Question about grow room

[BigSmokie]

I have a 2' by 2' by 4' grow box and there is no carbon fiter in it and I don't want to build a new one so my question is can I add a small room to the top of the box for my filter and just cut some vent holes to connect the two room togather? Here is a pic of what I am thinking (I would only be adding room 2 and the filter)

 

[Insider]

Sure you could, think you should make those vent holes between rooms quite big.
Guessing your extractor is outside the room.