I have a 50year old house, two story, with 1/3 of the second story dedicated as an attic. The attic is unfinished/ uninsulated, except for the pine tongue and groove floor. Under the floorboards are approximately 7" of insulation, 3" of which is older yellow fiberglass on top of which is another 4" of loose insulation, white cotton fluffy stuff. Combined they fill the joists. My question is do I need to remove the floorboards completely to add more insulation or can I simply lay new insulation directly on the floor boards??