I would suck air thru the filter ,then thru the hood , and then thru the fan and out.
If you try to blow air thru a hood , you would have to seal the hood completely in order to keep from blowing hot air out around the glass ect..(unless its a cooltube) Where as sucking it thru the hood ,if you have a little air leak know big deal.
I would definately suggest getting the biggest fan you can afford(within reason)And I would suggest a CanFan
Using a carbonfilter, ducting and cooling a hood will cause a bit of static preasure,and i have found that the squirrelcage fans just dont cut the mustard when it comes to preasure.
I use a 8" Canfan HO 756cfm .I divided the duct into 2 6" ducts .1 duct cools 2 1000s and the other cools 3 400s.
Hope this helps
hondo Reviewed by hondo on . Ventilation Question Ventilation question I need answering, two potential setups, which one would work better? 1) Carbon filter at the top of the room, connected directly to an extraction fan. Fan sucking air through the filter, blowing air through ducting into an air cooled reflector, ducting connecting the adjacent end of the reflector taking air out of the grow room. 2) Carbon filter at top of the room, filter connected directly to ducting, ducting connected to air cooled reflector, adjacent end of Rating: 5