Fans Only Work When You're Sweaty

An article published in Wired this past week (http://www.wired.com/2015/08/fans-dont-always-make-things-cooler/) explored the myths and reality of cooling off with a fan.  The researchers performed several tests that demonstrated how running fans on a warm day could actually be counter-productive.

The problem arises around the fact that fans are electrical devices, and that in order for those devices to work, they need to be fed with energy. Running a fan on low will consume a little bit of energy; running it on high will consume more energy.  With all of the electricity flowing through the fan, the wires and motors will heat up.  If you've ever touched the backside of the fan running on full-blast, you've surely noticed that it can get quite warm.

As air passes over and around the motor before being shot out the front, it will heat up.  In the test performed by the researchers that simulated an extreme example of a closed room, whereby the fan was placed inside a styrofoam box, the temperature inside the box heated up at a very steady rate of two degrees (Fahrenheit) a minute.  Imagine then having this inside a bedroom.  If there is no window or other source of cooler air, the air inside the room will continue to pass over the heated motor and the temperature will continue to rise.  Perhaps this is why waking up after running a fan all night, you sometime feel like you're in a sauna.

The one variable that can alter this behavior however, is sweat.  Sweat, being the body's natural air conditioning system, will actually lower body temperature as they evaporate.  Enter the fan.

While running a fan has been shown to heat air to a higher temperature, particularly in a closed room, standing in front of a fan will cool you off.  The air rushing over the beads of sweat will cause them to evaporate quicker, which in turn will cool you off quicker.  So fans definitely do have their place in the hot summer months.  Just remember though, if you're not sweating, running the fan may be working against you; unless of course your goal is to raise the temperature of the room to the point that you are sweating, in which case, maybe you should save some money on your energy bill by ditching the fan and just opening a window.