Insulation Materials: Fiberglass vs. Cellulose vs. Spray Foam vs. Mineral Wool

Selecting the right insulation material is one of the most important decisions in any home renovation project for energy efficiency and comfort. Four popular options that often cause confusion are fiberglass, cellulose, spray foam, and mineral wool. While they all serve the fundamental purpose of reducing heat transfer, they have distinct differences in thermal performance, installation complexity, cost, and environmental impact. This comprehensive comparison will help you understand the key differences between these materials so you can make an informed decision for your home.

Introduction

Insulation is critical for maintaining comfortable indoor temperatures, reducing energy costs, and improving overall home performance. The right insulation material should provide excellent thermal performance while fitting your budget, installation preferences, and environmental values. Understanding the characteristics of fiberglass, cellulose, spray foam, and mineral wool will help you choose the best option for your specific needs, climate, and renovation scope.

What is Fiberglass Insulation?

Fiberglass insulation is made from fine glass fibers and is one of the most widely used insulation materials in residential construction:

Composition and Manufacturing

• Base material: Fine glass fibers bound together with binder
• Manufacturing process: Molten glass spun into fibers and formed into batts or loose-fill
• Forms: Batts, rolls, or loose-fill for different applications
• Density: Lightweight with low thermal mass
• R-value: 2.2-4.3 per inch depending on density

Key Characteristics

• Cost-effective: Most affordable insulation option
• Easy installation: Simple DIY installation for batts
• Variety: Available in numerous forms and densities
• Non-combustible: Does not burn or contribute to fire spread
• Moisture resistance: Resistant to moisture but can absorb water

Fiberglass is ideal for homeowners who want an affordable, easy-to-install insulation option.

What is Cellulose Insulation?

Cellulose insulation is made from recycled paper products treated with fire retardants, offering excellent thermal performance and environmental benefits:

Composition and Manufacturing

• Base material: Recycled newspaper and cardboard treated with borate fire retardants
• Manufacturing process: Paper shredded and chemically treated for fire and pest resistance
• Forms: Loose-fill for blowing into cavities
• Density: Denser than fiberglass, providing better air sealing
• R-value: 3.2-3.8 per inch

Key Characteristics

• Environmental friendly: Made from recycled materials
• Excellent air sealing: Dense packing fills gaps and voids
• Fire resistance: Treated with borate fire retardants
• Pest resistance: Chemical treatment deters insects and rodents
• Sound dampening: Excellent acoustic performance

Cellulose is ideal for homeowners who prioritize environmental sustainability and excellent air sealing.

What is Spray Foam Insulation?

Spray foam insulation is a chemical product that expands to fill cavities, providing superior air sealing and thermal performance:

Composition and Manufacturing

• Base material: Polyurethane chemicals that react and expand when mixed
• Manufacturing process: Two-component system mixed at point of application
• Forms: Open-cell or closed-cell formulations
• Density: Varies by formulation (0.5-2.0 pounds per cubic foot)
• R-value: 3.5-7.0 per inch depending on formulation

Key Characteristics

• Superior air sealing: Expands to fill all gaps and voids
• Excellent thermal performance: Among highest R-values available
• Moisture resistance: Closed-cell foam is water-resistant
• Structural benefits: Adds rigidity to wall assemblies
• Permanent installation: Cannot be removed or relocated

Spray foam is ideal for homeowners who want maximum thermal performance and air sealing.

What is Mineral Wool Insulation?

Mineral wool insulation is made from volcanic rock or steel slag, offering excellent fire resistance and thermal performance:

Composition and Manufacturing

• Base material: Volcanic rock (basalt) or steel slag melted and spun into fibers
• Manufacturing process: Molten material spun into fibers and formed into batts or loose-fill
• Forms: Batts, rolls, or loose-fill for different applications
• Density: Heavier than fiberglass, providing better thermal mass
• R-value: 3.0-4.2 per inch

Key Characteristics

• Fire resistance: Non-combustible and melts at extremely high temperatures
• Moisture management: Resistant to water but allows vapor permeability
• Sound dampening: Excellent acoustic performance
• Durability: Long-lasting and resistant to settling
• Environmental friendly: Made from natural materials and industrial byproducts

Mineral wool is ideal for homeowners who prioritize fire resistance and sound dampening.

Cost Comparison

Fiberglass Insulation

• Material cost: $0.30-$1.50 per square foot for quality options
• Installation cost: $0.50-$2.00 per square foot for DIY, $1.00-$3.00 for professional
• Total installed cost: $0.80-$4.50 per square foot
• Premium options: High-density batts can exceed $2.00 per square foot

Cellulose Insulation

• Material cost: $0.50-$2.00 per square foot for quality options
• Installation cost: $1.00-$3.00 per square foot for professional installation
• Total installed cost: $1.50-$5.00 per square foot
• Premium options: Dense-packed applications can exceed $6.00 per square foot

Spray Foam Insulation

• Material cost: $1.50-$5.00 per square foot depending on formulation
• Installation cost: $2.00-$6.00 per square foot for professional installation
• Total installed cost: $3.50-$11.00 per square foot
• Premium options: Closed-cell foam can exceed $15.00 per square foot

Mineral Wool Insulation

• Material cost: $0.75-$2.50 per square foot for quality options
• Installation cost: $1.00-$3.00 per square foot for professional installation
• Total installed cost: $1.75-$5.50 per square foot
• Premium options: High-density options can exceed $7.00 per square foot

Fiberglass offers the best value, while spray foam commands a premium price.

Thermal Performance and R-Value

Fiberglass Insulation

• R-value per inch: 2.2-4.3 depending on density
• Typical applications: R-11 to R-38 in residential walls and attics
• Air sealing: Poor; requires careful installation to minimize gaps
• Thermal bridging: Susceptible to thermal bridging through framing
• Performance factors: Compression reduces effectiveness

Cellulose Insulation

• R-value per inch: 3.2-3.8
• Typical applications: R-13 to R-60 in residential walls and attics
• Air sealing: Excellent; dense packing eliminates most air gaps
• Thermal bridging: Reduced due to dense packing and air sealing
• Performance factors: Settling can reduce effectiveness over time

Spray Foam Insulation

• R-value per inch: 3.5-7.0 depending on formulation
• Typical applications: R-13 to R-60+ in residential walls and attics
• Air sealing: Superior; creates monolithic air barrier
• Thermal bridging: Eliminated due to continuous coverage
• Performance factors: Thickness and formulation affect performance

Mineral Wool Insulation

• R-value per inch: 3.0-4.2
• Typical applications: R-11 to R-38 in residential walls and attics
• Air sealing: Good; requires proper installation for best results
• Thermal bridging: Reduced due to higher density and thermal mass
• Performance factors: Compression and moisture affect performance

Spray foam offers the highest R-value, while cellulose provides excellent performance with good air sealing.

Installation Complexity

Fiberglass Insulation

• Skill level: Beginner-friendly DIY project
• Tools required: Basic measuring, cutting, and stapling tools
• Installation time: 1-3 days for average home retrofit
• Professional recommended: Not necessary for simple applications
• Special considerations: Wear protective gear during installation

Cellulose Insulation

• Skill level: Intermediate DIY project
• Tools required: Specialized blowing equipment and protective gear
• Installation time: 1-2 days for average home retrofit
• Professional recommended: Recommended for best results
• Special considerations: Requires specialized equipment and proper density

Spray Foam Insulation

• Skill level: Professional installation strongly recommended
• Tools required: Specialized spraying equipment and protective gear
• Installation time: 1-3 days for average home retrofit
• Professional recommended: Essential for proper application
• Special considerations: Requires trained technicians and proper ventilation

Mineral Wool Insulation

• Skill level: Intermediate DIY project
• Tools required: Basic measuring, cutting, and stapling tools
• Installation time: 1-3 days for average home retrofit
• Professional recommended: Not necessary for simple applications
• Special considerations: Wear protective gear during installation

Fiberglass and mineral wool are easiest for DIY installation, while spray foam requires professional expertise.

Environmental Impact

Fiberglass Insulation

• Raw materials: Sand and recycled glass with chemical binders
• Manufacturing impact: Energy-intensive melting and spinning process
• End of life: Difficult to recycle due to mixed materials
• Sustainability: Some manufacturers use recycled content
• Indoor air quality: Can release fibers during installation

Cellulose Insulation

• Raw materials: Recycled newspaper and cardboard with borate treatments
• Manufacturing impact: Low energy processing with chemical treatments
• End of life: Biodegradable and compostable
• Sustainability: High percentage of recycled content
• Indoor air quality: Low VOC emissions when properly installed

Spray Foam Insulation

• Raw materials: Petroleum-based chemicals with blowing agents
• Manufacturing impact: Energy-intensive chemical synthesis
• End of life: Difficult to remove and dispose of safely
• Sustainability: Low recyclability and high embodied energy
• Indoor air quality: Can emit VOCs during and after installation

Mineral Wool Insulation

• Raw materials: Volcanic rock or steel slag with minimal chemical additives
• Manufacturing impact: Energy-intensive melting and spinning process
• End of life: Biodegradable and reusable in some applications
• Sustainability: Made from natural materials and industrial byproducts
• Indoor air quality: Low VOC emissions and natural materials

Cellulose and mineral wool are generally more environmentally friendly than fiberglass and spray foam.

Durability and Lifespan

Fiberglass Insulation

• Lifespan: 20-30 years with proper installation and maintenance
• Settling: Can settle over time, reducing effectiveness
• Compression: Loses effectiveness when compressed
• Moisture damage: Absorbs water, losing insulating properties
• Pest resistance: Susceptible to rodent damage

Cellulose Insulation

• Lifespan: 20-30 years with proper installation and maintenance
• Settling: Can settle over time, reducing effectiveness
• Compression: Loses effectiveness when compressed
• Moisture damage: Absorbs water, losing insulating properties
• Pest resistance: Borate treatment deters pests

Spray Foam Insulation

• Lifespan: 30-50 years with proper installation and maintenance
• Settling: None; permanently expands and sets
• Compression: Maintains effectiveness under compression
• Moisture damage: Closed-cell foam resists moisture
• Pest resistance: Not appealing to pests

Mineral Wool Insulation

• Lifespan: 30-50 years with proper installation and maintenance
• Settling: Minimal settling due to density
• Compression: Maintains effectiveness under compression
• Moisture damage: Resistant to water but allows vapor permeability
• Pest resistance: Not appealing to pests

Spray foam and mineral wool offer the best long-term durability, while fiberglass and cellulose may require attention over time.

Fire Resistance

Fiberglass Insulation

• Fire rating: Non-combustible; does not contribute to fire spread
• Melting point: Melts at approximately 1,100°F (593°C)
• Smoke production: Low smoke when exposed to extreme heat
• Flame spread: Class A fire rating
• Special considerations: Requires fire-rated barriers in some applications

Cellulose Insulation

• Fire rating: Treated with borate fire retardants
• Ignition temperature: Ignites at approximately 450°F (232°C)
• Smoke production: Low smoke when properly treated
• Flame spread: Class A fire rating when properly treated
• Special considerations: Treatment effectiveness decreases over time

Spray Foam Insulation

• Fire rating: Self-extinguishing when flame source is removed
• Ignition temperature: Ignites at approximately 700°F (371°C)
• Smoke production: Can produce toxic smoke when burned
• Flame spread: Class B fire rating for open-cell, Class A for closed-cell
• Special considerations: Requires fire-rated barriers in some applications

Mineral Wool Insulation

• Fire rating: Non-combustible; does not contribute to fire spread
• Melting point: Melts at approximately 2,150°F (1,177°C)
• Smoke production: Low smoke when exposed to extreme heat
• Flame spread: Class A fire rating
• Special considerations: Excellent fire resistance in extreme conditions

Mineral wool offers the best fire resistance, while all materials except cellulose are non-combustible.

Sound Dampening

Fiberglass Insulation

• Sound absorption: Good for mid to high frequencies
• STC rating: 30-40 for typical wall assemblies
• IIC rating: 40-50 for floor-ceiling assemblies
• Applications: Effective in standard residential construction
• Limitations: Less effective for low-frequency sounds

Cellulose Insulation

• Sound absorption: Excellent for all frequencies
• STC rating: 40-50 for typical wall assemblies
• IIC rating: 50-60 for floor-ceiling assemblies
• Applications: Superior performance in residential construction
• Limitations: Density affects performance consistency

Spray Foam Insulation

• Sound absorption: Excellent for air-borne sounds
• STC rating: 45-60 for typical wall assemblies
• IIC rating: 55-70 for floor-ceiling assemblies
• Applications: Superior performance in all construction types
• Limitations: Less effective for impact sounds without additional treatments

Mineral Wool Insulation

• Sound absorption: Excellent for all frequencies
• STC rating: 45-55 for typical wall assemblies
• IIC rating: 50-65 for floor-ceiling assemblies
• Applications: Superior performance in all construction types
• Limitations: Density affects performance consistency

Spray foam and mineral wool offer the best sound dampening performance, while cellulose provides excellent results.

Moisture Management

Fiberglass Insulation

• Water resistance: Poor; absorbs water readily
• Vapor permeability: High; allows moisture vapor transmission
• Drying capability: Good; dries out when moisture source is eliminated
• Mold resistance: Poor; can support mold growth when wet
• Special considerations: Requires vapor barriers in some applications

Cellulose Insulation

• Water resistance: Poor; absorbs water readily
• Vapor permeability: Moderate; allows some moisture vapor transmission
• Drying capability: Good; dries out when moisture source is eliminated
• Mold resistance: Good; borate treatment inhibits mold growth
• Special considerations: Requires vapor barriers in some applications

Spray Foam Insulation

• Water resistance: Excellent for closed-cell; good for open-cell
• Vapor permeability: Low for closed-cell; moderate for open-cell
• Drying capability: Poor; difficult to dry when wet
• Mold resistance: Good; closed-cell foam resists mold growth
• Special considerations: Closed-cell foam acts as vapor barrier

Mineral Wool Insulation

• Water resistance: Good; sheds water but absorbs some moisture
• Vapor permeability: High; allows moisture vapor transmission
• Drying capability: Excellent; dries quickly when moisture source is eliminated
• Mold resistance: Excellent; naturally resists mold growth
• Special considerations: Allows walls to breathe naturally

Mineral wool offers the best moisture management, while spray foam provides excellent water resistance.

Making the Right Choice

Choose Fiberglass If:

• Budget is a primary concern
• Planning a DIY installation
• Wanting maximum versatility in applications
• Needing a simple, straightforward solution
• Installing in dry areas with minimal moisture exposure

Choose Cellulose If:

• Environmental sustainability is important
• Wanting excellent air sealing and sound dampening
• Have access to experienced installers
• Installing in existing walls or hard-to-reach areas
• Looking for good thermal performance at moderate cost

Choose Spray Foam If:

• Maximum thermal performance is important
• Wanting superior air sealing and moisture resistance
• Willing to invest in premium materials
• Installing in new construction or major renovations
• Needing structural benefits in addition to insulation

Choose Mineral Wool If:

• Fire resistance is a primary concern
• Wanting excellent sound dampening and moisture management
• Prioritizing environmental sustainability
• Installing in areas with potential moisture exposure
• Looking for durable, long-lasting insulation

Conclusion

All four insulation materials - fiberglass, cellulose, spray foam, and mineral wool - have their place in home renovation projects. Fiberglass offers affordable, easy-to-install insulation for budget-conscious homeowners. Cellulose provides excellent environmental benefits and air sealing for those who prioritize sustainability. Spray foam delivers unmatched thermal performance and air sealing for homeowners willing to invest in premium materials. Mineral wool offers superior fire resistance and moisture management for those who prioritize safety and durability.

Consider your budget, installation preferences, environmental values, and specific needs when making your decision. Each material can provide years of energy savings and comfort when properly installed, but spray foam and mineral wool generally offer the best long-term performance for those willing to invest in premium insulation solutions.