Research on the Design of Green Roofs for Office Buildings in Xuzhou Based on Building Energy Consumption Evaluation

The roof is the building envelope that receives solar radiation for the longest duration. Green roofs significantly reduce air conditioning energy consumption in summer, demonstrating notable energy-saving effects. From the survey of 13 large-scale green roofs, it is evident that the green roofs of office buildings are well-maintained and frequently used. In Xuzhou, green roofs can be actively developed on the basis of sufficient economic support, warranting further in-depth research. This study conducted on-site measurements of green roofs on office buildings in Xuzhou. The results showed that under air conditioning conditions, compared to buildings without green roofs, the average maximum indoor temperature, outer surface temperature, and inner surface temperature of Building No. 2 in the Materials Market with a green roof were lower by 0.4℃, 11.5℃, and 3.9℃ respectively. The daily average air conditioning cooling load per unit building area of the top-floor rooms with a green roof was 1.05 kWh/m², which was 0.21 kWh/m² lower, achieving an energy-saving rate of 16.7%. Simulations using EnergyPlus for factors such as soil layer thickness, soil thermal conductivity, and leaf area index concluded that the soil thickness should not exceed 0.3 meters, the lower the soil thermal conductivity the better, and the larger the leaf area index the better. Finally, taking Building No. 2 in the Materials Market as an example for renovation, it was found that the energy-saving rate of the renovated green roof was 27.0%. Modular design steps for green roofs were provided, with a suggested cost of around 204 RMB/m², effectively applying the research to practice.