Can I put too much insulation in my attic?

Yes, you can put too much insulation in your attic in certain situations, but for most homes the bigger risk is too little, not too much. From an energy standpoint, there are diminishing returns. Going from R19 to R38 saves a lot of money, going from R38 to R60 saves a moderate amount, but going beyond R60 to R80 saves very little and is rarely cost-effective. The ways you can actually have too much are physical and safety-related. First is weight. Dense materials like multiple layers of fiberglass batts over old cellulose can add significant weight. Blown-in cellulose weighs about 1.5 pounds per cubic foot, so 16 inches over 1000 square feet is over 2000 pounds, which can stress older ceiling drywall. Second is blocking ventilation. If insulation is stuffed into soffit vents or covers can lights that are not IC-rated, you can cause overheating, fire hazards, and moisture buildup. Attics need airflow from soffits to ridge vents to prevent ice dams and mold. Third is moisture trapping. If you pile vapor-impermeable insulation like closed-cell foam or foil-faced batts in a way that traps moisture against wood, you can cause rot. Finally, covering electrical junction boxes so they cannot be accessed violates electrical code. As long as you maintain ventilation, keep insulation away from non-IC lights, and do not exceed the weight capacity, reaching R49 to R60 is ideal and not considered too much in most climate zones.