The Whole House/Attic Fan Ventilation Thread.

Diggin It · Feb 26, 2021

Some discussion creeped into the Power Wall thread, but it got me curious.

We had one of those monster in ceiling fans at one time. Windows had to be opened on the main floor. There was a spring loaded rotary timer switch to turn the fan on. It evacuated air out through vents mounted in the peaks of the outer walls.

Way back then, price per KwHr was no big deal, less than 5 cents as I recall. Monthly bill for a family with an electric stove was $30 or less. With that rate now well over 10 cents in most places and some up around 30 cents (an and infamous few at something like $9,000 :laughing:

), that can add up fast. Even a window fan can run close to 100 watts and leaving that running full time can add up. So, what do these monster attic fans cost now to operate? Have they become more efficient?

I only cool a single room with a 6K window shaker and don't leave it running more than a few hours in the late afternoon or early evening.

The big fans I remember are now running $300 or more and the 'quiet cool' suspended fans mentioned on the other thread are in the $1,000 + range, so I'm not sure I'm seeing an advantage there.

I see one model of those claiming to use 88 watts on low, but close to 300 watts on high. Another shows between 250 and 300 watts and one at a meter killing 660 watts.

Roadworthy · Feb 26, 2021

I guess you'd have to do the numbers for the specific fan in which your were interested and compare them to the numbers on your wall shaker. The wall shaker has a compressor and actually cools the air. The big sucker only draws in the cool evening air. You could also put in a big window fan and sit in front of it.

kenmac · Feb 26, 2021

I'm gonna guess when you say ceiling fan. You are referring to one of those large attic fans ? Usually mounted in the attic in the hall of a house and venter the air from the home into the attic ?

Aquamoose · Feb 26, 2021

I had an attic fan installed myself in the hallway ceiling and it was a major benefit to having them. We would come home, run the fan to push out the hot attic air and on really hot days, turn on the AC after the fan ran for 10-15 minutes so the AC doesn’t work twice as hard to cool the house. Most of the time, just the attic fan on low did the job well and created a comfortable breeze in the house which saved a boatload of $$$.

LS Tractor Owner · Feb 26, 2021

I installed one of these, used as a whole house fan. Very energy efficient, especially on "low", also so quiet, you can't hear that it is on.
When on "high", you definitely know it is on, but still not as loud as the old school louvered fans.
https://www.homedepot.com/p/QuietCo...RCH=REC-_-pipsem-_-206047381-_-314250784-_-N&

There is a greater cfm fan also, depending upon your needs.
https://www.homedepot.com/p/QuietCo...VwhitBh1-oQJAEAQYBCABEgIBjPD_BwE&gclsrc=aw.ds

I basically made a "plenum box" out of 1" thick foam insulation board. The fan got mounted to some 2x4 bracing I installed to the rafters and ceiling joists. When I mounted the fan to those braces, I used 1/2" thick rubber grommets between the wood and the fan and between the screw/washer and the fan.
I also found 2--12.5" self closing backdraft dampers and mounted them horizontally between the ceiling joist. Then just made a pine "picture frame" around that opening and mounted some simple return air grills to finish it off.
Soler & Palau CAR315 Steel Duct Backdraft Damper - 12.4-Inch

Something that I found with this fan unexpectedly, was that it is actually 2speed. It comes with a thermostat in which you can select either the high or low speeds by just changing the connection of one wire. COOL! .... I got a 2 speed whole house fan switch, connected up both wires and BINGO! Two speed fan!

During my extensive research, I found that this is the same exact fan, motor, and housing that is used in the whole house set up.... I just couldn't see spending $3-400 more for a short piece of flexable duct and a grill....

We have 2 minisplit units that we use when it gets really hot during the day, but being in the high desert mountains, it cools off quickly at sunset. We may use the fan on high for a short time, but then turn it to low for all night. By morning it is sometimes plain chilly....

Here are some pics of the finished ceiling cover, you can barely see the dampers. Unfortunately I had full build / mounting pics, but I deleted them

My whole cost for the project was under $200. I did use the higher volume red 3.0 version. I was able to find it elsewhere for $140.

kenmac · Feb 26, 2021

As a kid That's all my granddad had in his house. He would turn that thing on and open the windows. The curtains would begin flying in the air due to the suction of that fan.
Slept at night with the fan on and would wake up on cool night freezing.. LOL the good ole days !

Alan W. · Feb 26, 2021

I remember dad putting one up in our house. It really helped since we didnt have A/C. I can still remember the curtains standing out. Felt really good.
Of course there was the time dad accidentally hit the fan switch instead of the hall closet light. Wouldnt have been a problem but it was the dead of winter and the wood stove was going. Mom tore him a new one over that.