Numerical simulation of greening effects for idealised roofs with regional climate forcing
A numerical model was used to simulate temperature distribution in and above an extensive green roof with a long term forcing adopted from a regional climate model. Time variations of temperature for different time scales ranging from days to decades have been calculated. The results are in good agreement with selected field experiments and generally reinforce the understanding prevailing in literature regarding temperature differences of green roofs compared to a concrete roof. Green roofs result in a significant reduction of daytime human heat load and an improvement of thermal comfort conditions, while during night-time a concrete roof favours low temperatures and a low number of minimum temperatures above 20 C (tropical nights). A future shift in seasonal precipitation would necessitate irrigation in the summer months to ensure the vitality of roof vegetation. An estimation of the amount of additional watering and the increased number of watering days per year is given.