“Green Walls” Modelling

Vegetation on a building’s wall or roof modifies both the heat flux through the wall and the microclimate of its surroundings. This can result in a change in the energy demand for heating/cooling. A quantitative analysis of this phenomenon requires the use of a model that accounts for a range of phenomena such as radiation (solar and thermal) and energy processes within the plant. Vegetation also affects convection near the wall.

A simulation model representing the above phenomena was developed in the TRNSYS simulation environment and subsequently subjected to parametric sensitivity analysis (annual simulation with a time step of minutes) and experimental verification. The result is a tool enabling the assessment of the energy and economic efficiency of using climbing greenery on a wall as a factor improving a building’s energy balance. The analyses conducted take into account the climatic factor over the annual cycle and the associated growth cycle of selected plant species. Extended research covers the impact of green facades on the urban heat island effect and proposals for engineering solutions.

Research on the use of greenery in construction is co-funded by the European Commission under the FP7 research project CommONEnergy (FP7-2013-NMP-ENV-EeB-608678).

The figure below illustrates the effect of a green facade on reducing heat transfer through a wall, depending on geographical location. These results were obtained using TRNSYS software with the green facade module developed by CIM-mes.