mold in new root cellar

My root cellar was finished a couple of months ago and I have been canning and preserving loads.
Now I am seeing mold. Where sauerkraut overflowed from its jars, mold has appeared.
Humidity is 91%. Temperature a bit higher as ideal 20°F because it's early autumn.
What on earth am I doing wrong?

I have glass jars with silicone seals so the mold hopefully will not seep in.
I have heard vinegar kills mold, they use it on wood in construction. Should I spray the place with 12% vinegar?

Hey. I don’t think you’re doing anything wrong. You might need to leave some more air for the kraut to bubble next time.
With 90% humidity and oxygen it’s no surprise the kraut juice molded.
Vinegar is a good idea as far as I’m concerned

Humidity is what the problem is most likely.

Vinegar is good as well as baking soda, hydrogen peroxide, and citric acid.

I'm assuming you meant 20C for your temp?  I had a funky root cellar in my basement so I boraxed and limewashed it and that really helped.  I also got rid of most of the old/porous wood at the same time.  Here's a few pics: Submission for PEP Oddball Points

Spread a light layer of baking soda on the moldy areas and leave it there.

Thank you everybody ❤️
Gosh I love this forum!

Mold on wood or other porous materials can be killed and prevented by a strong solution of borax and/or boric acid painted or sprayed on the surface.  Simply dissolve as much of either or both as can dissolve in boiling water and apply it hot.  This will kill and prevent any kind of mold, wood rot, and insects; is bitter for animals so they won't lick it, and non-toxic to touch.  It even makes the wood more fire-resistant!  In areas where people and animals don't usually go (such as crawl spaces) the efficacy is improved by dissolving in ethylene glycol antifreeze, and then diluting half and half with water....this enables the solution to penetrate deeper into larger pieces of wood.  

Alder, thanks you so much! This was new to me. Will try it immediately!

I thought I'd do an update. During winter, the temps dipped to ideal just a bit above freezing, with humidity pretty stable at 95%. But the mold just got worse, whatever I did.

So I installed a rotating wind-driven ventilator on the roof. It solved everything. Strangely, the temperature did not change and neither did the humidity. Just the air started flowing much better.

I was going to suggest improving the air flow, its good to see it was effective.
Many people forget that.

Thank you for sharing that the wind ventilator worked. Do you have any vents also in the door or walls?

I am designing a root cellar and thought of having one vent low in the door and one high in the door, and not sure if this is enough, that wind vent might be a good idea here as well.

There are four air inlets two on each side, close to the floor,  with a fist-sized pipe. They connect behind the root cellar into a looooong pipe. The idea is that the inflowing air travels 30 feet deep underground before entering the root cellar. We need to stabilise temperature. We have hot summers and deadly winters.
Seems that the vent on the roof did not suck air forcefully enough. The 30 feet long underground pipe being the problem, probably. But problem solved now.

Kaarina Kreus wrote:There are four air inlets two on each side, close to the floor,  with a fist-sized pipe. They connect behind the root cellar into a looooong pipe. The idea is that the inflowing air travels 30 feet deep underground before entering the root cellar. We need to stabilise temperature. We have hot summers and deadly winters.
Seems that the vent on the roof did not suck air forcefully enough. The 30 feet long underground pipe being the problem, probably. But problem solved now.

I'm wondering if this could be implemented using some passive circulation tricks. Would anything from the passive greenhouse work without the pipes being exposed to sunlight through the glass...?