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Retrofitting buildings to achieve improved levels of energy performance is a key strategy in the transition to a low-/net zero carbon future. In China, there has been an enormous growth in residential construction in recent decades in response to the country's economic development and population growth. However, although these buildings are structurally solid and have long functional life spans, most have very poor thermal performance. Therefore, they would be very suitable for energy retrofitting. Because of the variety of retrofitting options, it is important to review the retrofit measures, regulations and possible outcomes to find effective, long-term solutions that strike a balance between the energy saved, the carbon emitted and the financial costs over a building's lifetime. This paper reviews suitable retrofit measures for the hot summer–cold winter region of China, because this is an area with huge numbers of residential buildings that are suitable for energy retrofitting. The study explores the current conditions of targeted residential buildings, retrofit schemes, building regulations, and policy gaps towards achieving China's 2060 carbon neutrality goal. The review indicates that current mandatory building energy regulations in this region are not ambitious enough to achieve a significantly lower carbon future, and one-step deep Passivhaus retrofit schemes are recommended to achieve decarbonization goals. [ABSTRACT FROM AUTHOR]

• The payback time for both retrofit scenarios is less than five years. • The operational carbon stage contributes significantly more than the embodied carbon stage. • Current regulation requirements are inadequate to meet the zero-carbon goals for dwellings. • Adding heat pump to the shallow retrofit increases the embodied carbon of the retrofit by 141%. • Deep retrofits result in more significant savings than shallow retrofit with heatpump. • Using natural materials would reduce the A1-3 and B1-5 environmental impacts greatly. In order to achieve its 2050 net-zero emissions goal, the UK government must significantly improve the energy performance of millions of hard-to-treat homes through retrofitting. However, questions over the embodied carbon emissions of retrofit projects arise, specifically deep retrofits, when the embodied carbon emissions of the retrofit are compared to a shallow retrofit or demolition. This study evaluates the carbon footprints of various retrofit interventions by comparing the impact of a deep retrofit based on the Passivhaus retrofit standard (EnerPHit) to a shallow or conventional retrofit following UK building regulations. The research also assesses the whole-life carbon impact of a 'heat-pump first' compared to a 'fabric-first' approach using natural insulation materials versus standard petrochemical-derived insulation. Finally, the study presents the carbon avoidance achieved through retrofitting compared to the carbon emissions from demolition and building new homes. The findings reveal that retrofitting buildings can reduce operational carbon emissions by 59% to 94%. Conventional retrofit scenarios generate 37% fewer energy savings than the EnerPHit standard with petrochemical materials but only result in 1% less embodied carbon. Low carbon technologies, such as photovoltaic panels or heat pumps, increase the embodied carbon by 38% to 117% but did significantly decrease operational carbon emissions by 71% (photovoltaics) and 61% (heat pumps). Using natural materials in both deep and shallow retrofits can reduce total embodied carbon by 7% to 14%. The study also found that the embodied carbon of the brick and timber, saved as a result of the refurbishment, is much greater than the product stage embodied carbon of deep or shallow retrofits. [ABSTRACT FROM AUTHOR]