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So the sun will to some extent heat up the car via the metal body, and so a dark body makes some difference, but it's the car interior we're talking about here. The larger contributor is I believe the windows, which pass short wavelength solar radiation in, and can't easily pass the "red-shifted" radiation back out - that's the greenhouse effect. Finally, if the upholstery is dark, it can be hotter than the interior generally, as it will then be soaking up much of that energy trapped inside.
Thanks, so what's the solution to this greenhouse effect? I also feel the upholstery is a moderate "contributor" to general heat, but not really the cause of the targeted sunlight problem, which is -- like you said -- is more of a window problem. (But then again, why didn't it happen to such an extent in other cars, just Nissan Altima?)
Thanks, so what's the solution to this greenhouse effect? I also feel the upholstery is a moderate "contributor" to general heat, but not really the cause of the targeted sunlight problem, which is -- like you said -- is more of a window problem. (But then again, why didn't it happen to such an extent in other cars, just Nissan Altima?)
Besides leaving the windows and sunroof cracked to let some of that hot air out, I think the best approach would be something like these WeatherTech reflective sunshades. The strategy they have is to try to avoid the redshift in the scattered/re-emitted radiation with the silvery reflective surface, and send it right back out again. Note that they have them not only for the windshield, but also a whole vehicle kit. This won't work perfectly, but I can see it helping a good deal. https://www.weathertech.com/sunshade/
Thanks, so what's the solution to this greenhouse effect? I also feel the upholstery is a moderate "contributor" to general heat, but not really the cause of the targeted sunlight problem, which is -- like you said -- is more of a window problem. (But then again, why didn't it happen to such an extent in other cars, just Nissan Altima?)
The overall shape/geometry of the car could play into this. The angle at which more sun hits the interior (including that dark upholstery) through the glass would affect how much heat it ends up absorbing. Body panels contain more insulating material than glass. If the windows and windshield are smaller and more vertically oriented, there's less glass surface area overhead sun can hit directly. So, the glass transmits less heat. An example that might help what I'm clumsily trying to suggest. Think about a early model VW bus. It was a minimally rounded box, with very vertical windshield and relatively smaller windows. Most of the direct sun would hit the roof, not the glass. It might keep that van slightly cooler than something like a 90s era Ford Aerostar minivan with its huge, shallowly sloped windshield and windows that exposed more of the dash, the upholstery, and the driver to more direct sun. Think of the "fishbowl" Pacer. Almost more glass than metal. Don't know if you've ever ridden in either one. They were ovens! The whole front part of those vans just cooked.
So, what to do? The fixes are fairly simple. If the car's too hot, put shades in the windows and windshield while its parked. You might try laying light colored sheets over the dark upholstery. While driving, if you aren't using the AC, open the windows part way. There's probably a combination of cracking rear and front windows that creates just the right amount of airflow to cool the cabin without you needing to sit in a gale and reducing the car's aerodynamics. IME with my various cars, trial and error usually helped me find each of their airflow sweet spots. I'm one of the old fogeys who miss the days when car windows were equipped with wind wings and wish they'd make a comeback. Crack one of those slightly and they cooled things down by directing fresh air right where it was needed; the driver and the dash.
Last edited by Parnassia; 05-11-2022 at 01:30 PM..
Besides leaving the windows and sunroof cracked to let some of that hot air out, I think the best approach would be something like these WeatherTech reflective sunshades. The strategy they have is to try to avoid the redshift in the scattered/re-emitted radiation with the silvery reflective surface, and send it right back out again. Note that they have them not only for the windshield, but also a whole vehicle kit. This won't work perfectly, but I can see it helping a good deal. https://www.weathertech.com/sunshade/
But you can't drive with these, they're opaque, right?
I can't really figure it out. I can tint my windows but I don't want them to be dark, so I'd have to go with like a 70-80% tint, I don't know if that would be enough. All I want is to drive normally in the car I have now. Any ideas what's going on?
The newer ceramic tints actually have high heat rejection values without being too dark.
As you can see here with Llumar's offerings. A very light 80% tint with their Air series rejects nearly 3 times as much heat as a dyed tint at 5% (limo tint) levels. https://cdn.llumar.com/drupal/na_auto_specs_l1748.pdf
I had that Air 80 put on a windshield and it made a huge difference. Prior to that the black leather interior and chrome surfaces like on the shifter were scalding. And it was near undetectable. Except if you were wearing polarized sunglasses, in which case you got that double polarization color shift that would make tires look purple and such.
But you can't drive with these, they're opaque, right?
Yes, this is for while the car is sitting parked, but while it's moving, you've got the A/C running, so it shouldn't be real hot then. As BostonMike said, another radiation barrier method would be getting tinted windows. You want all the UV blocked - that's energetic and doesn't contribute to vision, and it wouldn't hurt for NIR, IR to be blocked either... you can have some of the visible spectrum blocked, but of course you can't compromise visibility too much or it won't be safe to drive in low light conditions.
The OP can always install air deflectors over each window. Then he can leave the windows slightly opened if parked at home, or work.
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