Intake fan for grow tent, need suggestions.

[thelight413]

Hey all,
So I have a 4x4 tent with a air cooled reflector setup inside. I have a fan (400cfm inline)pulling air from my room though the reflector and out up into the attic. I also have another 400cfm pulling air from the tent, through a carbon filter and then up into the attic as well.
Now, I have a passive intake pulling air from my room(70-77 degrees usually)...I want to set up an intake for pulling in air from outside (natural CO2 source as well as an air conditioning tactic for when the lights are on at night). Fortunately I have a window near my tent where I could run ducting from my tent out the window pulling in cool air..my question is what KIND OF FAN will do the job. I really don't think I need another high powered cfm for this, maybe some sort of small booster fan? Is it possible that my fan that is pulling through the carbon filter will pull enough air to pull air from outside(through the ducting hooked up to the tent), or should I have a seperate fan for this. Passive intake is currently comin from vents in bottom of tent but there are ports where I could hook up more ventilation

Will post pictures to give you an idea of what it looks like when I make it home from work.

 

[thelight413]

<a href='http://i.imgur.com/UxEMFyv' title=''><img src='http://i.imgur.com/UxEMFyv.jpg' alt='' title='Hosted by imgur.com' /></a>

 

[thelight413]

Images of my setup
http://i.imgur.com/UxEMFyv.jpg
http://imgur.com/YwCixnm

 

[thelight413]

The red arrow points to a intake hole and the blue arrows are where I want to run ducting from (there is a window behind the tapestry)

 

[xavier7995]

If you are going to run some out the window, why not just do all of them instead of having stuff out the window and in the attic?

Something like this would probably work: http://www.htgsupply.com/Product-8in-Inline-Duct-Fan

I have one pulling air out of my tent, it works fine for venting but sucked balls in terms of keeping a growlight cool. They are sorta loud.

You might just try closing up the passive intakes and hooking up the ducts without any fans to see how it works. I would think with a strong fan pulling air out, it would be able to just pull what it needs in through the ducting. make sure to put a screen on the duct ends that are exposed to outside.

 

[thelight413]

Yea I assume my fan pulling air out the tent will pull enough to bring in air from outside, I'll let you know once I grab some ducting and try it out

 

[thelight413]

If you are going to run some out the window, why not just do all of them instead of having stuff out the window and in the attic?

Something like this would probably work: http://www.htgsupply.com/Product-8in-Inline-Duct-Fan

I have one pulling air out of my tent, it works fine for venting but sucked balls in terms of keeping a growlight cool. They are sorta loud.

You might just try closing up the passive intakes and hooking up the ducts without any fans to see how it works. I would think with a strong fan pulling air out, it would be able to just pull what it needs in through the ducting. make sure to put a screen on the duct ends that are exposed to outside.

For what it's worth also, if I decide to use that window, air will only be pulled from the outside not pushed out. Blowing air into the attic isn't really causing any problems.

 

[SBudz08]

There's a chart on here somewhere on space size and fan CFM's. Make sure you have a fan slightly more powerful than what you need and you can change it as needed with a controller. The idea is to have a small passive intake constantly sucking air in and maintaining negative pressure inside your tent.