Insulation works by trapping air. Once it's compressed, wet, or contaminated with rodent waste, it stops trapping air and starts doing nothing — while still sitting there looking like insulation.

In Atlanta attics we routinely find insulation that's decades old, settled to half its original depth, wet from a roof leak nobody knew about, or thoroughly contaminated by rodents. Rodent-contaminated insulation is also an indoor air quality problem, because attic air gets pulled into the house through gaps and leaky ductwork.

Removal has to be done carefully — the material is airborne and unpleasant, and doing it badly spreads contamination through the house. We vacuum it out into sealed bags rather than carrying it down through your hallway.