[bradknowles]

Thing is, you can block both IR and UV light, without impinging on the visible light spectrum.

The UV light will cause things inside your car to break down faster, and of course the IR is what carries the heat.

So, you don't need dark tint to block IR. You just need a different filter material.

[mensetmanusman]

Visibly transparent effective IR blockers are quite expensive due to the optics involved.

[bradknowles]

Thing is, the dark tint isn't that great at blocking IR. It's blocking more visible light than IR.

So, yeah -- the stuff that actually blocks IR is more expensive. But if you really want to block IR, then that's what you should be getting.

Otherwise, if you're getting the dark tint, then you should be honest with yourself about what it is that you're primarily blocking.