second and third floor windows

To create the vents in the archways I first tried to extrude the inside faces of the arch which took a few tries as it was making some weird shapes and was not going straight for me. After moving vertices and edges I got the right shape. I then selected the inner faces as seen in the image below. Then i extruded them in and then extruded in again but pushing the faces back to create a space for the vents. 

 My first attempt I selected the faces and rotated them but when I went into the side view and wire view it looks very confusing as extra edges were there and some of the lines were out of whack. I think when I selected faces to extrude that some of the back faces had been selected, I should have checked before extruding!

This resulting in weird shapes and me trying to delete things to make it better but didnt quite work out.

 After trying this out about  5 times I decided to smooth the arch, select the front faces and extrude them twice and on the third one I moved the faces back to create a rounded edge. I then deleted the edge loop which I had put around the edges as it was causing the edge to look sharp. I then deleted the extra vertices as well.

For the inside I ended up selecting of the arches (non extruded one) smoothing it and placing it inside the original arch. I then scaled it to the shape I wanted then used cubes for the vent.