Fiberglass Batt Insulation
Fiberglass batt insulation is the most widely used insulation product in residential construction. Manufactured from extremely fine glass fibers, batts come in pre-cut widths designed to fit standard 16-inch and 24-inch stud and joist cavities. Available in both faced (with a kraft paper or foil vapor retarder) and unfaced versions, fiberglass batts are lightweight, non-combustible, and resistant to moisture damage. They do not absorb water, though they lose thermal performance when wet. Installation requires careful attention to achieving full cavity fill without compression, as gaps and voids significantly reduce effective R-value. Fiberglass batts are available in R-11 through R-38 in standard thicknesses and can be layered for higher R-values in attics.
Fiberglass Batt Specifications
Best Applications for Fiberglass Batt
Fiberglass Batt is recommended for the following building components. Each application link shows the specific R-value requirements by climate zone and how Fiberglass Batt compares against other insulation options for that component.
Thickness Required by Climate Zone
The table below shows the thickness of Fiberglass Batt needed to achieve the DOE recommended R-value for each building component in every climate zone. Cells showing "N/R" indicate that insulation is not required for that component in that zone. Use this table to quickly determine how much Fiberglass Batt you need for your specific zone and application.
| Zone | Attic | Wall Cavity | Wall Cont. | Floor | Basement | Crawlspace | Cathedral | Garage |
|---|---|---|---|---|---|---|---|---|
| Zone 1 | 9.4" | 4.1" | N/R | 4.1" | N/R | N/R | 6.9" | 5.9" |
| Zone 2 | 11.9" | 4.1" | N/R | 4.1" | N/R | N/R | 6.9" | 5.9" |
| Zone 3 | 11.9" | 4.1" | N/R | 5.9" | 1.6" | 1.6" | 9.4" | 5.9" |
| Zone 4 | 15.3" | 4.1" | 1.6" | 7.8" | 3.1" | 3.1" | 11.9" | 9.4" |
| Zone 5 | 15.3" | 4.1" | 1.6" | 7.8" | 3.1" | 3.1" | 11.9" | 9.4" |
| Zone 6 | 18.8" | 4.1" | 3.1" | 7.8" | 4.7" | 3.1" | 15.3" | 11.9" |
| Zone 7 | 18.8" | 4.1" | 3.1" | 7.8" | 4.7" | 3.1" | 15.3" | 11.9" |
| Zone 8 | 18.8" | 4.1" | 4.7" | 7.8" | 5.9" | 3.1" | 15.3" | 11.9" |
Cost Estimates by Climate Zone (per 1,000 sq ft)
Material cost estimates for Fiberglass Batt at the DOE recommended R-value for each climate zone and component. These are material costs only and do not include labor. Professional installation typically adds 30-50% to the material cost shown below.
| Zone | Attic | Wall Cavity | Wall Cont. | Floor | Basement |
|---|---|---|---|---|---|
| Zone 1 | $3,600 | $1,560 | N/R | $1,560 | N/R |
| Zone 2 | $4,560 | $1,560 | N/R | $1,560 | N/R |
| Zone 3 | $4,560 | $1,560 | N/R | $2,280 | $600 |
| Zone 4 | $5,880 | $1,560 | $600 | $3,000 | $1,200 |
| Zone 5 | $5,880 | $1,560 | $600 | $3,000 | $1,200 |
| Zone 6 | $7,200 | $1,560 | $1,200 | $3,000 | $1,800 |
| Zone 7 | $7,200 | $1,560 | $1,200 | $3,000 | $1,800 |
| Zone 8 | $7,200 | $1,560 | $1,800 | $3,000 | $2,280 |
Advantages and Limitations
Every insulation type has trade-offs that affect its suitability for different applications. Understanding these trade-offs helps you select the right insulation for your specific project requirements, budget, and installation constraints.
Advantages of Fiberglass Batt
- Low material cost makes it budget-friendly for large areas
- Suitable for DIY installation, reducing labor costs
- Non-combustible — no thermal barrier required in most applications
- Well-suited for: Wall Cavity, Attic, Floor (Over Unconditioned Space), Garage Ceiling (Below Living Space)
Limitations of Fiberglass Batt
- Poor moisture resistance — not suitable for wet or below-grade locations
Compare Other Insulation Types
Browse specifications and cost analysis for other insulation materials to find the best option for your project.