How Dark to Go When Tinting Your Windows
Aside from which company is privileged with your business, one of the biggest and most important decisions you will make regarding tinting your windows is how dark of a percentage you have applied. There are a multitude of aspects one must consider when making this decision, and everyone has their own wants and needs. I've comprised some examples and information to help consumers gain more confidence in their decision after consulting with a professional or purchasing film for a DIY project. You can also go to our FILM VIEWER for a virtual sample of what your ride will look like with different percentages.
First, a little educating is in order.
Film darkness is measured by percentages. The percentage refers to what is called the Visible Light Transmittance, or VLT, VT, or Tvis for short. It determines how much visible light is transferred through the glass or glazing material (window tint, window film). The higher the number is the lighter the film, so in contrast, the lower the number the darker the film.
Sustainability Workshop describes it as such:
"The point of windows is to let light pass through. The percentage of visible light that passes through a window or other glazing unit is called the Visible Light Transmittance (T vis or VLT). An opaque wall would have a Tvis of 0%, while an empty opening would have 100%; many un-tinted glass and plastic materials have a Tvis of 90% or more. Tvis does not measure shorter-wavelength light like UV or longer-wavelength light like infrared--only visible light.
More light is often not better, as it can cause glare and overheating. Tints, frits, and coatings can be chosen to produce any Tvis; common values are often 30 - 80%..." CLICK HERE FOR FULL ARTICLE
Which percentages a shop carries varies on state laws, shop services and preferences as well as demand, but the most common percentages offered in the automotive industry seem to be 70%, 50%, 35%, 20%, 15%, and 5% VLT. I've seen it as light as 88% and as dark as 4% VLT.
Here's where it can get a little tricky...
Most newer auto windows look completely clear, but a VLT meter will actually meter them as low as 70%. Some even say it on the manufacturers markings in ceramic or etched in the bottom corner of the glass.
Here in Missouri, the law permits:
*35% VLT + or - 3% VLT leeway on the front two windows next to the driver (darkest being 32%)
*Any darkness on anything behind the driver, and
*Any darkness on the windshield down to the "AS-1 line" seen on most modern windshields on the side towards the top. (The darker you go the more functional the strip is.) CLICK HERE for Missouri State Highway Patrol Online PDF
If a true 35% VLT film is installed on a pane already at 70%, then the film can cause a reading on a meter as low as 28% VLT. Reading four points below the leeway isn't a good thing for customers and shops outside of states like Florida, which allow 28% VLT on the front driver and passenger windows. This is why most any professional tint shop in demographics such as ours use films that read 38%, 39%, 40%, or 43% VLT when manufactured, which read anywhere from 32%-39% VLT once installed on the car's window. (Glass and film manufacturer may cause variations of the same percent as well as an off reading from the meter.)
The back sides and back glass, as well as the front brow/glare strip, are non-issues in respect to darkness in MO, but the same physics apply to the percentages. For instance, CCGT's Epic Series 20% (which you see on the back of most trucks, vans and SUV's) can actually read 16% and usually has a VLT of that once installed. We also carry 5%, which reads at about 2.5% VLT, and some people like the UV protection of the full windshield application but don't want any added darkness. 80% or lighter is the route best taken for windshields. (Air 80)
The most popular choice made here is 40% on the front two and 20% on the back half of the car. The 40% keeps it legal in MO while the 20% adds more privacy without significant hindrances to vision at night or creating a substantial contrast between the front and back. The pictures below are with our Epic Series with 40% and 20%. You can see silhouettes with this film from the outside looking in, but not significant details.
The next most popular legal option is 40% on the front with 5% on the back sides and back glass. This is preferred by those who want to keep the vehicle legal while going as dark as possible for maximizing privacy, and for some, appearance. Downfall is the hindrance of vision out of the rear windows at night without direct light sourcing and the significant contrast between the front and back many that many do not prefer. Below is a 2016 Volkswagen Jetta with this combo.
Both of the Mercedes below are a nice showcase of the classiness that comes with a 40% all the way around the sides and back glass. This would explain why many classic car folks often pick it for their "ol' school" original, restoration or hot rod. Although it is a more lightly smoked film, it is still very functional, reaching 33% better heat rejection with our film and 99% UV blockage like all other quality films.
Sometimes people want to go darker than the law permits. Often, people want to "match" the front two windows on with the factory glass hued at 20% VLT on many trucks, SUV's, and vans. This is NOT LEGAL for you to have without a prescription in Missouri, but it is not illegal for a shop to install it. When done with quality film, many times the film will look different from the factory glass from the inside looking out, but it matches near perfectly from the outside looking in. This is due to the film being slightly darker and/or the hues being produced with different dyes and manufacturing techniques. It is completely normal and unavoidable. Those with cars who want darker than 40% on their front two often choose to go with 20% all around. Again, not legal without a prescription, but I must say, it is my personal favorite. It's not too dark, but also not too light. It keeps the classy without losing the privacy and function. Samples below below:
Another option some choose is 20% on the two front driver and passenger windows and 5% around the back half. Again, this is illegal without a script, but it is an option sought by those who want or need darker than 40% on their front two side windows and as much privacy as possible in the back. Examples below:
Eyebrows/Glare strips are also a common occurrence in the film industry. It is a strip that goes across the top of the windshield and can be seen in the 3rd picture up from this paragraph on the green Ford F-150. We used to offer them in 20%, and still can sometimes, but most generally we only apply 5% anymore. They are the most effective and are legal down to the AS-1 line. It is usually visible on the upper sides of the windshield.
For those who want 99% UV protection, as well as 43% better heat rejection, Llumar Air 80 is the way to go. It is practically clear, but it certainly does its job. Below is an Audi windshield and an RV that got both panes coated in Air 80.
Thank you for taking the time to read and look through this article. I will update it as requested or if I get a spark of enlightenment on something. For other informative blogs, check out CCGT's Blog Spot, and as always, please contact us however convenient for questions or help! Thank you!
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