Need help with glass or plexiglass in a shower.

The previous owners of my home placed glass blocks in the wall above the shower/tub. They were covered on the other side, so I decided I'd like to liberate them in order to allow some light into the shower when the curtain is closed. Demo not a problem. Plan is to build a small frame and put either glass or plexiglass behind it. But now I'm concerned about the possibility of condensation building up inside the wall. Should I drill some weep holes or would that actually make things worse? I do have a ceiling fan.