How long does attic insulation last, and how long should it last?
Short answer. Attic insulation can last for decades, often the life of the house, as long as it stays dry, uncompressed, and free of pests. Fiberglass and mineral wool do not break down on their own, cellulose can settle and lose some depth over time, and spray foam is generally expected to last as long as the roof deck it is applied to.
By material
- Fiberglass batts and loose fill: glass fibers do not rot or decompose. They lose effectiveness when compressed, wet, or clogged with dust and droppings.
- Cellulose: made from treated recycled paper. It settles somewhat after installation, which manufacturers account for in their coverage charts, and it can clump and lose value if it gets wet repeatedly.
- Mineral wool: resists moisture and fire well and holds its shape for a long time.
- Spray foam: bonded to the roof deck or framing, it is usually expected to last as long as the structure, provided the roof stays dry.
What actually shortens its life
- Roof leaks. Wet insulation loses much of its value and can harbor mold. Small, slow leaks often show up first as a matted, stained patch.
- Pests. Rodents and raccoons tunnel, nest, and contaminate insulation. In North Georgia, squirrels entering through damaged soffit and fascia are a frequent cause.
- Foot traffic and storage. Walking on loose fill or stacking boxes compresses it.
- Air leaks. Dark, dusty streaks show where house air is filtering through, which reduces performance.
- Contractor disturbance. HVAC, electrical, and cable work in the attic often leaves gaps.
How to tell if yours is still doing its job
Measure the depth. Many older Georgia attics have far less than the roughly R-49 that ENERGY STAR now recommends for an uninsulated attic in Climate Zone 3. If it is thin, wet, or dirty, it is time to top up or replace it. See attic heat and shingles and common roof leak causes.