conclusionPassive cooling is generally considered as the key benefit ofgreen roofs. Many studies from multidisciplinary perspectives havebeen conducted to enhance its understanding. Most investigationsfocus on upward cooling of ambient air, with inadequate assess-ment of downward indoor cooling. The knowledge gap on the intri-cate interactions between green roof and indoor thermal regimecould be filled by research. The findings could inform green-roofdesign, management and policies through knowledge exchangeendeavors. This study explores an outstanding research question:Will poorly-insulated buildings benefit more from green-roof pas-sive cooling. The issue has far-reaching implications as cities havemany old buildings with outdated and inadequate roof thermalinsulation. With increasing adoption of the green-roof innovation,it is necessary to find satisfactory answers to this conundrum.This study adopts a field experimental approach by comparingthree types of roof plots (control, Sedum and Peanut) on twobuilding thermal-insulation (BTI) states (with and without).Temperatures along a holistic vertical profile (outdoor, green-rooflayers, indoor) at each plot, and heat fluxes between each plot andthe apartment underneath, were analyzed in detail to decipherunderlying patterns and processes. From the findings, the followingmain