Due to the declining of physiological functions, the thermal requirements of elderly people at different ages are different. This paper aims to propose different indoor design parameters for different age intervals. Firstly, environmental parameters and subjective sensation are measured in two pensioners’ buildings. Elderly people are divided into three age groups: 60–74, 75–88 and 89+ years. The temperature and humidity sensitivity of the three age groups are analyzed, and the summer indoor design parameters for the three age groups are proposed. Finally, the energy benefits of the strategy of “different design parameters for different age intervals” are studied. The results indicate that, the temperature and humidity sensitivity of elderly people gradually decreases with age. The indoor design temperature of the three age groups is 27.5, 27.7 and 28.8°C, respectively. The indoor design relative humidity range is 56.5–66.1, 54.8–74.3 and 52.0–78.3%, respectively. When adopting different indoor design parameters for different age intervals, the energy consumption and CO2 emission are reduced by 680,000 kWh and 680,000 kg in Baoding, China. This study can provide data reference and design suggestions for controlling indoor environments in pensioners’ buildings balancing energy conservation and thermal comfort. •The elderly people are divided into three age groups: 60–74, 75–88 and 89+ years.•Temperature sensitivity and humidity sensitivity of three age groups are compared.•Strategy of “different design parameters for different age intervals” is proposed.•Indoor design temperature for the three age groups is 27.5, 27.7 and 28.8 °C.•The strategy can significantly reduce the energy consumption and CO2 emission.