Enhancing the insulation performance in residential buildings is essential to achieve a decarbonized society and protect occupants from cold indoor environments. While highly insulated houses are becoming more prevalent, their thermal environments are still not fully understood. To assess the thermal conditions of highly insulated houses and the effects of improved insulation, we conducted a measurement survey in six residences with insulation ratings exceeding Japan’s current standards for new houses. The energy consumption of these houses was analyzed using a Building Energy Simulation tool, and annual energy consumption data were also collected. The measurement survey revealed that the indoor temperature of highly insulated houses was significantly higher in summer and lower in winter under intermittent heating and cooling. Temperature fluctuations ranged from as low as 10°C in winter to as high as 34°C in summer. The breakdown of energy consumption based on simulation showed that the heating and cooling demand, as well as appliance energy usage, varied across households. The results of this study could be used to determine standards for future houses.
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SERIKAWA et al. (2026) studied this question.