Can I use a 1 1/4" PSE sheathing between the lats and not worry about moisture? I'm replacing a metal roof with metal roof.
It has 1 1/2' lats. Need to know if i need to worry abouts rotting of the lats from moisture or is the 1/4' air between PSE (Expanded polystyrene) and metal roof adequate.The roof is vented Do i need to use the foiled back PSE and if so which way to face the foil
If you have a vented attic, I assume your insulation is at your ceiling level. If this is the case, there is no need to add insulation at the roof plane as this would not do much good.
But to answer your question, I would not worry about moisture or the rotting of the lats if there is a 1/4" gap between them.
If you do insist on using the PSE for other reason or want to keep your attic cooler with the foil faced PSE, face the foil towards the attic. A radiant barrier must face an air space to be effective.