Insulation R-Value Calculator
Enter area, target R-value, and material type. Returns batts, rolls, or blown-in bags. Climate zone reference table included.
Area & Target
Material
Materials Needed
DOE climate zone recommendations (attics)
The Department of Energy publishes recommended R-values by climate zone for uninsulated attics:
- Zone 1 (southernmost FL/HI): R30–R49
- Zone 2 (southern US): R30–R60
- Zones 3–4 (central US): R38–R60
- Zones 5–6 (northern US, mountain west): R49–R60
- Zone 7 (Alaska interior, high altitude): R49–R60+
Existing attics with some insulation can use lower add-on values. Check ENERGY STAR's current guidance for your specific ZIP code and application (attic vs. wall vs. floor).
R per inch by material
Fiberglass batts: ~3.14 per inch. Mineral wool: ~3.7 per inch (denser, better sound). Cellulose blown-in: ~3.5 per inch. Blown fiberglass: ~2.5 per inch. Closed-cell spray foam: ~6.5 per inch (highest per inch, also acts as air barrier). Open-cell foam: ~3.7 per inch. This calculator uses the material you select to compute required depth.
Batts vs. blown-in
Batts are quick for open cavities but leave gaps around wires and pipes if not cut carefully. Blown-in fills irregular spaces better but requires a blower (rentable from big-box stores with bag purchases). For attic tops, blown-in cellulose or fiberglass is usually the best labor-per-dollar option.