Green roofs have good heat preservation and insulation performance, which plays an important role in reducing airconditioning load and reducing carbon dioxide emissions. Experimental research and numerical simulation analysis on the energy-savings and ecological benefits of green roofs in hot summer and cold winter areas in Wuxi, China (31°N, 120°E) are carried out. The experimental results show that a new type of Buddha grass can absorb 1.79 kg of CO 2 and release 1.3 kg of O 2 per square meter per year. In addition, the annual carbon emission reduction of the green roof in Wuxi was 9.35 kg m-2 , and the emission reduction benefit of the green roof was calculated to be USD $1.02 m-2 a-1. The energy consumption simulation shows that the green roof per unit area can save 11.53 kWh per year, and the annual quantitative ecological benefit of a green roof is USD $3.37 m-2. The calculated dynamic investment return is 10 years. A green roof has the benefits of heat preservation and insulation; meanwhile, it can reduce energy consumption. It is also worth mentioning that its energysaving potential and ecological benefits are substantial, and the investment payback time is short, which makes it worth promoting in a large area.

The rapid expansion of the worldwide tourism industry has significantly increased energy consumption in hotels. Hence, the renovation of existing hotel buildings is relevant to achieving the energy-saving goals of the construction sector. This study takes a hotel in eastern China as an example of energy-saving renovation. First, based on a BECS energy-saving design and SPSS statistical analysis software, the energy-saving effects of renovation of building envelope (windows, walls, and roofs) are dynamically simulated, and a comparison of various renovation schemes is carried out by adopting an orthogonal experimental method and conducting a variance analysis. Second, the energy performance of the lighting and air conditioning systems is analyzed during the entire renovation process. Third, the economic environmental and social benefits were comprehensively analyzed. The results show that energy-saving renovations can effectively reduce energy consumption in existing buildings as well as the associated CO 2 emissions. Specifically, the energy-savings rate of the building envelopes and the energy systems were 14%-20% and 60%-70% respectively. As for carbon emission, 947.55 tons of total CO 2 emissions per year were eliminated through the renovation project. Specifically, CO 2 emission reductions reach 247.65 tons per year through energy-saving renovation of building envelope, and CO 2 emissions reductions resulting from the renovation of the airconditioning system and lighting system were 220.88 tons and 479.09 tons per year respectively. Additionally, the dynamic investment payback period of the hotel energy-saving renovation project was calculated to be between 8-9 years. The demonstrates that the renovation of hotel buildings plays an essential role in benefiting the environment and the economy and social welfare.