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Estimating the R-Value of Automotive Glass

user-6184358 | Posted in General Questions on

I have a van life friend asking what is the R-value of laminated automotive glass?  The goofy foil reflective stuff seems to help a lot when a thermal camera is pointed at the van.
The best we can come up with is R-1, is this close?

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  1. Trevor_Lambert | | #1

    Probably a little less than that, but in that ball park. Note that you can't really trust thermal readings from reflective materials, unless the camera is sophisticated enough to recognize and compensate for the vastly different emissivity.

  2. Expert Member
    BILL WICHERS | | #2

    +1 for not trusting thermal cameras here. You'd be better off making a test with a thermometer inside the car. Keep the car in the sun for an hour, watch the temp rise. Do the same test, under the same conditions (same length of test, same time of day, same outdoor ambient air temperature and sun conditions, etc.), both WITH and WITHOUT the reflective stuff in place. You'll probably still find the reflective stuff is helping, but it's just a radiant barrier. The car's insulation value is holding heat in too, not just keeping it out. R value works both ways.

    I would expect the insulating value of auto glass to be R1 at best, probably less. Essentially all of your R value is coming from the air films clinging to the sides of the glass, not from the glass itself. You can test this by running a fan inside the car blowing over the glass, which should change your temperature measurements by a measurable amount.


  3. charlie_sullivan | | #3

    I'd call it R-1 parked, R-0.8 driving at any speed, at which point the exterior film goes away.

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