This paper presents a comprehensive review of building lifecycle carbon emissions (CEBL) and reduction approaches, analyzing over 300 recent publications and engaging in in-depth discussion of more than 100 key studies. The review systematically examines CO₂ emissions across all stages of a building's lifecycle, from material production and transportation to construction, operation, demolition, and material recycling. While existing research highlights the significance of operational energy efficiency, this review reveals critical research gaps in quantifying transportation emissions, accounting for on-site equipment emissions during construction, and addressing the unique characteristics of non-residential buildings. Furthermore, the paper underscores the urgent need for improved construction waste management practices, especially in developing countries where landfilling remains prevalent. For the building carbon reduction approaches, promising building carbon emission reduction approaches include leveraging carbon dioxide sinks, implementing integrated energy systems, integrating building-integrated photovoltaics (BIPV), and enacting effective policy interventions are separately discussed. By revealing data and theoretical limitations within current research, this review calls for more integrated and context-specific approaches to CEBL assessment, paving the way for a more sustainable built environment.

Aging and urbanization significantly impact the physical and mental well-being of the elderly population. Empirical investigations have highlighted the contribution of the built environment to promoting elderly health. However, there is a need for further exploration of the factors within the built environment that impact the subjective well-being (SWB) of the elderly. To address this, this study selected 50 communities in Guangzhou, where 1403 elderly people were surveyed. Employing the random forest, we have identified contributing factors of the built environment affecting the SWB of the elderly. Meanwhile, we used a prediction model constructed by random forest to predict the SWB level of the elderly. The results indicated that accessibility to parks (positive emotions (PA): 0.822, positive experiences (PE): 0.235), hospitals (PA: 0.680, PE: 0.546), and supermarkets (PA: 0.237, PE: 0.617) significantly contributed to PA and PE. On the other hand, factors such as population density had a significant contribution to negative emotions (NA: 0.431) and negative experiences (NE: 0.194). Based on the prediction results, the spatial distribution of SWB among the elderly can be derived. Overall, our study can provide planning and improvement strategies for built environments that promote SWB among the elderly.