To reduce the carbon emissions of existing residential buildings while pursuing maximum cost benefits, a multi-optimization design method for the existing residential building rooftops, retrofitted by attaching the solar photovoltaic panels and thermal collectors, was proposed in the study. At first, the life cycle carbon emission and cost benefit of the retrofitted buildings were assigned as the optimization objectives, and the models of carbon emission and cost benefit were developed. Furthermore, a typical existing residential community located in the cold zone of China was selected to perform the multi-optimization based on the Grasshopper platform. Meanwhile, the laying area, laying angle, and allocation ratio of the solar photovoltaic panels and thermal collectors were selected as the design parameters. And then the best retrofitting solution suitable for the existing residential buildings was proposed. The results show that the weightings of the carbon emission of retrofitting life cycle are 42.68%, and that for the cost benefit is 57.32%. Significantly, there is a 31% reduction in carbon emissions compared to the building before retrofitting, and a 24.7% reduction in cost benefit.

Han-Tang Western Region beacon towers hold significant historical value but suffer severe damage, with traditional restoration lacking visual references. This paper proposes a GAN-based image restoration method combining Pix2Pix and CycleGAN models. Experiments show Pix2Pix achieves higher accuracy but requires paired samples. We design a hybrid workflow: CycleGAN first generates restoration targets, then concatenates with original images for Pix2Pix input. AI-generated virtual beacon images enhance database diversity, significantly improving restoration stability and accuracy. This research innovatively applies deep learning to architectural heritage preservation, providing a feasible method for building image restoration with limited data. It efficiently supplies visual references for traditional restoration and offers a scalable technical pathway for beacon tower virtual reconstruction, providing valuable guidance for preservation work.