Fiberglass (Glass Fiber) Insulation: Definition and What it is
Common insulation material made from fine glass fibers, widely used in residential and commercial buildings.
What is Fiberglass (Glass Fiber) Insulation?
Fiberglass insulation consists of extremely fine glass fibers that trap air pockets to slow heat transfer. It's the most widely used insulation material in North America, available in batts, rolls, and loose-fill forms for virtually every residential and commercial application.
Manufactured by spinning molten glass into fine fibers, fiberglass insulation has been the industry standard since the 1930s. The fluffy pink, yellow, or white material is non-combustible, doesn't absorb moisture, and resists mold and mildew. Modern fiberglass products use recycled glass content (20-30%) and are available in formaldehyde-free formulations. The material works by trapping air in millions of tiny pockets between glass fibers, creating thermal resistance without chemical reaction or complex installation requirements.
Fiberglass Insulation Forms
- Batt and Roll: Pre-cut or continuous rolls for walls, floors, and ceilings, R-11 to R-38
- Loose-Fill Blown: For attics and retrofit applications, provides complete coverage around obstructions
- High-Density Batts: Enhanced R-value (up to R-15 in 2x4 wall) for better performance in standard cavities
- Encapsulated Batts: Wrapped in plastic for easier handling and improved performance
Proper Fiberglass Installation
Fiberglass performance depends entirely on proper installation—compressed or poorly fitted batts can lose 50% of their R-value. Cut batts to fit snugly without gaps or compression. Split batts around wiring and pipes rather than stuffing them behind. Ensure batts fill the entire cavity depth. For faced batts, install with facing toward the heated space and staple flanges to studs, not faces. In attics, maintain proper ventilation and don't block soffit vents. Wear protective gear during installation—gloves, long sleeves, dust mask, and eye protection.
Benefits of Fiberglass (Glass Fiber) Insulation
- Most affordable insulation option for most applications
- Non-combustible and fire-resistant
- Doesn't absorb moisture or support mold growth
- Easy DIY installation for batts and rolls
- Widely available at home improvement stores
- Effective thermal and acoustic performance when properly installed
Fiberglass (Glass Fiber) Insulation Cost
Fiberglass offers the best cost-to-performance ratio for traditional insulation applications.
- Material cost (batts: $0.30-$1.00/sq ft; blown: $1.50-$2.50/sq ft installed)
- R-value and thickness requirements
- Faced vs. unfaced formulations
- DIY installation vs. professional labor
- Project size and complexity
- High-density or specialty products cost more
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