Three Letters Re: Question on Burying a CONEX
Jim:
I have buried a CONEX for cold storage. I put a 6″ thick reinforced concrete slab on the top to ensure the 3-4′ of dirt on top would be supported. Also the shelving inside has a support post every 4′ on both sides of the CONEX and this helps support the roof. It takes a lot of waterproofing to ensure the metal sides and bottom won’t rust out. The only advantage of the CONEX is the excellent doors and locks. After finishing the project I would agree with you on simply building the room with poured reinforced concrete walls. I would do this using insulated concrete forms (ICFs). Using ICFs will allow anyone to be able to build an insulated storage room themselves [without having to hire a crane.] – Gary
Sir:
Regarding the recent post on burying a container to moderate the temperature.
I have extensive personal experience with using shipping containers for long term storage in adverse environments. I’ve run year long tests on containers with hourly data logging, so these comments are actual results, not speculation or parroting something I’ve read. Note that containers tend to amplify external temperature excursions. On a hot sunny day, inside temperatures can reach 150 degrees F and on cloudless nights, the interior temperature can actually drop below outside air temperature due to thermal radiation. Basically, the worst of both worlds.
The roof can support a layer of wet hay bales or 3-4 feet of snow, but that’s getting close to the limit. The roof and walls are not designed to handle large forces that push towards the inside of the container. However, the walls do give significant torsional and vertical strength to the container. If you cut openings in the walls exceeding 12″ or so, do not stack containers on top of each other or attempt to move the container when it’s loaded.
The internal temperature can be kept under control in the following ways, ordered by effectiveness;
1) Keep sun off the container. A wooden / cloth shelter with 1-2′ of space around the container for airflow will dramatically cut down the temperatures inside. If that is not an option, hay bales or almost any similar material can be stacked around the outside to insulate and shade. Use trees of other natural sun blocks if available. If no shade is available, try and orient the container so the front or back faces south to minimize surface area exposed to the sun. A cover for the container will also limit thermal radiation at night and thus provide additional warmth.
2) Glue 1″ foam insulation into the inside of the container. Cost will run around $500. This will keep interior temperatures reasonable pretty much anywhere in the USA. Expect temperatures under 100F in full sun, on a 90 degree day. Winter temperatures will be within 10 degrees of the average of daytime high and nighttime low,. If you need to prevent freezing, you will need burial to just under the frost line. In very cold locations like the northern midwest or Alaska, you will need some form of heating to keep the temperature above freezing.
3) Having the container full adds thermal mass, thus evening out the temperature excursions. If you have space, adding 55gal drums full of water can also help. However, if the drum leaks, the water will flood the content of the container, as they really are almost 100% water tight.
4) Partial burial (under 25% depth) is OK and helps with moderating temperature.
Combining methods 1, 2 and 4 will allow you to keep the interior temperature around 50-70 degrees year round.
I recommend buying two 20′ containers instead of one 40′. This limits the empty weight to under 5,000 lbs. Movable by most medium sized forklifts, cranes and trailers. 40′ containers are much harder to move. Two 20′ containers can be places side by side, with an air gap between them, thus providing shade to each other for 1/2 of the day. 3 or 4 containers can be arranged to do the same or one of them can be used as the “temperature sensitive” container and be placed such that it is 100% shaded by the other units.
Burial and hay bales trap water, so they may present long term rust issues. Come containers are made out of rust resistant steel. None of them are rust proof in the long term. Expect 15-20 year lifespan in a typical US environment and a non-burial application. In a marine environment, life can be as short as 5 years. With upkeep every 4-5 years (painting, gaskets, hinge lubrication) they will last virtually forever. – Cactus Jim
James,
My husband and I where close to being in the same boat as Karla. Do something, or not anything. We did something, I never thought was possible. We had looked into similar things, but realized they wouldn’t work.
We live in southwestern Missouri. It is flat land with no hills. It seemed impossible to have buried food storage. Until we researched. It was a daunting task, but it’s doable.
It took us the better part of a year, some favors, and some luck, but we did build a root cellar/tornado shelter. We built it for less than $3,000. I understand that seems like a lot. But we now have a concrete 8 foot x 12 foot structure that is buried four feet underground, and houses our potatoes, apples, melons and provides us with some needed tornado protection.
We laid each concrete block by hand, planned out each detail, laid every air duct and sealed it up. We did hire a back hoe operator, but he was a friend, and didn’t over charge. It was the longest year I remember but the reward is, peace of mind.
We’ve had a great deal of success over the past few years storing food.
One of the best books on the subject in my opinion is Root Cellaring: Natural Cold Storage of Fruits & Vegetables