A whole house fan works best in a very specific time of the day. Ideally, one would use it during the very coolest portion. This way, the whole house fan drags in the coolest air possible to cool the home.
Most figure that the best time period to turn the fan on is during the night. That is not only normally the coolest part of the day but also when coolness usually lasts the longest. The simplicity of a whole house fan also contributes to turning these machines on at night when someone is more likely to pay less attention to it.
Home Guides has a very simple guide to using these cooling systems:
“1) Open windows in your house when operating the whole-house fan to avoid creating concentrated suction in any one spot
2) Close any fireplace dampers before turning on the fan to avoid pulling soot into a room.
3) Turn on the whole-house fan when the air outdoors is cool and dry, particularly during the evening hours when temperatures have cooled. Turn off the fan during the day when temperatures outside rise higher than in the house.
4) Turn on the fan and open the windows during a hot day if maintaining an inside temperature about the same as the outside temperature is acceptable. The moving air helps make people inside feel more comfortable and uses less energy than an air conditioner.
5) Fully open the windows in any particular rooms you wish to cool, closing windows in other rooms. This helps increase the air movement where you need it most.
6) Use optional timers and thermostats only to turn off the fan. Do not use the controls to automatically switch on the fan as it is essential that you open windows and close the fireplace damper before operating the fan.”
Six steps may seem excessive but it details just how easy a whole house fan is and why most use them at night. Now, some ask what is the optimal time for a fan to be on. There is no simple answer for this question as it is so dependent on the environment and desired temperature of the home.
Running the fan throughout the night may not be a terrible idea if it will stay cold the entire night but if someone wakes up later than normal or if the heat picks up before waking up then it may be counterproductive to blast it all night long.
So, the optimal amount of time to use your whole house fan is exactly how long it will stay at its coldest. Whether that lasts for two hours or eight hours, it does not matter as long as it is as cool outside as one would want inside. That way, someone can even run it during hours that are not exactly the coldest because that may not be what they want their home to feel like.
Running a whole house fan, no matter the time period, is the smartest to use during the hours that outside is equal to the temperature someone would want in their home.