From Trailer to Mobile Cooler
This summer, we received a grant from LASA to help us make our dream a reality. We had been struggling through two seasons of shuffling everything around in our fridge in order to keep our produce from wilting and to extend its shelf life. We found that in order to have a profitable and sustainable business, we would need to invest in some serious infrastructure that could help us reduce waste. Below is a picture of our home fridge which was entirely full of vegetables nearly every day. It was not the ideal environment to cool down veggies quickly and efficiently but it was an attempt to be less wasteful and sell more vegetables.
Our farm is on leased land which brings another set of challenges. We have to be creative with investing in the property we farm on because only so much of our investments can be taken with us once we find a permanent home. That is where the idea for this cooler came from- something we could build and use on the farm we lease but can take with us once we move on.
Building this cooler was a challenge-we were inspired by this design from EverGood Farm but ultimately ended up making this up as we went as we were presented with several complications.
We began by taking off all of the trim and the wood from the walls. As we removed each piece of wood, we marked where it came from in sharpie because we intended to use the same wood for the walls once the insulation was installed.
After all the walls were taken down, we taped all of the electrical cords out of the way of any drills or saws. We will be blindly screwing through 4'' of insulation later so we don't want to accidentally hit any wires. We next measured and marked a rectangle for the AC casing to go through. If you notice, we cut our rectangle slightly to the right so we could get the most support. The distance between our metal studs was exactly the width of the AC plus the width of a metal stud, so we shifted the AC to be snug to the stud on the right and used the scrap of stud from the cutout to reinforce the left side. The AC unit is very heavy and we had to be sure that it would be supported even while moving on a bumpy road. We put 3 layers of 2x4 underneath and one piece above where the AC will rest so we can screw the case into something sturdy. Pop the AC unit in and it's almost time for insulation!
Before we could move on to insulation, we wanted to set up the wiring for the electric outlet for the AC unit and Coolbot. We purchased a RV electrical inlet like this one so we could plug in our trailer from the outside and not have to sneak an extension cord through the door. We cut a small hole through the wall and mounted a piece of wood with a matching hole to the inside to screw it into. We attached the wood to the studs with some metal brackets we had laying around. We then attached a length of wire to the inside of the inlet to attach to the outlet at a later time. I would suggest leaving yourself plenty of room on the wire since it has to go through 4 inches of insulation and a layer of plywood. After attaching the wires we put electrical tape over the connections to keep them safe.
Now, on to insulation! We used a layer first of a reflective bubble wrap on all surfaces of the walls and ceiling. This bubble wrap provides the best insulation when there is an air gap so we attached it to the studs with a spray adhesive and left a gap between the exterior wall and the bubble wrap. We used duct tape to seal the seams of the overlapping pieces. It is very important to mark the studs on the insulation so you know where they are for the plywood. We marked them on each layer of foam board as we added layers. Even with the markings we made we had an extremely difficult time hitting the studs so be super precise with your markings and take measurements and map them out/write them down. Taking photos of the studs inside before any insulation is a helpful tool.
We began with putting the foam board on the ceiling.We used a plain silicone adhesive to glue it to the ceiling and made props out of 2x4's and ladders with wood blocks to hold it in place as it was drying. We tried to measure pieces in order to use up as many scrap pieces as possible and tried not to waste much of the foam board as it is pretty expensive. Do some math and sketch it out so you can make the most efficient cuts. It is recommended to make the first layer going all in one direction and the second layer of insulation going in the opposite direction to reduce any air leaks. We cut the foam board with a reciprocating saw and a hand saw. All of the seams were duct taped before moving on to the next layer. We then did the first layer on the wall. We tried to cut the pieces 1/8'' long so that the top edge would help support the ceiling pieces and it would be a tight fit. If you cut the pieces tight enough you won't need any silicone to hold them up. They will be attached to the studs through the plywood so the silicone is just to keep things in place until that step. After the first layer is up, fill any large cracks or gaps with Great Stuff but keep in mind this stuff expands like crazy!! Best to do less than you think so you don't have to go around and cut the excess off. Let it dry for at least a few hours, better overnight and DO NOT get it on your hands (speaking from personal experience WEAR GLOVES!!!!!) In order to make hitting the studs later an easier task, try not to put too much of the foam sealer because it will push out the next layer of insulation and then your screws won't be long enough.
We decided to do the second layer of insulation on the ceiling before the walls and start with the plywood on the ceiling. Because of the layout of the studs on the ceiling, we didn't have that many studs to screw into near the edges of the plywood so we figured we would use the same method of using the next layer of insulation to help hold up the edges. The only screws long enough at our hardware store were Ledgerlok 5''. We also bought a super long drill bit to predrill into the studs. Here's where all your stud marks come in handy, you don't want to miss and drill through the top of your trailer! We used the same 2x4 supports to help hold up the wood as we screwed it in.
The second layer of insulation we applied horizontally in the same manner, trying to use up as many scraps as possible on the front wall.
Next came plywood for the walls. This is where the markings of where the pieces came from came in handy. We had to cut the pieces to fit the new dimensions of the trailer with the added insulation. This again proved to be very difficult because of the studs. We even had to use a few 6'' screws in some places because the studs were so hard to hit. We put a few layers of wood trim to act as washers around the hole so we wouldn't poke through the outside of the trailer! We drilled a hole for the electrical wire to go through and wired it to the outlet. We left some space around the AC unit so we could take it out if we needed to replace it. We just wedged a few pieces of insulation around it but did not glue them into place.
For the side and back doors, we put a layer of bubble wrap, two layers of insulation, and plywood in the same manner as the walls.
Next we built the wall in the middle. This part is optional, we wanted to have two separate spaces-one with direct cooling and one just insulated. We will eventually remove this wall as our business grows and the need for more cooler space increases. We very simply framed out a rectangle around the perimeter of the wall and attached plywood on one side. On the inside of the plywood we put a layer of bubble wrap and a single layer of foam board. Then more plywood from the other side. For insulating under the trailer, we took scraps and simply glued them from under the bottom of the trailer between all of the metal framework. We used scraps of wood and foam to hold the pieces up while the silicone cured. Also using a leftover piece of the bubble wrap protects your back from the gravel driveway during this step! Since we don't plan to use this as a trailer that will be driving on hot pavement often, we didn't feel the need to insulate the bottom super well. I would suggest spray insulation for filling all the gaps under the trailer if you are planning to drive with it often.
We caulked and painted the whole interior of all spaces using a porch & patio paint. It took about 3 gallons but if you aren't doing the wall in the center 2 would be fine. We installed the coolbot and plugged her in and she worked just fine! We used her for only a few months last year, we will report back after the 2018 season with more details.
Thanks for reading about our project, if you have any questions please feel free to reach out! We would also be happy to share our financials and materials lists for this project. Moonrosefarm@gmail.com