I am planning on putting a sheetrock ceiling up with rolled fiberglass insulation on top. Is there anything I should/need to do to the underside of the roof first? It is just a metal roof fastened to the trusses.
I'd think you'd want a good vapor barrier.
you should put a man-hole in order to get in the ceiling in the future
The attic space will need to be vented if it's not already. Often with a metal roof that's done with a ridge vent. Have you thought about blow in insulation instead of the batts?
It's usually cheaper, put in as much as you want and add to it any time.
Where would I put it? Between the sheet rock and insulation?