On a wooded property in Michigan, Steve dug a concrete root cellar into the ground and built a greenhouse on top of it. The cellar's roof is the greenhouse floor. The earth below stays around 55°F year-round — cool enough to store food in summer, warm enough to keep plants alive through a Michigan winter.

Two concrete pours. More than fifty rebar bars. Heated floors fed by ground temperature. A steel door he calls zombie-proof. And 14 months of building it almost entirely alone.