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Retro-fit in floor root cellar ideas anyone?  RSS feed

 
Posts: 28
Location: Finland, Minnesota Zone 4a
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So, we live in a rather small house (about 280 sq ft) and we plan on eventually (5 to 10 years) building a much larger house with better thought out everything etc....  But for now, we need a place to store squash, potatoes, kraut etc from our harvest...  We live in a pretty cold climate (zone 4a) and our house is built on sonotubes with an uninsulated  but fairly sealed treated plywood skirt between the tubes.  So here's what I'm thinking of doing for a root cellar that is "good enough for now".  Cutting a hole in the floor and digging down to bedrock (about 1 or 2 feet) and then putting some gravel down to level the hole, dry stacking cinder blocks up to the floor joists and then lining the outside of the cinder block wall with pink foam and then banking up some the the dug up dirt on the outside of the foam and calling it good.  I'll definitely insulate the floor door with pink foam as well.  I was also thinking of possibly running a couple 2 inch pipes in from the outside to create ventilation since I've read that's important.  If I do that I would be sure to put hardware cloth up to block critters. 

Another thing to mention, we're off-grid with a relatively small solar array so any electronic gizmos are not really an option.  And like I said, this is really only a "temporary" solution to our harvest storage, so I don't need to get too fancy. 

Anyhow, I was thinking I would put the pink foam on the outside just so I don't have to look at it, but would there be any advantages to having it inside the wall instead?  Any other thoughts or ideas in general about the design etc?  I do want to keep it simple and relatively cheap, but I am not set on this design and I am certainly open to other ideas or tweaks. 

Thanks in advance for any input!
 
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Location: Rainy Cold Temperate Harz Mountains Germany 450m South Facing River Valley
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Hi Steven George

I have campers who put in rain barrels burried up to the lid under the trailors for refridgeration and it keeps a relativly constant cool temperature 5 to 10 C. Lots of ground water flows through the soil (a few meters away from a river) so there is no drain and it needs to be opened every few days to vent. If its dry enough you could just bury an old fridge or freezer and put in a downwards reaching pipe to let any condensation drip away. Broken fridges and freezers I would think would be free (I find them at the dump ) and its a similar idea but pre-built being mostly insulation foam with a cleanable surface. Some from resturaunts even have locks and would keep racoons and children out. I don´t know what usda zone im at but it freezes between -10 to -20 C every winter and things don´t freeze in the barrels outside. I also think you might want to take the piping from the back off first im not sure what is inside of it.
 
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Location: Northern WI (zone 4)
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I'm sure that design will be perfect for some portion of the year.  I'm just not sure which.  IE, it will possibly be too cold in Jan and too warm in April.

For comparison, I have a root cellar in my basement.  One wall is the uninsulated block wall, the other three are cement walls with R10 styrofoam.  Ceiling is R10 pink as well.  I have two 4" vents and a duct fan to force air through as needed.

I struggle to get it cold enough until mid November.  I have to run the fan whenever the outside temp is lower to try to cool it off.  I'm in northern WI so it does get chilly here.  Once it gets cold, I'm good to go until Jan/Feb where if I get enough -10 at night, the root cellar can get down to 33 degrees and I have to crack the door to keep it from freezing.

Given my experiences, I'm guessing that burying yours will give you some moderation of temps but will delay the point at which the temps are "low" enough for good storage.  I'm guessing your crawlspace gets pretty cold in January?  Considering 3 sides and the top of my cellar is surrounded with 60 degree air, one side is frozen soil and the bottom is 40 degree subsoil and I have troubles with freezing, I'm thinking yours may freeze solid from mid Dec to mid Feb.

I'd suggest that you think about not putting insulation above the cellar and plumb a vent to the inside so you can send warm air down there if it gets too cold. 

Alternatively, have you considered a "normal" root cellar?  Just digging down a bit and allowing snow to cover/insulate it in the winter could be the fix.  By putting it in your crawlspace, it may have colder air above it than if it has a foot of snow directly on top of it.

Sorry I'm rambling...
 
Steven George
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Location: Finland, Minnesota Zone 4a
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Thanks for the thoughts. 
Taryn, a barrel or even a fridge is a bit smaller that I would probably need.  Also it gets quite a bit colder here that where you are, our frost line here is below bedrock everywhere around our house, so no way to dig below the frost line.  Coldest it has been so far this winter was about -31 C.  I do like the idea of a free pre-built already insulated box though, too bad I need more space. 

Mike, good point with the possibility of needing to heat it during the winter.  Now that you mention that, I will probably make the floor door insulation removable and put some kind of vent in the floor for heating it in the winter.  I'm not as worried about warmer temperatures in the fall.  I know it won't be 35 F under there but I figure how warm could it really possibly get under my house in October?  Unfortunately, a "normal" root cellar is probably out of the question for us for two reasons, one is the bedrock being at depths varying from just a few inches to maybe 3 or 4 feet and second because of our high water table during the thaw, basically any hole in the ground would get flooded.  This is why I plan to dig the hole and fill it most of the way with gravel.  If we were to build an external root cellar, we would probably have to build it on grade in a dry spot and then put several tons of dirt on top of it basically creating a large mound..... as I said keeping it simple and cheap for now so this is not an option.  Thanks again for the input about keeping stuff from freezing.  Curious whereabouts are you in Northern WI? 
 
Mike Jay
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Sent you a PM...
 
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I feel that /having an earthen floor and/or walls in a root cellar seems like it should be better for the roots than a sealed smooth thing like a fridge. I don't know if it's true, just how I feel.
 
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Cold is only part of the root storage story which comes in three parts; temperature, humidity and breathability (air exchange).

There are lots of ways to do this right but far more ways to do it wrong.

Earthen floors covered in pea gravel are the standard for "true" root cellars, this is because if the humidity gets to low you sprinkle water on the gravel floor to increase the humidity over a longer period of time.
The vents (at least two, one up high and one down low) allow air flow to keep molds from getting a grasp on things, these have to be sized to the interior space of the cellar.
The cold air you want to stay above freezing but below 45 degrees as much as possible. Caves usually have an average temperature of 55-45 degrees for a base knowledge.

Of course you can go "artificial " and build one in a basement, when done right they work great.
there are a lot of methods available on MEN too.

Redhawk
 
Steven George
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UPDATE....  I got the root-cellar finished about a month and a half ago and so far it has been working awesome!  So I'm back to post photos and give some details about construction....  I cut a 4 foot by 4 foot hole in our floor and re-framed the floor hole with double headers and double trimmers.  Then I dug approximately a 6 foot by 6 foot hole in the ground below until I got down to bedrock (only about a foot and a half in that spot).  I filled the hole back up almost to grade with approximately three small pickup loads of gravel.  I leveled the gravel at about 30.5 inches (the height of 4 courses of nominal 8x8x16 concrete blocks).  I meticulously leveled, plumbed and squared the first course of blocks and then dry stacked the rest on the blocks (56 blocks in all).  In opposite corners I set two of the blocks sideways so the holes were exposed for ventilation.  I put in 4 inch ventilation pipes, one for cold air intake at the bottom and one for warm exhaust at the top opposite corner.  The cold air intake is on the NW side of our house and the exhaust exits into our connected greenhouse.  I put metal screen on the ends of the pipes to keep critters out.  I jacked up the headers and trimmers just a tiny bit and shimmed between them and the stacked blocks (basically making the blocks part of our foundation).  I then went under the house and installed pink foam on the outside of the block wall and then backfilled all the dirt that I had dug out of the hole against the foam.  I also spray foamed the top seam (where the pink foam meets the bottom of the floor joists.  To regulate the temperature I stuff an old sweater in the cold air intake hole or just partially cover it.  So far I am just checking it once a day or so and I've been able to easily keep it between 32 and 40 degrees F (our house is usually 70 degrees)!  I did not use insulation or a vent in the floor.  The whole project cost less than $100 (but it was a TON of work).  The size is approximately 40 cubic feet (more if you count the area within the joists).  I turned half the floor cut out into a trap door and built a couple steps for easy access.  It has been a major life changer for us here!  I'll post a bunch of pictures below, any questions about more details I might have forgotten are welcome. 
 
Steven George
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Mike Jay
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Very nice!
 
Bryant RedHawk
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Fantastic job!
 
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That looks great!!
 
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Looks good, I'm lucky that my outside temperature doesn't drop below -10 and is normally higher than that  0 to -5C over winter so I get away with just using the barn room that has the chimney going through it. I have one comment, those carrots in my experience they will dry out like that, I find I have to keep them in damp sand to have good results, the same for parsnips and beets, though the potatos do fine just in bags.
 
Mike Jay
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Skandi Rogers wrote:I have one comment, those carrots in my experience they will dry out like that, I find I have to keep them in damp sand to have good results, the same for parsnips and beets, though the potatos do fine just in bags.



I agree.  I layer mine with damp wood shavings and they hold well into spring.
 
Steven George
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Good to know about the carrots.  Thanks.  We actually did have problems with our carrot storage this year and we weren't really sure the best way to store them.  We had em in ziplock plastic bags in the root cellar for the last month and a half and just noticed some of them starting to get a little moldy a few days ago, so I washed em off and put them in that box until we eat them (that box is the last of our carrots anyhow, so we should be through them pretty fast).  Thanks for the input though!  I've heard of sand being good, to store them.  We tried storing them in damp mulch before putting them in plastic bags, and they seemed to store ok, but a bin full of damp mulch was a bit cumbersome and took up too much space for our small cellar.  Mike can you elaborate on your wood shaving method?  Thanks
 
Mike Jay
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Sure, I take planer shavings and dampen them in a wheelbarrow until they're medium moist.  About wet enough that you wouldn't expect to be able to soak up a spill with them very well.  Or a bit drier than that.  It's hard to explain and it could be that a wide variety of dampness is just fine.

Then I use a square 5 gallon bucket and start with a 1" or less layer of shavings.  Then I arrange a layer of carrots.  Then I cover them with another inch of shavings, then more carrots, etc till it's full.  I try to end with a layer of shavings.  The goal (in my mind) is to keep the individual carrots from touching themselves or the bucket if possible.  Then I snap the lid on and put it in the root cellar.  I've heard that they need to breathe a bit and I shouldn't be snapping the lids on.  Last year I had one bucket with the lid just set on top but not snapped and they lasted till spring as well. 

I like the square buckets because they fill the space in my root cellar more fully and it's much easier to put a layer of carrots into a square foot print than into a round one.

I'm putting mine in storage in October and they're usually still good until April.  We do beets the same way and we were eating last years beets this summer.  Once the root cellar gets too warm we move the few remaining beets/carrots to the fridge.  We keep them in a plastic bag with more damp shavings while they're in the fridge.
 
Steven George
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Location: Finland, Minnesota Zone 4a
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Just found some more pictures of construction on my wife's camera











 
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