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A lot happened in 2017- now 2018 is here

Latest news as of May Day

Thorwaldson Whole House Fan Company is now the leader in performance with the ES-6400 attic mounted whole house fan pulling 6,320 CFM with just one motor and one blade and the ER-8000 rooftop mounted whole house fan for homes with no attic. The ER-8000 pulls 8,005 CFM at full speed. Both fans have infinitely variable speeds using a dial like a light dimmer. 6,320 CFM will move all the air in a 3000 square foot home with 8 foot ceilings in under 4 minutes.

QuietCool has lowered the performance specifications on nearly all models. Their top performance model, the ES-6400, uses two fans that are connected to one ceiling intake. At full speed the fans pull just 6,004 CFM, down from 6,315 in 2017. QuietCool says this model is recommended for homes up to 3,000 square feet. The Whole House Fan Guy says this model should be fine in larger homes and cannot understand this recommendation. Here is the data – If your home is 3000 square feet with 8 foot ceilings it has 24,000 cubic feet inside. Most of that is air. A 6000 CFM fan will move all that air in 4 minutes. If your home is two story, then it is likely only hot upstairs so the amount of air upstairs is likely just 12,000 cubic feet. That will all be moved out in 2 minutes. One room will be chilled it less than one minute.

No other attic mounted fans pull more than 5,400 CFM.




Airscape’s highest CFM is 5064
Airscape has a new line named Ventura that also is 5064 max.
Tamarack’s highest is 3400
Centric Air is not over 3860
Ventcool max is 5064

The history of whole house fans starts way back in the late 1800s when there was no air conditioning systems. As an example, I was called by a young man in Atlanta GA who said he was renovating a home built in 1902 that had a huge 50 inch diameter fan up over the upstairs landing. In those days big fans were the only way to effectively create a breeze in every home.

It was not until about 1930 that Mr. Carrier invented the first air conditioning system to compress coolant and then expand it to cool air. Carrier Corporation is still one of the leaders in hvac.

Until just about 15 years ago all we had were the big propellers in the ceiling. Then some alternative systems started showing up. Two young electricians in Southern California had been installing the Home Depot systems and they came up with a brilliant idea – instead of having one central machine, make smaller systems that are sized for one bedroom. Thus QuietCool was born and they have dominated the “rafter mounted” market ever since.

The most interesting debate is over how many CFM you should buy for YOUR home. I did a study of the different suppliers using my 2800 SF home as an example. Suggestions range from a low of 2700 CFM from CentricAir to a huge 14,421 CFM from Breezepower in Australia. Airscape says 2000 to 3510 if you are in the west or 2800 to 7,020 if you are in the midwest. Tamarack says you need 6 air changes per hour so for 2800 SF they recommend 2200 CFM.

One fact is irrefutable. You cannot have too much air flow within reason.

Here is an interesting factoid – if you open a 2 foot high window 6 inches, the opening is 1 square foot. If you have a 4000 CFM fan with only that window for air, the air coming in is 40 MPH! That’s right – 6,320 CFM will be 63 MPH!