Application of Gagge’s Energy Balance Model to Determine Humidity-Dependent Temperature Thresholds for Healthy Adults Using Electric Fans During Heatwaves

Author(s): Tartarini, Federico; Schiavon, Stefano; Jay, Ollie; Arens, Edward; Huizenga, Charlie | Abstract: Heatwaves are one of the most dangerous natural hazards causing more than 166,000deaths from 1998–2017. Their frequency is increasing, and they are becoming moreintense.nElectric fans are an efficient, and sustainable solution to cool people. They are, fornmost applications, the cheapest cooling technology available. However, many nationaland international health guidelines actively advise people not to use them when indoorair temperatures exceed the skin temperature, approximately 35◦C.nWe used a human energy balance model, to verify the validity of thoserecommendations and to determine under which environmental (air temperature,relative humidity, air speed and mean radiant temperature) and personal (metabolicrate, clothing) conditions the use of fans would be beneficial.nWe found that current guidelines are too restrictive. Electric fans can be used safelyneven if the indoor dry-bulb temperature exceeds 35◦C since they significantly increasethe amount of sweat that evaporates from the skin. The use of elevated air speedsn(0.8m/s) increases the critical operative temperature at which heat strain is expected tonoccur by an average of 1.4◦C for relative humidity values above 22%. We alsonanalysed the most extreme weather events from 1990 to 2014 recorded in the 115nmost populous cities worldwide, and we determined that in 103 of them the use of fansnwould have been beneficial.nWe developed a free, open-source, and easy-to-use online tool to help researchers,nbuilding practitioners, and policymakers better understand under which conditionsnelectric fans can be safely used to cool people.