I am looking at a residential (all kinds of ugly electrical) job in Ft. Worth Texas. Where the ambient temp in the summer is very hot in the attic ( any links to ambient temp in different parts of the country? I know I've seen them before). Someone has moved the service to the other side of the house to avoid the service drop over the pool. They used a old 125 amp zinsco MLO panel with 125 amp circuit breaker with 3- 1/0 feeders and # 6 solid GRN. approximately 60 '. to the sub panel ( branch circuits from existing panel). My question is about the sub feeders run through the attic with schedule 40 electrical PVC. What is the NEC code on the max temp and thermal expansion or any other problems dealing with PVC in a residential attic. Most electrical contractors, as I , will use EMT or what are the most efficient types of romex style cables SEU, USE, M/C , cable tray. Does the excessive heat with conductors in PVC cause toxic fumes also? Toxic fumes in a residential fire? Thanks for your support.