Is spray foam insulation worth the cost?

Spray foam costs 2-4x more than fiberglass but offers significant advantages: it creates an air barrier (up to 50% of energy loss is from air leaks), has higher R-value per inch (especially closed-cell at R-6 to R-7 per inch), lasts 30-50+ years (vs 15-25 for fiberglass), and doesn't settle or lose performance. Energy savings typically offset the higher cost over 5-15 years. It's especially worth it for drafty older homes, basements, crawl spaces, and extreme climates. What R-value do I need?

What R-value do I need?

It depends on your climate zone and location in the home. Attic: R-38 to R-60 (most climates). Exterior walls: R-13 to R-21. Basement walls: R-10 to R-19. Crawl space: R-19 to R-25. Floor over unheated space: R-25 to R-30. Colder climates need higher R-values. Check the DOE insulation recommendations for your specific ZIP code for exact requirements. Can I install spray foam insulation myself?

Can I install spray foam insulation myself?

Small DIY spray foam kits exist for targeted areas (rim joists, small gaps, around pipes and wires), costing $30-$80 per kit. However, full-room spray foam insulation requires professional installation with specialized spray equipment, safety gear, and training. The chemicals are hazardous before curing and require proper mixing ratios. Professional installation ensures proper thickness, coverage, and safety. Fiberglass batts, on the other hand, are very DIY-friendly. Does spray foam insulation cause moisture problems?

Does spray foam insulation cause moisture problems?

Closed-cell spray foam is waterproof and acts as a vapor barrier, actually preventing moisture problems. Open-cell spray foam can absorb water and should not be used below grade or in areas exposed to bulk water. Both types resist mold growth better than fiberglass. The key is choosing the right type for the application: closed-cell for basements, crawl spaces, and exterior walls where moisture is a concern; open-cell for interior walls and attics where moisture exposure is minimal.

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Comparisons

Spray Foam vs Fiberglass Insulation: Complete Comparison

Lumberama Editorial Team, Insulation & Energy Efficiency Specialists Jun 14, 2026 9 min read

What They Are

Fiberglass insulation: Glass fibers spun into batts (blankets) or loose-fill. Most common insulation in US homes. Available as batts (fit between studs) or blown-in (loose fill). Pink, yellow, or white fluffy material. Installed by DIY or professionals.

Spray foam insulation: Liquid chemicals sprayed that expand into foam. Two types: open-cell and closed-cell. Creates both insulation AND air barrier. Requires professional installation (special equipment). Expands to fill gaps, cracks, and irregular spaces.

R-Value Comparison

Fiberglass: Batts: R-3.1 to R-3.4 per inch. Blown-in: R-2.2 to R-2.7 per inch. 2x4 wall (3.5 inches): R-11 to R-13. 2x6 wall (5.5 inches): R-19 to R-21. Attic (12 inches blown): R-30 to R-38.

Open-cell spray foam: R-3.5 to R-3.7 per inch. 2x4 wall: R-12 to R-13. 2x6 wall: R-19 to R-20. Softer, flexible when cured. Absorbs water (not for exterior below grade).

Closed-cell spray foam: R-6.0 to R-7.0 per inch. 2x4 wall: R-21 to R-25. 2x6 wall: R-33 to R-39. Rigid when cured. Waterproof vapor barrier. Adds structural strength.

Winner: Closed-cell spray foam has significantly higher R-value per inch. Open-cell is comparable to fiberglass in R-value but adds air sealing.

Cost

Fiberglass batts: Materials: $0.30-$0.80/sq ft. Installed: $0.50-$1.50/sq ft. Attic (1,000 sq ft): $500-$1,500. Whole house walls: $1,500-$4,000.

Blown-in fiberglass: Installed: $0.80-$2.00/sq ft. Attic: $800-$2,000.

Open-cell spray foam: Installed: $0.50-$1.50/board foot. Attic (1,000 sq ft, 6 inches): $3,000-$9,000. Whole house: $5,000-$15,000.

Closed-cell spray foam: Installed: $1.00-$2.50/board foot. Attic (1,000 sq ft, 3 inches): $3,000-$7,500. Whole house: $8,000-$25,000.

Price difference: Spray foam costs 2-4x more than fiberglass. Closed-cell is the most expensive option. Energy savings can offset higher cost over 5-15 years.

Performance

Air sealing: Fiberglass: does NOT seal air gaps. Requires separate air barrier (house wrap, caulk). Air leaks significantly reduce effective R-value. Spray foam: creates a complete air barrier. Fills every gap and crack. Up to 50% of home energy loss is from air leaks.

Moisture: Fiberglass: absorbs water, loses R-value when wet. Can harbor mold if wet. Vapor barrier separate (poly sheeting). Open-cell foam: absorbs water (not waterproof). Still resists mold better than fiberglass. Closed-cell foam: waterproof, acts as vapor barrier. Best for basements, crawl spaces, exterior walls.

Sound: Fiberglass: good sound absorption. Open-cell foam: excellent sound absorption (better than fiberglass). Closed-cell foam: moderate sound absorption (rigid structure).

Longevity: Fiberglass: 15-25 years (settles and compresses over time). Spray foam: 30-50+ years (maintains R-value). Spray foam doesn't settle or compress.

Best Uses

Choose fiberglass if: Budget is the priority. Standard new construction (walls and attic). Accessible attic that can be DIY. Rental property or basic insulation need.

Choose open-cell spray foam if: Air sealing is important (drafty house). Soundproofing is needed. Interior walls, attics, between floors. Moderate budget increase is acceptable.

Choose closed-cell spray foam if: Basement or crawl space insulation. Exterior walls in extreme climates. Maximum R-value per inch needed (limited wall depth). Moisture barrier needed (below grade, coastal). Budget allows premium solution.

Combination approach: Spray foam in critical areas (rim joists, attic floor edges, around penetrations). Fiberglass in large open areas (attic floor, interior walls). Best value: targets air leaks with foam, fills large areas with fiberglass.