🔥 Ondol: Korea’s ancient underfloor heating Long before modern central heating, Koreans developed Ondol,a system that channels hot flue gases through undergro

🔥 Ondol: Korea’s ancient underfloor heating Long before modern central heating, Koreans developed Ondol,a system that channels hot flue gases through underground passages beneath stone floors. The heat warms the floor, the room, and the people above it before the smoke exits through a chimney. […