Cooling Effect Of Green Roofs-A Case Study In Zhengzhou

Functions of green roof include keeping the city ecological balance, purifying air、improvement of urban heat island effect, prolonging the service life of the building etc. With the process of urbanization, the energy consumption is increasing, so exploring and developing all kinds of technologies to reduce energy consumption and to improve the urban environment become as common concern.Two constructions were mainly focused as experimental sites, in order to measure the effect of green roof. First, the head office of Jianye is one test point, which is located in CBD at the junction of Dong Feng road and Ru Yi road; Second, a six-story office building as the second test point, which is located at the junction of Long Hai Road and West Three Ring Road. The benefits of this point is facing south as well as less building higher than six floor which is full of sunshine all day and measurement the relationship between Green roof and temperature change would be benefited from this.This research basic on references related with several surveys of Greed roof affecting environment. In the first point, comparison different temperature between the roof without planting and other three plants roofs(arbor mixed with shrub,shrub mixed with grass and grass) respectively as well as the cost was also be concerned. The second point focuses on the temperature changes before and after greening with effectively controlling on variable effect to ensure the accuracy.The content and result of research show below:(1) Results of roofs with different conditions: arbor mixed with shrub(3.6℃)>shrub mixed with grass(2.6℃)>grass(1.9℃).(2) Focusing on sunlight influence on indoor and outdoor temperature as well as top roof of construction before greening. The average temperature is 34.5℃ before the roof greening; The average temperature is 34.5℃ after the roof greening. And three is no significant differences between them. But the outdoor floor temperature is higher. There are significant differences between temperature differences of indoor and outdoor floor as well as temperature differences of indoor and outdoor.(3) Focusing on sunlight influence on indoor and outdoor temperature as well as different types of roofs after greening. The average temperature is 34.5℃ before the roof greening; The average temperature is 34.5℃ after the roof greening. And there are no significant differences between them. By comparison, there are significant differences between both temperature differences of three distinctive roofs as well as temperature differences between indoor and outdoor space.(4) Focusing on temperature changes between before and after greening. Before planting, the indoor temperature is higher than outdoor temperature; however, after planting, the outdoor temperature is higher than indoor temperature. The effect of green roof would become better when the outdoor temperature increase.(5) Focusing on the change of time lag effect after the roof greening and the difference between of time lag effect between different types of roof. The highest outdoor temperature is 0.7℃lower than the highest indoor temperature at top room and highest temperature delay 1 hour. On the contrast, after planting, the time lag effect of indoor surface roofs getting highest temperature is significant prolonged to 1.5 to 2.5 hours.