Insulation R-Value Guide: What R-Value Do I Need?

What Is R-Value?

R-value measures thermal resistance — how well insulation resists heat flow. Higher R-values mean better insulation. An R-38 batt is approximately twice as effective at blocking heat transfer as an R-19 batt.

R-values are additive. If you have existing R-19 insulation in your attic and add R-19 on top, you get R-38 total. This makes it easy to upgrade existing insulation without removing what is already there.

Recommended R-Values by Climate Zone

Zone 1 (Southern Florida, Hawaii): Attic R-30 to R-49, Walls R-13, Floor R-13.

Zone 2 (Southern states: TX, LA, MS, AL, GA, SC): Attic R-30 to R-60, Walls R-13 to R-16, Floor R-13 to R-19.

Zone 3 (Mid-southern states: AR, TN, NC, OK): Attic R-30 to R-60, Walls R-13 to R-21, Floor R-19 to R-25.

Zone 4 (Mid-Atlantic, lower Midwest: VA, KY, MO, KS): Attic R-38 to R-60, Walls R-13 to R-21, Floor R-25 to R-30.

Zone 5 (Upper Midwest, Northeast: IL, IN, OH, PA, NY, NJ, CT): Attic R-38 to R-60, Walls R-13 to R-21, Floor R-25 to R-30.

Zone 6-7 (Northern states: MN, WI, MI, ME, VT, NH, MT): Attic R-49 to R-60, Walls R-21 to R-28, Floor R-25 to R-30.

Use our insulation calculator to determine exactly how much material you need based on your target R-value and area.

Insulation Types Compared

Fiberglass batts: R-3.1 to R-3.4 per inch. Cost: $0.50-$1.50/sq ft. The most common DIY insulation. Available in pre-cut widths for standard framing. Best for open wall cavities and attic floors.

Blown-in cellulose: R-3.2 to R-3.8 per inch. Cost: $1.00-$2.50/sq ft installed. Made from recycled newspaper. Fills irregular cavities better than batts. Excellent for retrofitting existing walls and topping off attic insulation.

Blown-in fiberglass: R-2.2 to R-2.7 per inch. Cost: $1.00-$2.00/sq ft installed. Similar to cellulose but does not absorb moisture. Good for attics where moisture is a concern.

Open-cell spray foam: R-3.5 to R-3.7 per inch. Cost: $1.00-$2.00/sq ft. Expands to fill cavities completely. Good sound insulation. Must be covered with drywall (fire code).

Closed-cell spray foam: R-6.0 to R-7.0 per inch. Cost: $2.00-$4.50/sq ft. The highest R-value per inch. Also acts as air and moisture barrier. Adds structural rigidity. Best for basements, crawl spaces, and thin wall assemblies where space is limited.

Energy Savings from Insulation

The Department of Energy estimates that proper insulation saves 10-50% on heating and cooling costs, depending on your current insulation level and climate. For an average US home spending $2,000/year on energy, that is $200-$1,000 in annual savings.

Attic insulation provides the best return on investment because heat rises — an under-insulated attic is responsible for 25-30% of a home's total heat loss. Upgrading from R-11 to R-38 in the attic typically pays for itself in 2-4 years.

Wall insulation is the second priority. Uninsulated exterior walls account for 35% of heat loss. Even adding R-13 batts to previously empty wall cavities dramatically improves comfort and reduces energy bills.

DIY Insulation Tips

Attic insulation is the easiest DIY insulation project. Lay fiberglass batts perpendicular to existing insulation, or rent a cellulose blowing machine ($50-$100/day from most home centers — often free with purchase of 20+ bags).

Wear proper PPE: N95 respirator mask, safety goggles, long sleeves, gloves, and long pants when handling fiberglass. Cellulose is less irritating but still requires respiratory protection.

Air seal before insulating. Caulk and foam around all penetrations (electrical boxes, plumbing pipes, recessed lights, attic hatch) before adding insulation. Air leaks can reduce insulation effectiveness by 25-40%.