What UV actually does over time
Constant sun exposure chalks fibreglass and gel-coat panels, fades printed decals, and dries out rubber seals until they crack. None of it happens overnight — it's cumulative, which is exactly why it's easy to underestimate until a van's a few years old and visibly duller than it was.
Vans stored outdoors year-round, with no shed, carport or shade cloth, see this happen noticeably faster than ones with any kind of cover.
How a coating creates a barrier
A ceramic coating sits on top of the panel as a sacrificial layer — UV degrades the coating first, rather than the panel underneath it. That's the mechanism: it doesn't block UV outright, it gives the sun something else to wear down before it reaches the gel-coat or paint.
That's also why a coating isn't a one-time, forever fix — it wears down and needs reapplying over time, typically every 1-3 years depending on how much direct sun the van actually gets.
What it doesn't fix
Coating protects a sound, healthy panel going forward — it doesn't reverse chalking or fading that's already happened. If a van's panels are already visibly dull or oxidised, that's a different conversation about what's realistically achievable before coating is worth applying.