Heat-mitigation effects of protective sheets in the construction industry for the prevention of heat stress disorders.

PURPOSE: This study experimentally investigated whether highly heat-shielding protective sheets used at construction sites could reduce heat stress. METHODS: A construction-site simulation apparatus was installed in an artificial climate chamber, and direct solar radiation was simulated using infrared heating. Tempered glass partitions allowed the installation of different sheet materials. Wet bulb globe temperature (WBGT), air temperature (Ta), globe temperature (Tg), and relative humidity (RH) were continuously measured on both the indoor and outdoor sides. Three environmental conditions were tested: Ta 30°C, 75% RH, Ta 35°C, 60% RH, and Ta 40°C, 35% RH. Four sheet conditions were evaluated: No-sheet, Brown-sheet, Aluminum-sheet, and Lace sheet. Data collected during the steady-state period (60-120 min) were used for comparison. RESULTS: WBGT was significantly lower under all sheet-installed conditions than under No-sheet condition across all environmental settings. Under Ta 30°C, 75% RH and Ta 35°C, 60% RH environments, Ta and Tg were also significantly lower with sheet installation, suggesting that the sheets reduced radiant heat by blocking infrared radiation. In contrast, under the extremely hot condition of Ta 40°C, 35% RH, no significant differences in Ta or Tg were observed according to sheet installation. Because sheet installation was associated with increased RH, additional measures such as appropriate ventilation may further enhance heat-stress reduction. CONCLUSIONS: Protective sheets may reduce heat stress by attenuating radiant heat under moderately hot conditions, but their heat-shielding effect appears limited under extremely hot conditions. Additional measures, such as appropriate ventilation, may further enhance heat-stress reduction.