Challenges in the low-carbon adaptation of China's apartment towers

Low-carbon building retrofit will contribute to delivering China's policy to reduce carbon emissions. This paper proposes viable low-carbon adaptation strategies for a recurrent building type within the Hot Summer and Cold Winter (HSCW) zone. An existing 23-storey tower in Hangzhou is investigated within the context of a representative city environment. Indoor air temperatures and energy consumption were monitored across a typical floor and simulated in EnergyPlus. Outdoor and indoor airflow patterns were modelled in an advanced computational fluid dynamics (CFD) tool, FLUIDITY. Across a typical floor, observations and modelling show marked variations. South-facing flats overheat significantly in summer largely due to solar radiation. External sun-shading structures are proposed and evaluated to counter summer overheating. An innovative wind catcher and exhaust-stack natural ventilation system is proposed to enhance indoor thermal comfort using natural ventilation. Modelling of this integrated ventilation system indicates that the proposed retrofit system will improve indoor thermal comfort even in the lower floors. The proposed building retrofit strategy is costed using locally established construction cost estimates. Predicted energy savings suggest that the adaptation strategy proposed is potentially viable with significant implications for policy-makers, developers, constructors and designers in this challenging climate zone in China.