7
How did you start?
(lemm.ee)
Ponds, barns, livestock, gardens, food preservation, fishing, hunting, tractors, pigs, chickens, cattle, worms, 4H, permaculture, organic, grazing, canning, aquaculture, trees, woodland, farmers, agriculture, agronomy, horticulture, wwoofers, bees, honey, wildcrafting, dairy, goats, nuts, berries, vegetables, sustainability, off grid, wood stoves, chainsaws, wood heat, tools, welding, green woodworking, farmers markets, composting toilets, straw bale homes, cob building...
These are called "earth tubes" or "ground-coupled heat exchangers" and they work because the ground below frost line maintains a constant ~55°F (13°C) year round - super efficent for passive cooling in summer without needing electricity, tho you gotta watch for condensation/mold issues.