Overheating

Hello,
I have a wooden grow box that measures 17" x 15" x18" (inside). I am running 3 26w cfl's on a powerstrip with adapters. Eventually I would like to have four bulbs. I have an 80mm, 29 cfm pc fan running on a 12v adaptor. The fan is on the left side of the box, 3" from the top. I have five 1/2" passive intake holes along the lower right side (opposite the fan). I plan to add a diy carbon filter to the exhaust as well. My problem is that after the lights run for several hours (with the door closed), the temp inside the box reaches 90f. I understand this is too high (I am not using Co2), and am looking for suggestions to lower the temp. Would adding more intake holes (possibly at the height of the bulbs) help? Or perhaps I need a larger exhaust fan? Maybe use my current fan as an intake and then purchase a larger fan to use as an exhaust? If you reccomend a larger or additional fan, what cfm rating would you suggest, and where should I position it? I appreciate your time!

I just looked into placing a piece of glass/plexiglas between the bulbs and the plants to help isolate the heat so it is more easily exhausted. I realize this will take away some strength of the lighting, but I am also considering that as an option.

my guess is your intake holes are not big enough, you need a hole larger than the fan.

yeah that small of a space...you need a larger fan/more fans/more powerful noisy fan/bigger holes/etc

Or if making bigger wholes r not an option . I wud put the box in a cool area like basement if possible.

U could try putting a out take fan close to the lights as possible . .

I thought the intake was supposed to be smaller than the exhaust to maintain negative pressure?

yea you want negative pressure. Upgrade your fan, there are 200+ CFM PC fans out there on the internet, that's what you should use