Is spray foam insulation worth the cost?

Yes, for most applications. Spray foam costs 2-3x more than fiberglass but provides: higher R-value per inch, complete air sealing (eliminates 25-40% of energy loss from air leaks), moisture protection (closed cell), and longevity (does not settle, compress, or degrade). Typical energy savings: 30-50% on heating and cooling. Payback period: 3-7 years. For crawl spaces and rim joists: spray foam is the clear winner.

Open cell vs closed cell spray foam?

Open cell: R-3.5-3.7/inch, softer, better sound blocking, absorbs moisture, costs $1-$3/sq ft. Best for: interior walls and attic rooflines. Closed cell: R-6-7/inch, rigid, moisture barrier, structural strength, costs $2-$7/sq ft. Best for: crawl spaces, basements, rim joists, and limited-space walls. Choose based on location and whether moisture resistance is needed.

Can I spray foam insulation myself?

For small areas (rim joists, small cavities, spot air sealing): yes, using DIY spray foam kits ($300-$800 for 200-600 sq ft). For large areas (attic, walls, crawl space): professional installation is strongly recommended. Professional equipment provides consistent mixing, temperature control, and application that DIY kits cannot match. Improper mixing causes poor adhesion and off-gassing.

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Comparisons

Spray Foam Insulation Guide: Open Cell vs Closed Cell

Q: How much does spray foam insulation cost?

Open cell (professional): $1-$3 per square foot of coverage. Closed cell (professional): $2-$7/sq ft. Typical attic (1,500 sq ft, open cell): $1,500-$4,500. Typical crawl space (800 sq ft, closed cell): $2,400-$5,600. DIY kits: $300-$800 for small areas (200-600 sq ft). Professional installation is recommended for whole-house applications.

Lumberama Editorial Team, Insulation & Energy Efficiency Specialists Jun 11, 2026 13 min read

What Is Spray Foam Insulation

Spray foam insulation is a two-component liquid that is sprayed onto surfaces where it expands and hardens into a solid foam. It fills every gap, crack, and cavity — creating both insulation and an air barrier in one application. Spray foam has the highest R-value per inch of any common insulation material and eliminates air leaks that account for 25-40% of a home’s energy loss. It is the premium insulation choice for new construction and renovations.

Open Cell Spray Foam

Open cell foam has a soft, spongy texture. The cells are not completely closed, giving the foam a lower density.

R-value: R-3.5 to R-3.7 per inch.

Density: 0.5 lb/cubic foot.

Air barrier: Yes (at 3+ inches).

Moisture barrier: No (absorbs water — not suitable for below-grade or high-moisture areas).

Sound blocking: Excellent (the soft texture absorbs sound).

Cost: $0.50-$1.00 per square foot per inch of thickness ($1.50-$3.00/sq ft for a typical 3.5-inch wall application).

Best for: Interior walls (sound deadening), attic rooflines (cathedral ceilings), and above-grade wall cavities.

Not suitable for: Crawl spaces, basements, or any area with water contact.

Closed Cell Spray Foam

Closed cell foam has a rigid, dense texture. The cells are completely sealed, trapping gas that provides superior insulation.

R-value: R-6.0 to R-7.0 per inch (the highest of any common insulation).

Density: 2.0 lb/cubic foot.

Air barrier: Yes.

Moisture barrier: Yes (acts as a vapor barrier at 1.5+ inches — Class II vapor retarder).

Structural strength: Adds racking strength to walls (measurable structural benefit).

Cost: $1.00-$2.00 per square foot per inch ($3.00-$7.00/sq ft for a typical 3-inch application).

Best for: Crawl spaces, basement walls, rim joists, exterior walls (maximum R-value in limited space), metal buildings, and any area where moisture resistance is needed.

The premium option.

Head-to-Head Comparison

R-value: Closed cell wins (R-6-7/inch vs. R-3.5-3.7/inch).

Cost: Open cell wins (roughly half the cost).

Moisture resistance: Closed cell wins (vapor barrier).

Sound blocking: Open cell wins (softer, absorbs sound).

Air sealing: Tie (both are excellent air barriers).

Structural contribution: Closed cell wins (adds racking strength).

Expansion: Open cell expands 100x (fills large cavities easily). Closed cell expands 30-40x (better for controlled application).

When to Use Each

Open cell: interior walls between rooms (sound), attic rooflines where moisture is not a concern, and budget-friendly whole-house insulation. Closed cell: crawl spaces, basements, rim joists (the #1 air leak spot), exterior walls where space is limited (maximum R-value in a 2x4 wall), metal buildings, and coastal/flood-prone areas.

DIY vs Professional

Spray foam is almost always professionally installed. The equipment (spray rig, heated hoses, proportioners) costs $30,000-$50,
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DIY spray foam kits exist ($300-$800 for small kits covering 200-600 sq ft) and are suitable for: rim joists, small areas, and spot air sealing. For whole-house applications: hire a professional ($1-$3/sq ft for open cell, $2-$7/sq ft for closed cell, including labor).