ChaDol is a radiant floor cooling system inspired by Korea’s traditional ondol, circulating chilled water at approximately 20°C as a sustainable alternative to conventional air conditioning. The prototype achieved a 6–7°C temperature reduction and maintained stable cooling for six days, while aluminum tape improved cooling performance by an additional 9–10%. The project demonstrates the potential for a water-efficient, energy-saving, and scalable cooling system that could help reduce electricity demand and CO₂ emissions.