Okay, y'all are going to think this is just silly.  But I tend to
favor darker spaces and privacy when hopping between the shower and
where my clothes are, and have been reading about the merits of
radiant barriers when properly used.

I'm making a set of new window shades for the house out of Reflectix,
that thin metallized radiant-barrier stuff you can get in 25' rolls
at Orangeland's insulation department.  It's basically bubble-wrap
silvered on both sides and completely opaque, and when hung with the
more flexible direction oriented horizontally, can easily roll or
fold up like several existing styles of window shade I've seen.  And
combined with the already low SHGC of the new windows, will let *no*
radiative heating in on the south side in summer and probably give a
little boost to overall fenestration R-value in winter.  It weighs
next to nothing and doesn't seem to burn particularly readily, or
very slowly when it does.

On the inside it diffusely reflects back whatever light [or lack
thereof] you decided to color your interior space with, thus is
automatically neutral but adds more artificial-light brightness into
a room when that's what you want. You could enhance your photographic
lighting quality by simply aiming your harsh point-source worklight
at the hanging shade instead of the subject, and let the shade serve
as sort of a soft-box.

On the outside it doesn't look particularly weird, especially behind
slightly tinted glass; nobody thinks twice about those silvered sun
shields people put under windshields, and this isn't much different.

A thin piece of trim wood, or as it's turning out some of the scrap
from ripping down the interior window-box trim boards themselves,
serves as a batten at the top that the Reflectix gets accurately
stapled to.  The assembly hangs on a couple of very small hooks up
into the box, and threading same in or out one or two more turns can
fine-tune positioning and levelness.  A batten at the bottom helps
it hang straight and provide something to grab, and a matched hook
and eye between top and bottom battens allows hanging the bottom one
for a half-up position as shown.  [This works far better than my
original concept using corner grommets.]  The whole thing can be
trivially removed for full-frame access, and if I construct them
right they should all be uniform and interchangeable among any
windows of a particular size.

The new jamb extensions to the exterior are generously deep as one
can see, as the whole house has fattened up by 5" at each wall, and for
the moment it makes sense to place all this out near where the window
sits as opposed to trying to cover the entire opening on the interior.
The half-up belly curve nests nicely into there and doesn't intrude
into the room.  Sightlines get completely blocked but a little light
filters in around the edge of the piece, which is okay.  Probably
will become less depending on how I wind up staining all this wood.

_H*