not sure what your budget is, but why not just make a can house?
My grandparents had one that was recessed into the bank (south facing). It stayed around the low 50s, year round in there. We kept all of our canned goods and potatoes in there. Potatoes would last till summer with a few going bad here and there.
EDIT: it was made from cement blocks and had a tin roof for part of it that stuck out from the bank
Edited by Hines, 16 September 2022 - 06:17 AM.