Enter the area you need to insulate in square feet, select your desired R-value from the dropdown, and pick your insulation type. The calculator instantly estimates how many inches of insulation you need, the quantity of material (rolls, bags, board feet, or sheets depending on type), and the approximate cost. Change any input and the results update automatically.
The most common and budget-friendly option. R-3.14 per inch. Easy to cut and install in standard framing cavities. Best for new construction or accessible attics with regular joist spacing. Downside: gaps and compression can significantly reduce effectiveness. Cost: ~$0.50/sqft at R-13.
Made from recycled paper, treated for fire resistance. R-3.70 per inch — slightly better than fiberglass. Excels at filling irregular spaces, around wiring, and in existing wall cavities. Requires a blowing machine (usually free with a minimum purchase). Cost: ~$0.80/sqft at R-13.
Expands to fill every gap and crack. R-3.70 per inch. Softer and more flexible than closed cell, making it great for walls and sound dampening. Allows moisture to pass through (not a vapor barrier). Requires professional installation. Cost: ~$1.50/sqft at R-13.
The highest R-value per inch at R-6.5. Dense, rigid, and acts as its own vapor barrier and air barrier. Ideal for basements, crawl spaces, and areas prone to moisture. Also adds structural strength to walls. The most expensive option. Cost: ~$2.50/sqft at R-13.
Available in EPS, XPS, and polyiso varieties, averaging R-5 per inch. Great for basement walls, foundation exteriors, and continuous insulation. Easy to cut with a utility knife. Must be sealed at joints to prevent air leaks. Cost: ~$1.00/sqft at R-13.
The Department of Energy divides the US into climate zones. Here are the recommended R-values for attics and walls:
| Climate Zone | Attic | Wall Cavity |
|---|---|---|
| 1 (Florida, Hawaii) | R-30 | R-13 |
| 2 (Gulf Coast, S. AZ) | R-30 | R-13 |
| 3 (CA coast, Carolinas) | R-30 | R-15 |
| 4 (Mid-Atlantic, KS) | R-38 | R-15 |
| 5 (NE, IL, IA, NE) | R-38 | R-21 |
| 6 (MN, WI, MT) | R-49 | R-21 |
| 7 (ND, AK interior) | R-49 | R-21 |
| 8 (AK, high elev.) | R-60 | R-21 |
For a 1,000 sq ft attic at R-38 using fiberglass batts, you'd need about 56 rolls (each covering ~18 sq ft at R-38) and about 12 inches of insulation. With blown-in cellulose, you'd need roughly 97 bags. Costs vary widely by material — use the calculator above for exact numbers.
Open cell spray foam is softer, expands more to fill cavities, has an R-value of about 3.7 per inch, and costs less. Closed cell spray foam is denser, provides its own moisture barrier, offers R-6.5 per inch, and costs more. Use closed cell in basements and moisture-prone areas; open cell for walls and sound dampening.
Cellulose has a higher R-value per inch (3.7 vs 3.14) and fills gaps better, making it superior for retrofitting existing walls and irregular spaces. Fiberglass batts are cheaper and easier for DIY in open framing. Both work well when properly installed — the best choice depends on your project.
It depends on your climate zone. Zones 1–3 need R-30 to R-38, zones 4–5 need R-38 to R-49, and zones 6–8 need R-49 to R-60. Check the DOE climate zone map above and your local building codes for specific requirements.
Yes, in most cases. Remove any wet or damaged insulation first. Don't install a vapor barrier between layers. Unfaced batts or blown-in insulation work best over existing material. Avoid compressing the old insulation, which reduces its R-value.