Foam Board vs Fiberglass Insulation: A Practical Comparison

When choosing insulation materials for your home or commercial project, two of the most common options are foam board insulation and fiberglass insulation. Both offer advantages, but understanding their differences is key to making the right decision for energy efficiency, budget, and installation complexity.

What Is Fiberglass Insulation?

Fiberglass insulation is made of tiny glass fibers and is available in rolls (batts) or rigid fiberglass insulation boards. It is often used in walls, attics, and ceilings. One popular option is the rigid fiberglass insulation board, known for its high R-value and sound absorption capabilities.

Products like Owens Corning fiberglass insulation board and Johns Manville fiberglass insulation data sheet highlight excellent thermal and fire-resistant properties. For HVAC systems or ductwork, fiberglass duct board insulation and semi-rigid fiberglass insulation board are commonly used.

What Is Foam Board Insulation?

Foam board insulation—made of polystyrene, polyisocyanurate, or polyurethane—comes in lightweight, stiff sheets. It’s often installed in basements, crawlspaces, attics, or beneath siding. The rigid foam board vs fiberglass insulation debate usually centers on moisture resistance and compressive strength.

Many builders use foil-faced foam board insulation for radiant barriers or combine foam board over fiberglass insulation to boost thermal performance in basements or attics.

Key Differences: Foam Board vs Fiberglass

Can You Combine Them?

Yes, in many retrofit or high-performance applications, professionals use foam board and fiberglass insulation together. For instance, placing foam board over fiberglass insulation in the attic can add thermal performance and moisture protection.

The reverse—fiberglass insulation over foam board—is sometimes seen in basement insulation projects. Just ensure proper vapor barrier placement to avoid trapped moisture.

Choosing Based on Application

• Attic or Roof : Use foam board insulation vs fiberglass if moisture is a concern.

• Interior Walls or Soundproofing: Fiberglass board insulation or rigid fiberglass insulation panels offer superior acoustics.

• Basement : Foam board vs fiberglass insulation basement comparisons often favor foam for its moisture resistance.

• Garage : Evaluate foam board vs fiberglass insulation garage use cases based on exposure and cost.

Conclusion

While both materials have their strengths, combining foam board and fiberglass insulation strategically can provide the best of both worlds—high R-value, moisture control, and cost-efficiency. Whether you're upgrading an attic or insulating ductwork with fiberglass board insulation for ductwork, the key is choosing the right material—or combination—for the job.

If you need guidance choosing between fiberglass or foam board insulation, always consult technical data like the Knauf fiberglass insulation data sheet or Owens Corning fiberglass pipe insulation data sheet for optimal performance.