Vermiculite (Loose Fill) Insulation
Vermiculite is a naturally occurring mineral that expands when heated, creating a lightweight, granular insulation material. It was commonly used in attic insulation from the 1920s through the 1980s and is still found in many older homes. While vermiculite itself is not hazardous, some vermiculite mined from the Libby, Montana deposit (sold under the brand name Zonolite) was contaminated with asbestos. Homeowners discovering vermiculite insulation in their attics should have it tested for asbestos before disturbing it. New, asbestos-free vermiculite is still available and is sometimes used in specialty applications such as filling concrete block cores for fireproofing, but its low R-value per inch makes it uncompetitive with modern insulation products for most thermal applications.
Vermiculite (Loose Fill) Specifications
Best Applications for Vermiculite (Loose Fill)
Vermiculite (Loose Fill) is recommended for the following building components. Each application link shows the specific R-value requirements by climate zone and how Vermiculite (Loose Fill) compares against other insulation options for that component.
Thickness Required by Climate Zone
The table below shows the thickness of Vermiculite (Loose Fill) 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 Vermiculite (Loose Fill) you need for your specific zone and application.
| Zone | Attic | Wall Cavity | Wall Cont. | Floor | Basement | Crawlspace | Cathedral | Garage |
|---|---|---|---|---|---|---|---|---|
| Zone 1 | 14.3" | 6.2" | N/R | 6.2" | N/R | N/R | 10.5" | 9" |
| Zone 2 | 18.1" | 6.2" | N/R | 6.2" | N/R | N/R | 10.5" | 9" |
| Zone 3 | 18.1" | 6.2" | N/R | 9" | 2.4" | 2.4" | 14.3" | 9" |
| Zone 4 | 23.3" | 6.2" | 2.4" | 11.9" | 4.8" | 4.8" | 18.1" | 14.3" |
| Zone 5 | 23.3" | 6.2" | 2.4" | 11.9" | 4.8" | 4.8" | 18.1" | 14.3" |
| Zone 6 | 28.6" | 6.2" | 4.8" | 11.9" | 7.1" | 4.8" | 23.3" | 18.1" |
| Zone 7 | 28.6" | 6.2" | 4.8" | 11.9" | 7.1" | 4.8" | 23.3" | 18.1" |
| Zone 8 | 28.6" | 6.2" | 7.1" | 11.9" | 9" | 4.8" | 23.3" | 18.1" |
Cost Estimates by Climate Zone (per 1,000 sq ft)
Material cost estimates for Vermiculite (Loose Fill) 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 | $3,000 | $1,300 | N/R | $1,300 | N/R |
| Zone 2 | $3,800 | $1,300 | N/R | $1,300 | N/R |
| Zone 3 | $3,800 | $1,300 | N/R | $1,900 | $500 |
| Zone 4 | $4,900 | $1,300 | $500 | $2,500 | $1,000 |
| Zone 5 | $4,900 | $1,300 | $500 | $2,500 | $1,000 |
| Zone 6 | $6,000 | $1,300 | $1,000 | $2,500 | $1,500 |
| Zone 7 | $6,000 | $1,300 | $1,000 | $2,500 | $1,500 |
| Zone 8 | $6,000 | $1,300 | $1,500 | $2,500 | $1,900 |
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 Vermiculite (Loose Fill)
- 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: Attic
Limitations of Vermiculite (Loose Fill)
- Low R-value per inch requires greater thickness
- Poor moisture resistance — not suitable for wet or below-grade locations
- Historical vermiculite may contain asbestos — test before disturbing
Compare Other Insulation Types
Browse specifications and cost analysis for other insulation materials to find the best option for your project.