FRPs do have a high thermal Energy Efficiency - if your comparing skins. FRP is higher compared to metal - no comparison. The FRP thickness and insulation R factor surpasses widely all aluminum sheet alternatives. The finished product enables your trucks, vans and trailers to hold temperatures up to minus -10 degrees F. The oriented strand board outer skin on FRPs is exterior rated Exposure I by the American Plywood Association (APA). FRP panels decrease cooling and heating costs even more than their R rating would seem to indicate 'because they form a solid thermal envelope around the structure, uninterrupted by studs, sills or headers. This substantially reduces air infiltration compared with conventional construction techniques. The panel's solid core of insulation also eliminates the convection looping that can occur in the gaps and spaces typical in batt insulation.
Many of the FRPs can be purchased sandwiched with EPS. Expanded Polystyrene (EPS) foam insulation is used for all types of construction. EPS has a 35 year history of proven performance as a rigid foam insulation. EPS foam provides optimum cost value when compared to other rigid foam insulations of the same R-value design. Your freezer container trucks and building construction coolers are made of the same stuff.
Other FRPs are sandwiched with Polyiso. Polyisocyanurate is one of the nation's most widely-used and cost-effective insulation products and has been cited by the U.S. Environmental Protection Agency for its responsible impact on the environment. Polyisocyanurate is a closed-cell, rigid foam board insulation used primarily on the roofs of offices, health facilities, warehouses, retail and industrial manufacturing facilities and educational institutions.
Other brands are sandwiched with Styrofoam types. STYROFOAM insulation products feature closed cell structure and maintain their R-value over time. The extruded polystyrene insulation products offer the highest moisture resistance of any foam plastic insulation. The result is high compressive strength and unparalleled resistance to water penetration.
As for lasting – FRPs will outlast any plywood particulates – long past. Studies have shown that they outlast your standard galvanized skins as well – much longer. Many truck containers designs have changed to these FRPs for these very reasons. Many of the newer ultra lite RVs are made of FRP construction.
Not sure why yours has degraded in such a fashion. It looks like an older stippled design – maybe the thin nature of design. Some of the older FRPs had delaminating issues. But rot has generally not been an associated with them. The older FRPs were susceptible to weathering. The outdoor weathering properties of FRP are generally good. However, there is a certain susceptibility to ultraviolet rays which require that ultra-violet absorber be specified for translucent laminates. Originally, UV absorbers were not required for gel coat because the pigments and fillers act as absorbers. Today, all exposed laminates should have a 'smooth' gel coat or a glass surfacing mat specified for the exposed surfaces to prevent fiber ‘blooming’ or surface exposure of the fibers. The high gloss 'smooth' gel coats are the preferred method for this reason. I work with FRPs and Polycarbinates in the construction business.
The other alternative is LEXAN polycarbinates - you can't distroy this stuff - hurricane shutters and impact glass use them.