An innovative control strategy for Breathing Walls aimed at both heating and cooling energy savings

Breathing Wall technology, which is based on the thermal interaction between porous envelope layers and ventilation airflow, is a prominent Dynamic Insulation system for buildings due to its energy-saving potential and adaptability. Previous studies identify two working regimes: pro-flux and contra-flux, depending on heat flux and airflow directions. The efficacy of Breathing Wall technology during winter, using the contra-flux regime with inward flow, has been demonstrated. However, the effectiveness in dissipating heat during summer of the pro-flux regime, traditionally associated with outward airflow, has been tested only by few studies affected by some limitations. This work presents a numerical investigation of the effectiveness of Breathing Wall technology in reducing air conditioning energy needs throughout the year, focusing on defining a control strategy for highly variable outdoor summer conditions. A virtual case study of an office building in Milan (Italy) is analysed using TRNsys 18 in combination with a Matlab script, to compare the combination of Breathing Wall components and dedicated ventilation units to a reference building with a non-permeable envelope and a traditional ventilation system. Results show savings of up to 22% in winter and, due to the innovative control strategy, 14% ÷ 16% in summer. Over the entire year, the total electricity consumption for thermal use and ventilation is reduced by up to 18% compared to the reference case. This work also provides a deeper understanding of the underlying physics and a framework for adapting the control strategy to different contexts, increasing the flexibility of this technology and its adaptability to future climate conditions. • Winter and summer performance analysis of a building with Breathing Walls envelope. • Optimization of a control strategy to operate the Breathing Wall envelope in summer. • HVAC yearly electricity use 18% lower than in a reference building. • The airflow direction affects the pro and contra flux working regime effectiveness. • Improved understanding of dynamic interaction between Breathing Wall and buildings.