A bedroom in Shanghai was used for numerical calculations and twooperation modes were assumed. The energy consumed for heating and cooling and the thermal comfort during the offperiods were measured. The results show that the temperatures are closer to the design temperatures at the air conditioner (AC) start moment when placing the insulation layers on the outside of the exterior walls. The temperature variation speeds of the bedroom are faster when placing the insulation layers on the inside of the exterior walls. Taking the energy used during the AC onperiods and the thermal comfort during the offperiods into considerations, the thermal performance is better when placing the insulation layers on the outside of the exterior walls.