Well after doing some reading here on the forum it becomes more and more clear that one of the things that may be able to help the Leaf is to control the interior temps in the car. There are several ways to approach that topic, but in this post I want to talk about window tint.
Window tint isn't just an appearance thing for a car. Some like the appearance of tinted windows, some don't. But I wanted to touch on some reasons that you might consider tinting your windows beyond appearance and some of the things you should look for.
When I started digging into this a few weeks ago I knew going into it that there is some very interesting science going on in window tints and window coverings, but I really didn't know just how convoluted and complex this topic would become. There is a fair amount of controversy in the window tinting industry over some of the hot buzz words and marketing methods used which can make for quite a confusing process when it comes to understanding window tint and the performance of those tints.
The light spectrum as it pertains to window tint and the energy we are trying to redirect and manage:
1. Visible light
2. Ultra Violet Light ( the stuff they tell us to avoid for skin damage and damage to the things it hits)
3. Near Infrared Light(IR) This is the spectrum that produces the heat that you feel on your skin
In each area of the spectrum listed above we have different frequencies of energy and the objective of the automotive window tint is to reflect/reject or absorb the energy so that it does not make it into the cabin of your car. Each of these areas have to be addressed if we want to have a chance to control the heat and comfort levels in the car.
Most car manufacturers already provide some level of UV protection on the glass, but not as high as what you will find with these window tints. Most window tints that I ran across were blocking or rejecting 98+% of UV light. So the playing field in the UV spectrum is all pretty close in the tints.
The two big areas with the biggest portions of the spectrum and possible gains are in the Visible Light and in the IR bands. In a nutshell they refer to the visible light transmission through the tint into the car as VLT. Most states have laws that require a certain VLT and they will also tell you what it must be for each of the windows in your car. Some states require more VLT and some less, some will allow different VLT's for different windows. So it would be very wise to look at the laws in your state as it pertains to how much visible light must be allowed through the tint to be legal.
The more visible light(VLT), the more energy you are allowing into the car which will affect temperature, glare, and comfort levels. How do the VLT numbers work? If you see a number of a VLT of 20% it means that it blocks 80% of the visible light coming through the tint. A VLT of 35 means that it allows 35% of the light to pass. On a windshield you typically will have a very light VLT of a 90 or a 70. 90 being it allows 90% of the light to pass, or 70 being 70% of the light to pass. Make sure you look at the specs very closely for the tints you are considering. Many tints I saw might say they are a 35% VLT, but on the light meter the tint is only passing 29%. So you will want to look at the actual specs closely to make sure the tint will pass enough light to keep you tint legal. Also look at the laws in your state. Some states will give you some wiggle room of say 3-5%. So if they state that the limit is 35%, but they will give you wiggle room of up to 5% then if the tint is close to the 35% then you should be OK.
So typically the darker tints are by logical deduction reducing the visible light and making it easier to control temps. Some tints are more reflective than others, some absorb more of the energy than others. The general rule of thumb is to try to find the darkest level of tint that is legal for your state and from there keep in mind that when it is dark out the darker tints can affect visibility. If you don't like that aesthetic appearance of dark tint try to find the darkest shade you are comfortable with.
You will find if you start looking at the specs and performance data you are looking for the highest Total Solar Energy Rejection(TSER) that you can find. This is the industry standard that most use today to measure the performance of window tint. However that is becoming more and more controversial as testing is showing 2 window films rated at the same TSER can let significantly different amounts of heat through them. TSER can help you get an idea of how well a film performs, but there is more to it than that.
You will typically find the the higher the TSER is associated with the darker the tint. However that isn't always the case as some films are beginning to focus more on the IR spectrum to reduce heat and increase performance. I found in my research over the last few weeks that if you can find a good TSER number and a really high IR rejection number you will find yourself looking at the top performing window films for tinting.
Now the area of probably the most controversy at the moment is with the IR spectrum. This is the spectrum where you feel the heat as it hits you. Sadly there wasn't a lot of data on IR in the window film industry not that long ago. What little data was published in marketing etc was rather misleading in some cases or very incomplete as there were no standards for judging IR performance. This is now beginning to change, but it is a minefield as you try to sort through the missing, misleading, inaccurate, and poorly documented product information.
Because there was no baseline or standard the numbers reported for IR rejection or IRR were not good. Some manufacturers took liberty to post numbers that sounded great, but when you dug into the numbers you found out that they only took a snapshot of the data from a very small portion of the IR spectrum. The IR spectrum is from 780nm - 2500nm. But some of these companies if they posted anything at all they posted data in the 900-1000nm IR spectrum which as you can see is a very small subset of the IR hitting your glass and coming into your car. New standards have been published for testing and by the end of 2017 manufacturers will be required to provide the data for the entire IR spectrum in their published data and not just a little snippet in the frequencies that their film performed the best. I am going to call out one manufacturer that is really bad about this at the moment by publishing they reject 97+% of IR. That is the 3M Crystalline product. The published materials are completely misleading. Is Crystalline a horrible product? No, but the real IR rejection figures when examining the entire spectrum is around 84-85%. Not horrible, but a long shot from the 97+% they advertise.
IR rejection is important because it is the heat that you feel. It is also important because for the most part window tints can only go so far when blocking visible light to control the heat, comfort, and glare in the car. The biggest gains today are being made in the improving IR rejection performance of these films. So the race is on for better performance in the IRR arena. The more cutting edge films are pushing these numbers into the 90+% IR rejection and that would be a good place to start looking at window tint is in this 90+% IR rejection performance.
What makes this so hard to sort out what is really going on with window tint is the lack of standards for testing in some regards, and the slow to evolve measure of TSER as the benchmark for performance when it is becoming more clear that the biggest gains in environmental control are being made in the IR spectrum and how that is managed.
There is still a lot of work that needs to be done in the window tints and films as far as measurement of re-radiated heat from the glass as it has been absorbed vs that which is rejected/reflected away. This will be the focus as we see this move forward with some very interesting science and technology.
Deceptive tests all over the place! You will see a lot of tests posted online showing the use of a BTU meter as a way to measure the heat blocked. What they don't tell you is the frequency of the spectrum that the BTU meters test is very narrow and is pretty easy for a film to focus on that spectrum to get numbers that look very impressive. The BTU meter is not a very good gauge. We are better off actually measuring temps in as close to real world use cases as possible. For the consumer that walks into a dealers show room this is hard because they are not going to be able to do that for you. So do as much homework as you can before you go to the local dealer. You will likely find that because you spend so much time researching this that you will probably know more about the products than even your dealer knows! Also watch for the IR lamp demo's that many shops like to show. The IR lamp again does not produce the full spectrum of light that your tint has to block. It can give you an idea, but be aware this is also still selective in what it is blocking. Doing real world temp measurements will give you and idea of how much heat is transferred and how fast.
Over time the interior of your car is still going to heat up. The question will be how fast will it heat up? Also will there be any real temp reduction? Depending on the product you choose you can see 20 or more degree heat reduction once the temps have stabilized. If your car is parked outside in the sun you may still want to investigate windows shades, but tint will help reduce the temps and reduce the speed at which the temps climb. This will mean you will be able to run your AC on lower fan setting and possibly at a higher temp than before which will translate into more miles per charge for you!
A few things to know about window films:
1. Standard window films which are typically dyed.
- these films are largely for aesthetics, but do not work well at rejecting the IR spectrum and are typically the least expensive films on the market. Some dyed films are notorious for fading so you will want to look for a film that provides a long warranty period against fading and an installer that you can trust to work with you should you need to have the film replaced.
2. Carbon films typically are more expensive than dyed films and they use carbon particles to darken the tint. They are better at rejecting/absorbing some of the IR spectrum and typically fall into the middle of the IR performance. Again look for good warranties on any film should you have any issues.
3. Ceramic films block even more of the IR spectrum and offer some of the best performance in window tints. The prices have come down on ceramics recently as the technology continues to improve.
4. Nano films, we are starting to see nano films are taking center stage at the moment and are at the higher end of cost and performance. Nano in some cases is really rebranded ceramics, but in other cases we are seeing a variety of oxides and particles being introduced to the films that are taking the IR and thermal management in vehicles to a new level.
5. Metalized films, these films can perform very well in IR and reflecting the suns energy away from your vehicle. They run the gamut in pricing from affordable middle tier tints to high end tints like Huper Optic Select Drei. However it should be noted that some of these metal tint affect GPS, cell phone, radio signals. Also some have noted that some metalized tints are more reflective and may produce a visual appearance that you may not like. You will have to search out some of these films for yourself and see pictures of vehicles with that tint applied.
All that being said you are going to find the biggest performance improvements in the ceramic and nano films. Personally I avoided the metalized films as I didn't want any possible issues with cell phone, radio, gps etc.
My own general rules of thumb as I got deeper into this:
1. I started noticing the better TSER numbers were in the better performing films. This will be subjective as far as where you set the bar in your search, but I noticed one of the standard bearers in the industry is 3M Crystalline which has a TSER of 60% in their darker tints which is the CR40. So I knew I wanted to be somewhere near this 60% TSER if possible.
2. I know my local laws and what the visible light transmittance(VLT) requirement is. My local laws allow me to go to a tint that is darker than I wanted to go. I also was keeping in mind that if I move to another location my car will have to meet those laws as well. So I knew I was looking for a VLT around 35% to make sure it was legal if and when I move which is currently in my plans so I knew the tint laws in the location I am moving to.
3. I was looking at the IR performance numbers of the better window tints I heard mentioned in the forums and on youtube. So it appeared that the best performers would be in the 90+% IR rejection across the entire IR spectrum, not just a snapshot.
So with that information in hand I started digging around. I would have to caution you to make sure you are sitting down when you start calling around for pricing on these window films. The prices go from mild to WILD in a hurry. Also you will find that prices are completely dependent on where you live. You might hear a price quoted for a product and a tint job that sounds completely reasonable, and then have someone else report they paid A LOT more for the same product in a different location. So location does matter and you will have to call around your area to get an idea.
Now down to some of the nitty gritty. What is a good tint? How do you pick it? That will all come down to you. Every persons specific wish list is going to be different. Your budget may be different than mine as well so your options may be different based on those needs and constraints.
My objective here was to control the solar gain as much as possible reducing the heat and felt heat while in the car. I still fully intend to use window shades when my car is parked to eliminate as much heat as possible when the car is parked. But when the windows are exposed I am trying to reduce that solar gain as much as possible. My goal was to have a TSER that was at least close to or better than 60%, and an IR rejection of 90%+.
Here are some products that I found were coming up in my searches as I was investigating the specs. These are in no particular order with a target VLT near 35% when looking at the specs and looking for test data:
1. Spectra Photosync
2. 3M Crystalline CR40
3. Huper Optik Drei
4. Huper Optic Ceramic
6. Llumar Formula One Stratos
7. Madico Wincos 30
8. Llumar Forumula One Pinnacle
9. and others....
What did I find? The specs for the IR figures have to be looked at closely to determine if the product was tested across the entire IR spectrum. I also found in some cases that independent tests by regular people with good test equipment showed that the specs provided by the manufacturer don't always line up with what they stated. Two examples that come to mind are 3M Crystalline which only tests on the 900-1000nm IR spectrum, and Huper Optik Drei which reports some amazing IR figures of 98% across the full IR spectrum which really was closer to the 90-91% IR blocking across the entire spectrum. So finding someone who has the right equipment to do some of the testing is a huge help.
There is a window tinter on Youtube in Naples FL that has a meter that can test across a wider portion of the IR spectrum and he has done some quick videos showing these performance differences. He of course is promoting products he sells, but some good info there none the less.
The top dogs in the industry at the moment:
1. Spectra Photosync is one of the more interesting products on the market at the moment. But the price tag is pretty pricey. This tint has a reactive layer that responds to light and will actually get darker under the suns light. Think of it as "transitions lenses" for your cars windows. They have provided some of the most impressive specs sheets out there for their product, but sadly we are only a few years into this company selling this product and we still don't have any independent tests. Also I noted that some reported the active element in the tint that changes the tint darkness levels actually begins to degrade and is estimated to only be good for about 5 years. This tint is still too new to know if it will continue to function this way with the darkening feature which aids this tint in being able to report some of the highest IR rejection and TSER numbers out there with the help of the SAC layer. Without independent tests these numbers should be questioned. One thing I don't question is that Tesla owners appear to love this tint as I found lots of info on their forums with people using Photosync. With Photosync I would have to assume the info about the activation layer called SAC wearing out is true. That being the case I looked at the base IR rejection numbers before activation of SAC to get an idea of what the real world might be long term after SAC wears out. The IR numbers even without SAC are pretty good with a base starting around 89% for the VLT 35 film. However I found that the VLT 35 film with SAC activated darkens down to a VLT of 29% which would make it illegal for me to use when I move to a new state with a tint law of 35% - 3% wiggle room. So the challenge here for Photosync in my own circumstance was that the VLT for the 35% becomes too dark. The next jump up is a 45% which darkens down to a 38% VLT which isn't bad when it darkens, but in the future will it darken or will it get stuck at a leven somewhere in between? We just don't know how this will hold up over time. The base IR rejection actually climbs in the 45% VLT to 93% base before SAC activation so the IR figures were better with the lighter film. But I also noted the TSER values drop to as still respectable 66%, but again with no independent testing for any of this it is really hard to judge the real merits of this film. This is one of the more expensive films on the market which made it hard to justify the price with my budget. It was significantly higher priced than 3M Crystalline in my local area.
2. 3M Crystalline was one of the films I was after when I started this research. It appeared to be the standard bearer for performance that many are judge by due to the pretty good TSER numbers. The product has a long track record in the market place so we have a decent idea how it will hold up over time. However some of the draw backs are that it is reported that this film is easy to scratch, and may not be as durable as some of the other films out there. The cost is high as it is considered a premium product. But lastly it was the revelation that crystalline's IR numbers were not what they advertised with a real performance number around 84-85% IR rejection. One last thing to note with Crystalline is that it tends to have a bronze tint to it before being applied. It seemed like almost every car I saw it installed on in my search the colors were different from the same tint. Some cases I thought it looked really good and in other cases the color was off. Some of that boils down to the base color of the glass the tint is being applied to and any coating there may be already on it. I saw many examples of Teslas rear glass and front glass coating interacting with Crystalline and giving it a purple or very off color. Each car is different. I did see a picture of a Leaf with Crystalline and it looked fine from what I could see in the pic, but I would want to see the car from multiple angles with the sun just to be sure.
3. Huper Optic Select Drei is a precious metals metalized film that is top of the Huper line. It was especially designed for commercial/residential applications. It tends to be more reflective than many other films. The performance specs of a 70% TSER and a 98% IR rejection were very impressive on paper(one of the best on paper), but when I saw some of the testing on Youtube I noted the performance does not line up with those claims. Still very near the top in specifications in the market place, but the price tag on this film is very high. I didn't feel that the performance warranted the price tag once I saw the tests. Also I had seen multiple reports of problems with cell phones, gps, radio reception etc with Huper films. I talked to a company rep and they said that should not be the case. So your mileage may vary as far as these reception issues with Huper.
4. Llumar Formula One Stratos. This is one of the newest films in the market. This is a nano-hybrid film that appears to be ready to take the window tint film to a new level of technology. The specs are very good with a 97% IR rejection across the NIR spectrum and a respectable TSER around 58% according to the manufacturer. However this film is so new that nobody in my area has it yet and those dealers that said they could get it the price tag was at the very top end of the film prices I was quoted. Since we have not seen anyone with this film to independently test it, and the fact that my budget could not justify this cost and to be the first "test subject" with this film I decided to pass on this product. If you are looking for a film that the manufacturer claims to be one of the best on paper then you might take a look at Stratos. Personally I would recommend waiting until we can see what the numbers look like with independent tests before plunking down your hard earned dollars. Just my two cents.
So what did I choose? I didn't choose any of the top dogs listed here. I started off ready to buy 3M Crystalline, but the more I dug into it the more I found that the newest technology in some ways has already surpassed Crystalline. I was surprised that I was given a good price quote for Crystalline so I did not rule out Crystalline based on price, it was a performance decision. I did continue to grind through the numbers and chase down specs and data to find a window tint that would get me most of the features of the top dogs at a little more conservative price tag. My choice still was not cheap, but far more comfortable for me to swallow given what I feel is the importance of heat management inside of the Leaf.
I had a few tints that seemed to get many of the things I was looking for and at a price point that was acceptable for my budget. Ultimately it came down to what was available in my local area that checked off as many boxes as I had on my list. It didn't do me a lot of good to get excited about products that weren't available in my local area. The one I ended up circling back to was Madico Wincos 30. Let me make it clear I am not recommending this product, only telling you what I chose. I just had it installed on my car and now I need some time with it to see how I like it. Here is what I can tell you about it so far. I could get it at a decent price(still spendy, but far from the top dogs prices I was quoted), the TSER is 57%, and the IR numbers across the entire spectrum was a very respectable 91-92% for the side windows. I had the windshield also done. The windshield is probably the most sensitive in regards to local laws, but also is one of the largest pieces of glass in your car so I wanted the best IR rejection figure I could get in a very light tint. I went with a 70% VLT on the front glass with a IR rejection of 89%. The 70% is light enough that I don't think a police officer would harass anyone with a VLT 70 film on the windshield unless they were really looking for a reason to pull you over. It is pretty light and looks good.
There is a lot more to this topic of window tints than I am able to cover here it turned out to take me a lot longer than I had planned and it was quite frustrating at times as the data just isn't there to compare. If you have any questions about window tint please feel free to hit me up before I evacuate this information from my brain. I will be glad to help if you have any questions or if you have a window tint story to share.
Many of the products out there on the market in the carbon, ceramic, and nano films will give you an appreciable improvement in thermal management and appearance. You probably don't have to do to the degree I did and grind through all these numbers and chase down all these details to get a product that will work. If you want to go to the next level looking for the best performance then I would recommend start off with a base TSER number you want, and then look for the best full spectrum IR rejection you can find. Then start weeding them out. I hope this book helps someone.