Re: screw pops due to bad insulation?
Howdy. First how much insulation? # of "s
How far apart are the ceiling joists? Is it a truss roof system?
Do you live where its is winter - like snow hanging on the roof?
So if the joists are 24" on center apart and you had R38 or more blowing then the weight if a 1/2" drywall can do just what you are describing.
Roof leaks an cellulose - water is soaked up and heavy can also cause this problem.
Truss with a heavy snow load can casue deflection problem like this too.
clear as mud is it not?
Any an all of my comments are just my opinion and not to be confused with facts.