mobilehomerepair.com

I have a metal roof with 2x4 rafters, no attic. There is rock wool insulation plus a layer of batt insulation covered with think plastic sheet. I installed a wall heater with a 4 inch B-vent through the roof. I'm concerned about the plastic film getting too hot in the small space above the ceiling. I peeled the plastic back a few inches from the B-vent. Any comments welcomed

What does the manufacturer say? I would contact them for the best answer. Lacking that I would use a 4" ceiling thimble to protect anything near the pipe.

Greg