Window Tint Guide: Understand
TSER, IR Rejection and UV Explained: Reading a Tint Spec Sheet
A tint spec sheet looks like a wall of percentages: VLT, TSER, IRER, SIRR, IRR, UV, glare reduction, reflectance. Most shoppers see one big number, often an infrared figure in the 80s or 90s, and assume that is how much heat the film stops. It usually is not.
This guide explains each column, which number actually predicts how hot your car will feel, and the measurement tricks that make two films hard to compare. The examples use LLumar's published automotive performance sheet, because it lists several ways of measuring infrared side by side for the same films.
The short answer
Total solar energy rejection (TSER) is the best single number for comparing how much heat a tint film blocks, because it covers the whole solar spectrum: UV, visible light and infrared. Infrared rejection figures cover only part of the spectrum, and some are measured over a narrow band or on film without glass, so they run much higher than TSER. UV figures are near 99% for almost all quality films and rarely separate them.
Key points
- TSER covers all solar energy and is the fairest heat comparison between films.
- Infrared figures (IRER, SIRR, IRR) measure only part of the spectrum, and the narrower the band, the higher the number.
- Spec sheets are measured on a standard piece of clear glass, so your car's numbers will differ.
- UV rejection is above 99% for quality films at every shade, so it rarely decides between them.
- Compare films only when they were measured the same way, ideally from the same type of document.
The columns
What Each Number on a Spec Sheet Means
- VLT: visible light transmissionDarkness
- The percentage of visible light that passes through. Lower is darker. It is the only figure South Carolina law regulates, and it says nothing about heat or UV. VLT and the 27% math
- TSER: total solar energy rejectionThe heat number
- The share of all incoming solar energy (UV, visible and infrared) that does not end up inside, counting energy that is reflected and the part of absorbed energy that is shed outward. Higher means less solar heat gets in.
- IRER: infrared energy rejectionInfrared, counted fully
- Rejection of solar infrared over 780 to 2,500 nanometers. LLumar describes it as a more complete measure of infrared heat because it includes energy that is absorbed by the film and re-radiated into the car.
- SIRR or IRR: selective infrared rejectionInfrared, counted generously
- Measures infrared that is not directly transmitted. It ignores absorbed heat that later re-radiates inward, and some versions use only a narrow slice of the infrared band. These numbers are always the highest on the sheet.
- UV rejectionSkin and interior
- The share of ultraviolet blocked, usually over 300 to 380 nanometers. Quality films list 99% or more regardless of shade.
- Glare reduction and visible reflectanceComfort and looks
- Glare reduction is how much the film cuts visible light compared with bare glass. Visible reflectance shows how mirror-like the film looks. South Carolina requires nonreflective film.
The trap
Why Infrared Numbers Look So High
LLumar's performance sheet is useful here because it prints three heat measurements for each film. Its IRX 35 ceramic film is listed at 54% TSER, 60% IRER and 87% SIRR. All three describe the same film on the same glass. The difference is what each one counts.
SIRR leaves out infrared that the film absorbs and later re-radiates into the car, so it looks better than IRER. Narrower measurements look better still. One major film manufacturer's comparison guide defines its IR rejection figure over just 900 to 1,000 nanometers, measured on the film with its liner and no glass; in that guide, a series rated at up to 99% by that measure is rated at up to 63% TSER.
None of this is dishonest when it is labeled. The trap is comparing one film's narrow-band infrared figure with another film's TSER, or treating a 90-something infrared number as the share of heat stopped. Infrared is only part of the sun's energy; visible light also carries heat into the cabin.
Example
Four Films at About the Same Shade
The table below pulls four films from LLumar's published sheet, all sold as a 35 shade, plus one nearly clear film. It shows how film technology, not darkness, drives heat rejection. All five block more than 99% of UV.
Notice the dyed film: it has nearly the same darkness as the others but much lower TSER. Notice the clear AIR 80: at 77% VLT, it rejects more total solar energy (43%) than the dyed 35 shade (35%). That is the nano-ceramic effect in one row.
Glass matters
Spec Sheets Are Measured on Lab Glass
LLumar states that its data is captured using NFRC guidelines on single-pane, quarter-inch (6 mm) clear glass, and that actual performance will vary with glass type and properties. Other manufacturers measure on similar standard glass. That makes films comparable to each other, but it does not tell you exactly what happens on your car.
Automotive side glass is thinner and often slightly tinted green or gray, and rear privacy glass is very different again. AGC, an automotive glass maker, lists total energy transmission of 59% to 70% for its normal vision glass and as low as 29% to 45% for its privacy glass. Adding film to glass that already absorbs a lot of heat changes the picture. Use the sheet to rank films, not to predict an exact cabin temperature.
The shade name is nominal, too. On the same sheet, films sold as a 35 measure 37% to 39% VLT on clear glass. That affects the legal math once they go on your factory glass.
How to compare
A Five-Step Way to Compare Two Films
Start with the legal shade
Work out the darkest shade your car can legally take, accounting for factory glass. There is no point comparing films at a shade you cannot run.
Compare TSER at that shade
Line up the films you are considering at the same or similar VLT and compare TSER. A difference of a few points is real but small; a difference of ten or more is noticeable on a sunny day.
Check the infrared figure is the same kind
If you compare infrared numbers, confirm both are IRER, or both are SIRR, over the same wavelength range. Read the footnotes.
Confirm UV and reflectance
Expect 99% or better UV. Check that visible reflectance is low, because South Carolina requires a nonreflective film.
Ask for the source document
Real numbers come from the manufacturer's published sheet for a named product. A shop quoting a heat figure without naming the film is not giving you something you can check.
Real world
What the Numbers Will Not Tell You
- How hot a parked car gets. A sealed car in the sun still heats far above outdoor temperature; film slows that, but it does not prevent it.
- How much the windshield contributes. It is one of the largest pieces of glass on the car, and in South Carolina it can only carry film above the AS1 line.
- How the installation was done. Spec numbers assume a properly installed film with no gaps.
- How the film looks at night. Lower VLT means less light for your eyes in the dark, whatever the TSER.
- Whether the film will hold its color. That depends on how the color is made, and on the manufacturer's warranty terms.
| Film (type) | VLT | TSER | IRER | SIRR | Visible reflection |
|---|---|---|---|---|---|
| ATC 35 (dyed) | 38% | 35% | 22% | 29% | 6% |
| ATR 35 (metallized) | 37% | 44% | 40% | 53% | 8% |
| CTX 35 (ceramic) | 37% | 48% | 48% | 69% | 6% |
| IRX 35 (IR ceramic) | 39% | 54% | 60% | 87% | 6% |
| AIR 80 (clear ceramic) | 77% | 43% | 60% | 86% | 9% |
Source: LLumar Window Film Performance Data (LL0116NAEN, 03/26), measured on single-pane 6 mm clear glass using NFRC guidelines. All listed films show more than 99% UV protection (300 to 380 nm). These are LLumar's published figures for named products, not results on any specific vehicle.
Want More Heat Rejection Without Going Darker?
The Auto Show installs LLumar Ceramic, whose nano-ceramic particles reject more of the sun's infrared heat so the cabin stays cooler without needing the darkest shade, and LLumar Carbon for look and privacy.
Common questions
What is a good TSER for car window tint?
It depends on the shade and film type. On LLumar's published sheet, its dyed films run roughly 28% to 44% TSER, its CTX ceramic 43% to 58%, and its IRX ceramic 50% to 62%. Compare films at the shade you can legally use, because darker shades of the same film always score higher.
Why does one tint claim 99% IR rejection and another 60%?
They are probably measuring different things. A narrow-band figure, or one that ignores absorbed heat re-radiated into the car, runs much higher than infrared energy rejection over the full 780 to 2,500 nanometer range. Ask which measurement the number is and compare like with like, or use TSER instead.
Do handheld heat lamp demos prove a film works?
They show that a film blocks the output of that particular lamp, which is mostly infrared and not the same as sunlight. A demo can be a useful feel for the difference between films, but it is not a measurement. The manufacturer's published TSER is a more reliable comparison.
Does UV rejection differ much between films?
Rarely among quality films. On LLumar's sheet, every automotive film from 5% to 87% VLT lists more than 99% UV protection. UV blocking comes mainly from inhibitors in the adhesive rather than darkness, so a light film protects skin and interiors from UV about as well as a dark one.
Sources
- LLumar Window Film Performance Data (LL0116NAEN), Eastman Performance Films (https://www.llumar.com/content/dam/eastman/performance-films/llumar/documents/LL0116NAEN_AutoSpecs_screen.pdf), accessed October 2026
- Automotive Window Film Product Comparison Guide (January 2025), 3M (https://multimedia.3m.com/mws/media/2538245O/personal-auto-awf-product-comparison-guide.pdf), accessed October 2026
- Window Film Fundamentals, Whole Building Design Guide, National Institute of Building Sciences (https://legacy.wbdg.org/resources/window-film-fundamentals), accessed October 2026
- Privacy Glass, AGC Automotive (https://www.agc-automotive.com/products-and-solutions/privacy-glass), accessed October 2026
- Ceramic Window Tint, LLumar / Eastman Performance Films (https://www.llumar.com/en/tint/ceramic/), accessed October 2026
- S.C. Code Ann. § 56-5-5015, South Carolina Legislature (https://www.scstatehouse.gov/code/t56c005.php), accessed October 2026
Prices on this page are The Auto Show’s published starting prices. Film ratings and warranty terms come from the manufacturer. This guide explains South Carolina law in plain words; it is not legal advice.