When it comes to insulation, it's essential to evaluate the condition of the existing material before deciding whether to keep it or replace it. If the insulation is very old, damaged, and not performing well, then it should be completely removed and replaced with new insulation. However, if the insulation is in good shape, then a new layer can be placed on top without any difficulty. The method of application will depend on the type of insulation that is already installed. Generally speaking, replacing old insulation may not be worth it if the old insulation is dry, dust-free, and not crushed.
In this case, there is no need for removal. In fact, leaving the old insulation in place can be very advantageous as you'll continue to benefit from it and have an extra layer of insulation on top. Therefore, if the old insulation has a joist depth, try to place a new insulation crosswise. Unless the old attic insulation is damp, new insulation can be installed over the existing one. Any moisture that gets trapped between the two layers will form mold and rot the attic floor and beams. When considering whether to keep your old attic insulation or replace it with new material, it's important to assess its condition first.
If it's in good shape and dry, then there's no need to remove it. You can simply add a new layer on top for extra protection. However, if the existing insulation is damp or damaged, then you should replace it with new material to ensure your attic is properly insulated.
