I am on 18/6 in a 12' by 12' upstairs room. Recently I've been buying larger fans to accommodate the heat but I'm having problems with ducting/exhaust sizes. All my old fans have 4" openings for exhaust and I bought hoods with 4" exhaust holes. I've started been buying inline fans with higher cfm, recently bought one around 700cfm with 8" exhaust holes, but all my hoods only have 4" openings. Right now I use downsizing connectors to exhaust heat from my hoods which are 4" to my 8" fan. Even with this more powerful fan the temps are still way too high in this small room. The inline fan exhausts 2 hoods with 1000w bulbs (one MH and one HPS right now). In addition, I also have 2 smaller fans (not inline, 300 - 400cfm i think), one which exhausts only one other hood and one which just exhausts from the room in general. The air in comes from outside (a problem on 80 degree days like yesterday...) and vents out into the house and/or attic space. With summer here, even with these 3 fans there is no way I can run all 3 lights without the temps getting up to 100 degrees F. I can't even really run 2 when it's up to high 80s or 90s. Would new hoods with 8" or even 6" exhaust openings help at all? Does anybody have any ideas how I can get the heat down? Any ideas would be greatly appreciated