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
Mineral Wool - Formaldehyde Free Only on a Bay Area Home
Mineral Wool - Formaldehyde Free Only is part of how we build a sustainable home that is also a comfortable one. Our wall and roof assemblies are modeled in PHPP before anything is ordered, so insulation, cladding and finish all have to perform together.
If you are planning a new house or a deep remodel and you want this level of material control, that is the whole job we do. Earth Bound Homes builds in Menlo Park, Redwood City, San Mateo County and across the San Francisco Bay Area.
Related materials we specify
- Cellulose Insulation
- Cork Insulation
- Pumice & Volcanic Aggregate Insulation
- Recycled Glass / Cellular Glass Insulation