In short
In the manufacturer documents we read, four mineral wool insulation products (two stone wool, two glass wool) declare a thermal conductivity of 0.035 to 0.038 W/(m·K) and Euroclass A1.[1][2][3][4][5] Four plant- and animal-fibre products declare 0.037 to 0.043 and Euroclass E, except that one cellulose declaration also gives B-s2, d0 from 100 mm.[7][9][11][12] The ranges overlap, and the test conditions differ. The EPD carbon figures use four different units and cannot be set side by side.[4][6][8][10][13] We do not rank these products. For background, see our profiles of wood fibre, cellulose, hemp and sheep wool insulation.
Mineral wool insulation is the usual reference point for natural fibre insulations, so a specifier often has to read both kinds of document. This article lines up what each document declares and says where units or conditions differ. We read eight products from eight makers; they are examples, not the market.
What counts as mineral wool?
Two materials, both sold as factory-made batts, rolls or slabs under EN 13162, which ROCKWOOL's datasheet titles "Factory made mineral wool (MW) products".[2]
- Stone wool. According to the ROCKWOOL Nordics EPD, it is made primarily from volcanic rock, recycled stone wool and a cured resin binder: over 95 % mineral wool, under 5 % binder, under 1 % de-duster and water-repellent oil.[6] PAROC says its product is about 2 % fibre and 98 % air, with a melting point above 1,000 °C by an internal test.[1]
- Glass wool. According to the Knauf EPD, glass mineral wool has at least 92 % inert material, mostly recycled glass (up to 80 %) with sand and dolomite, plus up to 8 % bio-based binder from plant starch; the same EPD's content table gives the binder as 2 to 15 % by weight.[4]
What do the declared values say, side by side?
| Product (type) | Maker | λ W/(m·K) | Density kg/m³ | Vapour resistance factor μ | Reaction to fire | Source |
|---|---|---|---|---|---|---|
| PAROC eXtra (stone wool slab) | PAROC | λD 0.036 | Not stated | 1 (EN 12086) | Euroclass A1 (EN 13501-1) | [1] |
| Flexi (stone wool slab, UK) | ROCKWOOL | 0.038; 0.035 at 140 mm and above (BS EN 13162) | Not stated | Not stated (the datasheet says "vapour permeable") | Euroclass A1 (EN 13501-1) | [2] |
| FrameTherm Roll 35 (glass wool roll) | Knauf Insulation | 0.035 at 10 °C (EN 12667) | 19.1 ± 10 % (EN 1602; the EPD says for LCA calculations only) | 1 (EN 12086) | Euroclass A1 (EN 13501-1) | [3][4] |
| Uniroll Classic (glass wool roll, Austria) | Saint-Gobain ISOVER | λD 0.038 | Not stated | 1 | Euroclass A1 (ÖNORM EN 13501-1) | [5] |
| STEICOflex 038 (wood fibre batt) | STEICO | λD 0.038 nominal; design values 0.040 (DE), 0.039 (AT), 0.038 (CH); the EPD prints 0.036 (not used here) | About 50 | 2 | Euroclass E (DIN EN 13501-1) | [7][8] |
| Loose-fill cellulose, ETA-06/0076 (blown or injected) | ISOCELL | λD 0.037 | No product density printed; the EPD declared unit assumes 45 | 3 | Euroclass E (40 mm to under 100 mm); B-s2, d0 (100 mm and above) (EN 13501-1:2009) | [9][10] |
| Thermo Hanf Premium / Premium Plus / Combi Jute (hemp and hemp-jute mats) | HempFlax | λD(23,50) 0.041 / 0.043 / 0.038 | 35–48 / 35–48 / 34–46 | 1 to 2 | Euroclass E (EN 13501-1:2018) | [11] |
| CosyWool roll (sheep wool) | Thermafleece (Eden Renewable Innovations) | 0.039 | 18 | 1.27 dry, 0.80 wet; vapour resistivity 9 MN·s/(g·m) | Euroclass E (standard not printed) | [12] |
The documents are of different kinds: a European Technical Assessment (Thermo Hanf), a declaration of performance (ISOCELL), datasheets, and EPD technical data. Conditions differ too. Knauf's EPD gives 0.035 measured at 10 °C under EN 12667, and the Thermo Hanf ETA declares values for 23 °C and 50 % relative humidity after testing at 10 °C.[4][11] The PAROC, ROCKWOOL and ISOVER sheets print no test temperature.[1][2][5] STEICO's EPD, an average of three plants in Poland and France, prints 0.036 for STEICOflex where the 038 datasheet prints 0.038; we use the datasheet value.[7][8] Thermafleece prints μ and a resistivity, ROCKWOOL only "vapour permeable".[2][12] Printed thermal resistance shows what small λ differences mean: Knauf prints R 4.00 m²K/W at 140 mm and PAROC R 4.00 at 145 mm, from different documents and not a controlled comparison.[1][3]
Can the EPD carbon figures be compared?
Not directly. Five of the products have an EPD we opened, and each declares a different unit.
| EPD (programme, number) | Declared unit | Reference service life | A1–A3 GWP-total (fossil; biogenic) | End of life, as printed | Module D | Source |
|---|---|---|---|---|---|---|
| Knauf FrameTherm Roll 35 and others (International EPD System, S-P-10838) | 1 m² at 140 mm, R 4.00 m²K/W, 2.67 kg | At least 60 years | 2.00 (2.36; −0.364) | C2 +0.0104; C4 +0.266 (100 % landfill scenario) | −0.0933 | [4] |
| ROCKWOOL Flexibatts, Swedish-market average (EPD-Global, NEPD-14588-15178) | 1 m² at R 1 m²K/W (reference product 37 mm, 29 kg/m³, 1.1 kg) | 60 years | 0.421 (0.494; −0.0727) | C2 +0.00342; C4 +0.0167 (landfill) | −0.0401 | [6] |
| Thermafleece CosyWool roll (International EPD System, S-P-04468) | 1 m² at R 1 m²K/W, plus packaging | Lifetime of the building | 0.0500 (0.903; −0.858) | C2 +0.000614; C3 +0.000929; C4 +0.895 (release of stored biogenic carbon) | −1.26 | [13] |
| STEICOflex (EPD-Global, NEPD-11346-11346-2) | 1 m³, 50 kg | Not defined | −47.8 (35.9; −83.8) | C3 +82.9 (incineration with energy recovery) | −30.0 | [8] |
| ISOCELL loose-fill cellulose (IBU, EPD-ISC-20240568-CCA1-EN) | 1 kg at 45 kg/m³ | 50 years | −1.42 (0.132; −1.55) | C3 +1.53 (incineration with energy recovery) | −0.499 | [10] |
We do not convert between the units, because equal volume or mass does not mean equal thermal resistance. End-of-life scenarios also differ: landfill in the Knauf and ROCKWOOL EPDs, incineration with energy recovery in the STEICO and ISOCELL EPDs, where the biogenic carbon counted in A1–A3 is released again in C3.[4][6][8][10] Thermafleece's EPD assumes incineration at end of life, includes waste treatment in C3 and declares the release of the biogenic carbon stored in the wool in C4.[13] The Thermafleece EPD expires on 31 October 2026, twelve days after our check; the Knauf and Thermafleece library entries showed "Valid" on 19 October 2026, so check the library for a successor before using the Thermafleece figures.[4][13] We opened no EPD for ROCKWOOL Flexi, PAROC eXtra, ISOVER Uniroll Classic or Thermo Hanf.
Where is each documented to suit, and where not?
These are the uses and limits the documents themselves state, not recommendations; none compares one product with another.
- Frames, partitions and roofs. ROCKWOOL describes Flexi as a friction-fit slab for walls, partitions, floors and roofs, with tested partition build-ups from Rw 42 dB to Rw 60 dB, each for a stated construction.[2] Knauf lists its rolls for timber frame walls and warm pitched roofs, PAROC eXtra for framed walls, sloping roofs and attic floors, and STEICO its batt for partition and lining cavities in Germany, Austria and Switzerland.[1][3][7] The Thermo Hanf ETA covers timber frame cavities, spaces between rafters and topmost-storey ceilings without foot traffic, and excludes compression loads.[11]
- Loose-fill. ISOCELL's declaration covers cellulose injected into hollow spaces or blown onto horizontal or slightly inclined surfaces (up to 10°) where it lies freely.[9] We read no mineral wool loose-fill document.
- Wetting. Knauf says its rolls must be stored dry and covered, and that damaged, contaminated or wet product must not be used.[3] PAROC prints short-term water absorption of 1 kg/m² or less and long-term of 3 kg/m² or less.[1] The Thermo Hanf ETA says its performance applies only if the product is protected from precipitation and wetting in the building, in transport, storage and installation.[11] Thermafleece prints moisture contents of 7.21 % by mass at 50 % relative humidity and 14.84 % at 95 %.[12] These are not like-for-like measures, and we found no test after real wetting.
- Fire. A Euroclass classifies the product; assembly fire resistance is separate. ROCKWOOL prints a one-hour floor result from a BS 476-21 test of a build-up with 100 mm Flexi, apart from the A1 class.[2] The natural fibre documents we read give no assembly result.
- Sound. Only ROCKWOOL (assembly values from a named test report) and Thermafleece (NRC 1.05 at 100 mm, Rw 40 dB at 75 mm) print sound reduction or absorption results; PAROC, STEICO and ISOCELL print airflow resistance values only.[1][2][7][9][12] The set-ups differ, so we draw no comparison.
The documents give no climate-specific guidance, no vapour-control rules and no durability data for natural fibres under repeated wetting, so we state nothing on those points.
What do the documents say about health and safety?
Mineral wool. In Commission Directive 97/69/EC, which introduced Note Q, the carcinogen classification of mineral wool need not apply if one of four conditions is shown: a short-term inhalation test with a weighted half-life under 10 days for fibres longer than 20 µm; an intratracheal instillation test with a half-life under 40 days; an intraperitoneal test showing no excess carcinogenicity; or no relevant pathogenicity or neoplastic changes in a suitable long-term inhalation test.[14] We could not open the current text of Regulation (EC) No 1272/2008, so this is the 1997 wording and the current wording may differ.
The makers state, as printed: Knauf says its mineral wool is made of non-classified fibres certified by EUCEB, which it describes as a voluntary industry initiative and an independent certification authority guaranteeing the Note Q criteria.[3] PAROC's Swedish sheet says the EUCEB mark confirms its fibres meet the biosolubility requirements of EU 1272/2008 (translation ours).[1] ISOVER Austria's sheet calls its glass wool "freigezeichnet" (cleared of classification) under Directive 97/69/EC and CLP Note Q (translation ours).[5] ROCKWOOL's UK datasheet says its UK stone wool has no hazardous classifications under EU and UK REACH, and the ROCKWOOL Nordics EPD lists no REACH Candidate List substances.[2][6] None prints the underlying test result. Binders are declared too: under 5 % cured resin (ROCKWOOL EPD) and bio-based binder in the Knauf EPD, whose text says up to 8 % while its content table gives 2 to 15 % (both as printed; the EPD and datasheet say the binder contains no added formaldehyde or phenol).[3][4][6]
Natural fibres. The ISOCELL EPD lists 92 % recovered paper and 8 % mineral flame retardants, states that boric acid (CAS 10043-35-3) is on the SVHC candidate list as toxic to reproduction above 0.1 % by mass and does not exceed 3.5 %, and says no biocide products were added.[10] STEICOflex 038 lists wood fibre, polyolefin fibre and ammonium sulfate.[7] The Thermo Hanf ETA says its mats contain binding fibres and a fire retardant it does not name.[11] Thermafleece's EPD lists 0.527 kg sheep wool, 0.105 kg recycled PET and 0.070 kg PET per declared unit and no SVHC substances; its sheet prints a moth and beetle test pass (ISO 3998) without naming a treatment, TVOC of 9 µg/m³ at 3 days (not detected at 28) and formaldehyde below 2 µg/m³.[12][13] We did not open the ECHA candidate list or an emission test report.
What we could not check
- PAROC eXtra, ROCKWOOL Flexi and ISOVER Uniroll Classic print no density in the documents we read, and Flexi prints no μ. We opened no current PAROC or ROCKWOOL UK EPD; the PAROC EPD link we found returned a 404 error.
- The ROCKWOOL Nordics EPD covers Swedish-market Flexibatts, not the UK Flexi product.
- The Knauf and ISOVER sheets are copies hosted by SpecifiedBy and a distributor; we did not check the makers' sites for later versions.
- We did not read the test reports behind any λ value, EN 13162, EN 13501-1, a EUCEB certificate or the current Regulation (EC) No 1272/2008 (EUR-Lex returned no text to automated access), and we could not find the IBU register entry for the ISOCELL EPD.
Frequently asked questions about mineral wool and natural insulation
What is the declared thermal conductivity of mineral wool and natural fibre insulation?
In the documents we read, the stone wool and glass wool products declare 0.035 to 0.038 W/(m·K), and the plant- and animal-fibre products 0.037 to 0.043 (ISOCELL cellulose 0.037, STEICOflex 038 0.038, Thermafleece CosyWool 0.039, Thermo Hanf 0.038 to 0.043). The documents use different test and declaration conditions, so small differences are not a ranking.
Do mineral wool and natural fibre insulation declare the same fire class?
No. All four mineral wool documents we read declare Euroclass A1. STEICOflex 038, Thermo Hanf and Thermafleece CosyWool declare Euroclass E, and the ISOCELL declaration of performance gives E for 40 mm to under 100 mm and B-s2, d0 from 100 mm. A Euroclass describes the product as classified, not a wall or floor assembly.
Can the EPD carbon figures of these products be compared directly?
No. The five EPDs we opened declare different units (1 m² at R 4.00, 1 m² at R 1, 1 m³ and 1 kg), service lives and end-of-life scenarios, so each figure describes only its own product. We do not convert units or rank.
Is mineral wool classified as a carcinogen?
Knauf Insulation and ISOVER state in their documents that their fibres meet or are cleared under Note Q, PAROC states that its fibres meet the biosolubility requirements of Regulation (EC) No 1272/2008, and ROCKWOOL's UK datasheet states that its stone wool carries no hazardous classification under EU and UK REACH. Note Q, as first worded in Commission Directive 97/69/EC, says the carcinogen classification need not apply if one of four test conditions is shown. We opened no EUCEB certificate or test report.
Do natural fibre insulations contain binders and fire treatments?
Yes. The ISOCELL EPD lists 8 % mineral flame retardants and states that boric acid does not exceed 3.5 %. STEICOflex 038 lists polyolefin fibre and ammonium sulfate, Thermo Hanf contains binding fibres and a fire retardant, and Thermafleece CosyWool contains recycled PET and PET. Mineral wool also contains binder: under 5 % in the ROCKWOOL Nordics EPD, and in the Knauf EPD up to 8 % in its text and 2 to 15 % in its content table.
Related reading
For the materials themselves, see our profiles of wood fibre, cellulose, hemp, sheep wool and flax insulation. A direct comparison of two natural fibres is in Hemp Insulation vs Wood Fibre Insulation.
Sources
EPDs registered with the International EPD System are cited by registration number. The latest version of each is published in the EPD Library at www.environdec.com, linked where a library entry exists. Figures from these EPDs were retrieved manually and may deviate from the source, for example after an EPD is updated: check the library entry before relying on a value.
- PAROC AB, "PAROC eXtra, Flexibel isoleringsskiva" product sheet (Swedish, printed date 2026-10-07) and PAROC Danmark, "PAROC eXtra" product sheet (Danish, last revised 28.1.2025). Used for λD 0.036, μ 1, Euroclass A1, test standards (Danish sheet), water absorption, EUCEB and RAL statements, application, R table and the stone content. Manufacturer datasheets; full text read. PDF (Swedish) · PDF (Danish)
- ROCKWOOL Limited, technical datasheet "Flexi", version 1.05, November 2025. Used for λ, Euroclass A1, applications, partition and floor assemblies, the "vapour permeable" statement, the REACH statement and the EN 13162 title. Manufacturer datasheet; full text read. PDF
- Knauf Insulation, "FrameTherm Rolls 32, 35, and 40" datasheet KINE1506DAT-V0825, valid from August 2025. Used for application, storage, EUCEB and binder statements, printed R values and the link to EPD S-P-10838. Manufacturer datasheet, copy hosted by SpecifiedBy; full text read. PDF
- Knauf Insulation, Environmental Product Declaration "FrameTherm Roll 35, Kalzip Plus 35, Acoustic Roll (25 mm), Insulation Strip, Fugefilt", The International EPD System, registration EPD-IES-0010838 (S-P-10838), published 2023-10-23, valid to 2028-10-23; the PDF cover prints "Version: 2" with a date of update of 2025-11-18, while its version history lists 2025-11-18 as version 3, and the library entry shows EPD-IES-0010838:005; EN 15804+A2; verification by EPD process certification (Bureau Veritas). Used for λ, μ, density, composition, declared unit, modules and GWP figures. Manufacturer-authored, third-party verified; full text read. PCR 2019:14 version 1.2.5 per the PDF (the registry entry shows 1.3.4; the PDF is the source of truth). Library entry opened 19 October 2026: status "Valid". EPD Library entry
- Saint-Gobain ISOVER Austria, "ISOVER Produktinformation: Uniroll Classic (UNI)", MKT 05/2022 (German). Used for λD 0.038, μ = 1, Euroclass A1 and the "freigezeichnet" statement. Manufacturer datasheet, copy hosted by the distributor Frischeis; full text read. PDF
- ROCKWOOL Nordics, Environmental Product Declaration "ROCKWOOL stone wool thermal insulation, General Building Insulation for the Swedish market (2025 update)", EPD-Global, NEPD-14588-15178, issued 05.01.2026, valid to 05.01.2031; EN 15804+A2, NPCR 012:2022; EPD tool verification. Used for composition, declared unit, scenarios and GWP figures. Manufacturer-authored; full text read; the registry PDF is identical to the distributor copy (xlbygg.se) first read. Registry entry opened 19 October 2026: registered 05.01.2026, valid to 05.01.2031. EPD-Global entry
- STEICO SE, "Technisches Merkblatt STEICOflex 038", version 8, 2026-09-21 (German; valid for DEU, AUT, CHE). Used for λ, density, μ, Euroclass E, composition, applications and storage. Manufacturer datasheet; full text read. PDF
- STEICO SE, Environmental Product Declaration "STEICOflex", EPD-Global, NEPD-11346-11346-2, issued 27.03.2026, valid to 26.03.2031; declared unit 1 m³; EN 15804+A2; the verifier name is printed as "xxxxxxxx"; an average of three plants (two in Poland, one in France), markets named as Poland and France, and the 038 grade is not named. Used for the technical-data λ, composition, scenarios and GWP figures. Manufacturer-authored; full text read. Registry entry opened 19 October 2026: registered 27.03.2026, valid to 26.03.2031. EPD-Global entry
- ISOCELL GmbH & Co KG, Declaration of Performance No. 2023BE01 (signed 26.06.2023), loose unbound cellulose fibres according to ETA-06/0076 of 08.05.2018. Used for λD, μ, fire classes, settlement results and intended use. Manufacturer document; full text read. PDF
- ISOCELL GmbH und Co KG, Environmental Product Declaration "ISOCELL Zellulose Einblasdämmung", Institut Bauen und Umwelt e.V. (IBU), EPD-ISC-20240568-CCA1-EN, issued 02/05/2025, valid to 01/05/2030; EN 15804+A2; external verifier Stephen Forson. Used for composition, boric acid, declared unit and GWP per module. Manufacturer-authored, third-party verified; full text read from a copy hosted by heinze.de, not linked. IBU registry (on 19 October 2026 the IBU published-EPD list did not load and the site search returned no entry, so validity is as printed in the PDF)
- Deutsches Institut für Bautechnik, European Technical Assessment ETA-05/0037 of 27 March 2026 (English translation by DIBt), "Thermo Hanf Premium", "Premium Plus" and "Combi Jute", C-HempFlax Building Solutions GmbH, EAD 040005-00-1201. Used for λD(23,50), density, μ, fire class, moisture values, composition and intended use. Independent assessment body; full text read. PDF
- Eden Renewable Innovations Ltd, "Technical Data Sheet" Thermafleece CosyWool, v7 (undated). Used for λ, density, μ, resistivity, sorption, fire class, moth test, emissions and acoustics. Manufacturer datasheet; full text read. PDF
- Eden Renewable Innovations Ltd, Environmental Product Declaration "Thermafleece: CosyWool, UltraWool", The International EPD System, registration EPD-IES-0004468 (S-P-04468), published 2021-11-01, valid to 2026-10-31; LCA by Renuables Ltd; third-party verifier Dr Hudai Kara (Metsims). Used for content, declared unit and GWP figures. Manufacturer-owned, third-party verified; full text read. PCR 2019:14 version 1.11 per the PDF (the registry entry shows 1.3.4; the PDF is the source of truth). Library entry opened 19 October 2026: status "Valid". EPD Library entry
- Commission Directive 97/69/EC of 5 December 1997 adapting to technical progress for the 23rd time Council Directive 67/548/EEC (OJ L 343, 13.12.1997), Article 1(1)(c), Note Q. Used for the wording of Note Q. Primary legal text; the original 1997 text, not the current consolidated Regulation (EC) No 1272/2008. EUR-Lex
