Modifying an underground space into a root cellar

I live in eastern Pa, 35 miles north of Philly, zone 6. On the north side my old house in a small room that houses the well, which is on the floor and not intrusive into the room, dug 4 feet below ground level. The outside wall, parallel to the house, extends a foot above ground level. The floor dimensions are 6' from inside wall to outside and 5'4'' across. The height on the inside wall is 6 1/2 feet which slopes down to the 1 foot above ground level. The little room is newly roofed and enclosed. The basement stairs go down on one side. I can see gaps, mostly close to the house side. Gravel over the dirt floor.

Additionally there is a 16" knee concrete block wall extending 26" from the outside wall filled with dirt. The walls are also made of concrete blocks.

It smells very earthy in there!

Right now there is no door but there is a doorway where it would be easy to attach a door.

What are my best options for turning this into a root cellar? Insulate, not insulate? I have some blue board panels that I could use. Cover the dirt filled knee wall with more gravel or something  more impermeable? Put in a fan to keep the air moving when I want or to pull in cool air? I plan to store mostly veggies such as cabbage, kohlrabi, not sure what all and to keep other things cool like my ferments (kimchi. sauerkraut, kombucha etc

Thanks, folks!

It has been a long time since I have created a root cellar. Some  points that come to mind are to get a door in it.  Seal the gaps.   Monitor the temperature.   Monitor and remove moisture.   I would hold on insulation and blueboard until I had more data on temperature and insulation.  Others here have more recent use of a root cellar.

A well room is a perfect place for a root cellar. Attached to the house (for convenient access and heat if needed) yet easily insulated if needed. But basically, if the well system and piping doesn't freeze, neither will your root vegetables. Lucky you!

I know! It just smells so damp and earthy - the musty kind of earthy, not so great.

What is a master pollinator?

Okay, I see. Earthy is okay, musty not so much. It means there's a lot of mold spore floating around, which is not good for lungs nor vegetables. It usually takes the perfect combination of humidity and temperature to make this happen. Any ideas about the source?

I guess master pollinator is just an arbitrary title granted to a person who is given extra Q-tips and toss-able apples as a reward for buzzing from thread to thread (flower to flower) and doing the bee dance.

I remember reading Elliot Coleman saying that most vegetables require something close to 90% humidity in a root cellar. He spoke of tossing buckets of water on the floor, if necessary, to achieve such.
I always wondered about that causing mold issues.
I plan on constructing a root cellar on my property. Any words of advice or essential reading suggestions from anyone?

What I gather from your post is that this room sits mostly below grade, like 4-5 feet below grade. If true, that is some of the best insulation you can get. The roof structue sounds exposed to the elements, but it's northern exposure, so excessive solar heating shouldn't be an issue. Not sure if I would suggest insulating the roof or not. You will have to collect data on temperature variation over the year to detemine whether you need to insulate anything. If I recall correctly, you want the temperature in a root cellar to maintain a 10 degree maximum vaiation between the low and high temps.

The dirt-filled kneewall area sounds like someone built a mushoom bed. Maybe you should investigate the potential for growing some shrooms in that. If you could post some photos of this room, (inside and out) it would help. I'm a very visual person.

Moisture intrusion could be an issue as concrete blocks are quite pourous. Ideally, water proofing should have been applied to the outside face of the block before backfilling with dirt. This is never a permanent thing, and will beak down over time. An additional layer could be applied directly to the inside wall. Typically an asphalt emulsion (diveway/roof/foundation sealer) is used. You can get this in a 5-gallon bucket from most home improvement stores for about $60(?)

Will take some pics. Not sure how to send from my phone but will figure out.

Not sure when this was built but it's been here as long as I can remember - my parents moved into this house in 1962 so it's lasted this long without the walls breaking down. I don't remember ever seeing water trickling in. No one every grew mushrooms in there but I was so focused on the veggies and ferments, I forgot about the mushrooms! This makes getting it ready to go even more exciting!

I can see a little daylight in a couple of places.

Looks like the humidity should be very high - 85-90%,  so the important thing might be to just keep the air moving. Have to get a moisture meter but I put a dehumidifier in there before I knew about the 85-90%. Just plugged it in- 88% - perfect!
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After I posted this,  I talked to our local permaculture teacher (Adam Dusen, Hundred Fruit Farm) and while this isn't his area of expertise, he recommended the fan as did another very knowledgeable friend. A friend has an 8" fan we could install.


Elliot Coleman is right, of course! It just smells musty in there but maybe they all do if the original dirt is exposed.

Thank you all, will do the pics when I have time on Sunday - making soup for the last day of the Wrightstown Farmers Market - mushroom/pumpkin, all from local ingredients (except for the olive oil). We have a wonderful mushroom grower here, Primordia.

Thank you all for your input!

There might be a way to get adequate  air circulation without the fan.

If you can see some daylight through cracks and crevices,  there’s already some air exchange happening.

I think it might be worth while to do some research before making permanent or expensive changes.  The rigid insulation may bring vocs with it, likewise the asphalt emulsion.

You may want separate storage areas that do not share air, as some veggies and fruits are not good storage companions, essentially accelerating decomposition in each other, sorry, can’t think of an example I am sure of, just sure it’s germane.

And there are different humidity requirements too.  Awful surprises can be discouraging!  If it was my situation, I would approach it as a “see what happens “ experiment.

In my last house I had a basement (high desert).  I wanted to put food down there, but, it being more than a century old, there was a resident mouse population.  I built a mouse proof enclosure out of pallets and aluminum window screen.  I was studying refining the system when I moved away.  

Two books, "Root Cellaring - Natural Cold Storage of Fruits and Vegetables" by Nancy and Mike Bubel, at least 2 editions and easily found used.  "The Complete Root Cellar Book", by Steve Maxwell and Jennifer MacKenzie.  They both have building plans.  I really like the passive ventilation systems, no need for a fan.

Thanks, I'll see if I can find those books and once I looked up Nancy's book, I remembered seeing it and I've known her name for years from her articles in Organic Gardening. I live in the same region as she does or did, not sure where she is now.

My root cellar is set up, with the latest haul from our local farmers's market so I'm pretty happy.

I don't have any plans for anything expensive or extensive or asphalt emulsion. The polystyrene blue board I was thinking of reusing only because my brother had put it there years earlier but after thinking about it, realized how unnecessary it was. It's ancient anyway, vocs probably long gone!

I do want a door to keep the raccoons and possums out. probably nothing I can do about the mice and rats (which are around, unfortunately, except set traps.

Thank you all, for you advice and help. I'm pretty new to my cell phone so can't yet send pics to this site but hope to figure that out soon.