looking for advice

I have a cabinet I built 11.5 x 4 x4 with a 400cfm fan/filter combo.

Is it better to have 2 6in air intakes or one bigger one? Based on square area if my air intake (passive) is 9in in diameter that puts me just over 2x the size of my exhaust. Is that roughly what I need? Or when they say 2x-3x bigger than exhaust they mean 2-3 6in intakes?


Also I dont want to cut any holes in the side of my house for fresh air or do I want to open a window. I was planning on pulling fresh air directly from the soffit and cutting a hold into the ceiling to provide fresh air into the room. Anyone done this?

With your fan/filter combo, you will be pushing it to cycle the air in the room at 2x's per minute ( still adequate for co2). 11.5x4x4=184 cubic feet . 184/400(cfm)= 46% of max advertised airflow, which in actuality, will not be at 400 with a filter placed inline.
If you don't have much air circulating inside the grow chamber, then multiple holes may be more beneficial (but then again, you may not see much a difference) in terms of dispersing useable co2 and cooler air throughout the garden,
Will you be using fresh air for cooling or co2? If your temps and humidity are in check, supplement with co2 if you can afford it. Otherwise, take the following into consideration. Regardless of where you pull your air from, don't forget warm air rises, cool air falls, and because of this, the source of your air intake can increase or decrease ambient temps in the chamber.

Well would a 45o cfm be sufficient for a 8x4x6.5 with 250 going in from the bedroom its blows exhaust into inner wall through out house ways from tent

In my experience, you want your exhaust to be greater than the intake to create negative pressure.

thatguytom said:

Well would a 45o cfm be sufficient for a 8x4x6.5 with 250 going in from the bedroom its blows exhaust into inner wall through out house ways from tent

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If you are using 450 cfm of fan total, you are exchanging the room twice in less than a minute (in a perfect world), which is definitely above the bare minimum. In some instances, temps and humidity can be manipulated with adjustment to airflow as well. So there can't be a true guarantee without trying, or dialing in your system. Good luck.