Modelling green façades radiative exchanges within the TEB (town energy balance) urban canopy model

In order to mitigate the impacts of climate change in urban areas, there is a growing emphasis on the promotion of nature-based solutions (NBS) with expected benefits for biodiversity, rainwater management, evaporative cooling, and carbon sequestration. Among the various possible NBS, green facades have the advantage of being deployable in already built area. The environmental evaluation of greening policies through the implementation of green facades requires integrated physical-based numerical model to simulate radiative, energy, and carbon exchange processes at building scale but within a modelling framework that can also address interactions at the neighbourhood and city level.

Here, the urban canopy model Town Energy Balance (TEB, Masson, 2000) is revised with the implementation of a new green façade module informed with micrometeorological and ecophysiological observations collected on an experimental green façade site located in Berlin, Germany (Hölscher et al, 2016). The first step is the improvement of short- and long-wave radiative exchanges in TEB by considering an additional vegetation layer fixed to the wall. We now take into account the processes of interception of radiation by the vegetated layer, of transmission through it (depending of leaf density), and of absorption, as well as the inter-reflections within the canyon including new contributions from green façade.

First results show that the model is able to represent the effect of the vegetation foliage and its evolution on the radiative balance. This constitutes the first step in achieving the fully integrated modelling of the impact of green façades on the urban climate in TEB.

 

Reference :

Hölscher, M.-T., Nehls, T., Jänicke, B. and Wessolek, G., 2016. Quantifying cooling effects of facade greening: Shading, transpiration and insulation. Energy and Buildings, 114: 283–290.

Masson, V., 2000. A physically-based scheme for the urban energy budget in atmospheric models. Boundary-Layer Meteorology 94: 357–397.