Where the Reflection Actually Forms
A Low-E window's reflective coating and its concave curvature both live on the exterior glass surface. Sunlight hits that outer surface, gets concentrated, and leaves as a focused beam — all before it ever reaches the interior pane.
That single fact determines everything: to stop the beam, you must alter the outer surface where it forms.
Why Interior Film Can't Help
Interior film is applied to the inside of the glass, behind the point where the reflection is created. The beam forms and exits on the outside, so interior film never touches it.
Homeowners who tint the inside consistently report no change — the melted stripe keeps returning.
- Reflection forms on the exterior surface
- Interior film sits behind the reflection
- The beam exits before reaching interior film
Why Interior Film Often Makes It Worse
Many interior films are reflective or metallic. Adding a reflective layer to the assembly can increase the total energy bounced back outward, intensifying the very beam melting your turf.
So the common advice to 'just tint the windows' can actively backfire when applied to the wrong side.
Why Exterior Film Is the Only Solution
Exterior anti-reflective (perforated) film is applied to the outer surface, exactly where the beam forms, and its micro-structure scatters the light so it can't converge.
It's the only approach that addresses the physics of the problem — which is why it's the standard professional fix.