Upper Bunk or Lower Bunk, Which Will You Choose? How Bed Position Shapes University Students’ Physiological and Psychological Well-Being in China

University dormitories, as crucial living spaces for students, significantly influence their physical and mental health based on the quality of spatial design. However, whether the use of an upper bunk (UB) or lower bunk (LB) induces differential physiological and psychological effects remains unclear. This study aimed to measure participants’ physiological and psychological responses in UB and LB environments to explore the differential impact of bunk bed positions on student comfort. A crossover experiment was conducted with 28 participants (14 male, 14 female). Dormitory scenes were recreated using point cloud scanning and virtual reality technology, and a crossover experimental design was implemented. Physiological and psychological responses during the use of UB and LB spaces were measured via heart rate variability (HRV), electroencephalography (EEG), and the Profile of Mood States (POMS). Key findings indicated that the UB space promoted a state of deeper relaxation, evidenced by significantly higher Delta activity (p = 0.039) and lower heart rate (p = 0.042) compared to the LB. Psychologically, participants reported significantly higher vitality (Vigor, p = 0.032) and lower total mood disturbance (TMD, p = 0.038) in the UB. Conversely, the LB environment tended to trigger neural alertness, with significantly elevated High Beta waves (p = 0.009). Furthermore, gender significantly moderated emotional responses, particularly for Vigor (p = 0.045). Overall, from the perspective of promoting physical and mental health, the UB space provided greater comfort than the LB. These findings offer empirical evidence to inform the optimization of dormitory spatial design.