Foam Board vs Fiberglass Insulation: Which is Right for Your Project?

When choosing the right insulation material, homeowners and contractors often compare foam board vs fiberglass insulation. Both materials serve the same purpose—thermal resistance—but differ significantly in cost, installation, and performance. Understanding their strengths and weaknesses can help you make the best decision for your application.

Understanding the Basics

Fiberglass insulation boards are made from extremely fine strands of glass woven into a wool-like structure. These panels are available in various densities and sizes, including the popular rigid fiberglass insulation board, often used in HVAC systems and industrial settings. Fiberglass offers excellent fire resistance and soundproofing, making it suitable for both residential and commercial uses.

Foam board insulation, on the other hand, is a rigid panel made from polystyrene, polyisocyanurate, or polyurethane. It's widely used for insulating foundations, walls, and roofing systems due to its high compressive strength and moisture resistance.

Thermal Performance Comparison

When comparing foam board insulation vs fiberglass, one key factor is the R-value—a measure of thermal resistance. While rigid fiberglass board insulation typically ranges from R-4 to R-6 per inch, foam boards like polyiso can reach R-values of up to R-7. However, performance also depends on environmental conditions and application.

If you're insulating an attic, foam board over fiberglass insulation may offer better air sealing. But for walls and ceilings, fiberglass insulation panels often provide better acoustic control and are easier to install in irregular spaces.

Moisture & Fire Resistance

Fiberglass insulation is naturally non-combustible and does not support mold growth, making it ideal for areas with high humidity. Some variations, like foil faced fiberglass insulation board, offer extra protection against moisture and radiant heat. Foam boards, while moisture-resistant, may require fire-retardant treatments and vapor barriers, especially when used indoors.

Installation and Cost

In terms of ease of use, fiberglass board insulation is lightweight and simple to cut and fit between studs or joists. It is also more cost-effective, especially in large-scale applications. Foam board may require adhesives, cutting tools, and professional handling to prevent off-gassing and warping.

Many contractors prefer fiberglass duct insulation board and fiberglass electrical insulation board for precise, safe installations in commercial HVAC and electrical systems.

Applications and Recommendations

Use compressed fiberglass insulation board for dense, high-performance wall applications. For ductwork, fiberglass board insulation for ductwork provides reliable thermal and sound insulation. Foam board vs fiberglass insulation for soundproofing? Fiberglass wins again, thanks to its fibrous structure that absorbs sound waves.

If you’re purchasing in bulk, brands like Owens Corning fiberglass insulation board and Johns Manville fiberglass insulation offer quality and consistency. For high-density needs, GTOFRP™’s fiberglass insulation boards deliver superior durability and performance.

Conclusion

Both foam and fiberglass insulation have their pros and cons. If fire resistance, noise reduction, and affordability are priorities, fiberglass insulation boards may be your best bet. When you need moisture protection and high R-values in a thin profile, foam board might be preferable. Choose based on your specific building needs, climate, and code requirements to get the most out of your insulation.