Help deciding how to rig my box's exhaust?

My friend has 4 plants in a 10sqft box and a 400cfm blower doing nothing but circulating the air in the box through a can charcoal filter. In the box it is still quite odorous. Outside it is odor free. He tried reducing the cfm output with a controller but anything less than full allowed the odor to invade the room outside the box.

As for venting out the ducting window and low noise, just vent into the attic as far from any opening as possible to keep noise to a minimum. The attic gable fan should vent enough to clear the attic of that heat.

The odor of flowering plants is much more than most think it will be.

Originally Posted by CannaMatt

As for venting out the ducting window and low noise, just vent into the attic as far from any opening as possible to keep noise to a minimum. The attic gable fan should vent enough to clear the attic of that heat.

The odor of flowering plants is much more than most think it will be.

Yeah, for my first grow (10 years ago), I vented directly into my bedroom. My whole apartment reeked by a few weeks into flowering.

However, I really don't want my attic full of the odor. I would much rather vent it outside directly, where it can quickly dissipate, rather than allowing it to stink up my house by seeping in from the attic. The attic is basically a 3rd floor window, and the ceilings are quite high on each floor below, so it might be closer to a 4th floor. The lots are wooded and well-spaced in the neighborhood, so it's unlikely anyone will smell it or know where the smell is coming from, once it's blowing through the trees. I'm not worried about the noises from the outside, I'm worried about people inside my house being able to hear the fans or smell the grow.

So, back to my original question: Is there an affordable, extremely quiet fan that can effectively vent a grow box that will be about 20-25 cubic feet? Or at least kinda relatively affordable?

And I forgot to add that I will add a charcoal filter to the exhaust if I start to notice the smell from my driveway, or even worse from the street in front of the house. So I want a fan that is quiet but capable of venting that space through the added resistance of a charcoal filter, if necessary.

I have the same size box for drying buds and i use this fan and filter can't smell a thing. http://www.thehydrosource.com/Fan_Fi...n_Filter_Combo

Originally Posted by GreenMeds4All

I have the same size box for drying buds and i use this fan and filter can't smell a thing. http://www.thehydrosource.com/Fan_Fi...n_Filter_Combo

How quiet is it? Would you probably be able to hear it in a room if it were basically attached to the a/c duct that ran to that room through the ceiling? My passive intake will be directly tapping into an a/c duct, so there will be nothing to muffle the sounds between the grow box and the a/c ducts in the house. That's why I want silence above all else. I want the quietest fan I can get that will move enough air to cool the grow box. I am thinking I probably won't even need a filter since I'm venting directly into the outside air, but I might add one later if I'm proven wrong.

Two words, Electrostatic Filters. They have worked like a charm for me. jmi as I said they have worked wonders for me. 3M makes them and for my flower room I built a box and bought a 22"X28" 3M premium electro filter that costs just under 30$. The thing lasts over 90 days at a time and is washable and reusable several times over. Another nice feature or result is NEVER a trace of static. That was a big difference. Anywho,,,,,,, it has worked nicely so far.
Cheers,
Chase