Indoor wet-bulb globe temperature (WBGT) was extensively used to evaluate the indoor hot environment in a naturally ventilated building, but it does not consider the effect of air movement caused by the hot surface. A potential evaluation index, which is a difference between the mean radiant temperature and the air temperature (Δt_r–a), was introduced to be integrated with the indoor WBGT to evaluate the indoor hot environment with hot surface. Subjective evaluation of the occupant's thermal perceptions and objective measurement of indoor physical parameters were carried out in a typical naturally ventilated room with hot surface ranged from 50°C to 250°C. The results show that the indoor air temperature, mean radiant temperature and WBGT were increased by 8.6°C–12.9°C, 11.2°C–29.7°C and 4.7°C–7.5°C, respectively, with participant's light activity, and by 9.9°C–13.5°C, 14.9°C–29.4°C and 5.7°C–8.0°C, respectively, with participant's heavy activity. Indoor air temperature was increased linearly with the indoor WBGT, whereas the mean radiant temperature was increased non-linearly with the indoor WBGT. Besides, the non-linear relationship between the occupant's thermal perceptions and Δt_r−a coincided very well with those between occupant's thermal perceptions and indoor WBGT. This suggests that the Δt_r–a may be a potential index to be integrated with the indoor WBGT for evaluating the indoor hot environment in naturally ventilated building with hot surface.

室内湿球温度（WBGT）被广泛用于评价自然通风建筑物的室内热环境，但它没有考虑热表面引起的空气流动的影响。一个潜在的评价指数，它是平均辐射温度与气温之间的差值（Δt _r–a)，被引入与室内WBGT集成以评估具有热表面的室内热环境。对居住者热感知的主观评估和室内物理参数的客观测量在典型的自然通风房间内进行，热表面温度范围为 50°C 至 250°C。结果表明，室内空气温度、平均辐射温度和 WBGT 在参与者的光活动下分别增加了 8.6°C–12.9°C、11.2°C–29.7°C 和 4.7°C–7.5°C，以及分别为 9.9°C–13.5°C、14.9°C–29.4°C 和 5.7°C–8.0°C，参与者活动量大。室内空气温度随室内 WBGT 线性增加，而平均辐射温度随室内 WBGT 非线性增加。此外，乘员之间的非线性关系_r-a与居住者的热感知和室内 WBGT 之间的值非常吻合。这表明Δt _r-a可能是一个潜在的指标，可以与室内WBGT 结合用于评估具有热表面的自然通风建筑的室内热环境。