We have the obligatory "Fraidy-hole" storm shelter here in Oklahoma, for when rotary weather stops being a spectator sport and gets serious. We squeezed a little more out of the budget and bought what amounts to an oversized unit for two people and a dog. It's nominally rated for "12 People," though I would want the other 11 to be very good friends. It's big enough for a set of shelves and a stack of milk crates for cabbage and potatoes, and a few apples. So, I guess we're "stacking functions."
We buried ours, although it's rated for 1/3 exposure for critical storm performance. It has two vents, so we put a 4" PVC DWV tube for a convection ventilation system. Doesn't freeze in the winter, but the steel door, set at a 40º angle, does tend to bake in the sun, even though the rest of the structure is under at least 10" of soil. I'm going to build a shed roof over it all this summer and put an insulated door on the front. Should work quite well.