Are you sure it's drywall and not foam insulation board? My house had an addition built with a crawlspace and I had foam insulation board installed against the joists. It made a huge difference in my heating bill and room comfort (the floor was no longer cold in winter).

There could be many reasons your crawl space ceiling has been drywalled. If the floor joists used for the first floor are pre-engineered (I- joists)and not solid members (2" X 10"), many codes require that the bottom be drywalled or the crawl space sprinkled.

@party_music50 yeah I'm certain it's not insulation board. One other thing that I realized could be the case, is that it could be the remnants of a lower floor, since the house was moved at one time. I had a theory that maybe they started or had a lower floor, but then got rid of it for one reason or another. Not sure how likely that is, but I noticed some of the beams have pieces of drywall on them too that look like they may have been part of a wall.

@Michael Menn Ltd. do you think I should be concerned about the holes punched in the drywall in certain places? Also what do you mean by 'sprinkled'?

Thanks!