The study analyzes the thermal environment and energy-saving performance of nearly net-zero energy apartments in Japan during winter by measurement and questionnaire. Results show the average indoor temperatures exceeded 18°C even without air conditioning, due to superior insulation performance. Energy consumption for heating was 58.9% to 62.9% of the national average, and residents perceived their homes as warmer, leading to lower temperature settings of airconditioner. However, there were several challenges, such as the low ratings by residents of non-heated rooms during winter.* 1 法政大学大学院デザイン工学研究科建築学専攻 (〒 162-0843 東京都新宿区市谷田町 2-33) * 2 法政大学デザイン工学部建築学科 教授・博士(工学)