Keep garage cool

Wouldn't we all.
Seriously though, thats kind of a loaded request, don't you think?
For one thing nobody knows where in the world this garage is. I mean, is it in the SouthEast United States or England or is it in Siberia perhaps? How big is it? Whats its volume?
For another thing, what types of food are we talking about storing here? Canned, fresh eggs, live Snails? And for how long?
Oh! then there is the part about "inexpensively," thats the real kicker isn't it? I mean, take for example, $5.00 per watt for PV modules not installed. Thats expensive to me but everyone else would appear to be applauding this price.

At first I thought of Earth tubes, but then I thought, if I had to dig, why not just make a root cellar, then I can still park the motorcar in the garage. I could give you some links but then that would take the fun out of doing your own search about root cellars. Aww, what the heck. I just can't help myself.
http://www.seedsofknowledge.com/rootcellar.html