Whole house fans are used to cool a house by replacing the hot air inside with the cool air from outside. They are easy to use and their proper use will reduce your energy bills considerably.
This article is a comprehensive guide on how to use a whole house fan.
How to use a whole house fan – Steps
Time needed: 5 minutes.
Before using a whole house fan make sure that the temperature outside is lower than the temperature inside the house. Since whole-house fans cool the house by replacing it with outside air, they are effective only if the outside air is cooler. The best times to operate a whole house fan are the early mornings, evenings, and nights.
Make sure your air conditioner is switched off
Whole house fans suck the air out of your house. So if your air conditioner is switched on, the fan will remove that cool air from the house, which is counterproductive. So you cannot have an air conditioner and a whole house fan working together. Before switching on your whole house fan make sure that the air conditioner is switched off.
Open a few windows
As mentioned above, whole house fans draw air from the outside. And this air is drawn through the windows. So it is important to open a few windows before starting the fan. Since these fans are very powerful, running them with closed windows will create a negative pressure inside the house and this can also affect the working of furnaces and HVAC appliances.
Close fireplace dampers
If you have a fireplace, you know that it is full of ashes and soot. As whole house fans create a negative pressure inside the house which is enough to draw outside air, it is very likely that this soot and ashes will be blown throughout the house unless the fireplace dampers are closed.
Close the attic stair if you have one
Whole house fans push the hot air into the attic. If the attic stair is kept open, this air will be recirculated into the house instead of being removed to the outside through the attic vents. This is counterproductive and it hugely affects the efficiency of the whole process. So the attic stairs must be insulated and closed before starting a whole house fan.
Turn ON the whole house fan
Flip the switch and run the whole house fan at its highest speed for around half an hour. Once the home is cool enough you can change the speed to a lower setting to reduce the fan’s energy consumption.
Turn OFF the fan when it gets hot outside
The worst thing you can do with a whole house fan is to run it when the outside temperature is higher than that is inside the house. This will bring hot air from the outside and make the house hotter. Whole house fans should be switched off when it is getting hot, preferably just after the mornings. The best thing to cool a house in this situation is to use your air conditioner.
How many windows should I open?
Opening two or three windows is more than adequate to run a whole house fan in most cases. But this depends on the square foot area of your house. The larger the house, the more will be the CFM of the fan, and may be you need to open more windows. There is no clear guidelines on how many windows need to be open as this is usually found out by trial and error. Opening too many windows will spread out the air circulation and hence that is not recommended. Opening just enough windows will create a cool breeze throughout the house, and this is the most recommended setting. So do some trial and error and find out how many windows you want to keep opened.
Also opening the windows opposite to the sun, and those which are far away from the location of the fan will help to draw cooler air and to circulate it through more areas of the house.
How long should I run a whole house fan?
This depends on your personal preference. It is okay to run a whole house fan as long as the outside temperature is cooler than that inside. Many companies recommend them running throughout the night to keep the house consistently cool so in the morning the air conditioner will have an easy job keeping the house cool.
What is the best time to run a whole house fan?
As mentioned above whole house fans can be run whenever the outside temperature is lower than that is inside. Usually evenings, nights and early mornings are most suitable times to run a whole house fan but this depends on the location you live.
How to run a whole house fan in a two-story house?
Running a whole house fan in a two-story house is the same as running one in a one-story house. The steps are exactly the same however in this case you need to open a window on the top floor as well. The air will also come through the windows on the ground floor blowing through the stairs into the first floor and into the attic. You can limit this circulation by opening more windows on the first floor. Also in a two-story house, the ground floor will remain relatively cooler, it is the upper floor that usually needs cooling. In most cases, the whole house fans will be installed above the stairs. Therefore, proper cooling of the first floor is possible only if windows on that floor are open.
What speed settings should I use?
Some whole house fans come with multiple speed settings. You cn use whichever speed setting you feel is right for you. However, I reccommend starting the fan at its highest speed to quickly cool the house, and then switching to a lower speed to save energy.