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Effective Cooling Strategies with Only a Fan
1. Where to Place Your Fan for the Coolest Room?
Cooling Hacks for Fan-Only Spaces.
On the Hacker News forum, someone curiously asked: if the room temperature is 30°C and the outside temperature is around 20°C, is it better to position the fan inward or outward? Grasping the essence of the question and recognizing the urgency of the answer, Quartz journalists sought the truth.
A meme from a decade ago: 'He must be famous, with so many 'fans' like that.'
Optimal Fan Placement: Inward or Outward?
Fans circulate air in a specific direction, pulling air from behind and pushing it forward. According to Persily, fans can reduce room temperature by eliminating heat. However, this cooling effect only occurs if the hot room is connected to a space with a lower temperature. By drawing hot air from inside the room, low air pressure will pull in air from anywhere; assuming the outside temperature is lower than the room temperature, cool air will flow into the room. However, most of the air the fan takes will come from the adjacent room (as the fan sucks air with its motor, it doesn't care much about air pressure).
Additionally, since fans are electric devices, they generate heat when operating. If the power source for the fan is inside the room (electric or plugged in), it will slightly increase the room's temperature, although it's negligible and hard to notice.
In conclusion, in this case, the best way to cool the room is to open the door and position the fan inward. Cold air from outside entering the room will cool your overheated body, promoting higher heat dissipation speed.
Optimizing Your Fan in Hot Summer Days
Shifting the scenario a bit, in the current weather, rooms are as hot as the outdoors, making this the most relatable situation. In this case, the room temperature is likely to be lower than outside. Another assumption is that we want to keep body heat from getting too high, so the crucial point is still the direction the fan blows, which will help sweat evaporate quickly.
If there's wind outside, opening the door will bring in a fresh breeze and make you feel cooler. However, predicting the wind is unpredictable, and sometimes you might let cool air inside escape. One way to maintain a stable airflow is to combine both air conditioning and a fan: to bring cold air from room A - with air conditioning - to room B - hot, place the fan at the threshold between the two rooms and point it towards room B. This may sound obvious, but it's worth mentioning.
If there's no air conditioning, the best way is to close all doors and run the fan directly at yourself.
'A fan doesn't make the room cooler; it cools your body temperature through air circulation,' Persily says. And importantly, since they don't cool the room, never leave a fan running in a room and walk away to work elsewhere, as the heat from the fan motor will warm the room and consume electricity.
There's one more crucial factor in cooling: temperature isn't everything; sometimes you need a bit of air movement too.
