My basement has floor joists above (about 12') and support beams extending throughout the basement about 1.5' below the joists. Because of the HVAC system, I'll need to have a lower ceiling. My question is, how do you "frame out" a ceiling (essentially, dropping the ceiling 2' so I can have something to hang the drywall to)? Do I just buy long pieces of 2x6 or something similar and fasten them to the support beams and the top of the outer walls?