## 5 Discussion  
As the effects of new productivity and green technology innovation on carbon reduction become increasingly evident [44; 51], clarifying the interaction mechanism between new productivity, green technology innovation, and carbon reduction in the construction industry has become a key issue that needs to be addressed to promote high-quality development in China's construction sector. This study used panel data from 30 provinces of China from 2013 to 2021 to reveal and analyze the interactive relationships among the three factors and their spatial-temporal evolution characteristics. The results show that during the study period, the development levels of RGIT, NQP, and CRCI exhibited a continuous upward trend. Moreover, the econometric model reveals a significant negative impact of RGIT on CEICI, and that NQP serves as a crucial mediating factor in this relationship. This indicates that regions can effectively suppress carbon emissions and enhance their carbon emission performance by developing green technology innovation and promoting the green technology innovation capacity of construction enterprises. Although green technology innovation has previously been shown to suppress carbon emissions at both the industry and regional levels [52; 53], this study further extends the carbon reduction effects of green technology innovation to the construction industry. Previous research has also validated this viewpoint. For example, [PERSON] et al. (2023) found through panel data from 30 provinces in China between 2005 and 2020 that green innovation has a significant positive impact on carbon dioxide reduction in China's construction industry and that environmental regulation plays a facilitating role in this process [24]. Furthermore, the coupled coordination degree model reveals that the overall level of coordinated development among the three has improved from a state of mild disorder at 0.373 in 2013 to a state of barely coordinated at 0.528. This indicates that as the levels of RGIT, NQP, and CRCI continuously rose during the study period, their coordinated development has also shown a continuous upward trend, reflecting a positive and beneficial interaction among the three. However, significant regional differences in the coordinated development among the three were also observed, particularly in the eastern region, where RGIT, NQP, and CRCI exhibit strong synergistic effects. For example, in economically developed coastal regions such as Beijing, Tianjin, Jiangsu, Zhejiang, and Guangdong, the coupling coordination degree values are all no lower than 0.600, indicating progress to the intermediate coordination stage. [PERSON] et al. [54] also demonstrated this pattern through the spatial distribution of NQP in 271 prefecture-level cities in China. Similarly, [PERSON] et al. [55] found a similar trend in their study of the dynamic evolution of new productivity and carbon total factor productivity in 30 provinces and municipalities in China. This phenomenon mainly arises from the comparative advantages of these regions in terms of economic level, technological accumulation, and resource aggregation. The eastern region, with its high level of new productivity, actively promotes the deep application of intelligent and digital technologies in the construction sector, which not only enhances resource allocation efficiency significantly but also accelerates the penetration of green technologies in the construction industry, thereby achieving significant carbon reduction effects. The underlying logic may be that the continuous improvement of new productivity not only provides a solid foundation for the widespread application of green technologies but also further stimulates the emission reduction potential of these technologies. However, despite certain progress in RGIT, NQP, and CRCI in recent years, the effectiveness of carbon reduction in the construction industry in the central, western, and northeastern regions remains insufficient.