Stone Wool Insulation: GWP Battle of Three Titans
Stone wool eats fire for breakfast and shrugs at mold, yet its embodied carbon story still decides who wins the spec. We sift through 2024–25 EPDs to see how ROCKWOOL, Owens Corning, and Knauf stack up on global-warming potential, indoor-air credentials, and end-of-life loops.
The carbon math behind the molten rock
Stone wool is born in cupolas hotter than a Metallica pyrotechnics show, so energy use can look scary on paper. The good news: recent furnace upgrades and more recycled slag keep driving cradle-to-gate global-warming potential (GWP) down (IBU, 2025). That means the gap between brands is now big enough to sway bids—if you read the fine print on their EPDs.
GWP scoreboard (cradle to gate)
- ROCKWOOL: 1.1–16 kg CO₂e / m² depending on product thickness; a new unfaced 37 mm board lands at 1.07 kg (IBU EPD-RWI-20240078, 2025).
- Owens Corning Thermafiber: 0.88–9.7 kg CO₂e / m²; the 35 mm SAFB™ batt posts 0.878 kg (UL EPD 4790011847.102.1, 2024).
- Knauf: 1.3–2.4 kg CO₂e / m² for common wall boards; a 100 mm faced slab reports 1.30 kg (S-P-07917, 2023).
Numbers bounce with density and R-value, but Knauf currently wears the most consistent low-carbon crown, while Owens Corning hits the single-lowest data point. ROCKWOOL shows the widest spread because it serves every niche from rainscreen to heavy roof decks.
Breathing room: VOC and binder chemistry
All three brands now claim third-party low-emitting badges, yet they take different routes:
- ROCKWOOL sticks with phenol-formaldehyde but cures away most residues and holds GREENGUARD Gold for interior lines (ROCKWOOL Product Transparency, 2025).
- Owens Corning offers formaldehyde-free Thermafiber SKUs that also carry GREENGUARD Gold plus DECLARE labels (IDI specs, 2024).
- Knauf’s plant-based ECOSE® binder nabs Eurofins Indoor Air Comfort Gold and DECLARE “Red List Free” status (Knauf ECOSE, 2025).
For IAQ-sensitive projects—schools, health care—specifiers often leap straight to ECOSE or Thermafiber FF lines. ROCKWOOL still qualifies, yet you may field extra questions about residual phenols.
Closing the loop: who takes back off-cuts?
ROCKWOOL’s Rockcycle® now runs in 24 countries and targets 30 by 2030, hauling scrap back to furnaces for endless reuse (Rockcycle, 2024). Owens Corning leans on its Paroc Rewool model in the EU and pilots county-scale reuse around its Missouri plant (Owens Corning Circularity, 2022). Knauf pledges zero production waste to landfill and aims to reclaim 25 % of site scrap by 2025, already running take-back routes in five nations (Knauf “For a Better World”, 2024).
If your jobsite runs lean on dumpsters, Rockcycle’s ready freight network can save headaches today, while Knauf and Owens Corning may require a custom haul plan.
What the data means for your next EPD
When an architect asks for “the lowest carbon mineral wool,” hand them a table normalized by R-value, not millimetres. Module A1-A3 figures above show Owens Corning’s newest batt squeaks past Knauf’s slabs, yet Knauf keeps a narrow band across multiple SKUs, simplifying bids. ROCKWOOL’s high-density boards punch up the carbon score but may still win on fire or wind-load criteria—so beware apples-to-oranges comparisons.
Speed matters when carbon rules shift
New municipal Buy Clean ordinances often give manufacturers less than six months to show updated EPDs. Whoever can refresh data first grabs the spec while laggards scramble. Make sure your LCA partner has the muscle to yank utility bills from your ERP, chase suppliers, and publish before the deadline—you’d be suprised how many bids hinge on a PDF timestamp.
Frequently Asked Questions
Do I need separate EPDs for each stone wool thickness?
Usually not. Most insulation PCRs let you publish a single declaration that covers a range of densities or R-values by scaling impacts (EN 16783). Check whether the program operator allows a tabular annex before paying for extra models.
Can I compare GWP numbers from different program operators?
Yes—but tread lightly. Make sure all EPDs follow EN 15804 +A2 (or UL Part B) and report cradle-to-gate (A1–A3) before lining up figures. If one report bundles A4 or installer credits, the math goes off the rails.
Will formaldehyde-free binders change my fire rating?
No. Owens Corning and Knauf both certify their formaldehyde-free lines to the same ASTM E136 non-combustibility standard as conventional phenolic-bound boards.
How soon can I refresh an expiring PCR for mineral wool?
If a new PCR version drops, you can still cite the old one until your EPD’s five-year renewal date. At that point the new rulebook applies, so budget a data refresh 6–9 months ahead.
About the Author
Eric works at the intersection of sustainability, regulation, and business strategy, helping manufacturers navigate the evolving landscape of EPDs and LCAs. Having spoken with hundreds of teams across North America, brings a deep understanding of what drives ROI, what regulators are asking for, and how companies can stay ahead with smart, scalable approaches to environmental reporting.
