Effect of Roof Plants on the Building Internal Temperature for the Urban Landscape and Heat-Island Reduction

Abstract

The objectives of this study are to investigate the effect of plant type on the roof of a model building on the temperature of the interior space, and to provide the suitable plant species for a green roof. On the roof of scaled model building, grass (GR: Zoysia japonica), sedum (SE: Sedum makinoi Aurea), maekmundong (MM: Liriope platyphylla), and jasanhong (JH: Rhododendron schippenbachii) was planted. From June 28 to August 28, i.e., for 63 days, the internal and external temperature of the model building and the light intensity were measured and compared with the control model building (CON: no plant and substrate on the roof). With increased global radiation, the maximum temperature was increased from 28.2℃ to 51.74℃ for CON, from 27.2℃ to 47.7℃ for GR, from 27.7℃ to 49.3℃ for SE, from 27.9℃ to 48.3℃ for MM, from 27.5℃ to 48.9℃ for RD, whereas the outside temperature increased between 25.5℃ and 34.6℃. A positive linear relationship was observed between global radiation and the internal temperature (r=0.987-0.989) and hence, the temperature difference between the internal and external model building (ΔT) was larger with increased radiation. A positive linear relationship was shown between light intensity and ΔT at difference radiation levels. The regression coefficient was estimated as 0.99-1.00℃/[100W/m2] under 500 J/cm2, 1.10-1.15℃/[100W/m2] at averaged radiation 1,800J/cm2, whereas the large decrease in the coefficient, i.e., 0.76-0.86℃ /[100W/m2] was observed for above 1,800J/cm2 radiation level. The ΔT per unit of light intensity observed a significantly different between treatments. With the planted grass on the roof of the model building, the lowest ΔT per unit solar radiation was observed, which means that the covered roof with grass causes the building internal temperature to be less affected by the sun radiation.