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I read an article today about how UPS has covered some of their trucks with frosted glass to allow drivers to see and find their packages with greater ease. However, one of the drivers noted the temperatures in the truck (due to inadequate ventilation, I suspect) rise quickly and stay at temperatures well over 110 to 130 degrees.

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Is it impossible to create glass which could allow visible light but not allow the wavelengths associated with infrared light, which heats the interior of spaces with lots of glass and no ventilation (like our cars during summer)?

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Or is this process more complex than I am thinking? If not, why not?

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Visible light carries heat as well.

Regular windows actually are somewhat translucent in the infrared spectrum (I think they are almost opaque in IR).

The visible light can heat up objects in the truck; and those objects would emit IR radiation, which would actually make it very warm, as the IR would not be able to escape. I feel like that is what may be happening here; the trucks heat up because this glass does block IR; allowing all the black body radiation from the packages to remain trapped in the truck.

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  • $\begingroup$ So the supposition is the visible light strikes the object and returns IR which in turn heats the air in the car. Then perhaps the question should be reversed. Would it be possible to make glass which would allow the bounced IR to escape the vehicle instead? $\endgroup$ – Thaddeus Howze Jun 30 '17 at 20:15
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    $\begingroup$ @ThaddeusHowze Unless you did a special coating that allowed IR out and not in (I'm not sure if that's possible or exists currently) I don't think that would help. $\endgroup$ – JMac Jun 30 '17 at 20:21
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"Is it impossible to create glass which could allow visible light but not allow the wavelengths associated with infrared light, which heats the interior of spaces with lots of glass and no ventilation (like our cars during summer)?"

No, it is possible, but may cost more money.

band-limiting is typically done with coatings, rather than implantation of chromophores within the glass

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Actually this is possibly, although not so much in absolute term. We can say that with current technology and near-future technology it's impossible to block 100% infrared and to allow a 100% of visible light to pass through (even glass is not a 100% transparent and that's good).

However this kind of glass exists but is still rather expensive. It's called low emissivity glass and usually works by using a thin metal layer which is optically transparent but blocks most of the infrared and uv. This is a longer article here that goes into more detail. http://www.buzzle.com/articles/low-e-glass-working-principle-properties-and-advantages.html

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What IR are you talking about?

Glass glasses do not transmit thermal radiation, as can be seen in IR pictures of people. Have a look at the picture on this page. Note the dark glasses, which do not pass the body heat. If the glasses passed IR you would be able to see the eyes.

This is also true for most security glasses as used in cars. With an infrared camera you can't see the people in the cars. Here again, note the "black" windows.

The problem with heating up is, that the materials in the car absorb light and turn it into infrared, i.e. heat radiation, which then is not able to dissipate, because it does not pass through the windows.

Mitigations that are usually used are coatings to reduce the amount of energy introduced into the interior without much reducing the light (reddish coatings of windshields) or black toned windows.

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