This past winter I purchased an older home and upon surveying the attic I found that the previous owners made no attempt to update the insulation. Meaning; I still have the older insulation that at best resembles big piles of lint. My question is two-fold. Does the old insulation have to be removed from the attic or can I further insulate over the top, and will I then be able to replace the the old flooring material with either pressboard or plywood? This is my first house and the first big project I need to tackle so any info would be greatly appreciated. Thanks so much!

I am in the process of framing around my furnace (gas, forced hot air) and water heater. The two units sit diagonally across from eachother in an area of about 5 feet by 6 fit. I intend to box in this area fairly tight with a large door on one side large enough to be able to remove/replace each of the units. Am I allowing for enough air for the two units? I also intend to include a couple of air vents on the surrounding wall and a vent on the door. Thanks in advance!