on top of the insulation to serve as a more druable and fire retardant surface.  This sheeting was all screwed directly to the concrete walls to avoid the thermal breaks in the insulation that are typically caused by wall studs.  Drilling through concrete was my "favorite" part of the project. 

I neglected to take any photos while framing the interior wall of the cooler, but in the above photo, you can see a portion of a wall on the right side.  This is the one interior wall of the cooler.  It is framed with 2 by 4 lumber and insulated with 4.5 inches of rigid foam with 3.5 inches between the studs and 1 inch over the entire wall.   This wall contains the cooler door and the opening for the air conditioner.


Next came the painting and finish work.  The walls were painted with a moisture resistant acrylic paint and the seams were all caulked.  The ceiling of the cooler is quite low so we used to 6 watt LED light strips for our lighting needs.  They are incredibly thin and bright.  These lights will be activated by a motion sensor so they will turn on when the door opens and turn off when the room is empty just like a typical refrigerator.



The door opening was too short for a standard exterior door so I modified an old fur door to fit the opening and added insulation to make it 3" thick.  We will use the white board on the door to help keep track of cooler contents.  The air conditioner is also shown in the photo below. Because it is located indoors, it will serve a dual purpose of removing heat from the cooler space and adding heat to our cool basement.  For those interested in specifics, it is a 10 000 BTU Danby model.



The air conditioner will keep the cooler cool in summer, but in winter there is plenty of cold air outside that we can use to do the same job for free.  The 4" PVC vents in the photo below will allow us to circulate cold outdoor air as needed in the winter.   The lower vent will extend to the floor of the cooler to allow cold air to enter the room, and the upper vent will exhaust the warmer air from the upper region of the cooler.  It is important that one vent leads to the floor and the other exhausts from the top so that a natural convection current can drive the circulation of the air.  



So there is our walk-in cooler build in a nutshell.  All that remains is to plug in the CoolBot and let it work its magic.  The next improvement we plan to make to this system is to install a photovoltaic system to offset the electricity that the cooler uses.  




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