Hello
I live in mid Michigan with cold winter climates.  I am in the process of air sealing all penetrations from my 2nd floor ceiling into my attic space.  And also I am venting the existing 2 bath fan vents thru the roof.  After that I want to add blow in cellulose insulation on top of my existing insulation.  I currently have around 6” deep of loose fill insulation.  I have had moisture issue in the past and I have a couple spots of mold showing on bottom side of my roof sheathing.  That is why I am doing this upgrade to hopefully fix my attic moisture issues.  My roof pitch it 3/12 so there is very little attic space clearance to work in.  I’m wondering  if I can just blow in cellulose insulation on top of my existing insulation?  Or is it a better idea to remove all the existing insulation and then add a vapor barrier and blow in all new insulation on top of the vapor barrier?  The space is so tight in the attic at the eaves that I think my only option is for the attic insulation to touch the bottom of roof ply.  I have no soffits or overhangs.  I’m confident that I have good attic ventilation.  My home was built in 1970.  I moved in 2014 and I plan to live here forever so I am trying to make the proper upgrades.   There is many issues with this house.  Any guidance offered would greatly be appreciated.  Thank you