What are the differences between the standard whole house fan and a multi-room whole house fan? Which system makes more sense for my house? Is there a huge cost difference between the two? How many windows do I need to open for the whole house fan to work efficiently? Are whole house fans wort the money? After going thru many website learning about the fans, this is what I came up with.
The main difference between a standard and the multi-room whole house fan is that standard whole house fan has only one register in the middle of the house that connects to a single fan. The multi-room whole house fan also has one fan but it branches out to multiple registers spread out throughout the house with a ductwork. Having multiple registers in different rooms cools down the house equally even with only one open window.
As the weather all across the United States warms up, homeowners everywhere start thinking about the best way to keep cool while also keeping their electric bill as low as possible. Sure, electric fans are great, to a point, but if you live somewhere the mercury really climbs high you’ll need something more powerful to keep you from feeling like a roasting chicken. Most homeowners would likely switch to their AC unit or an in-window AC unit but, in many cases, a whole house fan will do the trick and keep the electric bill lower too.
In this article, What Are the Differences Between a Multi-Room Whole House Fan and a Standard Whole House Fan, we’ll take a closer look at both types of whole house fans to determine what the features and benefits of both happen to be, and any negative aspects they might have. When we’re done, you’ll have a better idea about how both systems function and be able to make an informed decision on which to purchase for your home.
What Exactly is a Whole House Fan?
Like a regular standing fan or box fan, a whole house fan is a cooling system for your home. However, unlike those types of fans, a whole house fan is more like your AC system in that it uses a ventilation and duct system to bring cool air from outside to the entire house. Whole house fans are energy efficient, relatively quiet and have been used in the United States since the 1960s, although oftentimes without the help of the ventilation system.
How Do Whole House Fans Keep Your Home Cool?
Basically speaking, a whole house fan works by pulling cooler air from outside of your home into your home via the ductwork of your home’s ventilation system. When it’s working, the whole house fan also creates active cross breezes with any windows or screened-in doors that are open.
The best time of day to run a whole house fan is usually at night or in the morning when the air outside is cooler. To get started, all a homeowner needs to do is open a few windows and turn on the whole house fan, which is usually located in the attic. If sized correctly, a whole house fan is incredibly fast and efficient and can exchange the hot air in an entire 3 bedroom home for cooler air in about 4 minutes!
Even better, a whole house fan causes something called ‘thermal mass cooling’ if left on for a few hours. That means it cools down the inside of the house itself, not just the air, so that your home stays cooler the next day. The fact is, with a whole house fan your entire home will stay fresher and cooler while keeping your electric bill lower.
What Can Be Done to Make a Whole House Fan Even More Efficient?
With a whole house fan, you could open all the windows in your home and it would still work well, but if you only open a few select windows, and only open them about 5 or 6 inches, the cooling cross-breeze will be much more potent. Also, opening one window per room, the one that is furthest away from the air intake, will increase the breeze even more.
To cool down your entire house even further using thermal mass cooling (as we talked about above) the whole house fan should be left on for a few hours at night. What that does is actually cool down the house and everything inside, like sofas, walls, beds and, well, everything. Then, in the early morning, the whole house fan can be turned off, the windows closed and the drapes drawn so that the sun doesn’t heat the house up as quickly and it stays cool throughout the day.
What is a Single-Room Standard Whole House Fan?
Typically installed in the hallway of a house, a standard whole house fan has one register where hot air is pulled up into the attic and out of the house. The fan itself is still in the attic but the register is located in the hallway or a corridor (as mentioned). Single-room whole house fans only have 1 duct that connects the single register to the fan.
The register is simply a grille that has moving parts so that it can be opened and/or closed. Also, the slats in the grille can be positioned so that airflow can be made to go in a specific direction.
With a single-room whole house fan, you would need to open the windows in every room of the house and also the doors leading into those rooms so that the fan could suck out the hot ar from every room. (See diagram above)
Single-Room Whole House Fan PROs
- Energy-efficient cooling for the entire house
- Lowers energy bills
- Less expensive than running the AC
- Slightly less expensive than multi-room systems (less ductwork and registers)
Single-Room Whole House Fan CONs
- Multiple doors and windows must be opened to function best
- Bedroom doors must remain open
What is a Multi-Room Whole House Fan?
Similar to a single-room whole house fan a multi-room whole house fan sucks the hot air out of your home and brings in cooler, outside air. The big difference between the two systems is that, instead of 1 register and 1 duct that the single-room fan offers, the multi-room system has several registers in several rooms and ductwork that connects all of them to the fan, which is located in the attic like the single-room system.
To work correctly, each register of the multi-room system has what’s called a ‘branch duct’ and they come together via a wye fitting, which is an adaptor that allows different tubes, ducts and so forth to be connected together.
The biggest benefit of having a multi-room whole house fan over a single-room system is that, only 1 door or window needs to be opened and all of the connected rooms will then be cooled down. (See diagram above) The big benefit here is that, if someone in the house wanted to cool their room but not open any windows and keep their door closed, they could, unlike with a single-room system. For more information on how to build a multi-room whole house fan click here.
A multi-room whole house fan also has what’s known as a backdraft damper, which is located right next to the fan. The backdraft damper allows warm air to leave the house but doesn’t let hot attic air enter back into the house when the whole house fan isn’t being used.
Multi-Room Whole House Fan PROs
- Energy-efficient cooling for the entire house
- Lowers energy bills
- Less expensive than running the AC
- Only 1 door or window needs to be opened
- Bedroom doors can stay closed if needed
- May eliminate the need for AC completely
Multi-Room Whole House Fan CONs
- Slightly more expensive than single-room systems (more ductwork and registers)
How Much Cheaper is it to Run a Whole House Fan Over and Air Conditioner?
Depending on where you live the biggest benefit of either a single-room or multi-room whole house fan is that it can lower your electricity usage substantially. A whole house fan is much cheaper to run than using your home’s HVAC AC unit or even a single window AC unit. How much cheaper? Experts agree that using a whole house fan can reduce your energy bills by as much as 80%, which is a huge amount of savings. The average AC unit uses about 3000 watts an hour and a whole house fan uses about 500 watts an hour.
Plus, whole-house fans are ‘greener’ than using your AC unit, quieter, remove stale air from your home and, depending on the time of year, can fill your home with fresh, cool air in a very short amount of time. The newest models of whole-house fans are even more energy-efficient and greener than older models because they take advantage of the latest technology.
Both a standard and a multi-room whole house fan can lower your energy bills, keep your home fresh and cool for a fraction of the price of your AC unit, and are ecologically greener. The biggest difference between the two systems is that the multi-room system can be operated when only 1 window or door is open, allowing for more privacy for anyone who wants to keep their door closed when the system is working.
2 thoughts on “What Are the Differences Between a Multi-Room Whole House Fan and a Standard Whole House Fan?”
Thanks for the info on the 2 different types of Whole House Fans. I’m trying to determine my ROI & more importantly will it work in my geo?
I have a small 785 sqft 1942 Bungalow 2 bedrooms 1 bath. During the major renovations I knocked out wall dividing kitchen & living rm which take up 60% w 2 bedrooms divided by bath w small hall connecting then 40% of the sqft. I removed the costume HVAC that used natural gas for heat replacing w 3 zone mini split system. I chose the ceiling cassettes, cost tad bit more but much sleeker for small rooms. The mini split system & all required materials except electric wire which I had cost approx $3500 including delivery. My son helped me with the install, too heavy for me, & I did ask the wiring & running the lines. Prior to releasing the freon I had HVAC tech come out to make sure everything worked, vacuum tested, & removed any moisture. He reflanged my lines, appears I did them like a brake line. That cost $500. An entire heating/ coming system for only $4k vs $12k for me HVAC that was only rated 80% efficient & used natural gas $$$$$ for heat.
* I do not have any insulation in my walls, except 2 that I tore down to studs, crawl space is not sealed or insulated & attic needs insulation added
** All windows were replaced in Jan 2020. Only my east windows receiving morning sun. The south & west facing windows r dummy protected from summer sun
I keep my air set 75-76° when the humidity & temp get really high I drop it down to 74
Jul 2020 1900 kwh HVAC
Jul 2021 900 kwh window units
Jul 2022 605 kwh mini split- this was an EXTREME summer!! Day highs 103-112° F with night time lows never dropping below 84°. The first week of May we experienced temps above 100 (I don’t want to talk about my garden). Finally 2nd week of Sept night temps r dropping down to low 68-74°, next week will heat up again. Forecast tells us to prepare for another hot spring & summer 1-2° warmer than this yr.
So if these extremes are the new “normal” air conditioning starts in April & runs into Oct which is extremely hard for me who needs windows open, even in my drafty house it’s like I can’t breath.
Then u add the humidity here, why >60 days w no rain then the rain we got wasn’t measurable but still have humidity >90%. With the TMI I just put u through, b do you believe a Whole House Fan would work for me? I’ve been trying to find a tool/ formula to determine my ROI. I’m extremely cautious of my energy use, when I’m not using heat or air I use 70% I’ve only teddy l lowered my bill by 21%! I was really hoping for more cash in pocket than that.
Best of luck everyone & stay
No matter what, it will save you a lot of money on electricity.
Better than using a high efficiency HVAC is using ZERO HVAC.
Some modern whole house systems are very inexpensive (I got mine on amazon for $300l and it came in a kit with absolutely everything needed. It was a super easy DYI project that took me less than one hour to complete.
The ROI was less than one year, considering energy costs in Los Angeles.
I literally didn’t use the A/C for the whole spring and 1/3 of the summer That’s FOUR MONTHS not turning the ac on at all and dropping my A/C use to an average 2 months per year.
Of course, WHF relies on external air quality, so there will always be one or other day that you cannot use it simply because the outside air is too polluted with smoke, etc. But that is VERY rare, even being in bushfireland.
Other thing I noticed is how I also helps A LOT in the winter. Of course, nobody wants to throw away air that costed.money to be heated, but often, you feel the air quality inside home is getting poor, simply because the air is stale and being constantly “recycled” by the furnace. Anyway, it reaches a point you don’t feel comfortable anymore. You simply run the WHF for about 3 minutes, of course you will lose hot air and your furnace will need to recover that, but the gain in comfort and air quality is impressive, you can feel the difference very quick.
Other thing that WHF are wonderful is dealing with smells. Even if you have the very best range hood ever made, if you make bacon or fry fish, you will definitely notice all over the house. Guess where I put one of the the registers (the other is on the hallway). Together, hood and WHF creates a huge negative pressure in the kitchen, so even with the door open, I have the air from the whole house pushing towards the kitchen and it works beautifully to remove smells before they can spread.