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Insulation Calculator

R-value, material quantity, total cost — and how many years until your insulation pays for itself.

Total cost

$1,620–$2,760

Payback

7.3 yrs

Project details

Climate zone

Auto-suggests target R-values: attic R-49, walls R-19, basement R-15.

Areas to insulate

Area 1

Application

Lengthft

Widthft

Current R-value

0 = no insulation. Existing fiberglass batts ~R-19

Target R-valueR-49

Gap: R-30, ~8.6" thick

1200 sq ftNeed R-30 more

Total1200 sq ft

Insulation material

Type

Blown-in Cellulose — Recycled paper. Best blown-in option. Better R per inch than blown FG. Slightly higher cost.

Best for: Existing attics, walls

Have a quote? Custom $/sq ft/ sq ft

Optional override

Energy savings

Your annual heating + cooling cost$ / yr

Roughly the sum of your gas/electric bills attributable to HVAC

Estimated savings

$300 / year

15% reduction in HVAC costs based on application + R-gap

Extras

Air-sealing (highly recommended)

Adds ~$0.15–$0.40/sq ft

Hire a pro instead of DIY

Most fiberglass and blown-in is DIY-able

Utility rebate (if any)$

Many utilities offer $0.10-0.50/sq ft rebates. Search '[your utility] insulation rebate'

Cost & payback breakdown

Materials, labor, and how fast it pays for itself.

Blown-in Cellulose · 1200 sq ft$1,440 – $2,280

Air-sealing$180 – $480

Total project cost$1,620 – $2,760

Annual energy savings+$300 / year

Payback period7.3 years

50-year savings (after payback)+$12,810

Insulation material comparison

All 7 materials at a glance — pick the right tool for the job.

Material	R/in	$/sq ft	Best for	Pro?
FG batts	R-3.2	$0.60–$1.50	Open framing cavities	DIY ok
MW batts	R-3.7	$0.90–$2.00	Fire/sound-rated walls	DIY ok
Blown FG	R-2.5	$1.00–$1.60	Existing attics	DIY ok
CelluloseYOUR PICK	R-3.5	$1.20–$1.90	Existing attics, walls	DIY ok
Open-cell foam	R-3.7	$0.50–$1.25	Walls, ceilings	Yes
Closed-cell foam	R-6.5	$1.00–$2.50	Rim joists, basements, tight spaces	Yes
Rigid XPS	R-5	$0.50–$1.50	Basement walls, exterior, foundations	DIY ok

Shopping list

Major materials for this project.

Blown-in Cellulose~40 bags
Caulk (acrylic latex)~6 tubes
Spray foam cans (Great Stuff)~3-5 cans
Weatherstripping (attic hatch)1 roll
Utility knife & staple gun1 set
Blower rental (free with bags at Home Depot)1 day
N95 mask, goggles, gloves1 set
Coveralls1
Drop light or headlamp1

Save $$ on energy

Most utilities offer free home energy audits. Search "[your utility] energy audit" for instant rebates.

Find audit →

How to use this calculator

Pick your climate zone (warm/mild/moderate/cold) and the calculator suggests the right R-value target for your application — attic, walls, floor, or basement. Enter your current R-value (or 0 if uninsulated) and the calculator computes the gap, thickness needed, and material units.

Add your annual heating and cooling cost, and the calculator estimates your annual savings and payback period. Most attic insulation pays back in 3–7 years.

Pro tips

Air-seal first. Insulation works by trapping still air. If air can leak around the insulation (top plates, recessed lights, attic hatches), R-value drops 30–50%. Caulk and foam-seal all penetrations before adding insulation.

Attic gives the best ROI. Heat rises — most home heat loss is through the attic. Going from R-19 to R-49 in the attic is the single highest-payback insulation upgrade for most homes. Walls and floors come second.

Check for utility rebates.Most utility companies offer $0.10–$0.50 per square foot rebates for adding attic insulation (and sometimes free professional audits). Some states pay 50% of the cost. Search "[your utility] insulation rebate" before buying.

Spray foam is for problem cases. Closed-cell spray foam has the highest R-per-inch (R-6.5) and acts as an air barrier. Worth the higher cost in: rim joists, cathedral ceilings, irregular cavities, and where space is tight. For straightforward attic floors, fiberglass batts or cellulose are 70% cheaper.

Frequently asked questions

What R-value should my attic be?▾

Energy Star recommendations: Warm climates (FL, southern TX): R-30 to R-49. Mild (CA, Carolinas): R-38 to R-49. Moderate (most US): R-49 to R-60. Cold (northern states): R-49 to R-60. The calculator pre-fills these based on your climate zone.

How long until insulation pays for itself?▾

Attic insulation upgrades typically pay back in 3–7 years through reduced heating and cooling bills. Wall insulation: 5–10 years. Floor/basement: 7–12 years. Add utility rebates and the payback gets faster. After payback, the savings continue for the life of the insulation (50+ years).

Fiberglass batts vs. blown-in vs. spray foam — which is best?▾

Fiberglass batts ($0.60–$1.50/sq ft): cheapest, easiest DIY, best for new framing with empty cavities. Blown-in cellulose or fiberglass ($1–$2/sq ft): best for existing attics, fills around obstructions. Spray foam ($1–$2.50 per board foot): highest R-value per inch and air-sealing, but 3–5× more expensive.

Can I insulate my attic myself?▾

Fiberglass batts: yes, easy DIY. Blown-in: yes — most home improvement stores rent the blower for free with a minimum bag purchase. Spray foam: closed-cell requires a pro (the chemistry is dangerous and short pot-life makes mistakes expensive). Open-cell DIY kits exist but pro install is recommended.

How much will I save by adding insulation?▾

Going from no/low insulation to code-recommended R-value typically reduces heating and cooling costs 15–25%. For a home with $2,000/year in heating + cooling, that's $300–$500/year saved. The calculator estimates your specific savings based on application and current R-value.

Is air-sealing necessary before insulating?▾

Yes — non-negotiable. Insulation traps still air to slow heat transfer. If air can leak through gaps and penetrations, the insulation's R-value can drop 30–50%. Spend a weekend caulking and foam-sealing all penetrations (top plates, recessed lights, attic hatch) before adding insulation. The calculator includes air-sealing as a budget line item.

How thick is R-49 attic insulation?▾

Depends on material. Fiberglass batts: ~15 inches. Blown-in fiberglass: ~20 inches. Blown-in cellulose: ~14 inches. Open-cell spray foam: ~14 inches. Closed-cell spray foam: ~8 inches. The calculator shows the exact thickness needed for your chosen material.

Disclaimer. Energy savings are estimates based on typical reductions and your inputs. Actual savings vary by climate, fuel costs, home tightness, occupancy patterns, and HVAC efficiency. Consult an energy auditor for a precise analysis.