We thought about glass block. Might still do it. We have little
vetilation on the this floor, though, and the added air through the
window is nice in this non-air conditioned house.

I might have to do the tile, too, due to budget constraints.

Goedjn, the roofing felt was a suggestion from a well-regarded web
site: http://www.thetiledoctor.com/index.cfm