What size fan for my room?

First off, what is the height of your room? You need to figure out the cubic footage. Let's say your room is 12'x12'x8'=1152 cubic feet. As a rule of thumb you need to exchange your airspace 1-5 times. So you'll need a fan with a minimum 1152 cfm rating. And yes, for a fan with such a high cfm 8" duct would probably work best. TBH you could get away with a lower cfm fan, but your girls need all the fresh, dry CO2 they can get.

Also, if your room is close to what my example describes, a DIY carbon filter attached to such a high cfm fan may not cut it depending on the quality of the filter you are constructing. You may want to purchase one if you can. Canfans are fantastic.

Hope this helps and Happy Growing!

Thanks! Yes they are 8' ceilings. I will probably buy a filter then (unless anyone knows a guide for making a carbon filter good enough for my size room?)

Originally Posted by Delta223

Thanks! Yes they are 8' ceilings. I will probably buy a filter then (unless anyone knows a guide for making a carbon filter good enough for my size room?)

What kind of DIY filter are you building? It might be suitable. It's just that I've seen some that use the activated carbon air purifier pads that would be absolutley useless with the fan you need. But there are some great DIY designs out there!