Hey @mpilas!
Nice to see you again 
I remember your posts in this thread: Failed simulation in building wind CFD - how is the setup you want to realize different from the old one? Is it just about the pressure drop itself?
Regarding porous media, that is indeed possible but you would need to know the properties or at least approximate the filter behavior. This post here by @varsey might help you out: Setting Up a Simulation Using Porous Media - #3 by varsey. Regarding blocking maybe @varsey can give you some parameter examples to accomplish this. If you want to have the flow blocked in two directions and have it concentrated in one direction you can set the coefficients to a high value.
Regarding the louvers I would not approach this with porous media as this will definitely has an influence on the flow behavior and certainly makes a difference in terms of modeling. Just upload adapted CAD models and make changes accordingly, that way you have at least a distinct modeling we can also work with.
Best,
Jousef