Spray Foam vs. Fiberglass: Which Insulation Is Right for Your Home?

The two most common residential insulation materials are fiberglass batts and spray polyurethane foam (SPF). Each has a distinct performance profile, and the right choice depends on your home's construction, your priorities, and your budget.

Fiberglass Batts

Fiberglass is the material most homeowners recognize — the pink or yellow rolls and batts that fit between studs and joists. It's economical, widely available, and performs well when installed correctly in new-construction walls where the cavity is clean and accessible.

R-value: Approximately R-3.2 per inch.
Best for: Standard 2×4 or 2×6 stud walls, attic floors, and accessible crawlspace joist bays.
Limitations: It doesn't air-seal. Even perfectly installed fiberglass leaves convective air paths that reduce effective performance.

Spray Foam

Spray polyurethane foam expands on contact and fills gaps, cracks, and irregular cavities that batts can't reach. Open-cell foam is softer and vapor-permeable; closed-cell foam is rigid and doubles as a moisture barrier with a higher R-value per inch.

R-value: Open-cell: ~R-3.7/inch. Closed-cell: ~R-6.5/inch.
Best for: Attic roof decks (cathedralized attics), rim joists, irregular cavities, crawlspaces, and anywhere air-sealing is critical.
Limitations: Higher upfront cost. Requires professional installation. Some formulations need an ignition barrier.

The Hybrid Approach

Many of our best projects use both: a layer of closed-cell foam at the rim joist and key penetrations for air sealing, then blown-in fiberglass or cellulose for the bulk of the attic cavity. You get the air-sealing performance of foam at a fraction of the all-foam cost.

Getting an Honest Recommendation

We don't upsell spray foam if fiberglass will serve your goals. Schedule a free assessment and we'll walk through what each option actually delivers for your specific home — with no pressure.