Following the rapid economic development in today’s China, the low-energy building standard has become essential when considering sustainable energy technologies within the residential building environment. Chinese national legislation and building research is paying more attention to energy savings using construction renovation, envelope insulation materials in extreme climate conditions, energy efficiency of appliances and even operational schedules for occupant activities. However, achieving building thermal comfort is not necessarily an easy target with low energy target set in the Chinese ‘five-year plan’, which puts forward more critical aims of energy savings from the beginning of new century. Simulation work using DesignBuilder has been carried out to express the comfortable period in a current Chinese low-energy building. Two apartment prototypes are modelled for the building simulation study, which is also based on the healthy housing technical essential. The outcome achieved for heating and cooling design on thermal performance of a low-energy building was not very positive and the findings have shown that an insulated external wall construction cannot satisfy all the thermal comfort potentials.