Is it a good idea to remove my lose fill in fibergl insulation, it's super dirty, old and doing a lousy job?

I'm planning on putting in new fibergl batt insulation with an R-38 value up in the attic, I was thinking about removing the old loose fill in trash bags, should I just keep it and put unfaced batt insulation on top of it? or just remove this lousy insulation and put in new faced R-38 ? What is the best thing to do. Like I said the old fill in fibergl insulation has no vapor barrier, it's super dirty with what looks like shingle particles, but it's not because the roof has never leaked. What would you do in this case? See I'm afraid if I keep this old non-efficient loose insulation there and unfaced on top, it won't be as effective as just getting rid of it altogether. This loose fill in stuff is already compact and lost it's fluffiness and it's SPARSELY TERED in some places. My heating and air conditioning is leaking through, since my heater takes so long to heat up the house and the house gets cold real fast and has to restart over and over. Thanks for your advicem especially if your a home improvement pro or roofing specialist.