Calculate how much insulation you need by area and desired R-value. Covers batts, blown-in, and spray foam.
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📐 How We Calculate — Learn about our calculation methodology, data sources, and quality standards.
Recommended R-Value by Location & Climate Zone
Location
Zone 1–3 (warm)
Zone 4–5 (mixed)
Zone 6–8 (cold)
Attic
R-30 to R-38
R-38 to R-49
R-49 to R-60
Walls (2×4)
R-13
R-13 to R-15
R-13 + R-5 sheathing
Walls (2×6)
R-19
R-19 to R-21
R-21 + R-5 sheathing
Floor over crawlspace
R-13
R-19 to R-25
R-25 to R-30
Basement wall
R-0 to R-10
R-10 to R-15
R-15 to R-19
Cost by Material (Materials Only, per sq ft)
Material
R-per-inch
Cost/sq ft
Best For
Fiberglass batt
R-3.1 to R-3.8
$0.60–1.20
DIY, open stud bays
Blown cellulose
R-3.1 to R-3.7
$1.00–2.00
Attics, irregular cavities
Rock wool batt
R-3.0 to R-3.3
$1.40–2.10
Fire + soundproofing
Open-cell spray foam
R-3.5 to R-3.7
$1.50–3.00
Air sealing, interior walls
Closed-cell spray foam
R-6.0 to R-6.5
$2.00–5.00
Thin spaces, moisture barrier
Rigid foam board
R-4.0 to R-5.0
$0.80–1.60
Basement walls, exterior
Frequently Asked Questions
What does R-value mean?
R-value measures thermal resistance. Higher R = better insulation. It is the inverse of U-factor (heat flow rate). R-38 blocks roughly 97% of heat transfer.
What R-value do I need for my climate zone?
US DOE recommendations: Zone 1–2 (FL, TX south) attic R-30 to R-49; Zone 3–4 (most southern US) attic R-38 to R-60; Zone 5–7 (northern US, mountains) attic R-49 to R-60. Walls: R-13 for 2×4 studs, R-19 for 2×6 in most zones; add R-5 continuous sheathing in cold climates.
Fiberglass batt vs blown cellulose vs spray foam: which is best?
Fiberglass batts ($0.60–1.20/sq ft) are cheapest and DIY-friendly. Blown cellulose ($1–2) fills irregular attic cavities best. Open-cell spray foam ($1.50–3) seals air gaps; closed-cell ($2–5) has the highest R-per-inch (R-6.5) and adds structural + moisture barrier. Rock wool is best for fire + sound resistance.
How much does insulation cost per square foot?
Materials only: fiberglass $0.60–1.20, cellulose $1–2, rock wool $1.40–2.10, open-cell foam $1.50–3, closed-cell foam $2–5. Installed (with labor), roughly double. A typical 1,200 sq ft attic upgrade to R-49 runs $1,500–4,500 installed.
Can I install insulation myself?
Batts and rolls are the easiest DIY option — measure, cut, press-fit between studs or joists. Blown-in cellulose requires renting a blower ($30–80/day, often free with bag purchase). Spray foam is not DIY-friendly; professional installation is required because of chemical safety and proper curing control.
Does adding insulation qualify for US tax credits?
Yes. Under IRS Section 25C (Energy Efficient Home Improvement Credit, extended through 2032), homeowners can claim 30% of insulation material costs up to $1,200/year. Labor does not qualify. Keep receipts and the manufacturer's certification statement. Check irs.gov for the latest limits.