Assessing the energy performance of integrated living wall systems: a dynamic numerical model coupled with TRNSYS for building energy simulations

Integrating natural ecosystems into building envelopes significantly enhances energy performance and environmental sustainability, contributing positively to urban transformation and green transition. This paper presents a novel dynamic model of Living Walls (LWs) for integration into building facades, developed and implemented in the MATLAB® environment. To account for interactions with building fabrics, inputs and outputs were appropriately managed to enable seamless interfacing with TRNSYS®. This allows for carrying out dynamic energy evaluations of the whole building-plant system, considering both sensible and latent thermal exchanges occurring within LWs. Validation was performed against experimental data, specifically monitoring temperatures at two layers of the LW, the inner surface heat flux, and the growing medium water content. The Root Mean Square Error (RMSE) and the coefficient of determination (R2) values confirm an excellent agreement with the measured data over a five-day period characterized by variable climatic conditions. After validation, the model was used to evaluate the energy performance of a case study by varying the living wall orientation and the irrigation rate. Based on real climatic data, TRNSYS results indicated that the cooling energy savings relative to the baseline building with a bare wall, with an irrigation rate exceeding 0.0004 kg/s∙m−2 amount to 8 kWh/m2 and 6 kWh/m2 for south and east exposures, respectively. To minimize the negative impact of latent cooling in winter, irrigation was scheduled only during the summer season; therefore, the winter performance does not vary with the irrigation rate, and the heating energy savings achieved by adding the green layer equal 10 kWh/m2 and 6 kWh/m2 for south and east exposures, respectively. Finally, a sensitivity analysis was conducted to evaluate how vegetation parameters influence building energy performance. This paper proposes a dynamic numerical model coupled with TRNSYS simulations to address the limitations of conventional Building Energy Simulation (BES) tools, which currently lack robust methods for evaluating the impact of vertical greenery on building–plant energy performance.