Tesla owners in Orange County ask us the same question every summer: “Will ceramic film on the Model Y glass roof actually make a difference?” This week my brother pulled a Raytek infrared thermometer out of the shop drawer and we measured it.
The Setup
- 94°F ambient air, asphalt parking lot, noon, no shade.
- 2024 Model Y (customer's car, with permission).
- Three glass zones tested on the panoramic roof: bare glass, the customer's old carbon 5% film, and a fresh LLumar IRX sample.
- Raytek MT6 non-contact IR thermometer.
- Measured interior-side glass surface temperature — the temp you'd feel on your scalp.
The Numbers
| Zone | Glass surface temp | Delta from bare |
|---|---|---|
| Bare panoramic glass | 147°F | — |
| Old 5% carbon film | 128°F | −19°F |
| LLumar IRX ceramic | 111°F | −36°F |
The carbon film helped — about 13% cooler. The ceramic film cut the heat by 24%. On a 94° day, that's the difference between “my head feels hot” and “I don't notice.”
Why Ceramic Wins
Heat doesn't come from visible light. It comes from infrared radiation. Dark film blocks visible light. Ceramic film blocks IR. That's why a barely-tinted IRX film beats a pitch-black carbon film on heat.
The old carbon film on the customer's car was 5% VLT — dark enough that you can't see in from outside. The IRX sample we tested was 70% VLT — nearly clear. The ceramic still won by 17 degrees. Darkness and heat rejection are two different problems.
What This Means for You
- Model Y / X panoramic roof owners — IRX is the only film we'd recommend. The roof is the single biggest heat load in the cabin.
- Standard Model 3 / S (no panoramic) — CTX ceramic is plenty. Smaller glass area, less IR exposure.
- Budget-conscious — Rayno Phantom S5 still cuts IR by 50%. A real upgrade over dyed or carbon film at a lower price.
The Limits
One car, one day, one thermometer. Your results depend on glass type, ambient temp, angle of sun, and how long the car has been baking. But the direction is real — ceramic > carbon > nothing, in that order, every time.
If you want to run the same test on your own car, we're happy to let you hold the thermometer while we swap samples. Bring the car by on a hot day.