What VLT means, and how to choose a shade
VLT is the percentage of visible light that passes through the glass. It decides how dark the film looks, and it is not what decides how much heat is stopped.
Every film in our range is published with a VLT figure. It is the number people argue about most, and it is the number most often misunderstood.
VLT is only a light percentage
VLT stands for visible light transmission. It is the percentage of visible light that passes through the glass once the film is on it. A 70% VLT film passes 70% of the light and looks almost clear. An 18% VLT film passes 18% and looks dark.
That is the whole definition. VLT describes appearance and brightness. VLT does not describe heat.
Our own figures prove it
Our Nano HD is published in four shades. These are the figures we publish for all four, and you can check every one of them on the datasheet page.
| Code | VLT | Infrared rejection |
|---|---|---|
| HD 20 | 75% | 99% |
| HD 40 | 40% | 99% |
| HD 60 | 20% | 99% |
| HD 80 | 5% | 99% |
Look at the first column, then the second. The light passing through falls from 75% to 5%. The infrared rejection does not move at all. It stays at 99% at every shade.
The lightest film and the darkest film in the same line stop the same amount of infrared heat. That is not an opinion. Those are the numbers from the same data sheet.
Three figures people mix up
There are three figures on every specification sheet, and they measure different things.
VLT is the visible light passing through the glass. It decides the look.
Infrared rejection, or IRR, is the share of infrared heat that is stopped. Infrared is the heat you feel on your skin when you sit near a window. This is the figure you notice most in daily use, and it comes from the ceramic layer.
Total solar energy rejected, or TSER, counts all the solar energy that is stopped, including the energy carried by visible light. Because visible light is counted too, TSER does rise as a film gets darker. On Nano HD, TSER moves from 66% at HD 20 to 98% at HD 80.
This is where the confusion starts. Somebody sees TSER rise on a darker film and concludes that dark means cooler. What rose is the total calculation, because the room became dimmer. The infrared heat you actually feel is stopped at 99% at every shade.
Dark does not mean heat rejection
This is the part that leads people to choose wrongly. On nano-ceramic film, the heat rejection comes from the ceramic layer, not from how dark the film is.
For a car this matters, because the windscreen and the front side windows can stay light without losing heat rejection. A light shade on the windscreen does not raise the cabin temperature, as long as the film is nano-ceramic. Most owners fit a lighter windscreen with darker sides and rear. That is normal practice, not a rule.
Every film we fit stays clear to see through after dark. So the shade choice is about how much light you want, not about night driving.
For a building the reason is different. A dark film is not the only way to cut glare, so daylight still comes in and the people inside do not have to close the blinds at two in the afternoon. An office that fits a dark film only to cut glare will run its lights all day, and that electricity has a cost too.
About the purple question
A worry that comes up often: will the film turn purple after a few years.
No film in our range turns purple. That colour belongs to cheap dyed film, when the dye fades under sunlight. Our Sola-X line does use a dye, but a premium chip dye rather than a cheap one, so it holds its colour like the rest of the range. The other lines are nano-ceramic.
How to choose properly
The order goes like this.
- Decide the problem first. Heat, glare, privacy, UV and glass safety are five different needs, and one film does not solve all of them.
- Choose the film from the figures we publish: infrared rejection, total solar energy rejected, and UV.
- Choose the shade last, from appearance, privacy and your own comfort.
Shade is taste. The film is the decision. Many people reverse this order. They pick the darkest film they can find, then wonder why the cabin is still hot.
The three most common mistakes
Choosing the shade first and the film second. This is the reverse of the order above. The same shades are available across almost every line we carry, so choosing a shade first narrows nothing.
Treating one figure as the whole story. A film can be strong on UV and ordinary on infrared. That is why we publish each figure separately rather than one combined score.
Comparing figures from different test standards. Heat rejection numbers can only be compared if they were measured the same way. All our figures use one test standard, which is why the whole range can sit in a single table.
Where to check the figures
Every film, every shade and every figure we publish sits on the datasheet page, on one test standard. Read it there, or send us your car model or the type of building and we will help you choose before you spend anything.