First of all, it's nice to see that this thread is getting some interest I've been browsing some other pc-case grow logs and found only few systems that really worked. It seems to be quite a difficult task.

My first thought for the ventilation was pc fans, but it would have needed at least three of them and then the carbon filter would have been almost impossible to build. So now I mounted this 14W fan that's built for bathroom ventilation and it moves air 99m3/h, so thats plenty enough. The pc case of course is made of metal, not wood as my earlier grow closets and it makes the modifying bit difficult in home circumstances.