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There are some important points that should
be understood about infrared energy and how
it relates to window film and total solar
energy rejection.
The infrared spectrum is measured from 780 –
50,000nm and is broadly divided into two
distinct ranges, the near infrared (NIR) and
far infrared (FIR). Infrared energy accounts
for 49% of the solar spectrum.
The near infrared range is measured between
780 – 2,400nm and accounts for only 3.2% of
the entire infrared spectrum. Humans cannot
see near infrared radiation but we do
experience it as heat.
The far infrared range is measured between
2,400 and 50,000nm and accounts for 96.8% of
the infrared spectrum. Far infrared energy
is absorbed energy that is re-radiated.
Objects such as roads, rocks, sidewalks,
window glass and human beings that are
warmed by the sun, re-radiate that absorbed
energy in the form of far-infrared energy.
Window films alone cannot lower the
temperature of a room but they can
effectively reduce the rate that energy
enters a room which helps reduce the load
placed air conditioning systems. The greater
the glass area, the greater the impact
window film can have on heat transfer into
or out of a room. This makes window films an
essential component to creating a more
energy efficient building or home.
Note:
Companies that promote “IR cut” do not
normally state what wavelengths they are
measuring. A typical transmission meter is
designed to selectively measure only from
900 – 1000nm, which is a very narrow range
and therefore may not be relevant in
representing the total amount of solar
energy that is actually being rejected.
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