IRR vs IRER vs TSER: What Solar Film Numbers Really Mean

Why the biggest percentage isn’t always the better film

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IRR vs IRER vs TSER: How to Compare Solar Film Heat Rejection Properly

Solar film brochures often display impressive numbers such as 90%, 95%, 98% or even 99% infrared rejection, while another product may show a much lower-looking figure for IRER, and a third manufacturer may focus primarily on TSER. All of these figures can be technically valid, but the important point is that they may not be measuring the same thing at all.

This is one of the most common sources of confusion when comparing automotive and architectural solar films. A film advertising 96% infrared rejection cannot automatically be considered better than another film showing 60% IRER, because the two percentages may represent different wavelength ranges, different measurement methods, and entirely different aspects of solar performance. At Window-Cool, we believe the better way to compare solar films is not to search for the largest percentage, but to first understand what each percentage actually represents.

Solar Heat Cannot Be Described by One Number

Sunlight reaching a window contains energy across different parts of the solar spectrum, including ultraviolet radiation, visible light and infrared radiation. Solar film can interact differently with each part of that spectrum. Some films are designed to remain very clear while selectively controlling infrared energy, while others reduce considerably more visible light and therefore achieve higher overall solar-energy rejection. This is why several different measurements are used within the window-film industry, and the most commonly encountered are VLT (Visible Light Transmission), IRR (Infrared Rejection), IRER (Infrared Energy Rejection), SIRR (Selective Infrared Rejection) and TSER (Total Solar Energy Rejection). None of these should be treated as interchangeable with one another.

What Is VLT?

Visible Light Transmission, or VLT, measures how much visible light passes through the glazing. A film with 80% VLT allows considerably more visible light through than a film with 30% VLT, and this affects how light or dark the film appears, outward visibility, glare, daytime privacy and compliance with automotive regulations. VLT is particularly important when comparing solar films because two products can have similar infrared performance but very different levels of visible-light transmission. A darker film may also achieve higher overall solar-energy rejection simply because it is reducing more visible solar energy, not because its infrared technology is superior.

What Is IRR?

IRR generally refers to Infrared Rejection, though it is not always measured across the complete infrared portion of the solar spectrum. Depending on the manufacturer or instrument, an IRR figure may represent performance at a particular wavelength, across a relatively narrow wavelength band, or across a defined infrared range. This means a figure such as 95% or 96% infrared rejection can be completely legitimate while still not meaning that the film rejects 95% or 96% of all solar heat. The wavelength being measured matters just as much as the percentage itself.

What Is IRER?

IRER stands for Infrared Energy Rejection. Major manufacturers such as LLumar, 3M and XPEL use IRER to describe infrared performance across a much broader part of the infrared spectrum, commonly approximately 780 to 2,500 nanometres. IRER can also take into consideration infrared energy absorbed by the glass and film that may subsequently be reradiated inward, which is why an IRER percentage may appear lower than a narrower infrared-rejection figure even when the film itself provides excellent solar-control performance. The two numbers are simply describing different things.

What Is SIRR?

Some LLumar specifications also publish SIRR, or Selective Infrared Rejection, which describes infrared solar energy across a broad wavelength range that is not directly transmitted through the glazing. LLumar may therefore publish both an IRER and an SIRR figure for the same product, and a film can have an IRER around 60% while its SIRR is considerably higher. Neither number is incorrect; they are simply calculated differently, and this illustrates why comparing one manufacturer’s IR percentage directly with another manufacturer’s differently defined IR measurement can produce a misleading conclusion.

What Is TSER?

For someone primarily concerned about overall solar heat entering through glass, one of the most useful specifications to understand is TSER, or Total Solar Energy Rejection. TSER describes the percentage of total incident solar energy rejected by the filmed-glass system, which is different from looking only at infrared performance. It considers the overall solar-energy behaviour of the glazing system, including transmitted, reflected and absorbed energy. A film might therefore display 96% infrared rejection while having only 70% IRER and 61% TSER, and all three figures can coexist on the same technical specification because each represents something different. The 96% figure does not mean that 96% of all solar energy is being rejected.

A Real Example: Why One Film Can Have Several Different Heat-Rejection Numbers

Manufacturer specifications provide a useful demonstration of this principle. XPEL PRIME XR PLUS 30 has been published with approximately 31% VLT, 96% IR rejection at 1025 nm, 70% IRER across approximately 780 to 2,500 nm, and 61% TSER. This does not mean that one of the numbers is wrong; instead, the specifications show the film from different technical perspectives. The 96% figure describes very strong rejection at the stated infrared wavelength, the 70% IRER figure represents infrared-energy performance across a much wider infrared range, and the 61% TSER figure represents rejection of total solar energy through the tested glazing system. This is an excellent example of why consumers should avoid ranking solar films simply by selecting the largest number printed on the brochure.

3M Uses Different Infrared Measurements Too

3M also distinguishes between infrared measurements. For some of its automotive films, 3M publishes an IRR value measured over approximately 900 to 1,000 nm, while IRER covers approximately 780 to 2,500 nm. As a result, a 3M product may carry an IRR figure in the mid-to-high 90% range while its IRER is considerably lower, and again both measurements can be correct since the difference lies in what is being measured. This is useful evidence that different infrared percentages are not unique to one manufacturer or one film technology; they are simply part of the way solar-control performance is characterised across the industry.

LLumar Also Publishes More Than One Infrared Measurement

LLumar takes a similar approach. LLumar AIR80, for example, has been published at approximately 77% VLT, 43% TSER, 60% IRER, 86% SIRR and more than 99% UV rejection. Someone looking only at the IRER could see 60%, while someone looking at SIRR could see 86%, yet both describe the same film. This is exactly why it is better to ask what a measurement means rather than concluding that one number is superior simply because it is larger.

Does 96% IR Rejection Mean Better Performance Than 60% IRER?

Not necessarily, and the honest answer requires knowing how each figure was measured before drawing a comparison. If the 96% figure represents rejection at one specific wavelength while the 60% figure represents energy rejection across approximately 780 to 2,500 nm, the two are not directly comparable. A more meaningful comparison would involve examining VLT, TSER, broad-spectrum infrared performance, glass type, test methodology, wavelength range and the intended application together, and only after these factors are aligned does a percentage become genuinely useful for ranking one product against another.

Why High Infrared Rejection Is Still Valuable

None of this means that a high infrared-rejection percentage is meaningless. A film achieving 95%, 96% or even 99% rejection at a particular infrared wavelength can demonstrate sophisticated spectral-control technology, and the important question is simply what the percentage represents. A technically responsible comparison should preserve the manufacturer’s original definition, since stating “96% infrared rejection at 1025 nm” is considerably more informative than simply stating “96% heat rejection.” The first statement describes a technical measurement, while the second can easily be misread as meaning 96% of total solar heat, which is not necessarily what was tested.

Why TSER Is Particularly Useful for Comparing Overall Heat Performance

If the objective is to understand how much total solar energy is being rejected, TSER deserves significant attention because it includes more than infrared performance alone. Visible solar radiation also carries energy, which is why a darker solar film often achieves higher TSER than a very clear film even when their infrared performance is surprisingly similar. Consider two films for illustration: Film A carries 77% VLT, 60% IRER and 43% TSER, while Film B carries 33% VLT, 61% IRER and 56% TSER. Their IRER figures are almost identical, yet Film B rejects considerably more total solar energy because it also reduces much more visible solar radiation. Looking only at infrared rejection would miss that distinction completely.

A Very Clear Film Can Still Have Strong Infrared Performance

Modern spectrally selective films can allow large amounts of visible light through while selectively reducing infrared transmission, which is why the appearance of a solar film does not necessarily reveal how technically advanced it is. A very clear ceramic or spectrally selective film may provide substantial infrared reduction while remaining almost transparent, while conversely a dark film may achieve strong TSER partly because it blocks considerably more visible light. Darkness therefore does not automatically mean better infrared rejection, and high infrared rejection does not automatically mean high total solar-energy rejection. They are related characteristics, but they are not the same measurement.

Why Comparing TSER Between Brands Still Requires Care

TSER provides a broader view of solar performance, but even TSER figures should not always be compared without checking the test conditions, since different manufacturers may publish data using different glass thicknesses, glass compositions, test standards, measurement equipment and calculation methodologies. One manufacturer may publish data on 3 mm clear glass while another uses nominal 6 mm clear glass, and if two products both state 55% TSER but were tested on different glazing systems, the numbers are not necessarily perfectly equivalent. This does not make the data unreliable; it simply means that a technically accurate comparison should consider the test conditions as well as the final percentage.

Why Solar Film Meter Demonstrations Need Context

Infrared meters are commonly used to demonstrate solar-film performance and can be genuinely useful tools, but a meter reading should always be understood in context. If an infrared meter shows a reading of 95%, the useful question is at what wavelength or wavelength range the meter is measuring, since many handheld meters measure only selected portions of the infrared spectrum. A strong reading at that wavelength demonstrates that the film performs well there, but it should not automatically be converted into a claim that the product rejects the same percentage of total solar heat. The meter may be perfectly accurate; the interpretation of the result is what matters.

A Better Way to Compare Solar Films

When comparing two window films, Window-Cool recommends working through the specifications in a consistent order. Begin by establishing the intended application, whether that is a vehicle windscreen, front side windows, rear automotive glass, home windows, commercial glazing or a specialised application, since different applications require different balances between visibility, heat control, privacy and reflectivity. From there, compare films with a similar VLT to one another, since a 30% VLT film should ideally be measured against another film in approximately the same VLT category rather than against an 80% VLT film purely on TSER, which does not tell the complete story given how differently the two products are intended to be used.

Next, look at TSER for a sense of overall solar-energy rejection, then check how the infrared performance is actually defined, whether as IRR, IRER, SIRR or another manufacturer-specific measurement, and confirm the wavelength range behind it. If one product quotes performance at a single wavelength and another quotes a broad-spectrum measurement, the figures should not be ranked directly against each other. It is also worth checking the glass type and testing conditions, since film performance is affected by the glazing on which it is tested and ultimately installed. Finally, a specification sheet does not fully describe optical clarity, haze, colour stability, adhesive quality, manufacturing consistency or long-term durability, and these factors matter a great deal for a product that will remain installed for many years.

Why This Matters for Singapore Cars

In Singapore, heat rejection must also be considered together with LTA visible-light-transmission requirements. The finished combination of glass and solar film must provide at least 70% VLT for the front windscreen, 70% VLT for the two front side windows, 25% VLT for rear side windows and 25% VLT for the rear windscreen. The important word here is finished, because a solar film labelled 70%, 75% or 80% VLT does not automatically mean that the completed glass-plus-film system will achieve the same percentage, given that original automotive glass already has its own light-transmission characteristics. A suitable solar film for Singapore therefore needs to balance VLT compliance, TSER, infrared performance, glare reduction, optical clarity and durability all at once, and the product with the largest infrared percentage is not automatically the most suitable choice for a Singapore vehicle.

IRR, IRER or TSER: Which Number Should Consumers Trust?

The better approach is not to choose one number and disregard the others, since each provides different information. IRR can show infrared performance within a defined wavelength range, IRER provides a broader view of infrared-energy performance, SIRR offers another way of describing selective infrared behaviour, TSER provides a broader measurement of overall solar-energy rejection, and VLT tells you how much visible light remains. Together, these figures provide a much clearer picture than any single headline percentage ever could on its own.

Compare the Measurement Before Comparing the Percentage

Solar-film technology has advanced considerably, and manufacturers now have increasingly sophisticated ways of controlling different portions of the solar spectrum. That makes product specifications more informative, but it also makes them easier to misunderstand. A film advertising 96% infrared rejection can be an excellent product, and a different film showing 60% IRER can also be an excellent product, because the percentages alone do not establish which one provides better overall solar control when they represent entirely different measurements. The more useful questions to ask are what is being measured, across what wavelength range, what the VLT is, what the TSER is, what glass was used, and how the performance was tested. Once these questions are answered, solar-film specifications become far easier to compare.

At Window-Cool (S) Pte Ltd, we believe customers should understand the specifications behind the product rather than simply be presented with the largest percentage. Since 1999, our approach has been to recommend solar-control solutions according to the glazing, application and required performance rather than relying on a single headline number. Because ultimately, the objective is not to find the solar film with the biggest number; it is to select the film that delivers the right balance of solar control, visibility, optical quality and long-term performance for the application.

Frequently Asked Questions

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Does 96% IR rejection mean a solar film rejects 96% of heat?

No, it means the film achieved approximately 96% infrared rejection according to the stated measurement method. If that measurement relates to a particular wavelength or wavelength range, it does not automatically mean that 96% of total solar energy is rejected.

Can a 60% IRER film perform well even when another film claims 95% IR rejection?

Yes, the two measurements may not be equivalent at all. Broad-spectrum IRER and narrow-band IRR should not be compared simply by looking at the percentages side by side.

Why does the same solar film sometimes have two different IR numbers?

Manufacturers may publish several different infrared measurements for a single product. A film can have one IRER figure alongside a higher SIRR or narrow-band IRR figure, and each describes a different aspect of its spectral performance.

Is TSER more important than IR rejection?

TSER is particularly useful when the objective is overall solar-heat control because it describes total solar-energy rejection rather than infrared alone. It should still be considered together with VLT, infrared performance and test conditions rather than in isolation.

Is 99% infrared rejection possible?

Yes, at certain wavelengths or wavelength ranges this is achievable. The important question is what measurement methodology produced the 99% figure, since it should not automatically be interpreted as 99% total heat rejection.

Is a darker solar film always better at rejecting heat?

No, darker films generally reduce more visible solar energy and may therefore achieve higher TSER, but darkness alone does not determine infrared performance.

Why can a clear solar film still reject substantial heat?

Modern spectrally selective films are designed to transmit visible light while selectively reducing other parts of the solar spectrum, including infrared radiation, which allows relatively clear films to provide meaningful solar control.

Can I compare the TSER figures from two different manufacturers directly?

They provide a useful starting point, but the comparison is strongest when the products have similar VLT and have been tested on similar glass using comparable methodologies.

Are infrared heat lamps and meters useful when choosing solar film?

Yes, provided their limitations are understood, since they demonstrate performance within the wavelength range being measured and should be considered together with full manufacturer specifications rather than used as the sole measure of overall solar heat rejection.

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