Abstract
There are many research and engineering projects on extensive green roofs, however, there is still no design guide for green roofs` climate energy efficiency, which limits the further promotion and usage of it, especially in China containing five climate zones. Taking different climate zones of China as examples, the verified building model is used in the DesignBuilder software, and 2-4 typical cities in each climate zone are selected, then combined the genetic algorithm (GA-Ⅱ) to optimize the energy efficiency of the building under green roofs. The results show that in all the cities studied in the five climatic zones, extensive green roofs are more energy efficient than ordinary thermal insulation roofs, and the energy saving rate is between 1-26.4%; except for the Nenjiang, which the energy is mainly used for heating, the cooling energy consumption is reduced and the heating energy consumption is increased after the optimized green roof is adopted in other cities; it is also found that the energy saving rate of the green roof with optimization has a high correlation with the total annual solar radiation value of the city. In addition, the energy efficiency optimization of green roofs in all cities shows that a larger leaf area index is more conducive to energy conservation; however, in southern China, it is not recommended to use a thermal insulation layer in the roof structural layer below the soil.
Highlights
IntroductionThe building sector currently accounts about 30-40% of the world primary energy, which is responsible for onethird of greenhouse gas emissions (responsible for global warming) around the world
The building sector currently accounts about 30-40% of the world primary energy, which is responsible for onethird of greenhouse gas emissions around the world
The heating energy consumption of Guilin in the hot summer and cold winter zone increased by 113.2%, while the heating energy consumption of Nenjiang decreased by 1.1%
Summary
The building sector currently accounts about 30-40% of the world primary energy, which is responsible for onethird of greenhouse gas emissions (responsible for global warming) around the world. Most energy consumption is used for heating and cooling applications. Global concern of the environ-mental impacts of the fossil fuel usage has prompted the interest to search and use passive techniques for heating and cooling of the buildings[2], one of the most important solution is green roofs. Research and practice results have shown many advantages of green roofs which is included reducing urban heat-island effect, reducing stormwater runoff, enriching biodiversity, and cleaning runoff and air. It saves energy for cooling and heating spaces because of its thermal insulation, resulting in improved energy efficiency of buildings[5]
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