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BayArea says

“whole house fan”

They've been around for decades, called attic fans.

I have been wanting to install one. Did you DIY? By the way, attic fan are a different concept.

Instead of an AC or in addition to?

Waitup says

I have been wanting to install one. Did you DIY? By the way, attic fan are a different concept.

I installed one myself about 15 years ago. It's the best house upgrade ever in the 'vale, where the nights go down below 70 even in the middle of the summer.

The basic idea of operation (at least for me) is that in the evening when the outdoor temperature drops below the indoor temperature, I open a few windows located as far away from the fan as possible (install the fan in a strategic location). The fan pulls air in through the windows and pushes it into the attic. The outside cool air is thus run all the way from the open window(s) to the fan and cools everything in between. I run the fan occasionally up until I go to bed, hopefully getting the house down into the 60s before going to sleep. In the morning I close up all the windows to keep that cold air in the house during the day. With this system I often see 77 inside when the outside temperature is 97 at 3 PM, even with my poorly insulated house.

Obviously, if the temperature is 100+ outside the inside will rise to 90 by 7:30 PM. In the days before the cower-in-place, I would stay late at work and maybe go out to dinner as well. Arriving home at 8:30, the inside would be a toasty 90 degrees but outside is already falling to 80. I can close that 10 degree differential to less than 5 degrees in about 10 minutes and less than 2 degrees in about 40 minutes. By 10:00 PM the outside is probably 70 and the inside will be 72.

Fan selection and installing...
• To minimize noise, choose the largest fan that will fit between the ceiling joists. In my case, that was 30 inches. Other sizes are 36 and 24 inches. If 2 fans have the same airflow capability, the larger one will be both more efficient and quieter.
• Choose a belt driven fan instead of direct drive. The belt better isolates the vibrations (less noise) and moves the motor out of the opening in the ceiling (less noise).
• Choose a 2-speed fan (instead of 1-speed fan) that has more airflow than you need for your house. You might rig 2 fans in a bigger house to achieve plenty of airflow.
With a 2-speed, the lower speed is reasonably quiet. I run almost exclusively in low-speed mode.
• Instead of mounting the fan completely flush with the ceiling, build up a 2-foot-tall wall around the opening inside the attic and mount the noisy bits of the fan on top of that (the visible opening and louvers will see be mounted on the underside of the ceiling). This, again reduces noise. It might actually improve efficiency, as it gets the air moving more smoothly into the air blades — maybe.
• Choose an install location in the ceiling where the air can run from far-away windows to the fan and clear out all the air in your house between the windows and the fan. If you open a window near the fan, then all the air just goes from that short-path open window to the fan and the rest of the house stays hot. You also might consider a location that will lesson the noise. For me, the location was in the same hallway that houses the forced-air heating return duct.
• When the fan first starts, it draws quite a current — 8 amps for about 2 seconds in my case. Also note the continuous current (I think mine is 4 and 2 amps for high and low). Consider these values when determining if you can hook to an existing electrical circuit or need a new circuit.
• You'll probably install a new switch in the wall that controls the fan. Mine was a pretty simple 3-way switch (off, low, high) that I mounted in the hallway.

In the winter, I tape a large sheet of clear plastic over the entire fan opening so I don't have a giant heat leak. The louvers hardly prevent airflow. This is probably more important for me than others, as the fan is quite near the heater's air-return, which means the heater will be sucking air right through the fan (backwards) and drawing in colder attic air.

When you want to share your marijuana with the whole neighborhood.

BayArea says

The whole house fan works on principles of negative pressure.

I have a back bedroom in my house, it had a window air-conditioned in it until I finally put in a split AC.
One thing with the Window AC, it created negative pressure in the room. By the next morning if it was hot, the room would be room temp no matter how cold I set the AC.
But I also ran the window unit in the Winter when a cold snap would hit. I would wake up and the room would be around 60F to 70F, even though the temp outside could be in the high to low 30's.
If I leave the bedroom door open, the room would be ice cold the next morning. I finally realized negative pressure was creating an airlock insulating the room.
When I would open the door in the morning, there would be wooshing of air.

BayArea says

The whole house fan works on principles of negative pressure.

Like a vacuum cleaner. A fan blows the air out, and the compensating air comes in the windows instead of through a hose.

I've been looking at getting one of these and that price is not too bad. No AC in the house and we typically have 2 weeks of muggy uncomfortable weather a year where this would come in handy.

I refuse on principle to buy AC when 98% of the time our weather is perfect.

Stock up on some MERV12+ furnace filters for your windows during "smoke season".

socal2 says

No AC in the house and we typically have 2 weeks of muggy uncomfortable weather a year where this would come in handy.

I refuse on principle to buy AC when 98% of the time our weather is perfec

I was with you until we started having an annual smoke season in the Bay Area (we've been lucky so far this year). We end up having to close our windows to keep the smoke out and it becomes unbearably hot due to solar thermal gain from south facing windows.
I'm trying out this all in one reversible heat pump, aka mini-split in a box, aka window ac unit from Frigidaire. It's reversible so you can also use the heat pump in the winter.

Attic fan is nowhere near what a whole house fan is.

FuckCCP89 says

Instead of an AC or in addition to?

The fan uses about 10% the power that AC does.

The fan substitutes about 75% of our AC usage.

The fan is mostly intended in addition to the AC. The reason is that you don’t use the fan much during the day. The fan draws in outside air. Therefore it’s mostly used at night or in the morning. AC is still used during the day. Outside air must be cooler than inside air for the whole house fan to be effective.

These things have been around for years but have surged in popularity during the pandemic.

BayArea says

FuckCCP89 says

Instead of an AC or in addition to?

The fan uses about 10% the power that AC does.

The fan substitutes about 75% of our AC usage.

The fan is mostly intended in addition to the AC. The reason is that you don’t use the fan much during the day. The fan draws in outside air. Therefore it’s mostly used at night or in the morning. AC is still used during the day.

You can run your AC in fan-only mode with windows open after sundown. Not 100% the same as FHF, because no dedicated exhaust, but close.

FuckCCP89 says

BayArea says

FuckCCP89 says

Instead of an AC or in addition to?

The fan uses about 10% the power that AC does.

The fan substitutes about 75% of our AC usage.

The fan is mostly intended in addition to the AC. The reason is that you don’t use the fan much during the day. The fan draws in outside air. Therefore it’s mostly used at night or in the morning. AC is still used during the day.

You can run your AC in fan-only mode with windows open after sundown.

Tell me where it draws the air in that mode... it’s not drawing from the outside.

BayArea says

FuckCCP89 says

BayArea says

FuckCCP89 says

Instead of an AC or in addition to?

The fan uses about 10% the power that AC does.

The fan substitutes about 75% of our AC usage.

The fan is mostly intended in addition to the AC. The reason is that you don’t use the fan much during the day. The fan draws in outside air. Therefore it’s mostly used at night or in the morning. AC is still used during the day.

You can run your AC in fan-only mode with windows open after sundown.

Tell me where it draws the air in that mode...

From the open windows on the first floor and out of the windows on the second. Even simple convection will do the trick but if you circulate the air it'll happen faster. I agree that having a dedicated exhaust will make it more efficient, but absent that AC in tge fan-only mode does the trick too, albeit slower. I run it like that every night after a hot day.

ooops..I read it "Whore house fan" and got mighty interested until realized mistake.. LOLz.

I grew up in Torrance where no matter how hot, in the late afternoon the cool onshore wind was so reliable (except during Santa Ana conditions) that the local paper was named The Daily Breeze. I moved inland where it's hotter but it still cools down in the evening so I take advantage of this and open up the house when I get home. For a time I had a "whole house fan" setup which was just a box fan diagonally in the attic opening. It would make the roof turbines spin like they were overclocked, which was especially funny because I painted patterns on one and a crude globe on the other. Living this close to the coast I seldom need AC, yet on these cool evenings with windows open, all up and down the block you hear the din of AC compressors running now. It used to be I only heard that sound when we visited my Grandpa in the hot San Fernando Valley. Now every-goddamn-body has AC running constantly.

Most of the GFs I've had were the type to dress thoughtlessly and mash the thermostat to whichever extreme they wanted and the device running at 100% duty cycle. Summer run AC at minimum temp on thermostat, winter wear swimming trunks and a tank top around the house with the thermostat maxed at 85. These are the type of people who would pay 2 grand for a whole house fan, turn it on at noon on the first Saturday, declare "This stupid thing just makes the house HOTTER!" then get central air installed and never use the whole house fan again. There are some REAL shit systems out there too. In my neighborhood of postwar suburban houses, you see some crazy things like uninsulated ducts emerging from the roof and extending 15 feet to an add-on flat roof patio. My friend moved in to a house and after several years of suffering poor HVAC performance found himself in the hot cramped attic for other reasons and got to looking at the AC distribution plenum. It turned out there was a valve or valves that were never configured to allow air to be sent down half of the ducts! Someone installed that system like that and at least one family lived with it like that afterward!

I heard in Santa Cruz in an over 55 mobile home park, the park paid the gas bill for the residents. However, the old people would leave their windows wide open AND run the heat at the same time, creating massive and nearly overwhelming bills for the park, so they went back to private metering and billing. More tragedy of the commons.

I made an apartment version for less than $30 when I lived in Belmont. I had attic access so bought a box fan, removed the switch and extended the wiring down into my closet going up to the attic trap door where I'd placed the fan laying flat.

Worked great. Much noisier than a real whole house fan. Had the benefit of pushing the hot air out of the attic as well. That cheap ass building had zero insulation and when it was hot out the ceiling was hot to the touch.

NDrLoR says

They've been around for decades, called attic fans.

Whole house and attic fans are different an attic fan does not have access to the interior of the home only the attic and a whole house fan does have interior access so it can exchange the air inside the house with air being pulled from lower level (floor) which is cooler as well as outside, how much depends on a window open or not.

BayArea says

Tell me where it draws the air in that mode... it’s not drawing from the outside.

You would be surprised at how much air comes inside from various places from the outside, cracks etc. not to mention the circulation of the hot air from ceiling to the return air vents replacing the cooler air from the lower locations such as the duct work in the crawl space which can leak air as well and be pulled threw the system.

If you want to see if you can get more efficient have a energy audit done.

Can’t stress how happy I am with my whole house fan now that it’s summer again. Money well spent.

It instantly cools the home for a fraction of the cost of central AC

BayArea says

Can’t stress how happy I am with my whole house fan now that it’s summer again. Money well spent.

It instantly cools the home for a fraction of the cost of central AC

I'm singing those exact praises every summer day with my self-installed $400 fan. I can't believe any non-A/C house in the area (and there are a lot) doesn't have a whole house fan. How happy? Please go up to post #10 and seem how happy I am! When the days are hot and the nights are cool, the whole house fan makes total sense.

I’m spreading the word because up until very recently, I didn’t know these things existed

Even in this thread, someone incorrectly identified whole house fan as being attic fan. It’s not.

One pulls air from the outside and cools the house while the other evacuates air from the attic.

I’m in bed now running the whole house fan. Breeeeze!

If anyone is interested, I went with these guys:

https://quietcoolsystems.com/

You guys out in CA likely don't have high humidity and dew points. Here in IL it would only be practical for maybe 20-40 days a year, so AC it is to pull the moisture out of the air in the summer months. Spring and Fall we generally just open the windows and hit the HVAC fan to help pull air if it's not windy.

That said I probably will install a whole house fan when we build. It's a quick and cheap add on when building.

Not on topic, but thinking of doing the whole home vacuum setup as well. Much quieter. Haven't really looked into it too much, but I'm sure there's a way with low voltage wiring to activate/turn on in every room. Wrap up the hose and toss it on a shelf in the closet taking up less space than a bulk vertical standing vacuum. We'll have a ranch, but lugging that SOB up and down is a pain. We also have the robot now, but that doesn't do the best of jobs. We'd still use that though.

The whole house fan is a great idea, and will work in most locations.
(Attic fans are now required for new house construction in California.)

I’m buying a QuietCool fan soon for a little house in La Paz Baja California Sur.
Check out QuietCool, they look great.
A clever feature of the QuietCool house fan is the duct has a thermostat control so it shuts and the fan won’t suck out AC cooled air.

Here the temperature has been going down to 71F at night while 95F-100F in the daytime.
Until a few weeks ago it went down to the 60’s at night.

A house fan is great because the thing cools down the entire house when the temperature drops outside.
The walls, the floors, the furniture, appliances, everything is cooled down at night.
This is all “thermal mass” which is going to take a long time to heat up in the daytime.

I’m in a dry climate so I will get an evaporative cooler, you can also make one for fun.

There are also “AC/DC” mini split air conditioners which can run on some solar panels.
Here’s a solar fan by QuietCool, it’s an attic fan.

SunnyvaleCA says

• Instead of mounting the fan completely flush with the ceiling, build up a 2-foot-tall wall around the opening inside the attic and mount the noisy bits of the fan on top of that (the visible opening and louvers will see be mounted on the underside of the ceiling). This, again reduces noise. It might actually improve efficiency, as it gets the air moving more smoothly into the air blades — maybe.

They sell kits that reduce noise and vibration by using a flexible coupling. I bet it works pretty good, as vibration is probably nearly fully isolated, and noise is partially absorbed by the ducting.
https://www.homedepot.com/p/QuietCool-4195-CFM-Energy-Saver-Advanced-Whole-House-Fan-QC-ES-4700/206047351


That's how I plan to do it, although I might rig my own kit. The ones they sell seem expensive, although the intake plenum looks well made, they claim the ducting has extra acoustical absorption properties, and the fan may even be optimized to feed from a tube opposed to feed from open air.

Some years back I shallowly looked into the engineering of radiator fans and became aware of how important it was to match a fan to its intended application regarding static pressure differential and air entry/exit approach. A lot of fans are rated at high cfm if they can just operate with nothing in front or behind them, but as soon as a static pressure load is placed upon them to model real world operating conditions, performance drops off a cliff. But fans properly designed for it work well under load. Anyway.

I will also use a thick piece of rubber to hang the straps so as to not transmit vibrations into the roof truss. I also plan to add other attic ventilation, probably a couple small fans, to help exhaust the hot air from the attic so I can run those exhaust fans mid day (without running the house fan) to help keep the house from heating up in the first place. Then as evening approaches and the air outside becomes cooler than the house, I can turn on the house fan.