Here's the book with the answers.

I have a very old edition of this still-in-print classic. Its both practical and readable.

Both crawlspaces and unheated garages can indeed be good options under the right circumstances.

Here is a link that might be useful: Root Cellaring

As for coolers, I would say yes for certain items. My parents always used styrofoam coolers for storing potatoes, carrots, beets, and turnips- just layered dirt and roots, then pulled out when needed. Other items need air circulation, so were stored in baskets, milk crates, and burlap sacks- mainly cabbage, apples, and onions. Maybe if you do some searching on the Harvest forum you'll find other ideas, too! Like freezing, canning, pickling, fermenting, and dehydrating... did I forget anything? Cheers!

Sunni

A cooler will work but a rubbermaid or other plastic tote will work (cheaper). The trick is to layer the root veggies in dry sand. They can't be touching each other or they will rot. Then keep them in as cold a place as you can find but don't let them freeze. If they freeze they will either rot or be spongey.
I just pulled a bunch of carrots & rutabagas out of my totes full of sand this afternoon... they are cooking right now...yum

Winter storage of vegetables brings back memories. My parents stored some of theirs in a bomb shelter where we lived. However, due to all the frogs and toads that kept house there in winter, it was a super unpleasant task to be asked to go fetch carrots for dinner (in the dark with a flash light). Carrots, by the way, were stored in damp sand and retained their taste and texture well. Eventually the carrots would develop fine, white roots, which didn't diminish their quality (so far as I remember).

Ponce, you mention critters making appearances in both your crawl space and garage. So, some thoughts would have to be paid to food safety, and how to separate critters from food.

Mice can gnaw through plastic tubs, but metal cans I think are safe. Hardware cloth could possibly be used to top the cans that needed ventilation. You might find critter-proof storage containers in feed stores. (Annimal feed also have to be stored in critter-proof containers.)