Heat stress and thermal discomfort in construction: Implications for occupational safety and regulation

Heat stress (HS) significantly affects outdoor construction workers, increasing health, safety, and productivity risks, particularly in developing countries where the lack of formal regulations leads to unmanaged heat exposure and inadequate protective measures. Few studies have examined HS and thermal comfort (TC) at large spatial scales while considering variations across vertical positions on an hourly basis, leaving critical spatiotemporal patterns largely unaddressed. To fill these gaps, this study analyzes hourly meteorological data (2021–2024) and personal parameters during the summer months (April–May) across eight major urban cities in Bangladesh. HS, expressed as Physiological Equivalent Temperature (PET), and TC indices, including Predicted Mean Vote (PMV), Standard Effective Temperature (SET), and Predicted Percentage of Dissatisfied (PPD), were quantified for construction workers. Existing comfort-index methods were adapted for outdoor conditions by accounting for shortwave and longwave solar radiation, and the results were validated through stakeholder feedback. Meteorological parameters were stratified by occupational height to assess PET and PMV variations across the different levels at which construction workers perform their tasks, and spatial interpolation was employed to map national-scale distributions. Results indicate that In April, PET frequently exceeded 41 °C across most regions, with southern PMV values often surpassing 3.0, indicating extreme HS. Spatial analysis identified the southwest as the most vulnerable zone, where humidity exacerbated discomfort, whereas the northeast remained comparatively temperate. PET declined significantly with occupational height (R² = 0.95–0.99; slope = -0.023 to -0.029 °C/m), and PMV values were consistently higher at lower elevations (0–30 m), with the sharpest changes in some regions. Peak heat hours occurred between 11:00 and 17:00, which suggest that early morning or late afternoon work can reduce heat stress while maintaining productivity. Stakeholder feedback confirmed the framework's relevance for understanding HS distribution and mitigation strategies.