What kind of damage can squirrels do to an attic?

The damage can be extensive. They will shred and trample insulation, reducing its effectiveness and costing you money in energy bills. They chew on electrical wires, creating a serious fire hazard. They also chew on wood support beams, vents, and pipes. Their urine and feces can saturate insulation and drywall, leading to stains, odors, and mold growth.