Impact of Window Orientation and Window-to-Wall Ratio on Thermal Comfort and Daylight Performance Within an Educational Building in Saudi Arabia

Abstract

In this study, thermal comfort parameters and illuminance (E) are investigated in four differently oriented workspaces at Najran University, using an R data logger and an Extech HD450 lux meter in accordance with international standards. The findings reveal that the effect of orientation on indoor temperature is limited. Class (1), oriented northwest/northeast, consistently showed the highest temperatures when cooling was off. Meanwhile, the northeast-oriented office, which had a smaller WWR, maintained lower temperatures in the afternoon. The Predicted Mean Vote (PMV) comfort band was achieved only in the labor workspace and office at 13:00 and 15:00, and at 15:00 in Classes (1) and (2). Predicted Percentage of Dissatisfied (PPD) values were mostly below 10% at 13:00 and 15:00, meeting standards, but often exceeded 10% in Classes (1) and (2). The south-facing classroom received more daylight than the north-facing one, highlighting how orientation affects illuminance, despite both classrooms being identical in area, window-to-wall ratio (WWR), and window-to-floor ratio (WFR). Correlation analyses revealed the following: the WFR and mean general temperature (Ta) were strongly correlated (0.96), whereas the WFR and mean relative humidity (RH) were moderately correlated (0.59). WFR or WWR versus (Ta) had an R2 of 0.93 (p = 0.03), whereas RH had an R2 of 0.35 (p = 0.4). WFR or WWR versus E showed an R2 of 0.92 (p = 0.03), indicating strong relationships in this small dataset. Overall, the findings indicate that architects should adopt orientation-specific concepts that carefully balance WWR and glazing specifications, emphasizing the importance of field-validated evidence for façade optimization.