How effective is dirty insulation?
I have an 80 year old bungalow in Raleigh NC. It has previously had a thin layer (2-3 in) of fiber glass insulation blown into the attic. I have recently had an energy audit and know that I have LOTS of air leaks to take care of. The existing insulation is quite filthy (covered in black dust). I know I need more insulation, but my real question is given that it is covered and saturated with this black dust, is it doing any good? Would I be better off to brush it aside to get to all of the air leaks or go ahead and remove it all? Removal would be some cost, and it would up the cost of the planned insulation upgrade, but it would make it a LOT easier to find all of the potential air leaks.
Despite a few internet searches I’ve not found any discussions related to this topic. Any thoughts will be appreciated.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part