What size fan?

Im curious as to what size (cfm) fan i should use for my current setup.
im using a 4x2x8 closet. im only using 1 extractor fan on my cooltube atm which does the trick as it runs in a straight line and sucks air out of the room... BUT!!! i want to now run ducting from my ceiling down about 2-3 ft then onto the cooltube then back up near the ceiling and exited through an exhaust fan into a neighbouring closet. this whole run will only take up about 3-4 meter's of ducting at most. i wish to use 4inch/100mm ducting on my cooltube which is 6inch/150mm (i have the reducers).

what size exhaust fan should i use?
should i have it as an intake or extractor?


any help if much appreciated.... tyvm

any1? please advise........

to find out wat size you need. do 4x2x8 den divide by 5 dis will tell you.

ty for your reply but im confused, what does dividing it by 5 do? how does this tell what power fan i should use on my vent system?

str4ng3 said:

ty for your reply but im confused, what does dividing it by 5 do? how does this tell what power fan i should use on my vent system?

Click to expand...

shows how many cubic feet you need for one minute (hence CFM). The number is low though. try suthin like a small 4in inline fan or ductbooster.

awesome ty for ur help. where is the best place to put this in line fan? at the start as an intake or as an exhaust? or i guess trial and error might answer that one for me