Is there really a heat rejection tint

Absolutely.

If the SHGR or equivalent is not published, the manufacturer is hiding data you want. IR blockade is important to be sure, but it is not the entire story when it comes to keeping as much heat as possible from entering the cabin.

The factory glass already has high UV rejection (100% on the windshield, at least 89% on rest) so the only reason to get tints is either for cosmetics or solar heat rejection (especially with ceramics).

How about visible light blockade (aka 'privacy') ?

Window tint dose not have to have any color at all to block IR ( infrared ) this is what produces the heat when it hit a object. We were all thought this in 6th grade science class. Good quality glass on a car has some already built into it. This is why some times when someone replaces a good OE front windshield with a cheap $100 one from ( oh lets say South Africa ) as an example in a body shop in winter time. Then when summer roles around the driver may complain, ( oh dear it hot and my A/C is not working to good, it must be time to add freon ( refrigerant). A lot of misdiagnosis of a cars A/C system, replacing unneeded part, A/C recharge were done to 10s of thousands of customers every year. Wasting their money because of a bargain price peace of glass.

There are good window tints and bad. Looking at the darkness is not is not the only factor. If you painted your windows black your car will be as hot as HELL, and no light will get inside.

Thanks, SageBrush. I think I understand now. Although IR light does produce significant amounts of heat, all wavelengths of light will produce heat (including visible light). You want to know the total solar heat gain.

Privacy is a rather poor reason for getting tints. Drivers and pedestrians should be able to see your face for safety reasons and there's a reason why states have laws regulating visible light transmissions.

Keep in mind that UV cut rate is what's mostly advertised (at least for the Prius factory glass) and IR isn't the same as UV (which is a different spectrum and not all that you can actually feel).

Your probably right. I assumed UV = heat. So if the UV does not cause the burning heat feeling then maybe the window is blocking 91% of UV. That would just make my previous Llumars heat blocking.

UV is what fades colors in the plastics and fabric and cause plastic dash to crumble and turn to dust and crack. Also gives you sun burn. If the auto manufactures did not provide UV blocking in their glass they would have lots of warranty claims. They do nothing for free, it's to save them money.

Any good quality tint will quote TSER (total solar energy rejected). This is what you 'feel' coming through a window in terms of heat. TSER is the sum total of all the energy that could get to you that is now being blocked by a particular film as stated in %. The higher the number, the more that is staying outside.

VLT is how dark a film is. This is where folks talk about 35% or 20% or 5% (commonly called limo tint). VLT stands for visible light transmission. In this case, the lower the number, the less light that gets through a given film.

There are some good charts and information here:

Window film - Wikipedia, the free encyclopedia

Thanks, 32k. It's always good to get a refresher on high school science, since it's been a long time for me.

Thanks, jblackwell. I remembered SHGC, but I forgot about TSER. Most people understand tint percentages, but they don't know it's called VLT. Personally, I like a VLT of 20-25% and the highest possible TSER.

The Wikipedia article is interesting, but I had to laugh where they said, "The ceramic and metallic window films usually cost 10–15 percent more than regular window film." Maybe that's true for metallic, but not ceramic.

I finally made up my mind which tint to buy. This time around I'm going to include the front windshield also, a job that was quoted at $600/all windows using 3M crystalline. Too expensive for my blood, so instead I'll let the local shop tint just the windshield with the 3M crystalline for $200, and the other windows DIY $100 with CTX Llumar: 40% VLT in front, 30% in back and rear. Overall heat rejection about 50%. Total cost $300. I went this route to avoid dealing with the most difficult and important window myself and disliking the results.

The Llumar pre-cut film is bought from tintzoom.com. Pictures pending