Does Reflective Window Film Really Keep Out the Heat?

Aug. 05, 2025

Does Reflective Window Film Really Keep Out the Heat?

Reflective Window Tint For Your Home and Office Windows

Windows are an important component on how our homes and offices look and feel. They make the space open, airy, and light, which is something we all want. However, open windows can also allow strangers to see in and rooms hot and uncomfortable during the warm summer months. This might lead you to turn on the AC which will only make your energy bill go through the roof. So, what do you do?

NB contains other products and information you need, so please check it out.

Instead of pulling the blinds and living in the dark, modern window film technology not only lets you keep your outside views, it provides privacy and keeps your space feeling cool and comfortable. When deciding on a window film, many customers want both the heat blocking benefits of solar film and the privacy of reflective window film, but they often wonder, "does reflective window film really block the heat?"

To put it simply, yes. Reflective window film blocks a significant amount of heat, just like solar film. In fact, reflective window film provides the maximum heat rejection and American Window Film carries various kinds of reflective window film for whatever your needs are.

*Reader tip: Before we go any further, we wanted to let you know that this blog is loaded with cool window film performance statistics which we love, but we’re also window film geeks! To show the performance statistics in the simplest way to understand, we included graphs and limited the numbers. If you have any questions, please don't hesitate to comment on this blog and ask!

What is the best window film for heat reduction?

If you aren't familiar with window film, there are a ton of heat blocking window films available that are well-known solutions for uncomfortable heat and glare. Many of American Window Film's customers come to us wanting to know how to cool their homes and offices without darkening their space or losing any outside views. All of American Window Film’s window films will block harmful UVA and UVB rays, and most of our films reduce some amount of heat and glare. The question then, is which window film will block heat the best?

If you’re looking to cool your rooms and privacy isn’t a concern, solar film is a good option. Solar film comes in a variety of different colors and shades, all of which reduce some amount of heat and glare. While solar film will help reduce heat and reduce glare in your home or office, it doesn’t provide any added privacy.

If you are looking for both privacy and cooler rooms, solar film probably isn't the answer. Reflective window film on the other hand might be. Reflective window film reduces the maximum amount of heat, as well as increases privacy. Since the title of this blog has to do with window film, you're probably interested in learning more about that, so let's continue!

What is reflective window film?

Before we go even further, let’s first start by getting to know what reflective window film even is. Reflective window film is a type of window film that reflects light on the outside like a mirror, which is why it can also be known as a one-way mirror film. Reflective window film blocks people from seeing through your windows while still allowing you to see out. Meaning, it will increase privacy as well as reduce a significant amount of heat and glare.

How much heat does reflective window film keep out?

Your next question might be, how much heat does reflective window film keep out? That’s a great question with some great answers. We’ll go into the stats for different types of reflective window films later, but for starters, all reflective window films will reduce a large amount of heat and glare.

When we compare reflective window film to solar film, keep in mind that reflective window film is darker and thus blocks more heat than standard solar film. For example, American Window Film’s one-way mirror film (RN07) blocks the most heat, light, and glare. As we’ll see later, darker and more reflective tints offer greater heat rejection than lighter tints across the board.

Like we said earlier, reflective window film reflects the outside daytime light to whoever is looking at your windows. Reflective window film offers increased privacy while also reducing heat. Our reflective window films keep more than 99% of that nasty UV radiation outside, protecting your belongings from sun-fading and harmful sun rays. The one downside is that reflective window film only gives you privacy during the day--the outside light must be brighter than the light inside.

Window film manufacturer, Llumar,describes reflective window film as "technology on two sides, this reflective window film provides a high level of heat, glare and UV control that keeps people at ease in any area. Gives a uniform and contemporary look. Looks reflective looking out as well.” Let’s dig into some of our most popular reflective window films!

Click here to get a free, no obligation consultation

Reflective Window Film Options

If you want a reflective window film, then you have lots of options. Here's where the numbers and charts come in...so get ready. Don't worry, it won't be that bad!

Window film products have a lot of performance statistics and to make things easier, we put those stats into a graph and compared these four films with untreated clear glass. Let’s take a look…

To make it simple, untreated glass doesn't offer much privacy or protection from the sun's light or UV rays. Over 75% of all solar energy makes it through your bare glass windows. On the other hand, our reflective window films block 99% of UV light and block nearly 50% or more of solar energy and light and glare.

One-way mirror film

One-way mirror film (RN07) is best for when you want privacy during the day without blocking your view. Unlike a lot of reflective window films, Llumar’s RN07 has a higher outside and low inside reflectivity while still blocking heat and glare. RN07 blocks up to 82% of solar energy and 93% of glare.

Silver reflective window film

Llumar's silver reflective window film series is made up of R20, R35, and R50. R20 is a good compromise between maximal heat rejection, privacy, and cost. The number means that in the series, R20 lets in the least amount of light (20%) and so has the darkest reflective silver tint. It blocks more than 80% of sun glare.

R35 and R50 let in more light than R20 (here, 35% and 50% of light are let in, respectively), and so they are lighter than R20. The three films perform similarly otherwise, except in the numbers: R35 blocks 69% of glare, say, while R50 blocks 46%.

Dual-reflective window film

Llumar defines dual-reflective window film technology as “pairing a reflective outside-facing layer with a subtler inside-facing layer. This enables it to provide significant solar control while maintaining outside views after dark, while it looks less reflective from the interior looking out.” This means that dual-reflective window film tempers reflective window film’s interior night-time reflection, so you can see more outside when it’s dark.

For this blog, we’ll talk about the three most common dual-reflective films we offer: DR 15, DRN 25, and DRN 35. They all come in the pleasing shade of warm grey. Again, remember that 15 means the film let’s 15% of light, while 35 lets in 35% of light.

Let’s look at another graph of those films’ stats against the untreated glass (which has the same stats as the previous graph!)

As you can see, dual-reflective window film performs similarly to reflective window film, except they let more light in. The three dual-reflective film difference is that the DR15 provides the most heat rejection, while DR 35 provides the least of the three. Otherwise, they all block 99% of more of UV light, all improve your home or building’s windows’ look, and all reduce hot and cold spots by insulating your windows. They’re also all durable and scratch-resistant for easy cleaning.

Exterior window film

Exterior window film is a durable film built especially to withstand the elements outside (whereas most other window films are installed on the inside of your windows). Exterior window film offers the same heat blocking and privacy benefits and is reflective from the outside as well. Llumar’s definition describes it as possessing “impressively effective heat rejection, glare control, 99% UV ray protection.” Llumar’s exterior reflective window film has a strong, scratch-resistant coating that enables the film to stand up to the demands and exposure that are inevitable with exterior installation.

American Window Film carries many exterior window films, but we’ll look at the details for three in particular: RHE 20, RHE 35, and RHE 50. Again, the higher numbers let in more light!

We have one more graph that looks at how exterior window film compares to untreated glass (with the same specs as the other graphs).

For more information, please visit Heat Blocking Window Film.

Exterior window films perform similarly to reflective and dual-reflective window films, which is what makes window film so cool! When choosing a product, product performance is not the main concern, you just worry about the aesthetics and unique features.

All three are silver-toned. Between the three films featured here, the 20 offers the maximum amount of heat and glare reduction while the 50 offers the minimum.

So, which reflective window film should you choose?

American Window Film works with more than just homeowners. We work with business owners, general contractors, property managers, facility managers, and more, to install reflective window film on commercial buildings of all sizes. Glass is glass, and American Window Film’s window films work the same on both.

Now, like we said: reflective window film acts as a mirror to the outside daytime light, which means your windows will be dark on the outside. Reflective window film isn’t the first choice for homeowners as installing reflective window film changes the house’s exterior look. If your window’s outside appearance isn’t important, then a reflective window film is a great choice for you.

If you are concerned about how your home looks but still want some reflective privacy, dual-reflective window film is a great choice because it has some tint to it and looks less like a mirror. Dual reflective window film will also keep out a lot of heat. If you don’t want a reflective surface at all, then you should look at ceramic window tint instead.

Office buildings and businesses have different goals than homes, and reflective window film is common to commercial buildings. Commercial property managers often go with reflective window film because they get the maximum amount of heat rejection and privacy via mirror reflection. In the end, though, American Window Film’s window films work the same on home and commercial windows.

American Window Film Window Film

About Window Films - Fsec .ucf .edu

The basic principles presented on our pages titled "About Solar Gain," "Window Selection Guidelines," and "Q&A on Window Replacement" apply to windows with after-market or retrofit plastic window films as well. The difference is that window films are generally a retrofit option, intended to fix a problem with excessive solar heat gain and/or solar glare from an existing window while window coatings are generally applied in a glass factory, usually in a large vacuum chamber.

In the past, and in many cases still today, after-market films blocked more light than heat. Consequently, if they were dark enough to protect an interior from strong direct solar radiation, they also tended to make the room rather dim in appearance. With such films, the visible transmittance (VT) value was lower than the solar heat gain coefficient (SHGC), opposite from what is wanted in most U. S. climates. In worst cases, the window was so dark that you had to turn the electric lights on in the daytime to see properly, and you still had to suffer the consequences of excessive heat gain! Such films are still available, but should seldom be used in hot climates. Be careful to avoid them when you can.

The old-technology films are characterized by accomplishing their solar heat gain rejection through absorbing the whole solar spectrum, preventing its direct entry into the home. The problem is that the film heats up a lot and, when applied to a single pane of glass or the inner pane of a double pane window, most of their heat is conducted, radiated, and convected to the interior of the building, making the room hotter than it should be. This defeats the purpose of the film, to reduce solar heat gain, because much of the incident solar heat still enters the room. Less light is admitted as well.

Furthermore, many double pane window manufacturers void their warranties if the homeowner puts a window film on their product. One reason for this is that when the film gets hot, it makes the pane it is affixed to get hot as well. The glass expands, and expands more than the outer glass without the film. This difference in expansion can create stresses in the window which in worst cases can cause the window to break, through no fault of the window. If you wish to apply window film to a double pane window, make sure the window manufacturer will continue to back the window warranty.

Modern, High-Performance Window Films

To avoid the unfortunate consequences of excessive solar heat gain, window film manufacturers have been working to develop modern products which block more heat than light, doing it by reflection of the unwanted infrared radiation contained in the solar rays, while still admitting adequate amounts of visible light, necessary to see the outside, and to provide good daylight illumination of the interior.

In order to get the right kind of window film for your window, look for the Visible Transmittance (VT) value for the film when applied to a single pane of clear glass. Then find the Solar Heat Gain Coefficient (SHGC) for the combination. If the VT value is greater than the SHGC value, you have the right kind of film for a hot climate window, but be sure to check the window manufacturer's warranty before applying the film.

The Light-to-Solar-Gain (LSG) ratio is the VT value divided by the SHGC value. The higher this ratio, the more spectrally selective the film and the better it is for hot climates. It is difficult, however, to achieve LSG values greater than about 1.2 with window films. Soft multi layer coatings inside double pane windows, however, can achieve values as great as 1.6, providing good transmission of visible light (no dark appearance) as well as good solar heat gain rejection. In order to achieve good solar heat rejection with either a window coating or an applied window film, the SHGC value needs to be low (below approximately 0.3 to 0.5) to be effective—the lower the better. With an LSG ratio of only 1.1, for example, this means that the visible transmittance (VT) value will be about 0.33 to 0.55. Low values in this range can impart a dark appearance to the glass and may be objectionable. For sunrooms with vast expanses of glass exposed to the direct sun for much of the day, however, values as low as 0.3 to 0.4 for the VT should not be objectionable, especially since these values can produce SHGC values below 0.3 to 0.4 with window films having LSG values greater than 1.0.

Shiny Reflecting Appearance

The lightest LSG film is often made of metallic material or is otherwise reflective. The reason is that reflective films reflect the unwanted solar heat gain away from the window before it can be absorbed. Tinted or absorptive films block solar gain by absorbing it in the film, heating the film, and dissipating this heat to the inside and the outside of the room. Unfortunately, when applied to the inner surface of a window, much of this heat conducts, convects, and radiates to the interior, defeating much of the purpose for which the film was intended. Reflective films reduce the absorbed solar heat and reflect more of the blocked solar heat back outside.

Unfortunately, many homeowners associations object to the use of shiny- or mirror-appearing coatings on the windows of homes in their jurisdiction. The reflecting value of a film is quantified by its visible reflectance (VR) value. The higher the reflectance, the shinier the window will appear. This is objectionable on the inside at night because the window looks more like a mirror than a window and during the daytime the same is true when viewed from the outside.

If this is a potential problem for you, find the maximum value of the visible reflectance in your homeowner association's rules and make sure your window films do not exceed this value when applied to the inside surface of the window glass in your home.

Fortunately, high-LSG window films should be available which achieve their solar heat gain rejecting properties by being highly reflective over the invisible infrared portion of the solar spectrum while being only slightly reflective over the visible portion of that spectrum. The consequence is that such films reject by reflection most of the invisible infrared heat radiation from the sun while passing most of the visible light.

The infrared portion contains nearly half the heat of the solar spectrum, so reflecting all of this radiation would, by itself, reject almost half the solar heat gain while still permitting much of the visible light to pass through the window. This effect is more difficult to achieve with applied plastic window films than with multi layer coatings applied in a vacuum at the glass factory, which is why the latter generally achieve higher LSG values than can be found with plastic window films.

Shopping for Window Films

When shopping for window films intended for residences in hot climates, insist on high LSG products, having values exceeding 1.0. Then look for the lowest SHGC value you can find in a film that is not objectionably dark to the eye.

The human eye is very good at seeing small differences in brightness (illustrated by the differently tinted window panes in the photo to the left), but the eye is not that good at perceiving absolute brightness levels. The eye adapts to changing levels, and you can see just as well in a room illuminated with lux of light as in one having lux. The consequence is that a film sample held in the sales room or even placed over a window in the store may appear dark in comparison to the uncovered glass adjacent to it. But when it covers a large expanse of glass in your home, and there is no uncovered glass to compare it to, you might not be able to tell there is even a film on your windows! This makes it somewhat difficult to know from looking at samples in the store what film will be too dark for you when installed in your home. Perhaps the sales person has a room with window film on all the windows. If so, look at that room and decide if it is bright enough for you. Then ask the sales person what the visible transmittance is for that film. The room will appear darker on an overcast day than on a sunny one, and electric lighting can alter your perception of room brightness, so you may wish to make your observations with the electric lighting temporarily turned off.

If you cannot determine an acceptable VT value for your window film from the samples and demonstration windows in the store, you can use this guideline:

For moderately well shaded, vegetative exterior scenes, keep the visible transmittance (VT) value above about 0.45 to 0.55.

For a bright, unshaded exterior scene, especially one with bright, highly reflecting surfaces in view outside the window, choose lower VT values, in the range from 0.25 to 0.4. Be careful with values at the lower end of this range. If the application is for a sunroom, the result might be too dark for you. For a sleeping room, however, the somewhat darker film can help avoid window-produced glare. For more on this subject, see our short glare tutorial.

Color Issues

To obtain the highest LSG window films sometimes the resulting film has a slightly colored appearance. This color should not be evident when looking through the window from the inside, but it might be more obvious when looking at it from the outside. This is most likely a consequence of the manufacturer's efforts to achieve the high LSG ratio. By narrowing the spectral region through which solar radiation can pass to just the visible portion, sometimes light at the edges of the visible gets clipped, cutting out either some of the blue light or some of the red at the other end of the spectrum (or both). The best way to tell if this is objectionable when applied to the windows in your house is to place a fairly large film sample on your window and look at it from the outside. Try to look only at the patch of film sample in making your judgment. This way you are less likely to be biased by the subtle difference in color between the filmed and nonfilmed areas.

Are you interested in learning more about Protective Film for Aluminum? Contact us today to secure an expert consultation!

Previous: Top PET Tape Suppliers for Your Fixing Needs

Next: Ultimate Guide to China Metal Surface Protective Film

Comments

Please Join Us to post.

Guest Posts

If you are interested in sending in a Guest Blogger Submission,welcome to write for us.

Your Name: (required)

Your Email: (required)

Subject:

Your Message: (required)

0/2000