Spray Foam vs Fiberglass Insulation: Cost & Comparison
Updated
Fiberglass insulation costs about $1 to $2.40 per square foot installed, while spray foam runs $3 to $7. Fiberglass is cheaper and DIY-friendly; spray foam costs more but air-seals and delivers a higher R-value per inch, often cutting energy bills the most.
Fiberglass and spray foam are the two most common ways to insulate a home, and they sit at opposite ends of the price and performance scale. Choosing between them comes down to budget, the space you're insulating, and how much you value air-sealing.
This guide compares spray foam vs fiberglass on cost, R-value, air sealing, and best uses, so you can spend your insulation budget where it pays back fastest.
Key takeaways
- Fiberglass: $1–$2.40/ft²; spray foam: $3–$7/ft² installed.
- Spray foam air-seals and has a higher R-value per inch.
- Fiberglass is far cheaper and DIY-friendly.
- Closed-cell foam is best for rim joists, basements, and tight spaces.
- Many homes use a hybrid — foam to seal, fiberglass to fill.
Skip the math
Get instant numbers with the Insulation Calculator.
Side-by-side comparison
| Factor | Fiberglass | Spray foam |
|---|---|---|
| Cost installed | $1 – $2.40/ft² | $3 – $7/ft² |
| R-value per inch | R-3.1 | R-3.7 (open) to R-6.5 (closed) |
| Air sealing | No | Yes |
| DIY-friendly | Yes | No (pro install) |
| Best use | Walls, attics, budget | Sealing, rim joists, tight spots |
When fiberglass makes sense
Fiberglass batts and blown-in are the budget choice and cover large areas like attics and open walls cheaply. With careful installation (no gaps or compression) they perform well — and you can DIY them.
When spray foam is worth it
Spray foam expands to seal every gap, stopping air leaks that fiberglass can't. Closed-cell foam adds the highest R-value per inch and a moisture barrier, making it ideal for rim joists, basements, cathedral ceilings, and tight or irregular cavities.
The hybrid approach
Many homeowners get the best of both: a thin layer of closed-cell spray foam to air-seal, topped with fiberglass to reach the target R-value affordably. It balances performance and cost.
Estimating insulation cost
Multiply the area by the installed price for your chosen type. Our insulation calculator lets you pick the type and returns the square footage and a cost range.