One of the most useful things you can do when comparing window film is
stop treating shade and heat rejection as the same number. They measure
different things.
Visible Light Transmission, or VLT, tells you how much visible light
passes through the film and glass. A lower VLT looks darker. Total Solar
Energy Rejected, or TSER, is a broader measure of how much total solar
energy is rejected. Infrared Energy Rejection, or IRER, focuses on the
infrared range that contributes to the heat you feel.
XPEL's PRIME specification sheet
is a good example of why this matters. It reports VLT, TSER and IRER,
and it also lists a separate infrared rejection figure measured at
1025 nm. Those are not interchangeable measurements. A single impressive
IR percentage can be useful, but it should not be the only number used
to compare two different products.
When you are looking at two options, ask to see the specification sheet
for the exact film and shade you plan to install. Compare products at a
similar VLT and use the same type of performance metric. That gives you
a much cleaner apples-to-apples comparison.
This also helps prevent a common shopping mistake: comparing the strongest
marketing number from one film with a different measurement from another.
A 35% film and a 70% film are not an equal shade comparison, and an
infrared figure measured at one wavelength is not the same thing as a
full-range IRER value. The film that sounds more impressive in an ad may
not be the better match for your vehicle once the specifications are
lined up correctly.
If a shop can show you the manufacturer data for the exact product
being quoted, you can make the decision around the things you will
actually notice:
how much visible light you want, how much solar heat you want to reject,
how clear you want the view to remain, and what performance level fits
the budget. That is more useful than choosing carbon or ceramic by name
alone.
