The ultraviolet fades your interior, causes sunburn, etc.  That's why tint films are made to
block it.  Temp is a different issue.  Light (including UV) passes right through glass.  When
it hits a surface in the interior, it heats the interior.  The surface radiates this as
infrared.  Infrared cannot pass through glass whether or not it has tint on it, so the heat
accumulates.  The only way to prevent this is to keep the light from hitting the surfaces
inside the vehicle to begin with.  That's what tint does.  Depending upon the type of tint and
light transmission percentage, it keeps anywhere from 30% to over 70% of the solar energy from
entering the vehicle to begin with.

We did check interior temps before and after tinting our '81 Westy.  Naturally, this was not a
controlled experiment.  We tried to check on similar days with similar sun load, etc.  We live
in Arizona, so we get over 80% of possible sunshine (clouds are rare).  We saw a 15 to 20
degree difference after tinting.  Our tint (metallic) is 35% transmission on the door windows,
and 5% (limo tint) on all windows behind the driver.

Bill in the Southwest

----- Original Message -----
From: "caryccc" <caryccc@JUNO.COM>

>   Years ago, an intelligent person told me that non-tinted windows were
> better, because the UV rays that penetrated thru the glass could likewise
> exit almost as freely, but that a tinted window (which reflects most but not
> all UV rays) ultimately traps more UV (and therefore more heat) inside,
> because the UV that enters the car has greater difficulty reflecting back
> out of the interior.