metal building insulation

This isn't news so much as a homeowner's question posted to a building-science forum. The person has a steel-frame metal building in central Texas, which has a hot, humid climate, and wants to insulate it well enough to run air conditioning efficiently. The building already has a reflective wrap (an "Everbilt" radiant barrier-type product) installed between the steel columns and the exterior metal panels.

The person is weighing a few common approaches for insulating metal buildings: using 1 inch of closed-cell spray foam directly against the metal panels combined with 3.5 inches of open-cell spray foam plus the wrap already in place, or using mineral wool batts instead, either against the panels or inside a framed interior wall. These are all legitimate strategies builders use on metal buildings, since the metal skin conducts heat fast and can condense moisture if it's not handled carefully in humid climates.

At the time of posting, no one had responded with specific recommendations, so there's no answer yet on which approach works best for a Texas climate. If you have a metal building of your own, the general tradeoffs are similar: closed-cell foam against the metal panel controls condensation and adds some structural rigidity, open-cell foam is cheaper per inch but needs that vapor control layer, and mineral wool is easier to install and inspect but needs a separate air and moisture barrier against the metal skin. The right mix depends on your humidity levels and how the building is framed.