Can't open the windows if they are BRG.   That will probably not be a
selling point.

Also, scale up support for the windows.  BRG is *heavy*, particularly
if you want to stop .50 rounds.

I suspect you will loose whatever passive solar you gain to heat
leaking around the window mounting and/or transmitted through the
glass.

"Landlord's a bit of a nutter, but the rent is OK."

Side note, while BRG is sturdy, the surface finish is also kind of
fragile.  Which means some knob with a nail can scratch their initials
in the surface, and while there is no chance the glass will break,
mechanical etching is not a challenge.  (and special cleaning
requirements, blah blah blah....)

> Practical 3: My mother makes most of her income these days from
> monthly/weekly rentals. The biggest *expenses* she encounters come when
> renters move out, in the form of recarpeting floors, repairing punctured
> drywall and replacing broken windows. Poured concrete surfaces coated with
> diamond-hard epoxy resin solve the first two issues; fixed window panes
> crafted from bullet-resistant glass take care of the third.

carpet is both practical and aethetically pleasing.  Concrete is
practical, but for different reasons.

It sounds like you are renting something close to jail cells, minus the bars.

--

"Any sufficiently advanced parody is indistinguishable from a genuine
kook." -Alan Morgan