your room is looking great! Something you might consider doing that's not expensive but makes a huge difference in efficiency and comfort is caulking. Fiberglass will stop cold from radiating but the air can still get in. Run a bead of caulk along the subfloor and bottom plate. You can also do the seams on the subfloor and when the sheathing goes on, caulk along the top plate and sheathing in each stud cavity. Also where the new room attaches to the house. You can do the whole stud cavity to eliminate air movement in the walls. The contractor box of ALEX caulk is not expensive and will keep cold out in winter and humidity out in summer. Yesterday we found a 14/ gap between the sheathing and top plate in our corner bedroom. That corner was always cold and we had an ice dam in that corner roof a couple of winters ago. As soon as I caulked it warmed right up. Hubby is going to caulk each gable end like that from the attic.