Improvement of a Window Curtain with Thin Phase Change Materials to Promote Solar-Induced Ventilation in a Tropical Climate

Combining phase change materials (PCM) with a solar chimney is a natural ventilation strategy that extends ventilation duration and reduces energy use linked to global warming. However, its integration with thin fabric window curtains remains understudied compared with building envelope components such as walls or roofs. This study evaluated the thermal performance of a curtain-type PCM solar chimney with PCM thicknesses of 0.001 to 0.004 m and varying collector absorptance, using EnergyPlus simulations across 1533 hourly observations under tropical conditions. An autoregressive model, informed by sensitivity analysis, explained 59.3% of airflow variance (adjusted R2 = 0.593, p < 0.001), with no significant residual autocorrelation. The collector-to-room temperature differential was the strongest predictor (10.91 m3/h per 1 °C). A significant PCM–absorptance interaction showed that thin PCM (0.001 m) responds rapidly to solar gain, whereas thick PCM (0.004 m) sustains evening ventilation through latent heat storage. The optimal configuration, consisting of 0.004 m PCM with 0.95 absorptance, increased airflow by 23% and extended ventilation beyond 20 h/day, while low-to-medium absorptance combined with thin PCM maintained 38.4–55.6 m3/h for up to 23 h/day. These findings support a flexible, climate-responsive strategy for sustainable passive cooling in tropical buildings.