| Tinted Glass
Glass is available in a number of tints which absorb a portion
of the solar heat and block daylight. Tinting changes the color of the
window and can increase visual privacy. The primary uses for tinted glass
are reducing glare from the bright outdoors and reducing the amount of
solar energy transmitted through the glass.
Tinted glazings retain their transparency from the inside, although the
brightness of the outward view is reduced and the color is changed. The
most common colors are neutral gray, bronze, and blue-green, which do
not greatly alter the perceived color of the view and tend to blend well
with other architectural colors.
Traditional tinted glazing, bronze and gray, often force a trade-off
between visible light and solar gain. There is a greater reduction in
visible transmittance than in solar heat gain coefficient (Figure 3-14).
This can decrease glare by reducing the apparent brightness of the glass
surface, but it also diminishes the amount of daylight entering the room.
For windows where daylighting is desirable, it may be more satisfactory
to use a high-performance tint or coating along with other means of controlling
glare. Tinted glazings can provide a measure of visual privacy during
the day, when they reduce visibility from the outdoors. However, at night
the effect is reversed and it is more difficult to see outdoors from the
inside, especially if the tint is combined with a reflective coating.
To address the problem of reducing daylight with traditional tinted glazing,
glass manufacturers have developed high-performance tinted glass that
is sometimes referred to as spectrally selective . This glass preferentially
transmits the daylight portion of the solar spectrum but absorbs the near-infrared
part of sunlight. This is accomplished with special additives during the
float glass process. Like other tinted glass, it is durable and can be
used in both monolithic and multiple-glazed window applications.
Spectrally selective glazings have a light blue or light green tint and
have higher visible transmittance values than traditional bronze- or gray-tinted
glass, but have lower solar heat gain coefficients. Because they are absorptive,
they are best used as the outside glazing in a double-glazed unit. They
can also be combined with low-E coatings to enhance their performance
further. High-performance tinted glazings provide a substantial improvement
over conventional clear, bronze, and gray glass, and a modest improvement
over the existing green and blue-green color-tinted glasses that already
have some selectivity.
Tinted glazing is more common in commercial windows than in residential
windows. In retrofit situations, when windows are not being replaced,
tinted plastic film may be applied to the inside surface of the glazing.
The applied tinted films provide some reduction in solar gain compared
to clear glass but are not as effective as spectrally selective films
or reflective glue-on films, and are not as durable as tinted glass.
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