My doc has recommended I have my car windows tinted. I have lupus, and UVA rays tend to trigger flares, even when I wear sunblock, and my doc says cars are basically rolling greenhouses. The problem is I don’t like tinted glass. It’s illegal for a reason. Also, I don’t want to get pulled over, even if I can prove the tint is medically necessary.
I read somewhere that it’s possible to get a non-tinted UVA block on car windows, but I can’t find anything about it now.
Is there any way to block UVA in cars without tinting?
Tinted glass is legal everywhere in the US, but the percentage blocked or which windows varies. A modest tint is not dangerous.
Without any tinting, your windshield is very good at blocking UV. But your side windows may or may not block it. You can get clear films for the side windows.
The windshield is usually made out of laminated glass. It’s two layers of glass with a plastic layer in between so that if it breaks, the broken shards of glass will remain stuck to the plastic. The windshield can break, but unless there is some really severe damage, it will remain in one piece, which it is required to do by modern safety regulations.
Unlike your windshield, side windows are not required to stay in one piece and to retain all of the shards of broken glass during a crash. They are usually made out of tempered glass, and in an accident they are designed to shatter into a bunch of tiny but mostly harmless pieces.
The tempered glass in your side windows blocks a fair amount of UV, though nowhere near as much as the windshield. It’s the plastic layer in your windshield that blocks most of the UV, partly just because of the nature of the plastic and partly due to additives to the plastic. UV light tends to break down plastics, which is why a lot of plastic stuff will fade if you leave it in your car for long periods. The additives to the plastic layer are designed to protect the plastic from this degradation, and this also makes the plastic layer block more UV from getting through the windshield.
Assuming you are in Washington state, the tint laws there aren’t that strict. You can have 24% VLT on side and rear car windows, on SUVs you can have 24% sides and any darkness on the rear side and rear windows. Basically, really dark tint is illegal, everything else is fine. The lighter stuff shouldn’t be a problem, even at night.
Stop by a tint shop and talk to them about what tint will work best for you.
nelliebly - fyi I just got a quote for 3M crystalline - one front side window $65, both $125. Thanks for the reminder, by the way, I was looking at this last year and never got around to doing it. I live in Santa Fe at 7000 feet with 330 days of sunshine, so the exposure is significant.
I think nelliebly means the UVA rays trigger skin rashes because of her lupus. I don’t believe wrap-around sunglasses are going to protect against those, but then again, IANAMD.
Yup, I had seen numbers like $400-$500 on the web, but that’s for a whole car. You would only want to do that if you are concerned with keeping the car cooler. If the main concern is UVA (i.e. cancer risk or OP’s Lupus), then the laminated windshield already blocks it, so all you need to do is the driver side window (or more of the side windows if you drive frequently as a couple or a family).
I just had the front side windows done in Crystalline 70, the number refers to the % visible light percent transmitted. The tint is barely noticeable.
Greenhouses don’t make UV. They just stop the warm air convecting or blowing away.
The darkness of the tint is no evidence of UV filtering.
The clear glass on your vehicle may already be good UV filtering… there’s a little brand logo and glass type printed on it in the lower corner. Look up the glass type to find its UV filtering properties. You’ll need your windscreen UV proof - you might need to replace it to get that. Your state might disallow all tints on the windscreen, even if you can’t tell the difference.
When you have max legal tinted side windows, don’t wear sunglasses when driving, as you might not be able to see through the side windows when your sunnies are on. Two layers of darkening…
I appreciate the thorough explanation even I could understand. Cars back in the day must have had tempered glass windshields front and rear then, right? I was in the backseat of an old beater (I think maybe a mid- or late-sixties car) when I was in my teens, and we were hit by another car. The whole rear windshield caved in in tiny pieces.
I really appreciate the excellent explanation. Thanks much!
Exactly right. I have eye issues due to lupus, too, so I wear sunglasses even on cloudy days. Sunlight, especially combined with heat, gives me rashes and joint pain and makes me incredibly fatigued–like getting attacked by a flock of vampires, if vampires existed and flocked. I miss the sun and feel like a mushroom, but the effects it has on me have taught me caution.
Compact fluorescent lights also affect me. (Lupus patients are hypersensitive to UV light.) I couldn’t figure out why I got so sick after the rare trip to WalMart until I realized it must be the combination of fluorescent light and skylights, even with those high ceilings.
Isilder, are you saying the glass in greenhouses filters UV light? I know greenhouses don’t make UV light, but I didn’t think they filtered it, either. Then again, I’m pretty ignorant in this area.
Speedway Ryan, that’s excellent info. thanks.
In fact, thanks to everyone. I knew I was asking the right people!
Check out this figure from the paper beowulff linked to:
Along the bottom axis:
Around 300nm = UVB (sunburn & cancer risk)
320-400nm = UVA (no sunburn, but also contributes to cancer risk)
400-700nm = visible spectrum
The blue line is ordinary glass, like you might find in the side windows of your car or a greenhouse. You can see that it blocks very effectively up to about 340nm, so it blocks all the UVB, so you won’t burn. But the lack of sunburn in a car or inside a greenhouse can give a false sense of security, because you can see that it does transmit perhaps 50% of UVA between 350-400nm. It also (of course, it’s glass) transmits most of the visible light from 400-700nm.
The other colored lines are various low-tech tints. They block more of the UVA, but they also block a significant part of the visible spectrum too - that, of course, is the visible dark tint that you see.
What you are looking for ideally is a spectrum like the blue line of ordinary glass that rises sharply from blocking all the UV to transmitting most of the visible light; but shifted about 50nm to the right, so that it blocks all the UV including the UVA in the 350-400nm range. That’s exactly what 3M Crystalline claims to do. It’s also what front windshield laminated glass does, by virtue of a plastic layer in the lamination sandwich, as explained by engineer_comp_geek above.