FAQ
What R-value does my attic actually need?
Recommended attic insulation levels depend on your geographic Department of Energy climate zone. In southern regions (Zones 1 through 3), target an R-38 rating, which translates to roughly 11 to 14 inches of depth depending on the material. In northern and central regions (Zones 4 through 7), target R-49 to R-60, requiring between 14 and 19 inches of blown-in cellulose or layered fiberglass batts.
Can I install new insulation directly over old insulation?
Yes, provided the old insulation is completely dry, free of mold, and uncontaminated by rodents. Always use unfaced insulation when layering over existing batts; adding a second vapor barrier (such as kraft paper) on top of old material can trap rising moisture between the two layers, leading to wood rot and mildew growth.
How long does modern home insulation last before needing replacement?
High-quality fiberglass, mineral wool, and cellulose can maintain their thermal performance for 30 to 50 years under ideal conditions. However, insulation warning signs such as roof leaks, chronic attic humidity, pest infestations, or mechanical damage from contractors can degrade the material within a few months, necessitating localized removal and replacement.
How do I know if my existing insulation contains hazardous materials?
If your home was constructed prior to 1990 and contains loose, gravel-like, pebble-shaped insulation with a gold, silver, or gray sheen, it may be vermiculite contaminated with asbestos. Do not disturb or vacuum this material. Hire an accredited asbestos testing professional to take samples and verify safety before undertaking any attic insulation project.
