# Venting For Whole House Fan



## Bob Deb (Nov 19, 2010)

(I think I finally have the right forum) :laughing:

I've been wanting to install a "whole house fan" for some time & almost did once, but the local supplier made a point to tell me I should make sure that the attic is adequately vented before I force air into it. He simply explained that if I did not have enough venting, the fan would be over worked by trying to push more air than the attic vents can handle. It made sense, so I put off doing it until I knew more.

My attic has soffit & ridge vents only, but I could add a gable vent to one end of the house if needed. I've been in houses that have ceiling mounted fans pulling cool air in & I like it. I'd run my A/C a lot less if I could just cool off the house better. 

How do I determine what size fan I need as well as whether or not I have enough existing vents?

Thanks in advance for any advice. :thumbsup:


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## josall (May 7, 2011)

It depends on the fan, you might comb through this site it explains alot. 

http://www.wholehousefan.com/FIND/Your-Perfect-Fan.html


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## Jackofall1 (Dec 5, 2010)

Hello Bob and welcome to the best DIY'r site on the web.

The supplier you mention is full of it, I mean right up to his eye balls full, a fan will only reach its rated static pressure rating by moving air, if there is no where for the air to go then you won't move it. If you don't move the air you don't use the horse power.

The net effect of not having enough vent net free area will reduce the efficiency of the system, there-by adding costs to running a motor that is not providing its design intent.

Personally if you are going to install a whole house fan vent it directly to the out doors, you don't want to pressurize your attic, this will have negative effects on the whole concept.

Mark.

PS you have multiple posts of the same subject please only post once, this way you can track your responses much more easily.


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## Ron6519 (Mar 28, 2007)

Mount the fan on the gable end, blowing directly outside. Put a shutter in the ceiling the same size as the fan. A 24" fan means a 24" shutter.
When the fan is on, the shutter in the ceiling will open automatically.
In the Winter, cover the ceiling shutter with an insulated box.


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## Bob Deb (Nov 19, 2010)

Thanks for the replies & link. :thumbsup:

After reading some more, it seems that with the large volume of air space in my house due to all the cathedral ceilings, I may not have enough of a venting area with the existing vents in my attic. I did a rough estimate & have about 14,000 cubic feet.

This idea appears best.....



Ron6519 said:


> Mount the fan on the gable end, blowing directly outside. Put a shutter in the ceiling the same size as the fan. A 24" fan means a 24" shutter.
> When the fan is on, the shutter in the ceiling will open automatically.
> In the Winter, cover the ceiling shutter with an insulated box.


I saw the following photo & description & think something like this set up is what I need.

http://www.airscapefans.com/products/Shop/Natural-Cooling/Starter-Whole-House-Fans/Kohilo


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## Ron6519 (Mar 28, 2007)

This ducted model will isolate the house from the attic.


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