Impact of green roof and green facade on building thermal performance and carbon sequestration in subtropical climate of China

This paper investigates the case building’s cooling effect, energy saving, and carbon sequestration with green facade and green roof. The west and east GF is covered with wisteria, and the GR is planted with different kinds of vegetables. The cooling effect of the GF and GR is analyzed by field test. The cooling energy saving of the GF and GR is deeply discussed with EnergyPlus software simulation. Carbon sequestrations of the GF and GR are calculated considering both plant photosynthetic and energy saving with the field test and simulation. The results show that the average external surface temperature reduction of the west GF, east GF, and GR is 4.5°C, 4.2°C, and 9.7°C on sunny days, 1.3°C, 1.3°C, and 1.4°C respectively on cloudy days. The total cooling energy saving of the GF and GR is 4.75 kWh/m2. The cooling energy saving of the GR with seven kinds of vegetables varies from 529.6 to 2936.3 kWh, which is related to the LAI and height of vegetables. The daily cooling energy saving in hot sunny weather scenario is almost three times that in cool sunny. The carbon sequestration ability per planted GF area is 1.4 kg C/m2, and per planted GR area with seven different vegetables varies from 0.88 to 2.21 kg C/m2, in which the strongest is peanut, and the weakest is lettuce. At last, the cooling energy savings of GF in different orientations on hot, warm, and cool sunny days are discussed, which is shown that the cooling energy saving effect of the different oriented GF mainly depends on the received solar radiation amount in this orientation. The results of this research can provide some assistance in improving the design of the building GR and GF.