Semi gloss or gloss barn paint?

Anyone have any luck with barn paint? I painted my barn two years ago with a semigloss paint by Valspar (Lowes). The gloss has disappeared and it looks flat. The barn was painted previously with polyurethane. The Florida sun destroyed the polyurethane and it either peeled or wore off.

I’m thinking of putting on another coat of the valspar and putting some sort of gloss over that?

I don’t really want to pick a new barn color and start over and I don’t know if it is worth putting a gloss on it if the sun is going to destroy the paint. Any suggestions?

I wanted some sort of gloss coat to make cleaning the barn walls easier. And unfortunately the walls look moldy in addition to the paint being flat.

https://www.google.com/search?q=majic+barn+paint&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari#imgrc=rObJew54WqgwTM

I used the classic barn red oil based for my barn. TSC and Rural King carry it. It comes in a latex too. I’m not sure about mold issues and what you can do about that. Maybe someone in the paint dept could help you.