We are in the process of finishing the new addition on our house. The ductwork is within the crawl space. The crawl space has only 13-14" below the steel beams that hold the floor construction. The ductwork design called for 10" duct height (supply air). The duct segments were 20x10,18x10,14x10,10x10. The return duct was 20x12, single segment. The contractor used 26 Gauge Galvanized steel and R-6 duct wrap.
Due to tight space the duct ended up sitting on the gravel (actually on the plastic sheet that covers gravel throughout the crawl space).
Crawl space is completely closed without any vents. It will be slightly conditioned with the supply air duct which will have a few small openings (with a mesh) to provide a small amount of conditioned air.
Is there going to be any problem with the duct sitting on the ground/gravel?
If yes, what type of problems we may end up experiencing?