Thinking about a root cellar inside our Menard's building. Anyone have any incite into how this can

[Kolesar]

3. I think you need something "sub grade" and not on a slab

People wall off a room in the basement and then open a small window to the outside to chill it. The room is subgrade and subtly heated by the house above so that the building stays above freezing.

Vegetables are set onto a tray of damp sand. The moisture keeps the produce. It is rather intuitive with root crops, but other crops are stored in a moist storage area too.

I have seen off grid underground storage that is a perpendicular "drain tile" with a round lid. You would put that elsewhere from your metal building, of course.