Storage Shed for Keeping the Harvest?

It's barely spring and already I'm planing how to preserve this year's bounty. The question is, in late summer or early autumn I plan to build an 8x12 outdoor shed and aside from the snow blower and all the other gack that will live there, I've been wondering whether this uninsulated building could serve as an impromptu root cellar as well. If so, what might I need to build-in in terms of insulated boxes, trays, etc. for this to be effective and worthwhile? I live in Zone 5a, just north of New York City. I grow lots of onion family members, various root vegetables, squash. (The tomatoes never last long enough to even contemplate saving, except for making and freezing sauce.) I seem to be one of those folks whose potatoes, garlic and onions either sprout or shrivel up entirely depending on which part of the basement I try to keep them in.
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