Validation of energy simulations for multi-family residences with photovoltaic power and gas cogeneration: Case study on balancing energy efficiency and resident health

In Japan, the energy consumption of the residential sector is significantly high. Therefore, insulation retrofitting and behavioral changes have become critical to enhance energy efficiency. Although several studies have examined these factors, they have focused on standard dwelling units and generalized lifestyle patterns.

This study investigated, through simulations, the impacts of thermal insulation performance and lifestyle behavior on energy consumption, health, and economic efficiency of an actual Zero Energy House (ZEH)-certified dwelling installed with a dual-generation system combining photovoltaic panels and a solid oxide fuel cell. The simulation model was validated using energy consumption and indoor temperature data from the winter of 2024; resident interviews were also incorporated to reflect their behavior.

Results showed that the primary energy consumption exceeded the ZEH design values, mainly owing to higher-than-expected lighting and gas consumption. Lighting was used in unoccupied rooms, and water heating was frequently used. Operating floor heating systems for only approximately 3 h per day was sufficient to maintain indoor temperatures above 18 °C, the WHO-recommended minimum in winter. Regarding the building envelope performance, residents’ morning blood pressure was estimated at 127.5 mmHg; however, a lower thermal insulation performance resulted in an increase in blood pressure to 137.6 mmHg, exceeding the 135 mmHg threshold, indicating potential health risks.

Behavioral optimizations, such as controlling the use of unnecessary lighting, high-efficiency appliances, and water heating systems, reduce energy consumption by 15% and improved economic efficiency by 33%, without compromising health. Moreover, even when operating 24-hr floor heating, these behavioral optimizations contribute toward reducing energy consumption by 11% and improving economic efficiency by 25%.