Mineral Wool Batt Insulation
Mineral wool (also called rock wool or stone wool) batt insulation is manufactured from basalt rock and recycite steel slag that is melted and spun into fibers. It offers several advantages over fiberglass: higher density provides better sound attenuation, it is naturally fire-resistant up to approximately 2000 degrees Fahrenheit without chemical treatment, and its rigid structure allows batts to be friction-fit into cavities without fasteners. Mineral wool is hydrophobic, meaning it repels liquid water while remaining vapor-permeable. The higher density also means it resists settling and maintains its R-value over time better than lighter insulation products. Mineral wool batts are available in standard cavity widths and are increasingly popular in high-performance building projects.
Mineral Wool Batt Specifications
Best Applications for Mineral Wool Batt
Mineral Wool Batt is recommended for the following building components. Each application link shows the specific R-value requirements by climate zone and how Mineral Wool Batt compares against other insulation options for that component.
Thickness Required by Climate Zone
The table below shows the thickness of Mineral Wool 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 Mineral Wool Batt you need for your specific zone and application.
| Zone | Attic | Wall Cavity | Wall Cont. | Floor | Basement | Crawlspace | Cathedral | Garage |
|---|---|---|---|---|---|---|---|---|
| Zone 1 | 9.1" | 3.9" | N/R | 3.9" | N/R | N/R | 6.7" | 5.8" |
| Zone 2 | 11.5" | 3.9" | N/R | 3.9" | N/R | N/R | 6.7" | 5.8" |
| Zone 3 | 11.5" | 3.9" | N/R | 5.8" | 1.5" | 1.5" | 9.1" | 5.8" |
| Zone 4 | 14.8" | 3.9" | 1.5" | 7.6" | 3" | 3" | 11.5" | 9.1" |
| Zone 5 | 14.8" | 3.9" | 1.5" | 7.6" | 3" | 3" | 11.5" | 9.1" |
| Zone 6 | 18.2" | 3.9" | 3" | 7.6" | 4.5" | 3" | 14.8" | 11.5" |
| Zone 7 | 18.2" | 3.9" | 3" | 7.6" | 4.5" | 3" | 14.8" | 11.5" |
| Zone 8 | 18.2" | 3.9" | 4.5" | 7.6" | 5.8" | 3" | 14.8" | 11.5" |
Cost Estimates by Climate Zone (per 1,000 sq ft)
Material cost estimates for Mineral Wool 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 | $4,500 | $1,950 | N/R | $1,950 | N/R |
| Zone 2 | $5,700 | $1,950 | N/R | $1,950 | N/R |
| Zone 3 | $5,700 | $1,950 | N/R | $2,850 | $750 |
| Zone 4 | $7,350 | $1,950 | $750 | $3,750 | $1,500 |
| Zone 5 | $7,350 | $1,950 | $750 | $3,750 | $1,500 |
| Zone 6 | $9,000 | $1,950 | $1,500 | $3,750 | $2,250 |
| Zone 7 | $9,000 | $1,950 | $1,500 | $3,750 | $2,250 |
| Zone 8 | $9,000 | $1,950 | $2,250 | $3,750 | $2,850 |
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 Mineral Wool Batt
- Suitable for DIY installation, reducing labor costs
- Excellent moisture resistance for wet or below-grade applications
- Non-combustible — no thermal barrier required in most applications
- Superior fire resistance provides additional safety margin
- Well-suited for: Wall Cavity, Floor (Over Unconditioned Space), Attic
Limitations of Mineral Wool Batt
Compare Other Insulation Types
Browse specifications and cost analysis for other insulation materials to find the best option for your project.