growbox questions

hi all,i am planning my second grow,the first did not go so well ,but its all a learning curve eh!
anyway i amm planning to use a wooden box 2 ft x 1.5 ft x 4 ft high.
i have a 250 mh light for my veg,not got a hps for flower yet.
my main question is what kind of venting will i need,i hope to have 2 cuttings (fem)and am thinking of trying the screen of green method.
can anyone help me with any advice,thanks

I suggest installing at least one outtake fan and put a thermometer in there. Before putting plants inside, run everything to see how hot it gets door closed and everything. If it is still to hot, then you might need to either add another fan or install a larger one.

Peace
Dirty Kid

thanks dirty kid,do you mean an extractor fan like what is used in bathrooms?would i need 2 one to bring fresh air in and one to remove the (old) air.intake at the bottom and exhaust at the top.