Hot Climate Root Cellars

[johninfla]

I started this in another forum and realize maybe this would be the better place to ask it. As my name implies, we live in North Florida. Summer highs in the upper 90's and lows in the upper 70's. My ground water is 72 degrees year round. Here is my question: Will it do me any good to dig a root cellar for potatoes, etc or is it too warm to preserve them?

thanks

John

[steev]

Dude! Trade me some of that 72F water for my farm shower! My 55F well-water is such a shock, even my hair retracts!

[johninfla]

In the summer, we sometimes don't even use the hot water to take a shower. Your comment makes me think of George on Seinfeld......."do women know about shrinkage?"

[steev]

Mission accomplished.

[Joseph Lofthouse]

If 72 is the temperature of the ground water, that means it's the average temperature of the environment.... So a deep enough root cellar would tend towards 72 degrees year round. I store potatoes at that temperature for 2-3 months. Sure they go downhill faster than at 50F, but I don't require my potatoes to look like the green things that I get from the grocery store. I think that dark is a more important storage criteria than cold.

There are lots of clever tricks for keeping things cooler... For example the devices that are used to keep the permafrost frozen under buildings in Alaska, and under pipelines in the tundra could also be used to keep your root cellar cooler. Heat pipes work as one-way conductors of heat... So you stick them in the walls of your root cellar and under the floor, and then whenever the air temperature is cooler than the ground around the cellar, the heat is being exported to the air. If you ever get a clear night and have some radiant cooling, the heat is pouring out of the ground through the heat pipes. And during the cooler winter months that whole mass of ground is getting cooled. Heat pipes in my climate would turn the ground into permafrost, but in Florida they might create really favorable conditions for a cellar.

And heat pipes don't require electricity to operate. You set them and forget about them.

[raymondo]

How is it that the pipes only conduct one way? If the air temp was higher than the 'cellar' woudn't the heat tend to flow through the pipes to warm the cellar up? Or does this rely on simple thermosyphoning and gravity? Hot air rises!

[steev]

Exactamundo!

[Joseph Lofthouse]

Heat pipes are typically evacuated tubes with a little bit of liquid in them.

When the top of the pipe is colder than the bottom the liquid boils and carries heat upwards. The cooled drops then fall downward by gravity. An important design criteria is that the cooled liquid can flow to the bottom of the pipe. Because it's a 2 phase system, the falling liquid doesn't impede the rising gas (only a little).

But when the top of the pipe is hotter nothing happens, the heat in the top of the pipe just stays in the top of the pipe (and pressurizes the liquid to keep it from boiling).

Technically an evacuated tube isn't necessary, it just makes the process much more efficient. An example would be ice caves that form where cold winter (and/or nighttime) air settles into the bottom of a cavity and creates a permafrost in a location that would otherwise be too warm.

[johninfla]

OK, let me see if I get this right.... The heat pipes are in the ceiling of the root cellar and they will take the heat away on a cold night. I need to google this but it is interesting....is there anyone here with hands on experience w/ heat tubes?

Thanks;
John

[Joseph Lofthouse]

Mar 8, 2012 12:17:07 GMT -5 johninfla said:

OK, let me see if I get this right.... The heat pipes are in the ceiling of the root cellar and they will take the heat away on a cold night.

Put the heat pipes mostly on the sides, and under the floor, etc... Any time day-or-night summer-or-winter that the temperature of the ground is warmer than the outside air temperature (or the radiant cooling temperature) the heat pipes will be moving heat out of the ground. Store any cool temperatures you get during the winter in the ground surrounding the cellar.

[johninfla]

So, having given this a lot of thought, and having visited an old homestead (Dudley Farm State Park in Gainesville) we have decided to begin building a root cellar. This will be a long term project as the tractor has no bucket so we are digging by hand. We are planning to go ten feet deep and 12x12. I am thinking a poured floor, block walls and poured barrell vault ceiling. Time is our most abundant resource so we will use it!!!! If nothing else, the digging will help get me back into shape
The roof is a LONG ways away but it's never too early to dream and plan so I was looking at this fellows ideas www.flyingconcrete.com/vconstruct.htm they seem interesting. I built my own wood frame house but have little experience with concrete (that's part of why I want to build this ---because I have always wanted to play with mud but never had the chance.) Anyway I am wondering if anyone here has done something like this. This fellow here built his walls and ceiling with wood. www.survivalistboards.com/showthread.php?t=25078&highlight=cellar Opinions??


John

[Joseph Lofthouse]

May 11, 2012 8:50:38 GMT -5 johninfla said:

So, having given this a lot of thought, and having visited an old homestead (Dudley Farm State Park in Gainesville) we have decided to begin building a root cellar. This will be a long term project as the tractor has no bucket so we are digging by hand. We are planning to go ten feet deep and 12x12. I am thinking a poured floor, block walls and poured barrell vault ceiling.

Good plan. When I was a boy, we built a root cellar as described, except that the ceiling was only 8 feet high. It stuck out of the ground about 2 feet, so we only had to dig a 6 foot hole. The ceiling was a poured concrete slab which served as the floor of a garden shed/greenhouse we built on top of it. The stairs into the cellar were accessed by a trap door in the floor of the shed. The cellar is still holding up great after 40 years. The shed burned down decades ago and never got replaced.

[johno]

Having worked in construction most of my life, I have a few words.

Keep it simple. A barrel vault ceiling is very ambitious for a first time concrete project. It's a lot more headache and time than it first appears, I'd wager (I've never tackled one). I highly recommend a flat slab ceiling. We typically build a simple floor system designed beefy enough to hold the concrete slab, then cover it with corrugated steel roofing and pour away.

I totally get using your most abundant resource, time, but it may be well worth a phone call or two to get estimates from backhoe/bulldozer operators for digging the hole. My aversion to digging holes by hand is surely colored by a lifetime of digging holes in soil that is mostly rock... but still, that's a deep enough hole to get yourself in danger. A local with lots of experience is worth every penny. He/she will know how much bigger the hole needs to be to keep it from caving in, and to give you enough room to work, etc. Also, they will have a good feel for what kind of footings (monolithic or not) you need for that soil. They can probably tell you what the moisture barrier needs are for your location, too. A lt of bang for your buck, and it will be done quickly.

[johninfla]

Hi Johno,

thanks for the input! Digging is one thing that makes me glad my soil is pure sand!! I'm pretty good with wood frame construction but like I said I have almost zero experience with concrete, so any input is appreciated.

John

[steev]

That sandy soil sure does sound like a cave-in hazard while digging. I second johno's suggestion of digging from outside, with a backhoe, I think.