Mineral Wool - Formaldehyde Free Only (Not Available in North America)
Spun molten basalt or slag — naturally fire-resistant rock fiber that doesn't burn, melt, or off-gas.
Toxicity Screening — All Clear
This material screens clear across all seven independent toxicology authorities we use on every project.
Material Type
Mineral-Fiber Thermal & Acoustic Insulation
Material Description
Mineral wool (also called rock wool or slag wool) is made by melting volcanic rock or steel slag and spinning it into fiber. The result is a fire-resistant, water-shedding, dimensionally stable insulation that performs across a wide temperature range. Some mineral wool products historically used phenol-formaldehyde binders, which is why EBH specifies binder-free or formaldehyde-free formulations specifically. Modern formaldehyde-free mineral wool has no detectable VOC emissions and screens clear across our toxicology panel. The fiber is non-combustible, doesn't support mold, and works equally well as thermal and acoustic insulation.
Composition & Origin
Health Profile — All Endpoints Clear
Severity scored 0–10 against the same 10 hazard endpoints we use for the chemical families on the avoid list. Every score is 1–2 — essentially no signal across every endpoint.
Common Forms & Brands
- Rockwool Comfortbatt & Comfortboard
- Thermafiber Ultrabatt (formaldehyde-free)
- Knauf Earthwool (formaldehyde-free)
- Common framing: rigid mineral wool board, semi-rigid batt, loose-fill
Why We Use It
- Non-combustible — Class A fire rating
- Dimensionally stable — doesn't slump or settle over time
- Water-shedding without losing R-value when wet
- Excellent acoustic dampening properties
- Doesn't support mold or insect colonization
Where It Performs Best
- Exterior continuous-insulation rigid board
- Wall cavity batts
- Roof deck insulation
- Mechanical-room and interior fire-rated walls
Building Applications for Mineral Wool - Formaldehyde Free Only (Not Available in North America)
Listed alphabetically. Where in a home this material earns its keep.
Cavity Batts (Walls & Ceilings)
Exterior Continuous Insulation
Fire-Rated Partition Walls
Mechanical Room Sound Damping
Rigid Roof Deck Insulation
Sub-Slab Vertical Edge