I just received my exhaust fan. It is 100 cfm. I figured my box is less than 20 ft3.
Is that a good fan speed?/QUOTE]
Your box is 27.5*27.5*55. That is 2.29'x2.29'x4.58' which is 24 cubic feet. Your exhaust fan is rated at moving 100 cubic feet of air per minute. You don't make mention of an intake fan, so I will go on the premise that you are going with passive intake; exhaust fan 'pulling' air through an opening, preferably near the bottom of your box. If the passive opening is the same size or larger than your exhaust port, your fan should be operating at its maximum efficiency. Will it be enough? Other factors will play into that, like ambient room temperature, so bottom line, we gotta just experiment, be prepared for change... and go with the flow!

:thumbs: