When it's time to insulate or upgrade your home, the choice often comes down to spray foam or fiberglass. Both are excellent products, but they serve different needs. Here's an honest comparison to help you decide.
Performance Comparison
- R-Value per inch: Closed-cell spray foam: R-6.5 | Open-cell spray foam: R-3.7 | Fiberglass batts: R-3.2 | Blown-in fiberglass: R-2.5
- Air sealing: Spray foam seals air leaks as it insulates — fiberglass does not. Air can pass through and around fiberglass batts.
- Moisture: Closed-cell spray foam acts as a vapor barrier. Fiberglass absorbs moisture and loses R-value when wet.
- Longevity: Spray foam lasts 50+ years without settling. Fiberglass can settle 10-20% over time.
- Sound: Open-cell spray foam and mineral wool batts are the best for sound dampening.
Cost Comparison
- Fiberglass batts: $0.50-$1.50/sq ft installed — lowest upfront cost
- Blown-in fiberglass: $1.00-$2.50/sq ft installed
- Open-cell spray foam: $1.50-$3.50/sq ft installed
- Closed-cell spray foam: $3.00-$7.00/sq ft installed — highest upfront cost, best long-term value
When to Choose Each
Choose Fiberglass When:
- Budget is the primary concern
- Insulating standard wall cavities in new construction
- Adding insulation over existing in an attic
- The area is easily accessible for proper installation
Choose Spray Foam When:
- Air sealing is critical (crawl spaces, rim joists, attic roof deck)
- Moisture control is a concern
- You want maximum R-value in limited space
- The area has irregular shapes or hard-to-reach cavities
- You want the longest-lasting solution
The Bottom Line
There's no universally "best" insulation — the right choice depends on your application, budget, and performance goals. Many homes benefit from a combination: spray foam in critical areas (crawl space, rim joists) and blown-in or batts in the attic and walls. At Homeward Insulation, we recommend the most effective solution for your specific situation — not the most expensive one.