Recommendations When Using Your House Fan

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Whole house fans are an interactive system. The controls are manually operated so that you control when it comes on and you will have to actively open the appropriate windows for the rooms wish to be cooled or vented. It may take several days of use before you learn the most effective ways to cool and vent rooms in your home. You might even find experimenting rather fun as you discover different effects of air moving into and through your house.

These house fans are powerful and want to move a lot of air.  You must have windows open when they are in use. In fact you must have enough window (or screened door) open so that the fan can pull as much air as it needs to.  Otherwise it will pull air from places you do not want it coming from.  Like your wood stove, chimney, or water heater flue.  This can cause smokey smelling or hazardous air to be drawn into your home or shut down your heating appliance all together, known as “back drafting”.  Your boiler, furnace or water heater will likely have a safety shutoff if it begins to back draft and will shut down on its own. This occurrence is not uncommon for new users of whole house fans that have not read this advice.  It is a good thing if it shuts down, does not cause any damage and it is easy to restart by switching the “Reset” switch.  This process is slightly different for most manufacture’s appliances but it is usually quite simple and you should not need to call a service person.  If this has happened, try to take note of what speed setting your fan was at and how many windows were open during that period. Try to make sure the house fan has more open windows or “free air” space is available to keep it from wanting to pull air from your heating appliance flue.

Avoid Back Drafting

Back-drafting is easy to avoid. First, when it is time to use your fans for the first time of the year, make sure all the dampers on your wood stove or fireplace chimneys are closed. Second, make sure you have enough intake air ventilation space by having the appropriate number of windows open enough.  Generally speaking you want at least 3- 4 inches of open window space for every 1000 CFM of fan  you are operating.

For examples:

Smaller Fans

If you have a smaller fan like a QC -1500  in each bedroom to keep them cool. You should have at least one window open 4 inches or so in the bedroom with the door closed. Of course if the door was open and there was a window open in the kitchen too, you would have more than enough open but you would diminish the cooling  for the bedroom.  This is because some air would be pulled through each window.  Generally I like to get the bedroom as cool as possible but some nights it may be too cool for that, so I’ll open a window in the bedroom and another in another part of the house just to have fresh air coming in but reducing the the cooling effect in the bedroom.

Larger Fans

On the other hand, if you have a larger fan like a QC-4700. You should have at least 4 or 5 windows open in the house when it is operating at full speed.  Opening one door with a screen on it at the opposite side of the house than the fan works well too.  If you come home to a hot stuffy house, it is nice to open a few windows around the house, run the fan a full speed for a while to freshen up the house.  Then later close a few windows in rooms your not going to be spending time in so you can have the nicest cooling breeze in the space you are currently using.  Maybe turn the speed down to low if it’s a bit too much.

Here is another video that shows a simple demonstration of how opening and closing windows can make changes to how air moves through a room. click here

For Hotter Days/Nights

On the hottest days and nights. Run your fans all night. If you know it’s going to be hot the next day, close up all the windows by 9 AM.  This cools the entire home structure all night, then keeps the cool air in as long as possible. The exterior of you house will bake and begin to heat up during the day.  The insulation in your home will slow this heat from getting in but eventually it will start heating up inside too. Getting your house as cool as it can get at night will help it stay cooler longer into the day. This is a good time for just an attic fan which exchanges fresh air only in the attic.  It may be 80 plus degree air but it is better than the 150+ degree air that is building up from the sun heated roof. If you are home during the day, this can be a good time for floor and ceiling fans to blow air around you to keep you comfortable.

Watch the temperature later in the day, after thunderstorms or after a cold front comes through. Once it is as cool or cooler outside than it is inside, open some windows, flip the switch on your fans and start feeling that new air moving through your house!  It is so nice!

Home Is Exposed To Sun

If your home is exposed to the sun, the shaded sides of your house will have the cooler air. So in the morning you may want to close the windows on the east side of your home if the sun is heating that side.  The sun can heat up the siding of your house quickly and that heat can radiate into the air near your windows. So you should close up the east side windows, but you will notice the shady side of you house will still hold some nice cool air from the night before and you can keep those windows open longer.  Same goes for the evening, as the sun starts to set, the west side of your house, which has  already been pre-heated by the hot mid day air, will really start to bake as the sun goes down.  The east side however will likely be in the shade for several hours before the sun fully sets, and the air on the side of the home will be much cooler. You can open those windows and turn on your fan earlier in the evening.

Outside Smoke and Grills

Since the fans pull in air from outside, be aware of your outdoor cooking grills or outdoor fires while your fans are in use.  If your grill is near a screen door or window, your fan will pull that cooking heat, smoke and smell into the house. Same goes for smokey outdoor fires you may be having.  You will know quickly when your are bringing this smelly air into your house, and it will exhaust out quickly once you close the doors or windows near the grill/fire. Just be aware that this can happen and try to avoid it before it does.


Go ahead and experiment with your fans and windows.  Try different adjustments different times of day.  It won’t take long to figure out just how you like it.

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