How does window film keep heat out? How does it protect against fading and
unwanted glare? How does window film control light? The industry works to sell the
product every day, but does everyone really know how and why it work
s?

Back to Basics
Let’s start with a discussion of light, energy, heat, reflection, transmission and
absorption. Within the electromagnetic spectrum is a spectrum of energy in the
form of waves. Different wavelengths exist and three of them play a major part in
our discussion. Right in the middle of the spectrum is visible light and it sits in the
range of 400 to 700 billionths of a meter (nanometers). The energy in each wave is
proportional its wavelength (which is the distance between any two corresponding
points on successive waves) so if it is a shorter wavelength than it will have a
higher amount of energy; a longer wavelength a lower amount of energy.
Ultraviolet light (UV) is a part of the electromagnetic spectrum that has a frequency
greater than visible light and only accounts for about 3 percent of solar energy. It’s
also the most dangerous portion and can damage parts of the eye even though it
is not visible to the human eye. Infrared light, which has a frequency less than
visible light, makes up about 53 percent of solar energy and is also not visible to
the human eye.

These components of
solar energy—ultraviolet light, visible light and infrared
light—react in three ways when they hit a surface
. They are either reflected off
of the surface, transmitted through the surface or absorbed into the surface.

[Light can] be transmitted through like a piece of glass, absorbed into it like
a black car on a hot day or it can be reflected like a mirror,” says Ron Jones,
architectural programs manager for Sarasota, Fla.-based Sungard  

“Light can complete a combination of these actions, but they always have to equal
100 percent,” says Jones. “The mirror will reflect almost 100 percent. The black car
will absorb nearly 100 percent and the glass will transmit almost 100 percent.”


































Enter Window Film
Taking all of that science into consideration window film attempts to regulate the
amount of energy that is absorbed or transmitted in order to reduce energy
consumption, fading and glare.

“Obviously, the goal is to reduce transmission so that leaves window film the
opportunity to either absorb solar energy or reflect it,” says Jon Mitchell, technical
services representative for Solar Gard in San Diego.

The more window film can reflect, the more energy-efficient it is,” adds
Jones.
Most films are built with ultraviolet inhibitors in them to protect against UV
light.

“[Window films] have to have UV inhibitors built into them because the polyester
base that the film is made out of is destroyed by ultraviolet light,” says Jones. “That
is why nearly all window films block nearly 100% of the ultraviolet light because
they are protecting themselves. The extra benefit is that [film protects against] the

ultraviolet light
is the most damaging portion of the solar energy spectrum to fade,
skin, eyes, etc.” because the polyester base that the film is made out of is
destroyed by ultraviolet light,” says Jones.
“That is why nearly all window films
block nearly 100% of the ultraviolet light because they are protecting
themselves
. The extra benefit is that [film protects against] the ultraviolet light is
the most damaging portion of the
solar energy spectrum to fade, skin, eyes, etc.”

To understand film as a product you have to understand its origins. Dyed polyester
hasn’t always been the material used to make film. It’s compositions and materials
have changed dramatically over the years.

“The original window films were just vapor deposition aluminum or silver
films
. People think its all dyed polyester, but that actually came after the silver
films because the silver was too shiny,” recalls Jones. “
The silver was very
efficient at blocking a lot of solar energy and they realized the more they put
on there, the darker it got, the more efficient it was. It blocked more heat
because it was reflecting a lot of the visible light spectrum.”

Understanding the importance of the original silver films and the benefits to that
type of a film can help installers and dealers better understand newer products
liked dyed films.

“The original silver 20 ends up looking like a mirror, but it’s very effective
because it reflects energy away from the window,”
says Mitchell. “Any energy
that is reflected doesn’t need to be absorbed. It’s important because the energy
that is absorbed has to be released since objects want to become equal
temperatures with their surroundings. So a portion of that absorbed energy gets

released inward and contributes to heat gain.”

Light and Bright
Times have changed since the days of all silver films and now the emphasis seems to be on
letting as much natural light into the desired space. The architectural community refers to this
as natural daylighting. The window film industry has faced some misconceptions about its
ability to allow natural light in.

Visible light- The part of the electromagnetic spectrum that humans perceive. The infrared
and ultraviolet bands precede and follow visible light.

Ultraviolet light (UV)- Relating to electromagnetic radiation having frequencies higher than
those of visible light but lower than those of x-rays, approximately 1015-1016 hertz. Some
animals, such as bees, are capable of seeing ultraviolet radiation invisible to the human eye.

Infrared light- Relating to the invisible part of the electromagnetic spectrum with
wavelengths longer than those of visible red light but shorter than those of microwaves.

Absorption- The taking up and storing of energy, such as radiation, light, or sound, without it
being reflected or transmitted. During absorption, the energy may change from one form into
another. When radiation strikes the electrons in an atom, the electrons move to a higher orbit
or state of excitement by absorption of the radiation’s energy.

Transmission- To cause (light, heat, sound, etc.) to pass through air or some other medium.
• Reflection- The change in direction of a wave, such as a light or sound wave, away from a
boundary the wave encounters. Reflected waves remain in their original medium rather than
entering the medium they encounter.
visiable spectrum of light
The new direction of things is light and bright. Everybody seems to want lighter as
much of the infrared as you can.”
Being able to allow natural light in, but also keeping the heat out becomes vital to
creating comfortable and energy-efficient buildings.

“People only see visible light, but the other two portions are also contributing to
heat gain,” says Mitchell. “So when an architect or a specifier is looking for a
product that doesn’t transmit heat but does transmit visible light they would be
looking at a ratio between a solar heat gain coefficient (which encompasses all of
the heat coming in—ultraviolet, visible and infrared) compared to just how much
visible light people see. In the industry it’s called the
light-to-solar-gain-ratio. It’s
pretty simple to understand. A ratio of “People only see visible light, but the other
two portions are also contributing to heat gain,” says Mitchell. “So when an
architect or a specifier is looking for a product that doesn’t transmit heat but does
transmit visible light they would be looking at a ratio between a solar heat gain
coefficient (which encompasses all of the heat coming in—ultraviolet, visible and
infrared) compared to just how much visible light people see. In the industry it’s
called the
light-to-solar-gain-ratio. It’s pretty simple to understand. A ratio of one
means that you are
transmitting equal amounts of heat and light. The higher
over one you go the more light you are transmitting compared to solar heat. And
that is what we call spectrally selective.”

There are misconceptions when it comes to the capabilities of window film and what
is noticeable to the human eye though.

Typically there really is an over-abundance of light. On a shiny bright day
you are going to want to knock off about 65 percent of visible light. It’s so
much better for the human eyes,” explains Jones. “When your eye gets over-
exposed it is relaxed and then outside your eye gets bombarded with light
your brain wants to shut it down. It’s too much information.”

“The human eye has a natural ability to be able to open up to let in more light
when it gets darker so unless two different films were side by side you
probably wouldn’t be able to see a 10 percent difference
,”   

If an architect or a customer wants to allow visible light they are not going to get
100 percent blockage by film. The clearer the film the more visible light is coming
into the desired space.

The best they are going to get in 56 percent solar energy rejection,” says
Jones. “That 44 percent of visible light is there. If you have clear film then it
means that visible light is coming through.”

That doesn’t mean that film can’t provide a controlled amount of natural daylight.
Jones says he always thinks of film as a way to manage light. He says that with the
right film you won’t even notice that the film is there.

“With the new spectrally selective films you really can’t even notice it. The samples
at my house of the 60 percent film are practically invisible. If you put a 70 percent
film on a window it literally disappears,” says Jones.e
example light entering window
The Lessons of Light
and Window film
making window film at factory
making window film at the factory
inside sungard  warehouse
Johnson Window Film Ad
Johnson Window Films Wharehous
IWFA INFO BOOKLET ON RESIDENTIAL WINDOW TINTING
faded wood floor
By not having their
windows tinted while
living there the
damaging uv rays
faded the carpets
around where all the
furniture was.
Expensive wood floors
faded from the damaging
uv rays they wouldn't had
to refinish the floors. If they
would have install     
window tint on their      
windows they wouldn't of
had this problem
uv ray chart
Window Tinting
added to your
home,business or car
will protect your
family
uv ray and skin picture
Window Film is made to block
the suns harmful effects.  
Window film installed for
residential and commercial
block uv rays and glare and
heat and are made to do
much more than auto tinting
When needing to get the
a/c and hot spots in your
home or business under
control a high reflective film
is used like mirror
film..becuase of the high
heat rejection from the film
Installing solar bronze
reflective film on a home in
Lehigh Acres
While installing film in your
home. You will always notice
the film working right then