Newer Windows:
The metallic vapor deposition on the inner pane is transparent to the high-energy short-wave solar radiation. If the sun's rays hit your furniture, walls, ceilings, etc., they absorb the energy from the sun's rays, store it in between, and then release it as heat radiation. The resulting long-wave thermal radiation is largely reflected by the metallic vapor deposition. That Metallic vaporization lets in the light and warmth of the sun's rays, but not out again.

One device has metal casing to give more focus.