What is attic insulation, and how much do you need?
Short answer. Attic insulation is the layer of material, usually blown fiberglass, blown cellulose, fiberglass batts or spray foam, that slows heat moving between the living space and the attic. ENERGY STAR currently suggests about R49 for an uninsulated attic in most of Georgia (climate zone 3) and about R60 in the colder northern counties (zone 4), with somewhat less to add where a few inches already exist.
Types
- Blown fiberglass: loose fill, light, and common in newer Georgia homes.
- Blown cellulose: recycled paper treated with fire retardant, denser, good at filling gaps.
- Batts: fiberglass or mineral wool, effective only if cut neatly around framing without gaps.
- Spray foam: applied to the underside of the roof deck to create a sealed attic, or used to seal specific areas.
- Radiant barriers: foil layers that reflect heat. Helpful in hot climates, but not insulation in the R-value sense.
Rough depth guide
R-value per inch varies by product. Blown fiberglass often runs somewhere around R2.2 to R2.9 per inch, so R49 means very roughly 17 to 22 inches. Check the bag's coverage chart and the depth rulers in your attic.
Air sealing first
Insulation slows heat but does not stop air. Seal the top plates, wiring holes, recessed light housings, the attic hatch and plumbing chases before adding insulation, because they are much harder to reach once a foot or more of new material covers them.
Keep the vents clear
Install baffles at the eaves so new insulation does not bury the soffit vents, keeping at least 1 inch of air space under the deck. Read attic heat and shingles and roof ventilation basics.