Well the windshield tint works. It lets most light in (and it seems within the Cali legal limit in full sun). And it is definitely cooler on my hand and especially on the dash. At this hour on a full sun day like today my dash is too hot to hold my hand on for more than a short second. I can do it indefinitely now. The dash is more like "very warm" than really hot. That is the point of the tint. Here are my measurements of the light transmission. What think you?
Three light meter tests (no bearing on heat rejection)
1) Tint on tint difference (test done early afternoon)
Rear passenger window with one layer metalized dark, high quality heat rejecting commerical car tint.Full sun: 59,300 LUX
Tint: 10,300 (83% light reduction)
Rear driver side window with both tint layersFull sun: 59,300 LUX
Tint on tint: 6,100 (90% versus direct sun, 41% versus one-layer)
2) Windshield test (overcast cloudy sky 8:15 a.m.)
Overcast open air: 10,500 LUX
Windshield without tint: 6400 LUX
With tint: 4200 LUX (35% reduction over OEM, 60% reduction over direct sun)
3) Windshield test (full sun midday, cloudless blue sky)
Open air: 59,396 LUX (steady reading)
OEM glass alone: 59,396 LUX (steady reading)
Tint: 42,000 LUX (29% reduction). But this reading fluctuated a lot over minutes and ranged from lows of 40,000 LUX to a fairly steady high of about 49,000 LUX.