Window Film Blog

Fight the Greenhouse Effect with Window Film

Most of us are ready to get outdoors now that the days are longer and warmer. But the extended sunlight might not be welcome in all parts of the country – or in every room of your house.

If you live in an area with high temperatures and strong sun – or have a room in your house with large windows that get a lot of sun – your home may not be as comfortable as you want in the summer due to the greenhouse effect. But there is a solution: window film.

What is the Greenhouse Effect?

How do large windows and the sun conspire to make your home less than hospitable? Something called the “greenhouse effect”. The greenhouse effect from windows in your home refers to the phenomenon where sunlight enters through the windows, gets absorbed by surfaces inside the house, and then gets trapped, causing the indoor temperature to rise. This is similar to what happens in a greenhouse, where sunlight penetrates the glass, warms the air and surfaces inside, and creates a consistently warm environment for plants to grow.

In homes, large windows or glass surfaces can allow a significant amount of sunlight to enter, which can lead to an increase in indoor temperatures. The absorbed sunlight is converted into heat, which then radiates back into the room. Since the glass acts as a barrier, this heat gets trapped inside, causing the temperature to rise even more. This can lead to increased energy consumption for air conditioning and a less comfortable living environment, especially during hot summer months.

How Does Window Film Stop the Greenhouse Effect?

Window film can help reduce the greenhouse effect in homes by reflecting or absorbing a portion of the incoming sunlight, thereby decreasing the amount of heat that enters the interior spaces. This can lead to a more comfortable living environment and lower energy bills.

All window film has an “active ingredient” that either absorbs or reflects the sun’s energy. Common active ingredients are either a dye, metal, or other nano-particle (like ceramic). The most advanced films for buildings use ceramic to both reject and absorb the sun’s energy blocking it from entering the room.

Our ComforTech™ Ceramic Series film, for example, is made with a ceramic material called titanium nitride, which is extremely durable and reflective:

Comfortech Ceramic Series Window Film Construction Diagram

The ceramic particles are able to reject and absorb much of the sun’s energy keeping it out of your home. 

How much of the greenhouse effect can window film block?

You may be wondering how much of the greenhouse effect window film can stop. The amount of heat blocked from getting through window film depends on the amount of active ingredient used.

ComforTech™ has five shades of film that offer five levels of performance.

Window film performance is determined by industry standard measurements regulated by the National Fenestration Rating Council (NFRC). The NFRC is the same agency that rates windows in the United States. It’s important to purchase a film that has been tested and is rated by the NFRC.

The main indications of heat blockage among the measurements are Solar Heat Gain Coefficient (SHGC) and Total Solar Energy Rejected (TSER).

Solar Heat Gain Coefficient (SHGC):

The Solar Heat Gain Coefficient (SHGC) is the gold standard measure of the amount of solar radiation that enters a building through its windows, doors, and skylights. It represents the fraction of solar heat gain that is transmitted through the glazing and absorbed into the building’s interior.

The SHGC is expressed as a number between 0 and 1, with a lower number indicating less solar heat gain and a higher number indicating more solar heat gain. For example, a window with an SHGC of 0.25 will transmit 25% of the solar radiation that strikes it, while reflecting or absorbing the remaining 75%.

Read more about solar heat gain coefficient.

Total Solar Energy Rejected (TSER):

TSER is a complementary measure for understanding the heat rejection of window film.

Total solar energy refers to all of the sun’s energy that reaches the earth’s surface. This includes. visible light, infrared rays, and ultraviolet light (including UVA and UVB).

And total solar energy rejected is the percentage of solar energy rejected by a glazing system which is equal to solar reflectance plus the part of the solar absorption which is re-radiated outward.

ComforTech Window Film Specifications Chart

Since these two measurements track opposite things – SHGC measures solar energy that is entering and TSER measures solar energy that is rejected – if you add them both as percentages they equal around 100%. As you can see from the performance specifications above, that is roughly the case. The difference occurs because a small amount of the heat that the window absorbs still makes it into the home through convection.

Explore the full set of window film terms.

Performance Specifications Example

Our lightest film ComforTech™ 45 has a SHGC of .48 – so it lets in 48% of the sun’s energy and a TSER of 51 – meaning it rejects 51% of solar energy. In contrast, our darkest film ComforTech 05 lets in the least amount of heat with an SHGC of .18 and rejects the most with a TSER of 82.  

A window film’s performance will improve the darker and more reflective the film is. Something to keep in mind when you are choosing a shade of window film is that you are always trading off lightness for performance.

And be sure to know what you are buying by getting the performance specs of the film!


The Greenhouse Effect is a real issue with windows – especially in warm areas. Heat passes through the glass and then heats up objects in the house resulting in rising temperatures.

So, if you find yourself running your air conditioner non-stop on high and your electric bills get huge in the summer months, you may want to consider installing window film to help cut the heat!

And ComforTech™ Ceramic Series film gives you professional-grade results at a fraction of the cost because you install the film yourself.

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