Window Film Buyer’s Guide

In a Nutshell

If refurbishing all your windows is not within your budget, window film can be a viable alternative. 

When affixed to the interior of a window, door, skylight or curtain wall, you can bring privacy, solar control and security to buildings, vehicles and smart city infrastructure.

Typical Issues with Window Film

Although you can install it yourself, we recommend hiring a professional to avoid typical issues:-

• Bubbles forming under the film
• Color fading of some films under extreme sunlight
• Mobile phone interference (with metallic films)
• Delamination caused by humidity seeping into poorly-sealed edges
• Misalignment of the film with the glass during installation

Manufacturers avoid most of these issues by laminating the film inside the glass.

Investment and Return

Installing window film is a low up-front investment compared to replacing the entire window.

Getting a return on your investment though will depend on several factors :-

• whether the installation reduces air conditioning or heating costs
• whether natural daylighting minimizes artificial lighting costs and improves the health of your workforce, reducing sick leave
• whether the improved comfort for employees translates to increased productivity

The best solution is always going to involve insulated windows and robust building insulation if you want to bring down your energy bills and reduce your carbon footprint.

Having said that, let’s look at some reasons why you might consider using window film as opposed to refurbishing the windows outright.

Reasons to Buy Window Film

1. Hygiene

Window films applied to glass interiors can replace curtains, blinds and shades, avoiding the germs, bacteria and viruses that can reside within their porous surfaces. 

Examples include:-

• MRSA (Methicillin-resistant staphylococcus aureus)
• Clostridium difficile (C.diff) and 
• Norovirus, which leads to many cases of gastroenteritis.

Since film and glass are non-porous, germs cannot reside or grow within them.

Furthermore, window film can offer privacy, on-demand tint and aesthetics, while also welcoming in natural sunlight, which aids patient recovery times in healthcare environments.

All within a moderate budget.

The same reasoning applies to other businesses where hygiene may be a factor, such as hotels, restaurants, assisted-living residences and nurseries.

Our article on this subject explains the issue in more detail.

2. Safety

Some window films improve safety by keeping broken glass in place on the window, avoiding broken shards from upper floors falling on passers-by below.

The issue can be caused by severe weather, workplace accidents or other unintentional hazards.

Applicable standards include EN 12600 and ANSI Z97.1 which define safety glass as one where “the likelihood of cutting or piercing injuries that might result from contact is reduced.” 

One such product is the 3M™ Scotchshield™ series Ultra S800 safety film, which is applied to window interiors and retains broken glass fragments while maintaining optical clarity.

We are using 3M™ products as examples of what you can find in the market at this time. Other manufacturers exist.

3. Security

Security film minimizes the risk of intentional acts of violence, such as assailants who attempt to break into a home or business. 

The window film adds a layer of protection against violent threats conducted with firearms, axes or hammers. Security film is thus especially useful for luxury residences, banks, retail stores and museums.

An example is Scotchshield™ Security Window Film (S2400) from 3M™. The polyurethane layer resists breakage better than PET and retains glass fragments.

The film also remains optically clear and blocks UV but must be installed with specific sealants. 

Although classified as a security film, this product aims only to slow down ‘smash and grab’ burglars, not stop them.

4. Privacy

The acid-etched look of frosted glass can be created by applying privacy adhesive window film to bathrooms, meeting rooms and in hospitals. 

The film makes the glass look translucent, such that objects behind the glass are no longer recognizable but visible light is still transmitted. This brings daylight deeper into dark interiors without sacrificing privacy.

You can choose from static films which do not change their appearance and dynamic films, which can be controlled electrically.

Dynamic privacy film (normally based on polymer-dispersed liquid crystals, or PDLC) varies its opacity between translucent (where it scatters light) or transparent, when activated.

Changing the voltage alters the level of scattering from a maximum (when switched off) to a minimum (at the highest voltage), typically 3%-5%.

There are also PDLC technologies that work in the reverse direction. Contact us if you would like to know more.

You can buy (self-adhesive) liquid crystal smart film in our Samples shop, which comes with a USB-powered electronic controller, and see for yourself.

5. Data Cloaking

There is a window film technology that hides confidential information from public view. It is called Casper™ Cloaking Technology from Designtex. 

This innovative technology hides light emanating from LED displays. The glass surface otherwise maintains its normal level of transparency and clarity.

This reduces visual hacking, eavesdropping and improves confidentiality in open-plan corporate environments where not all eyes can be trusted.

6. Glare

Certain window films reduce the intensity of daylight reaching interior spaces, providing comfort in homes and reducing eye strain for office workers.

This eye strain can be particularly troublesome where light is reflected polarized by nearby building facades, and can cause migraine headaches.

There are several technologies that can prevent this, but most are available only in laminated glass formats. These include suspended particle devices (SPD) film, electrophoretic film and electrochromic film. 

However, there is also a self-adhesive film based on Dyed Liquid Crystals in our Samples shop that gives light control, minimizing glare, heat gain and offering privacy.

Buy a sample and try it out!

7. Heat Gain

This type of window film reflects solar infrared (i.e. heat), reducing its transmittance into buildings and vehicles.

This minimizes air conditioning costs and in the case of electric cars, prolongs battery life.

Low-emissivity (low-e) films are normally available only when deposited on insulated glass units (IGUs) during manufacturing. This is a ‘static’ smart film technology, since it does not alter its behavior.

On the other hand, dynamic smart films are also available and include:-

• Thermochromic smart film, which tints when heated by solar infrared, is normally available only as a laminated product.
• Photochromic smart film, which tints when struck by solar ultraviolet, is available as self-adhesive film and as laminated glass.

Both the above are examples of passive smart film technologies since they are not electrically-activated. You can buy samples of thermochromic smart glass and photochromic smart film in our samples shop.

An example of a dynamic active smart film which tints when operated electrically is the Dyed Liquid Crystal film we mentioned above, which reduces heat gain.

8. Color Fading

Ultraviolet (UV) can damage interior furnishings such as carpets, curtains and flooring. 

It can also deteriorate leather and silk garments, wiping the value off multi-million Dollar retail inventories, normally exhibited under high lighting conditions (800-1000 Lux).

Even more so, museums and private collectors know that UV can cause damage to artworks and historical items, hurting their investment value. Our parent company, ArtRatio has manufactured smart glass display cases since 2009, with the aim of minimizing this risk.

The most visible effect of UV damage is color fading, but prolonged exposure also causes internal damage to rare books, manuscripts and paintings. You can find more information on the ArtRatio blog.

Most laminated glass will block more than 99% of UV, but when this is not available UV-blocking films will do the same job. The 3M films mentioned above will help in this regard.

9. Projection Screens

Translucent window films provide privacy by scattering visible light as mentioned above, but can also be used as a passive projection screen, thanks to their uniform scattering effect.

Static films take on a permanently frosted appearance, whereas dynamic (switchable) films become transparent only when activated electrically.

This converts any glass surface into an effective marketing screen without taking up valuable floor space. The images can be projected from the front or the rear of the glass where the film is applied.

This can be useful for shopping malls, airports and retail stores.

10. Active Display

LED smart film is a relatively new product which can be adhered to existing glass and projects audiovisual images in an active (electrically-driven) manner. 

The LEDs are embedded inside the film and connected by transparent conductive polymers, such as ITO.  One such product is from Filmbase, who advertise this product as Skyscraper Media Glass.

This is also ideal for hotel lobbies, airports and train stations, or wherever large-format dynamic signage is required.

If you are looking for 3-dimensional active display, then you will need to look at holographic smart film, which is normally sold to transportations OEMs (automotive, railroad, marine, etc). This film is then laminated inside glass and connected to the rest of the vehicle electronics. 

You can read more in our learning article.

11. Protecting Biodiversity

An estimated 1 billion birds die each year due to window collisions, especially in built environments close to rural areas. This can cause drastic reductions in bird populations, and create a conservation threat to biodiversity.

Thankfully, there are window films designed to combat this issue, where solar ultraviolet is converted into blue light, which is visible to birds but less so to humans. This ensures the aesthetics of glass while reducing bird fatalities.

These films are available as plastic stickers (often called ‘decals’) that can be affixed to window interiors. 

Our learning article explains this technology in more detail and names manufacturers that you can reach out to.

12. Decoration

Decorative window films can be installed on window interiors to give a specific pattern or color scheme, often bringing a breath of fresh air to the building.

Such films are cost-effective and normally transmit sunlight, offering uplifting designs, thus making them especially beneficial for creches, primary schools and children’s hospitals.

One of our personal favorites is from Artscape, who manufacture hand-crafted film designs that bring elegance, transforming the window into a true work of art!

13. Generate Clean Electricity

Organic solar cells are able to convert sunlight into electricity while maintaining transparency, and are available as a film which is laminated between 2 panes of glass.

Some products are also available as roll-on, adhesive strips, such as the one from Heliatek, which requires professional installation.

Efficiencies of transparent photovoltaic (PV) glass are often much lower (3% – 5%) than traditional solar panels (typically around 20%). 

However, the front-facing PV layer can be used to power dynamic switchable film directly, obviating the need for cabling. This is a major cost saving for property developers.

This technology is still nascent but holds the promise of converting all building facades into generators of clean electricity.

Here are some manufacturers and researchers listed in alphabetical order:-

• Andluca
• ASCA
• NEXT Energy Technologies
• NREL

You can read more about this technology in our learning article.

14. Radio Frequency (RF) Barrier

These visually-clear window films contain multiple metallized layers that reflect RF signals outwards, acting as a barrier to potential eavesdropping and data security risks.

The layers also keep the building cool by reflecting solar infrared and also block UV, reducing color fading of interior furnishings. 

Typical visible light transmittance figures can be around 60% to 70%.

Ideally, you want to find a product with low visible light reflectance to ensure the best aesthetics when viewed from outside.

Some manufacturers, listed alphabetically are shown below:-

• EMR Shielding Solutions
• Pilkington
• Safe Living Technologies
• UK Window Films

Our learning article talks in more depth about these films.

Taxonomy of Window Films

The diagram below shows the taxonomy of all the window films we currently know of.

If we missed any, do drop us a line and let us know.

The technologies are grouped into static vs dynamic, depending on whether the film’s optical properties can be made to change on-demand or not.

The dynamic group could be further subdivided into passive vs active (electrically-controllable), but we wanted to keep the diagram simple.

Some of the dynamic window films are only sold within laminated glass, where the film is sold in rolls to glass processors, typically in wholesale quantities.

Here is the same taxonomy in textual format with links for further information:-

Static film (optical properties do not change)

• • Translucent (Privacy) Film
  • Decorative Film
  • Mirror Film
  • Solar (Heat-Reflecting) Film
  • Data Cloaking Film
  • Bird-Friendly Film

Dynamic film (optical properties can change)

• • • Photochromic film: changes tint with solar ultraviolet
    • Thermochromic film: changes tint with solar infrared (heat)
    • Liquid Crystal (PDLC) film: changes between transparent and translucent when electrically activated (takes seconds)
    • Suspended Particle Devices (SPD) film: changes tint when electrically activated (takes seconds)
    • Electrochromic film: changes tint when electrically activated (takes minutes normally)
    • Electrophoretic film: changes tint when electrically activated (takes seconds)
    • Holographic film: can turn a glass surface into a 3-dimensional informational surface
    • Transparent Photovoltaic (PV) film: converts sunlight to clean electricity while maintaining transparency
    • LED Display film: can turn any glass surface into an audiovisual display surface
    • RF Barrier film: radio-frequency blocking films that reduce the risk of eavesdropping and data security

Window Film Characteristics

We now look at the most important window film parameters you need to consider when purchasing these products.

You can also use our parameterized search to zoom in on specific values and locate suppliers more quickly.

Visible Light Transmittance (VLT)

The VLT is the amount of sunlight transmitted by the film, and is measured as a percentage. 

Higher VLT will translate into more sustainable daylighting, avoiding dark interiors and reducing artificial lighting costs.

Solar Heat Gain / G-Value

The ‘Heat Gain’ is the solar infrared transmitted by the film, so higher values mean that sunlight will passively warm the room, which is good in colder climates. 

Conversely, lower values are necessary in warmer climates to reject solar infrared heat, reducing air conditioning costs.

UV Rejection

As mentioned above, UV can damage furnishings and artworks, and laminated glass normally rejects 99.9% of UV. 

Many other window films will do the same by the nature of the materials used.

U-Value

This number is applied to the whole window, and does not carry much meaning for the window film itself. 

• In Europe it is expressed in Watts per square meter Kelvin. 
• In the US, it is expressed as British Thermal Units (Btu) per hour-square feet-degrees Fahrenheit: Btu/(h⋅ft2⋅°F). Quite a mouthful, we know.

This represents the heat lost through a window and depends on the thickness and cross-section of the frame, as well as the temperature difference across the frame.

Color Rendering Index (CRI)

This number (from 0 to 100) indicates how well colors in sunlight are portrayed (i.e. rendered) by the film. 

CRI is important for healthcare professionals, as doctors will often base diagnoses on skin and gum color. A poor CRI will leave otherwise-healthy patients looking seemingly ‘off-color’.

More on this subject in our learning article.

Visible Light Reflection (VLR)

Interior reflections can impede views on sunlit gardens. Exterior reflections can cause light pollution on nearby buildings. 

Reflections can also increase bird-window collisions when birds mistake the reflections of trees with the trees themselves.

VLR is stated as a percentage, applicable both for interior and exterior reflection.

Power Consumption

This parameter is only applicable to electrically-controlled dynamic film, such as PDLC, SPD, electrochromic and electrophoretic glass products. 

PDLC and SPD technologies need constant activation in order to maintain their transparency but change state in seconds.

Electrochromic films only need a small burst of electrical current to change state, but do take several minutes to tint.

In addition to the electrical power consumed, we also need to take into account the electrical power factor of connecting a capacitive load to the mains circuits (PDLC and SPD), which can waste energy and even result in fines from your electrical utility.

Power Generation

This parameter is only applicable to transparent photovoltaic film and is stated in Watts of power per square meter.

Quality and Warranty

The quality of the final installed window film will depend on:-

• Temperature and humidity fluctuations
• The building’s geography, orientation and height above sea level

Warranties of 15 years for commercial installations are typical, as long as the work has been carried out by the manufacturer.

Green Building (LEED v5) Credits

Check out our analysis of how smart film materials can help property developers and architects achieve LEED v5 compliance by allowing the building to meet its sustainability, wellness and conservation goals.

Outlook

The window film sector is projected to grow from USD 2.8 Billion in 2023 to USD 4.4 Billion by 2032, at a compound annual growth rate (CAGR) of 5.9%. 

The main drivers for growth are:-

• The push for energy efficiency as a means to achieve net zero energy usage
• The need to reduce the carbon footprint of the global building stock

The biggest factor though may be the payback period. 

Refurbishing windows requires a much larger investment, so the monetary benefits need to be much larger in order to meet a target payback period, such as 7 years.

The corresponding investment for retrofitting window film is much smaller, meaning that payback is achievable in a shorter time frame.

There is a market for both film and glass (static vs dynamic and passive vs active), and is strongly influenced by growing public-sector initiatives to combat the climate crisis.