Mineral Wool - ToddMaxey/Technical-Documentation GitHub Wiki
Mineral Wool Insulation Products
Comprehensive overview of mineral wool batts and exterior mineral wool boards, including composition, manufacturing, performance, and pros & cons.
Table of Contents
Mineral Wool Batts
What Are Mineral Wool Batts?
Mineral wool batts (also called rock wool or stone wool batts) are flexible mats of spun mineral fibers bound with a thermosetting binder. They are designed to friction-fit between wall studs, ceiling joists, or floor joists.
Composition & Manufacture
- Raw Materials: Basalt and/or blast-furnace slag.
- Melting: Heated in a furnace at 1 300–1 600 °C until molten.
- Fiberization: Melt is fiberized by high-speed spinning or air/steam blasting, creating fibers 2–6 µm diameter.
- Binder & Mat Formation: Fibers are coated with a phenolic/acrylic binder, deposited on a conveyor belt into a mat.
- Curing & Cutting: Mat passes through an oven to cure binder, then cut into standard batt sizes (e.g., 16″ or 24″ wide, various thicknesses).
Key Properties
- Thermal Performance: R-3.0 to R-3.3 per inch.
- Fire Resistance: Non-combustible; withstands > 1 000 °C without ignition.
- Moisture Resistance: Inorganic fibers resist mold; binder is hydrophobic.
- Acoustics: STC uplift of 7–10 points in partition walls.
- Lifetime: 40–50 years under dry, undisturbed conditions.
Pros & Cons
| Pros | Cons |
|---|---|
| Excellent fire resistance | Higher material cost than fiberglass batts |
| Superior acoustic dampening | Heavier; can be more difficult to handle |
| Dimensionally stable—no settling | Requires protective gear during installation |
| Inorganic—resists mold, pests, and degradation | Initial binder odor (dissipates in weeks) |
Exterior Mineral Wool Boards
What Are Mineral Wool Boards?
Rigid boards made of mineral wool fibers, used as continuous insulation on the exterior face of wall sheathing to eliminate thermal bridging and protect framing.
Composition & Manufacture
- Similar Fiberization Process as batts.
- Board Formation: Fibers mixed with binder are formed into high-density mats and pressed into rigid panels.
- Facings: Often laminated with foil or weather-resistive facings for moisture control and easy attachment of cladding.
Key Properties
- Thermal Performance:
- EPS boards: R-3.6–4.2 per inch
- XPS boards: R-5.0–5.5 per inch
- Polyiso boards: R-5.6–6.5 per inch
- Mineral wool boards: R-3.0–4.0 per inch
- Fire Resistance: Inherently non-combustible.
- Vapor Permeance: Vapor-open—lets assemblies dry outward.
- Acoustics: STC uplift of 5–8 points for exterior assemblies.
- Lifetime: 40–80 years with proper detailing.
Pros & Cons
| Pros | Cons |
|---|---|
| Eliminates thermal bridging | Higher installed cost |
| Protects framing from thermal & moisture swings | Requires precise flashing and weather-barrier detailing |
| Excellent fire and acoustic performance | Heavier; needs robust fasteners |
| Vapor-open boards allow wall drying | Embodied GWP higher in some foam variants |
References
- Mineral Wool – Wikipedia
- Rockwool® product literature and manufacturer datasheets.
- Thermal and acoustic performance tables from industry standards.