Quantification of ZERAF impacts on operational energy use of buildings

This report presents the results of the quantification of potential operational energy savings achieved by the ZERAF adaptive opaque façade technology through building-level energy simulations. This study evaluates the technology's impact compared to established benchmark façades across diverse European conditions, providing preliminary, non-validated results.

The assessment employed dynamic building energy simulations using three representative building archetypes (Single-Family House - SFH, Multi-Family House - MFH, and Office) derived from the IWG5 project. These models were simulated across six distinct European climates (Stockholm, Berlin, Bolzano, Milan, Athens, Madrid). ZERAF's performance was systematically compared against three passive envelope standards (Typical, Compliant, Gold) and two advanced passive façade concepts (Ventilated Façade variants and the INFINITE façade). Key metrics analyzed include annual heating, cooling, and total energy demand intensities (kWh/m²·year), supplemented by detailed hourly analysis of thermal performance during typical summer and winter weeks.

The simulation findings indicate that the ZERAF system consistently achieves the lowest total annual energy demand intensity across all climates for the SFH and MFH typologies, significantly outperforming even the highly insulated passive Gold standard. Reductions relative to the Typical baseline ranged from 82% to 93%, while savings compared to the Gold standard were particularly substantial in warmer climates (up to 66% further reduction in Athens) and still notable in colder climates (up to 39% further reduction in Bolzano). Crucially, unlike passive ventilated façades, which reduce cooling loads at the expense of increased heating demand, ZERAF demonstrated the ability to reduce both heating and cooling demands compared to the Gold standard, highlighting the benefit of active, adaptive control. In the Office archetype, where ZERAF was applied to a limited façade area, performance improvements over Gold were less pronounced but still consistently observed across all climates.

Detailed weekly analyses confirmed the synergistic operation of ZERAF's components. In summer, the combined action of KC (shading/ventilation) and ActIns (nighttime heat dissipation) led to lower indoor temperatures, reduced cooling peaks, and significantly lower cooling energy consumption compared to baseline conditions or the individual components operating alone. In winter, ZERAF effectively reduced heat loss through closed-loop active insulation (ActIns) and passive solar gain utilization (enabled by KC and ActIns), resulting in reduced heating demand and more stable indoor temperatures.

While these results strongly suggest significant energy-saving potential, they are preliminary and based on simulations. Key future work includes the experimental calibration of the specific KC and ActIns component models against laboratory data to increase confidence in their simulated behavior. Furthermore, optimization of the integrated control strategy is necessary, as analysis revealed specific conditions where performance could potentially be improved. Broadening the analysis to include realistic HVAC system interactions, optimizing ZERAF system control strategy, varying building thermal mass, diverse occupant behavior profiles, and performance under future climate scenarios will provide a more comprehensive assessment.

In conclusion, this simulation study provides compelling, albeit non-validated, evidence that the ZERAF active façade technology offers substantial potential for reducing building operational energy consumption across Europe, significantly surpassing the performance of both standard and advanced passive envelope solutions through its adaptive capabilities.