using old carpet for insulation???

I agree, find something cheap that acts as insulation rather than using an old dirty funky carpet. That aluminum bubble stuff is nice b/c it wont absorb any moisture ever. It may be a bit of a bitc* to lay down smooth over diverse contours of a floorboard as it is essentially bubble wrap coated with aluminum foil.

I like something tht I dont have to glue down so it can be replaced if needed.

We use the 5/16" bubble aluminum rolled stuff all the time to insulate telecom cabinets.