Why Houses Are Cold in Winter — Korean Ondol vs Japan's Lack of Insulation

One thing nearly 100% of Koreans in Japan say in winter: "The house is too cold." Why is it so different?

Korea: Ondol — The Floor Is Hot

Korea's core heating is ondol (floor heating). Dating back to the Goguryeo era, modern apartments circulate hot water through pipes under the entire floor.

• Entire floor uniformly warm (20-25°C)

• Heat rises from below, efficiently warming the whole space

• Many Koreans live in t-shirts and shorts at home in winter

• High apartment insulation standards minimize heat loss

• 24-hour whole-house heating is normal

Japan: Spot Heating — Only Where People Are

Japan's traditional heating philosophy: "Don't heat the house, heat the person."

• Kotatsu: Table with heater underneath — warm only if legs are in

• AC (heating mode): Warm air from ceiling — top warm, floor cold

• Kerosene heater: Heats one room only

• Kairo (ホッカイロ): Body-attached hand warmers

No whole-house heating → toilet, hallway, changing room are genuinely cold.

Why So Different?

Climate: Korea's continental climate brings extreme winter cold (-10 to -20°C). Japan's maritime climate is milder but humid.

Architecture: Traditional Japanese building prioritized summer heat/humidity response. The famous passage from Tsurezuregusa: "Houses should be built for summer."

Insulation standards: Korea legally requires high insulation for apartments. Japan only mandated insulation for new buildings starting 2025.

Heat Shock Problem

Japan's serious social issue: Heat shock — moving from warm room to cold bathroom causes sudden blood pressure changes → stroke/heart attack. Estimated ~19,000 bathing-related deaths annually in Japan. This problem barely exists in Korea due to uniform ondol heating.