Do car windows and windshields block ultraviolet light?

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I'm curious if car windshields / windows block UV (ultraviolet) light, the one from either the sun, or UV flashlights, like the Convoy S2+ Nichia 365nm.
 

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  • #2
anorlunda
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It is not an all/none situation, it is a question of how much and which frequencies. I found this study.

https://www.ncbi.nlm.nih.gov/pubmed/12925188 said:
RESULTS:
UV wavelengths longer than >335 nm were transmitted through car windows, and UV irradiation >380 nm was transmitted through compound glass windscreens. There was some variation in the spectral transmission of side windows according to the type of glass. On the arms, UV exposure was 3-4% of ambient radiation when the car windows were shut, and 25-31% of ambient radiation when the windows were open. In the open convertible car, the relative personal doses reached 62% of ambient radiation.

CONCLUSIONS:
The car glass types examined offer substantial protection against short-wave UV radiation. Professional drivers should keep car windows closed on sunny days to reduce occupational UV exposure. In individuals with polymorphic light eruption, produced by long-wave UVA, additional protection by plastic films, clothes or sunscreens appears necessary.
 
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  • #3
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I bought a new car in February, and as the seasons changed I noticed it wasn't nearly as hot inside the car left in the sunshine as my previous car. I did some asking around and found out that the major difference is in the chemical makeup of the glass itself. So not only does it depend on the frequencies, it also depends on the make, model and age of the car.
 
  • #5
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I bought a new car in February, and as the seasons changed I noticed it wasn't nearly as hot inside the car left in the sunshine as my previous car. I did some asking around and found out that the major difference is in the chemical makeup of the glass itself. So not only does it depend on the frequencies, it also depends on the make, model and age of the car.
Was it definitely the glass, or was it a coating on the glass?
I know NSG make vehicle glass with infrared reflective coating, which helps to keep the car cooler.
 
  • #6
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I bought a new car in February, and as the seasons changed I noticed it wasn't nearly as hot inside the car left in the sunshine as my previous car. I did some asking around and found out that the major difference is in the chemical makeup of the glass itself. So not only does it depend on the frequencies, it also depends on the make, model and age of the car.
Was it definitely the glass, or was it a coating on the glass?
I know NSG make vehicle glass with infrared reflective coating, which helps to keep the car cooler.
Yeah probably it was some anti-IR coating or higher glass thickness, because as far as I know UV does not cause heat, it's the IR mainly. Also, smaller windows or better bodywork insulation or better AC cooling system can lead you to think that.

If you mention the make, model and year of both cars, would be a good piece of information.
 
  • #7
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Could be a coating, don't know. It's definitely cooler inside when the car is left in the sunlight. 2018 Civic SI.
 
  • #8
marcusl
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Yeah probably it was some anti-IR coating or higher glass thickness, because as far as I know UV does not cause heat, it's the IR mainly.
Not so. Read about the greenhouse effect.
 
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  • #9
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Ok did the proper tests on my car. It's a Volkswagen Golf 4, and this is the additional hardware that I used:
The results are as follow:
  1. Direct sunlight on the UVM30A sensor: displays index 6-7.
  2. Direct sunlight all around the car and UVM30A on the other side of the windows and windshields: index 0.
  3. Nichia 365nm flashlight to UVM30A sensor, with windows in the middle, only the front windshield displays index 0. All other windows from the sides and the back display very high index values, so apparently they don't filter the 365nm wavelenght.
 
Last edited:
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  • #10
marcusl
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Very nice experiment that matches with manufacturing practice. Most car windows are made of tempered glass, which is just glass that is specially heat treated. The law requires windshields, however, to be made of laminate which has a plastic film sandwiched between two glass sheets. The plastic keeps the glass from shattering, and also absorbs UV light.
 
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  • #12
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Very nice experiment that matches with manufacturing practice. Most car windows are made of tempered glass, which is just glass that is specially heat treated. The law requires windshields, however, to be made of laminate which has a plastic film sandwiched between two glass sheets. The plastic keeps the glass from shattering, and also absorbs UV light.
I thought glass was generally a better UV blocker than plastic.
 
  • #13
davenn
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I thought glass was generally a better UV blocker than plastic.
depends on how the plastic was treated
 
  • #14
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I always found the colour of the car makes a big difference. Lighter cloured cars tend to not get as hot as darker coloured cars.
 
  • #15
davenn
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I always found the colour of the car makes a big difference. Lighter cloured cars tend to not get as hot as darker coloured cars.
True, but that has nothing to do with windscreens and whether they do or dont block UV
 
  • #16
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No it is nothing to do with the windscreen and if they do or don't block UV light. Post 4 refers to the difference in heat inside the car, I was responding to that to say the colour made a bigger difference than if the windows blocked UV light or not.
 
  • #17
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probably it was some anti-IR coating or higher glass thickness, because as far as I know UV does not cause heat, it's the IR mainly.
Not so. Read about the greenhouse effect.

Glass transmits near infrared light, such as infrared radiation from the Sun. In contrast, glass blocks long wavelength infrared radiation, such as thermal radiation from the ground in the greenhouse.
 

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