Spandrel glass is made by coating a vision glass with an opaque
coating. The is prevents people from looking through the glass and
seeing structural features inside the building. Spandrel glass is
most often used in curtain wall construction where the glass and
aluminum framing on a multi-story buiding passes on the exterior
side of the floor slabs. A typical high-rise building will have a
top-of-slab to top of slab distance of about 12 feet, but the
slab-to-ceiling height is usually 8 feet. The 4 feet above the
suspended ceiling contains the "spandrel beams" (the beams that
hold up the floor slabs), electrical wiring, plumbig, mechanical
ducts (heating and air conditioning) and fire suppression systems.
Since most of these items are rather ugly, spandrel glass is used
to high them from public view. Spandrel glass is not intended for
use in a "vision glass" area. If you look at spandrel glass from
the interior of a building looking out toward daylight, you will
see pinholes and variations in the density of the coating.
