The study investigated the influence of a green wall and its size on stress and restoration within the biophilic design integrating natural objects into environments. Despite its benefits in enhancing access to nature and stress reduction, visual stimuli properties may affect design outcomes. This research employed Immersive Virtual Environments (IVEs) combined with a climate chamber for thermally controlled conditions, where sixty participants experienced different virtual settings with and without green walls after performing a stressor task. The evaluation of stress involved recording physiological responses, including heart rate (HR), heart rate variability (HRV), and electrodermal activity (EDA) along with eye movements. Participants also completed a restoration state survey. Comparing physiological responses found no significant stress recovery in settings with green walls compared to baseline. Stress recovery was similar regardless of green wall size, indicating size may not affect stress. Restoration votes did not vary significantly across settings. These results were discussed focusing on the perceived lack of “naturalness” and “engagement” in virtual environments, as fixation time analysis indicated limited engagement: participants spent 18.63 % and 19.65 % of their time fixated on the green wall in small and large settings, respectively. The authors suggest design solutions to enhance the realism and engagement of virtual natural objects. Although this study did not find the impact of size, the minimum size of natural objects required for restoration is still unknown, suggesting a need for future research on different natural coverages to develop design guidelines for the successful integration of biophilic design into the built environments.
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