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Spray Foam vs Fiberglass Insulation Cost Calculator - 2026 Break-Even

See whether spray foam or fiberglass is actually cheaper for your home - weigh the higher up-front install against yearly energy savings and find the break-even year.

Spray Foam wins

$1,500 cheaper

Spray Foam

$24,750

Fiberglass

$26,250

Break-even

Year 10

Project

sqft
300 sqft
4000 sqft
$
800 $5000 $
yr
5 yr
30 yr

Energy Savings

%
15 %50 %
%
5 %35 %

Material Price

$/sqft
1 $/sqft5 $/sqft
$/sqft
0.2 $/sqft2 $/sqft

Spray Foam wins

Saves $1,500 over 15 years · breaks even in year 10

Best
Spray Foam

$24,750

Up-front$3,750
Per year$1,400
Fiberglass

$26,250

Up-front$750
Per year$1,700

Total cost over 15 years

Spray Foam$24,750
Fiberglass$26,250

Cumulative cost over time

Cumulative cost over time — crossover at year 10

What You'll Need

Great Stuff 157906 Insulating Foam Sealant, 12 oz, Cream

Great Stuff 157906 Insulating Foam Sealant, 12 oz, Cream

$8.004.6
View on Amazon
Owens Corning R-13 Pink Kraft Faced Fiberglass Insulation Roll 15 in. x 32 ft. (3)

Owens Corning R-13 Pink Kraft Faced Fiberglass Insulation Roll 15 in. x 32 ft. (3)

$157.264.4
View on Amazon
Great Stuff 157906 Insulating Foam Sealant, 12 oz, Cream

Great Stuff 157906 Insulating Foam Sealant, 12 oz, Cream

$8.004.6
View on Amazon
Owens Corning R-13 Pink Kraft Faced Fiberglass Insulation Roll 15 in. x 32 ft. (3)

Owens Corning R-13 Pink Kraft Faced Fiberglass Insulation Roll 15 in. x 32 ft. (3)

$157.264.4
View on Amazon

As an Amazon Associate, we earn from qualifying purchases.

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Example Calculations

1Default home - average savings

Inputs

Area to insulate1,500 sqft
Annual energy bill$2,000
Time horizon15 years
Energy savingsFoam 30% / Fiberglass 15%
Material priceFoam $2.50/sqft / Fiberglass $0.50/sqft

Result

Cheaper optionSpray foam - saves $1,500 over 15 yrs
Spray foam 15-year total$24,750
Fiberglass 15-year total$26,250
Break-evenYear 10

Foam costs $3,000 more to install ($3,750 vs $750), but its 30% savings vs fiberglass's 15% trims the $2,000 bill to $1,400/year versus $1,700 - $300/year less. The premium is recovered in year 10, then foam pulls ahead.

2Small efficiency gap - fiberglass wins

Inputs

Area to insulate1,500 sqft
Annual energy bill$2,000
Time horizon15 years
Energy savingsFoam 22% / Fiberglass 18%
Material priceFoam $2.50/sqft / Fiberglass $0.50/sqft

Result

Cheaper optionFiberglass - saves $1,800 over 15 yrs
Spray foam 15-year total$27,150
Fiberglass 15-year total$25,350
Break-evenYear 38 - beyond the horizon

When foam saves only 4 points more (22% vs 18%), it trims just $80/year ($1,560 vs $1,640), so the $3,000 install premium takes 38 years to recover - far past the horizon. Fiberglass is cheaper for the insulation's whole life.

3High bill, wide efficiency gap

Inputs

Area to insulate2,500 sqft
Annual energy bill$4,000
Time horizon20 years
Energy savingsFoam 35% / Fiberglass 15%
Material priceFoam $2.50/sqft / Fiberglass $0.50/sqft

Result

Cheaper optionSpray foam - saves $11,000 over 20 yrs
Spray foam 20-year total$58,250
Fiberglass 20-year total$69,250
Break-evenYear 7

A bigger 2,500 sqft home with a $4,000 bill and a wide 35% vs 15% gap makes foam's edge count: $2,600/year vs $3,400 - $800/year less. The $5,000 install premium is recovered in year 7 and foam saves $11,000 over 20 years.

Did You Know?

For a 1,500 sqft home with a $2,000 annual energy bill, spray foam costs about $3,750 to install and $1,400/year to run after ~30% savings, versus $750 and $1,700/year for fiberglass at ~15% savings. Foam costs about $3,000 more up front but trims $300/year, breaking even in year 10 and saving roughly $1,500 over 15 years. When foam's energy edge is small (say 22% vs 18%) or the bill is low, that $3,000 premium can take 30+ years to recover on bills alone, so fiberglass stays cheaper. Foam's real value is air-sealing, moisture control, and longevity - not pure energy ROI.

Frequently Asked Questions

Q

Is spray foam or fiberglass insulation cheaper?

Fiberglass is far cheaper to install - about $0.50/sqft versus $2.50/sqft for spray foam, so a 1,500 sqft job costs ~$750 vs ~$3,750. Foam wins back some of that gap on energy: it typically cuts a heating/cooling bill by ~30% versus ~15% for fiberglass, so on a $2,000 bill it runs ~$1,400/year vs ~$1,700. That $300/year edge recovers foam's ~$3,000 premium in about 10 years, after which foam is cheaper. But when the efficiency gap is small or the bill is low, foam's premium can take 30+ years to pay back on bills alone and fiberglass stays cheaper for the insulation's whole life.

  • Spray foam install: ~$2.50/sqft (~$3,750 for 1,500 sqft)
  • Fiberglass install: ~$0.50/sqft (~$750 for 1,500 sqft)
  • Foam saves more energy (~30% vs ~15%), so it runs ~$300/year less
  • Typical break-even: ~10 years on energy bills alone
  • Small savings gap or low bill: fiberglass stays cheaper
InsulationInstalled (1,500 sqft)Running / year15-Year Total
Spray foam (30% savings)$3,750~$1,400$24,750
Fiberglass (15% savings)$750~$1,700$26,250
Foam (small 22% gap)$3,750~$1,560$27,150
Q

What is the break-even year for spray foam vs fiberglass?

Break-even is when foam's lower running cost overtakes its higher install. Divide the up-front price gap by the yearly bill-savings gap: with a ~$3,000 higher foam install and ~$300/year saved, that is about 10 years. Widen the gap - a bigger home with a $4,000 bill and 35% vs 15% savings - and break-even drops to ~7 years. Shrink it to a 22% vs 18% edge and the yearly savings fall to ~$80, stretching break-even past 35 years, well beyond the insulation's useful life, so fiberglass wins. Because insulation lasts 20+ years, a break-even under ~12 years favors foam.

  • Break-even = install gap / yearly bill-savings gap
  • Typical: $3,000 / $300 = 10 years
  • Wide efficiency gap + high bill: ~7 years
  • Narrow gap (22% vs 18%): ~38 years - fiberglass wins
  • Insulation lasts 20+ yrs, so sub-12-yr favors foam
Q

Is spray foam worth the extra cost over fiberglass?

On energy bills alone, often not within a useful horizon - the ~$3,000 premium typically takes ~8 to 12 years and sometimes 30+ to recover, because foam's efficiency edge over fiberglass is real but modest. Foam's true value is not pure ROI: it air-seals cracks and gaps that fiberglass leaves open (air leakage drives roughly a third of energy loss), blocks moisture and vapor, delivers higher R-value per inch, and lasts 20+ years without sagging or settling. Closed-cell foam also adds structural rigidity. Pick foam for comfort, air-tightness, and problem spots like rim joists, cathedral ceilings, and humid climates - not just to chase the lowest bill.

  • Energy payback alone is often ~8-12 years, sometimes 30+
  • Foam air-seals; fiberglass slows heat but leaks air
  • Air leakage drives ~1/3 of heating/cooling loss
  • Foam adds moisture control and higher R-value per inch
  • Lasts 20+ yrs without sagging - a comfort/durability buy
Q

When is fiberglass the better choice?

Fiberglass wins on tight budgets, large open areas, and whenever the energy-savings gap is modest. It costs roughly five times less per square foot, is DIY-friendly, and pays back fast relative to its low price - ideal for standard attics and open stud walls where you just need R-value, not air-sealing. If your energy bill is low or your foam quote is not dramatically more efficient, fiberglass is the cheaper lifetime choice. Many homes use both: fiberglass for big open cavities and spray foam reserved for the air-sealing-critical spots fiberglass cannot handle.

  • ~5x cheaper per sqft and DIY-friendly
  • Best for large open areas - standard attics, open walls
  • Wins when the savings gap is small or the bill is low
  • Fast payback relative to its low install cost
  • Pair both: fiberglass for cavities, foam for sealing

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Last Updated: Jun 17, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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