Thermal Environment-Improving Effect and Water Retentivity of Base Block Produced with Lawned SHIRASU as Roof-top Greening Material

Abstract

We used a greening base hardened by shirasu to perform a trial execution of about 160 m² of rooftop greening materials on the rooftop of a building, and then evaluated the effect of this greening base in reducing the thermal environment by comparing the surface temperature on the roof surface with the ceiling under the slab. We also compared the water retentivity of the greening base with that of artificial lightweight soil. At the hottest time on a summer day, the surface temperature on the rooftop with greening materials fell to about 10 ℃lower than the non-greening area, and also fell to 13-16 ℃ lower on the ceiling surface below the greening base. As for the water retentivity of the greening base, the volumetric water content and water retentivity slightly exceeded those of artificial light weight soil three days after adding water, confirming the water-retention ability of the greening base.