Which insulation is best foran attic? | FUNAS Guide

Which Insulation Is Best for an Attic?

Professionals in the thermal insulation materials industry often need reliable guidance on choosing the best insulation for attics. This article addresses which insulation is best for an attic, discussing types, performance data, and application guidance, to help you meet energy efficiency, regulatory, and project needs.

Key Factors in Choosing Attic Insulation

• Thermal Resistance (R-Value):

  • Higher R-value indicates greater insulating effectiveness.
  • According to the U.S. Department of Energy, attics should achieve R-38 to R-60 (DOE, 2023).

• Material Durability:

  • Resistance to moisture, pests, and settling impacts long-term performance.
  • Fire resistance and safety certifications are crucial in many jurisdictions.

• Installation Method:

  • Consider ease of installation—batts, loose-fill, spray—impacting labor and cost.
  • Accessibility of the attic and existing insulation are factors.

• Environmental Considerations:

  • Evaluate sustainability, recycled content, and indoor air quality impact (EPA, 2022).

Types of Attic Insulation and Performance

Fiberglass Batts & Rolls

• R-Value: Typically R-2.9 to R-3.8 per inch.
• Pros: Cost-effective, widely available, easy to install.
• Cons: Can lose performance if compressed; air gaps reduce efficiency.
• Applications: New construction or open attic spaces.
• Sources: NAIMA (North American Insulation Manufacturers Association)

Blown-In (Loose-Fill) Insulation

• Materials: Fiberglass, cellulose, or mineral wool.
• R-Value:
  • Cellulose: ~R-3.2 to R-3.8 per inch
  • Fiberglass: ~R-2.2 to R-2.7 per inch
• Pros: Fills gaps and uneven spaces well; effective for retrofits.
• Cons: May settle over time, requiring periodic checks.
• Applications: Existing attics, especially those with obstructions.
• Sources: Oak Ridge National Laboratory

Spray Foam Insulation

• Types: Open-cell (R-3.5–R-3.6/in), closed-cell (R-6–R-7/in)
• Pros: Superior air sealing, high R-value per inch, acts as vapor barrier.
• Cons: Highest material and installation cost; professional application required.
• Applications: Difficult-to-reach or irregular attics; moisture-prone areas.
• Sources: Building Science Corporation, DOE

Rigid Foam Board

• Materials: Polyisocyanurate, XPS, EPS.
• R-Value: R-4 to R-6.5 per inch.
• Pros: High insulating value, moisture resistance.
• Cons: Best for targeted applications; may require additional fire protection.
• Applications: Attic doors, knee walls, custom retrofits.
• Sources: Insulation Institute

Comparative Summary Table

*Costs are averages in USD as of 2024 (HomeAdvisor, NAIMA).

Industry Best Practices

• Combine Approaches:
  • Layering blown-in insulation over batts increases efficiency.
• Focus on Air Sealing:
  • Air leaks can drastically reduce insulation performance.
• Verify Compliance:
  • Always check local codes and fire safety guidelines.

Sources and References

• U.S. Department of Energy: (https://www.energy.gov/energysaver/weatherize/insulation)
• EPA: (https://www.epa.gov/greenbuilding/green-building-materials)
• NAIMA: (https://insulationinstitute.org)
• Building Science Corporation: (https://buildingscience.com)

For further expert guidance or to request specialized material data sheets, contact the technical team at FUNAS.

End of article.