Fiberglass vs Spray Foam Insulation: The Ultimate Comparison
Choosing between fiberglass and spray foam insulation can be confusing. Both materials have their place in modern construction, but they serve different needs. This comprehensive comparison will help you make an informed decision for your home.
Basic Characteristics
Fiberglass Insulation
Fiberglass is the traditional insulation material made from fine glass fibers. It comes in batts, rolls, and loose-fill forms.
Key Properties:
- R-value: R-3.1 to R-4.3 per inch
- Cost: $0.50-$1.00 per square foot
- Installation: DIY-friendly for batts
- Lifespan: 50+ years with proper installation
Spray Foam Insulation
Spray foam is a modern, expanding foam that creates an air-tight seal. Available as open-cell and closed-cell varieties.
Key Properties:
- R-value: R-3.6 (open-cell) to R-6.5 (closed-cell) per inch
- Cost: $1.50-$4.50 per square foot
- Installation: Requires professional application
- Lifespan: 50+ years
Performance Comparison
Thermal Performance
Fiberglass:
- Good thermal resistance
- Can settle over time, reducing effectiveness
- Requires proper installation to maintain R-value
Spray Foam:
- Superior air sealing properties
- Maintains R-value throughout lifespan
- Better overall thermal performance due to air sealing
Air Sealing
Fiberglass:
- Poor air sealing capabilities
- Requires separate air sealing measures
- Gaps and voids reduce effectiveness
Spray Foam:
- Excellent air sealing
- Expands to fill all gaps and voids
- Creates continuous insulation layer
Moisture Control
Fiberglass:
- Absorbs moisture, reducing R-value
- Can promote mold growth if wet
- Requires vapor barriers
Spray Foam:
- Closed-cell acts as vapor barrier
- Resists moisture intrusion
- Some open-cell varieties allow moisture escape
Installation Differences
Fiberglass Installation
Pros:
- Relatively easy DIY installation
- Less expensive installation costs
- Can be installed in stages
- Less disruptive to living spaces
Cons:
- Requires proper fitting around obstacles
- Can be itchy and require protective gear
- Multiple pieces may not fit perfectly
- Requires air sealing separately
Spray Foam Installation
Pros:
- Fills irregular spaces perfectly
- Creates seamless air barrier
- Minimal callbacks for adjustments
- Better long-term performance
Cons:
- Requires professional installation
- More expensive upfront
- Can be disruptive during application
- Off-gassing during curing period
Cost Analysis
Material Costs
- Fiberglass: $0.50-$1.00/sq ft
- Spray Foam: $1.50-$4.50/sq ft
Installation Costs
- Fiberglass: $1.00-$2.00/sq ft (can be DIY)
- Spray Foam: $2.00-$6.00/sq ft (professional only)
Long-Term Costs
Fiberglass:
- Lower initial investment
- May require maintenance/replacement
- Higher lifetime energy costs
Spray Foam:
- Higher initial investment
- Lower maintenance costs
- Significant energy savings over time
Best Applications
When to Choose Fiberglass
- Budget-conscious projects
- DIY installations
- Attic spaces with regular access
- Retrofit projects with limited access
- Areas where future access is needed
When to Choose Spray Foam
- Maximum energy efficiency desired
- Air quality and comfort are priorities
- Irregular spaces and hard-to-reach areas
- Moisture-prone environments
- Soundproofing requirements
- New construction projects
Environmental Considerations
Fiberglass
- Made from recycled glass
- Energy-intensive manufacturing
- Recyclable at end of life
- No chemical off-gassing
Spray Foam
- Contains chemical blowing agents
- Some formulations use recycled content
- Not biodegradable
- Initial off-gassing (ventilation required)
Health and Safety
Fiberglass
- Skin irritation during installation
- Respiratory irritation from dust
- No long-term health concerns when properly installed
Spray Foam
- Chemical exposure during application
- Proper ventilation required during curing
- Some people sensitive to fumes
- Professional installation minimizes risks
Soundproofing Capabilities
Fiberglass:
- Good sound absorption
- Reduces airborne noise
- Less effective for impact noise
Spray Foam:
- Excellent sound dampening
- Reduces both airborne and impact noise
- Better for sound-sensitive applications
Maintenance and Longevity
Fiberglass
- Can settle over time
- May require occasional adjustment
- Susceptible to pest damage
- Lifespan: 30-50 years
Spray Foam
- Maintains shape and effectiveness
- Resistant to settling and pests
- May require occasional inspection
- Lifespan: 50+ years
Making the Right Choice
Consider Your Priorities
- Budget: Fiberglass for lower upfront costs
- Energy Savings: Spray foam for maximum efficiency
- Air Quality: Spray foam for better sealing
- Installation: Fiberglass if doing DIY
- Longevity: Both offer similar lifespans
Assess Your Home
- Climate: Colder climates benefit more from spray foam
- Age of Home: Older homes may need spray foam for air sealing
- Usage: Soundproofing needs favor spray foam
- Accessibility: Limited access favors spray foam
Calculate ROI
- Fiberglass: 5-10 year payback period
- Spray Foam: 3-7 year payback period
- Both: Increase home value by 5-15%
Common Questions
Can I install fiberglass myself?
Yes, fiberglass batts are DIY-friendly. However, proper installation is crucial for effectiveness.
Does spray foam off-gas?
Some formulations have initial off-gassing. Choose low-VOC options and ensure proper ventilation.
Which is better for attics?
Both work well, but spray foam provides better air sealing for maximum energy savings.
Can I combine both materials?
Yes, many homes use fiberglass in accessible areas and spray foam in hard-to-reach spaces.
Conclusion
The choice between fiberglass and spray foam depends on your specific needs, budget, and priorities. Fiberglass offers affordability and DIY installation, while spray foam provides superior performance and air sealing.
For most homeowners prioritizing energy efficiency and long-term savings, spray foam is the better choice despite higher upfront costs. However, fiberglass remains a solid option for budget-conscious projects.
Consult with a certified insulation professional to determine the best solution for your home. They can provide personalized recommendations based on your specific situation and goals.