Basement root cellar build w/ pics

I am building a basement-style root cellar for several reasons:

1. I need to install a radon mitigation system which means one hole through the concrete foundation - so why not 3?

2. The 22x22' area is under the garage and not being used well. The former owner had a wood shop here, but it's cold and very damp. Condensation sometimes forms on the concrete ceiling and drips onto things. I removed drywall and found condensation on the north wall and the NE/NW corners. I hope that by partitioning I get two useful rooms - a colder damp one, and a warmer dry one.

3. I have piles of used fiberglass insulation and boards from another project that would otherwise need stored or thrown out.

4. To have a root cellar.

Priority is about in that order. Thanks to Sean at Edible Acres for the idea. The wall will be R13 insulated 2x4 with 2" foam board on the root cellar side. Not quite sure how I'll do the door yet. My constraints are that I have a limited area to run the 3 vents through the wall - they all need to go through a ~2x2' section so they are hidden by a deck/stairway leading to the garage. The root cellar in/out vents need to be as far from the radon exhaust as possible to not suck radon back inside (typical building codes require radon exhaust be 10' horizontal distance from a window so I'm aiming to exceed that).

I'll follow this with a couple posts with pictures on my plans - and then more updates in a few weeks when I start getting shelves and walls up.

Radon Fan:

The interior root cellar wall needs to be at least 22' long to partition the room and I probably would have built about 4' deep (22x4'), but the radon fan must connect to a sump about 6' from the N wall. I have therefore decided to enclose the radon system within the root cellar. Since the fan might throw off a bit of heat, I'll fasten it as close to the ceiling as possible.

Side note: I do want to get my radon levels down - if I didn't care about that, the sump would be a great moisture source. I understant that it's harder to get the humidity high enough in root cellars without dirt floors. Further, the convection currents from the root cellar vents could potentially draw radon from the sump without the use fo the fan - off grid style. Or the radon fan could be used to pull humidity into the root cellar from under the slab. Heck, the radon may even irradiate the fruit and make it last longer for all I know. But enough with hypotheticals - Goal #1 is to get radon levesl down - so fan it is.

Venting:

I had a super, over-engineered venting plan that I sadly, most likely will be abandoning. I'd run the 4" air inlet (blue) on the west side straight down to the floor to a regulated elbow. Above that, a tee would reduce from 4" to 2" and transverse the 22' east with 6 more 2" tees to dump out cold air along the way. The exhaust (red) would be a 4" drainage pipe that ran across the top and pulled out the warm air through its holes. I could then, theoretically, regulate all the inlets/outlets and create different temps/humidity microclimates for different things.

Then I finished Mike & Nancy Bubel's root cellar book (last night). I learned the exhaust vents are probably better being flush with the exterior wall so warm/condensation pockets don't form around the pipe. I'd have to run my exhaust vent under an I-beam meaning warmer air would collect up there. I now think it would be best to run the cold pipe straight to the floor and then all the way across to the other side. I may or may not use some sections of the drain pipe for this to let some cold air seep out along the way.

Shelves:

I understand it's best to not have shelves against the wall b/c a root cellar needs air flow. I can fasten mine to the concrete studs which provide a 7" gap to the wall. I'll probably frame out the shelves with 2x3s (cheap) and use 1x3s for the shelf surface (with gaps between them). I have lots of used 1x3s from another project. I'll build the shelves first to support the venting and then build the interior root cellar wall afterward.

The Bubel book suggests heavier wood b/c the moisture will make it rot in a half decade or so, but I'll go with this to see what happens. I don't expect them to hold a lot of weight and they'll be fastened to the wall. I have plenty of room for anything canned/jarred on the dry side of the wall.


Monitoring:

I think I'll get one of those Acurite 4-zone temp/humidity monitors. I wanted to get a new one to monitor inside/outside temp anyway, and I could place the 2 other sensors in the root cellar and see the temps from upstairs in the kitchen. I believe they can be set up to signal alarms if the temps pass certain thresholds - say below 32 or above 40 - as well.

That's it for now. I'll have more to share when I get the shelves started and 2 more holes in the wall.

Thanks for the info, Mike. I'm faced with the similar situation-a 6x28 result when insulating 1/2 the basement to hinder the plumbing from freezing. Now I see that I have to install a six inch air inlet at the lower end of one side, and two six inch outlets at the upper end of the other side, and close them when it gets cold.

It has been a while since I posted on this. The project shows a lot of promise.

1. Radon levels of 4.0 pCi/L is where remediation is recommended. Within a day of installing the ~$140 radon fan, my level dropped from 12 pCi/L to somewhere between 0.1-0.4 pCi/L, depending on the day. I thought I would need to fix many more things to get the radon to acceptable levels - like plugging 3-4 gaping holes in the slab that are currently serving as drains, but the fan got me there immediately.

2. I was able to take some temp and humidity measurements before winter ended, when some nights were still below freezing and some days got up into the 60s. The cold air inlet / warm air outlet venting were only half complete, but temperatures were stable and hung in the low 40s +/- 2-3 degrees, and humidity remained above 70%. This is for the entire 22'x22' area - I expect that I'll have more control when air flow is confined to a very well insulated 22'x4' area.  

Below are 2 pics - a close up of the venting and a wider shot with shelving. I am using the cheapest 4" drain pipe and harbor freight dust collection regulators to manage air flow. I'll have to wait until next fall to know for sure, but I think it's going to work great. Next comes the walls and insulation. Then lighting and some kind of insulated door. After that I'll get a couple hundred pounds of root veggies and see how they last into 2020. I'll be able to monitor temp/humidity outdoors and inside the cellar and will post a few graphs to show how well the thermal mass of the cellar dampens the temp and humidity swings outside.  

Congratulations to you for taming an unruly basement:thumbup: My own 28x6' now has an example to emulate.

Someone mentioned storing potatoes in peat moss in order to avoid cross-contamination in spoilage. I figured it would be too dusty to work with in an enclosed area and might go with dry cedar shavings as an alternative. Peeking under the lid of a tote might be the easiest method of discovering where the bad apple is. Does anything smell worse than a rotten potato (dick-tater)?

Thanks. I sized my shelves to accommodate plastic "bread trays" which are 26x22x5" and can be found used for about $5 each. They stack and are ventilated so I hope this allows me to keep the spuds to about one layer per tray for air flow and easy inspection. I think your storing technique depends on your cellar's initial condition. The Bubels' excellent Root Cellaring book recommends temps 36-40F and humidity around 90% for white potatoes. If you are drier than that then sacks, straw or shavings may be a good idea to keep the moisture around the crop at the "ideal" level. I'd go with that over peat moss which sounds like a mess! We'll see. I'm only speaking from theory at this point. I hope to have more substance to share when I have real experience next winter/spring.

Update?