Exposure to excessive heat increases the chance of heat stress and presents a risk to employee health. Heat stress occurs when the body is unable to maintain a safe body temperature due to external stress. Heat stress can lead to injury and illness. As temperatures increase, productivity decreases due to physiological limitations that lead to increased errors and fatigue. Unconditioned facilities in warm and temperate climates are particularly prone to these conditions. In order to mitigate the impact of heat stress and productivity loss, employers often compensate with increased break time and experience costly employee turnover. The combination of HVLS fans and evaporative coolers can be used as a cost-effective solution to reduce the number of uncomfortable hours in a facility and in turn reduce productivity loss; creating a safer work environment.
A 47,000 square foot unconditioned warehouse with a 28’ tall ceiling was used as a test facility. The warehouse was modeled in Atlanta, Georgia (ASHRAE 3A), Dallas, Texas (ASHRAE 2A) and Ontario, California (ASHRAE 3B). An energy model was built for each location to calculate the indoor dry bulb temperature and the indoor relative humidity for each hour of the year. The DOE Commercial Prototype Building Model for a warehouse was used as a reference for the energy model. The CBE Thermal Comfort Tool was used to calculate the cooling effect of HVLS fans alone, and the combination of HVLS and evaporative coolers, would deliver. The heat index was calculated for every hour for the existing conditions, with HVLS fans only, as well as with HVLS fans and evaporative coolers. The number of hours in each National Weather Service Heat Index Classification was summed to determine the reduction of uncomfortable hours. The model generated by Seppänen, O., Fisk, W. J. and Lei, Q. H. (2006) was used to determine productivity loss in the form of lost wages.