Assessment of Direct and Indirect Impacts of Vegetation on Building Comfort: A Comparative Study of Lawns, Green Walls and Green Roofs

Following development and validation of the Solene-microclimat tool, the model was used to compare the impacts of various “greening strategies” on buildings’ summer energy consumption and indoor comfort. The studied strategies were greening walls, roofs, and ground (lawns). Solene-microclimat enables to simulate simultaneously a building's thermal behavior and the microclimate at the district scale, with the retroaction of buildings on climate. Distinguishing between direct (due to the modification of building’ characteristics) and indirect impacts (due to the modification of boundary conditions) of these surfaces is also possible. Thus, the strategies were successively implemented on the studied building, the surroundings, and both of them. The simulations were carried out using Solene-microclimat considering insulated vs. non-insulated buildings. Findings confirm that the direct and indirect effects of theses surfaces are almost negligible on insulted buildings. For non-insulated ones, green walls have a direct effect on indoor comfort throughout the entire building, whereas the effect of green roofs is primarily confined to the upper floor. Moreover, the indirect effect of a green wall is greater, mainly due to the drop in infrared emissions resulting from a lower surface temperature. It has also been proven that the indirect effects of green walls and surrounding lawns can help reduce the loads acting on a non-insulated building. Direct and indirect effect can’t be directly added. This is particularly interesting for heritage buildings or highly glazed ones the refurbishment of which is often difficult.