Years ago I let a company re-deck my roof when replacing the shingles - making an unholy mess on top of my insulation. I picked up the main chunks of plywood and left the terrible mess of splinters and sawdust. 2010 has been the hardest winter in Dallas ever and has made me revisit the idea of adding insulation. The existing fiberglass bats are in bad shape - very old. I hate the idea of laying new insulation over that mess and have some concern it might be a fire hazard. I've just spent a week and a half sweeping up the splinters and dust above the garage and bagged up a small portion of disintegrating insulation. I know now that I need a better mask and perhaps a portable wet/dry vaccum - to save my lungs and sinuses. My question is this: am I being too particular in wanting to clean out the old before putting in the new? Is it worth all my efforts on an old but charming home that will probably sell for lot value when I decide to move on? Many thanks.