have a 4'x4'x8' closet that i need to keep the temps steady. the intake will be coming from a plumbing access panel that is accessible to the crawl space. i need to know how big to make the intake hole and how big of a fan would i need to run a carbon scrubber in the attic?
4" fan should be enough, personally I might do a 6" depending on what your hood / lighting situation is going to be.
here's a link to my setup as it were. http://forum.grasscity.com/indoor-grow-journals/578123-lowryder-2-cfl-grow.html
how big should the intake be then? i was under the assumption that your exhaust should be close to double the size of the intake.
I have a 4x4x7 box, almost the same as yours. I have a 6 inch 275 cfm fan pulling through a CAN 33 carbon filter and then through the light fixture. The fan is outside the box, on top and exhausts to the garage. The carbon filter is hanging inside near the top of the box. For intake I have (2) two inch PVC pipes fitted and caulked through holes I cut in the bottom side and back of the box. When the fan runs the air pulls into the box enough to ruffle the leaves. I also have a 12 inch oscilating fan wall mouted in the box that goes 24/0.