Abstract:The goal of this paper was to quantify the influence of two different types of green roofs (a native green roof named green A

an international popular green roof named green B) in building energy benefits by field experiment in Chengdu

China.The temperatures of green A

green B and a non-vegetated concrete control roof(concrete R) had been continuously monitored for a period of 1 year.Results indicate that:(1)In summer and winter

green roofs

compared with concrete R

improved the energy efficiency of buildings

the internal surface average temperature of green A and green B respectively reduced by 1.6℃ and 1.2℃ during the period between June and August

and increased by 2.1℃ and 2.8℃ during the period between December and January.Due to the differences of the substrate layer and the drainage layer

the cooling effects of green A was slightly better

and the internal surface temperature of green A had smaller amplitude in summer

but the insulating effects of green B was better in winter.(2)Green roofs can significantly reduce the peak and the amplitude of the external surface temperature in summer

which was beneficial to prolong roofs life.(3)The effects of solar radiation was weakened by vertical layers of green roof from top to bottom

and the response to solar radiation was delayed layer by layer.At night

the temperature of each layer was stable and the temperature differences among layers was small.(4)Vegetation and substrate layers played a key role in thermal performance of green roofs.