room, and if I have my way a small barn area in the back and a root cellar in one of the corners. Just have to figure out how to insulate it so the root crops do not freeze in the winter and stay cool enough so they do not rot.

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.

but I remember a few issues ago Mother Earth magazine discussed making your own root cellars. You might be able to do a google search for it.

Sorry it's not much but I hope it helps.