In short
In the manufacturer documents we read, hemp-fibre batts declare a thermal conductivity of 0.038 to 0.043 W/(m·K) and wood fibre batts and boards 0.038 to 0.041 (datasheet values), under test and declaration conditions that differ between documents, and every product whose document states a fire class is Euroclass E.[1][3][5][6][7] The carbon figures cannot be set side by side: the hemp EPD declares 1 m² at 100 mm, the wood fibre EPDs declare 1 m³, and their service lives and end-of-life modules differ.[1][8][9] We do not rank the two. For material-level background, see our profiles of hemp and wood fibre insulation.
Hemp insulation and wood fibre insulation are both sold as vapour-open, bio-based batts and boards, and they are often listed as alternatives. This article lines up what their own documents declare, and states where those documents use different units or test conditions. Every value is attributed to a named document. We read two hemp-fibre products and four wood fibre products; they are examples, not the whole market. Loose-fill products are outside this comparison.
What do the declared values say, side by side?
| Product (type) | Conductivity W/(m·K) | Density kg/m³ | Vapour resistance | Fire (EN 13501-1) | Specific heat J/(kg·K) | Source |
|---|---|---|---|---|---|---|
| IndiTherm (hemp batt) | 0.039 (EPD); 0.039 declared value (BBA certificate) | 45 (EPD); nominal 45 (BBA) | μ 1.3 (EPD); 6.52 MN·s·g⁻¹·m⁻¹ (BBA, resistivity) | E, s1, d0 (EPD); E (BBA) | 2,371 (EPD) | [1][2] |
| Thermo Hanf Premium / Premium Plus / Combi Jute (hemp and hemp-jute mats) | 0.041 / 0.043 / 0.038 | 35–48 / 35–48 / 34–46 | μ 1 to 2 | E | — | [3] |
| STEICOflex 038 (wood fibre batt) | 0.038 nominal; design values 0.040 (DE), 0.039 (AT), 0.038 (CH); the EPD prints 0.036 (not used here) | about 50 | μ 2 | E | 2,100 | [5][9] |
| Pavaflex (wood fibre flexible board) | 0.038 (λd, EN 13171) | 50 | — | E | 2,100 | [6] |
| Pavatherm-Combi (wood fibre rigid board) | 0.041 (λd, EN 13171) | 145 | μ 3 | E | 2,100 | [7] |
| STEICOtop (wood fibre board, EPD only) | 0.04 (technical data in the EPD) | 140 (mass of 1 m³) | — | — | — | [8] |
The documents are of different kinds. The IndiTherm values come from an EPD and a BBA certificate, the Thermo Hanf values from a European Technical Assessment issued by DIBt, and the wood fibre values from manufacturer datasheets and an EPD. Different documents also state values under different conditions. According to ETA-05/0037, conductivity was tested at a reference temperature of 10 °C and the declared values apply to the moisture content at 23 °C and 50 % relative humidity.[3] According to the BBA certificate, IndiTherm was tested for conductivity against UKAD 040005-00-1201 : 2015 and its declared value is 0.039, the same as the IndiTherm EPD.[1][2] STEICO's datasheet states a nominal value of 0.038 and country-specific design values, while the STEICOflex EPD prints 0.036 as technical data; we use the datasheet value.[5][9] The Pavaflex and Pavatherm-Combi sheets cite EN 13171 and do not state a test temperature.[6][7] The small differences between 0.038 and 0.043 should therefore not be read as a ranking. The vapour resistance entries are also not interchangeable: the BBA certificate declares a resistivity, the others a dimensionless factor μ.[2][3][5][7]
Can the EPD carbon figures be compared?
Not directly. The three EPDs we opened use different declared units, service lives and end-of-life modules.
| IndiTherm | STEICOtop | STEICOflex | |
|---|---|---|---|
| Declared unit | 1 m² at 100 mm, R 2.56 m²K/W, 4.5 kg | 1 m³, 140 kg | 1 m³, 50 kg |
| Reference service life | Default 100 years assumed | 50 years | Not defined |
| A1–A3 GWP-total | −3.70 (fossil +4.15, biogenic −7.86) | −138 (fossil +105, biogenic −244) | −47.8 (fossil +35.9, biogenic −83.8) |
| End-of-life incineration | C4: +6.08 (biogenic +6.06) | C3: +239 (biogenic +237); C4 landfill: 0 | C3: +82.9 (biogenic +82.1); C4: 0 |
| Module D | −4.32 | −102 | −30.0 |
| Programme, LCA author, verification | EPD International; LCA by Renuables; individual verifier (Metsims) | EPD Global; LCA by STEICO SE; verification through EPD Global's tool route | EPD Global; LCA by STEICO SE; "Externally" box ticked, verifier name printed as "xxxxxxxx" |
| Validity printed | Valid until 13 April 2026 | Valid to 26 March 2031 | Valid to 26 March 2031 |
| Source | [1] | [8] | [9] |
One cubic metre is ten times the product volume of 1 m² at 100 mm, but equal volume does not mean equal thermal resistance, so we do not convert between the units. The documents also place incineration in different modules (C4 for IndiTherm, C3 for STEICO), and in all three the end-of-life scenario is incineration, which releases the biogenic carbon counted as stored in A1–A3.[1][8][9] The IndiTherm EPD itself says its results should be used with care because the LCI data are not yet based on one year of production.[1] On 8 October 2026 we searched the EPD International library for the product name, the company name and the registration number, and each search returned no results, so we do not know whether a renewed declaration exists.[10]
Which certificates and approvals sit behind each product?
- Thermo Hanf (hemp). ETA-05/0037 issued by DIBt on 27 March 2026 under EAD 040005-00-1201, replacing the version of 6 May 2025. The DIBt listing, read on 8 October 2026, shows no expiry date for the current version.[3][4]
- IndiTherm (hemp). BBA Agrément Certificate 23/7060 was first certified on 21 December 2023; we read Issue 2 of 8 May 2024, supplied by IndiNature. Product Sheet 1 covers a hemp fibre insulation slab for external timber frame walls of new and existing domestic and non-domestic buildings, with height restrictions; Product Sheets 2 and 3 cover pitched roofs and suspended timber floors. The certificate tells readers to check that it is the latest issue, and we did not check it on the BBA website.[2]
- STEICO and SOPREMA wood fibre. The STEICOtop and STEICOflex EPDs are issued by EPD Global and valid to 26 March 2031. The Pavatherm-Combi datasheet prints Keymark 011-7D021, which we did not look up in a register.[7][8][9] STEICO's datasheet also states PEFC-certified wood, QNG compliance and testing by the Institut für Baubiologie Rosenheim. We read these as manufacturer claims and did not open the underlying certificates.[5]
- Emissions labels. None of the documents we read for these six products contains an emissions test report or label certificate, and we did not open a natureplus or indoor-air certificate for them. For the labels in general, see our wood fibre insulation profile.
What use limits do the documents state?
- Thermo Hanf: not for compression loads; intended for cavities of timber frame walls, between rafters, topmost-storey ceilings not subject to foot traffic, and similar; must be protected from precipitation, wetting and weathering. The design value of conductivity is set by national provisions.[3]
- IndiTherm: per the BBA certificate, between inner leaf studs of timber frame walls with a timber or masonry outer leaf, behind a fire-resistant lining with an air and vapour control layer. In England, Wales and Northern Ireland it must not be used on buildings with a storey 18 m or more in height, and in England not on residential buildings with a storey 11 m or more in height. In Scotland, not on buildings with a storey 11 m or more, or within 1 m of a relevant boundary unless the external wall cladding is A1 or A2 and fire-resistance and unprotected-area requirements are met.[2]
- STEICOflex 038: this datasheet (version 8, 21 September 2026) covers 40, 60 and 80 mm batts for cavity insulation of partitions and linings, valid for Germany, Austria and Switzerland, and says to store dry.[5]
- Pavaflex: placed between rafters, girders and beams, and must be protected against weather after installation.[6]
- Pavatherm-Combi: the 40 mm thickness is on demand and not approved for roofs; it may be left exposed on a rear-ventilated facade for 60 days at most and must be installed dry.[7]
The documents differ in what they cover: the Pavaflex and Pavatherm-Combi sheets are undated, each BBA product sheet is for one application, and the ETA covers three variants under one assessment. Compare the application, thickness and region of each document, not only the product name.
What are the products made of?
According to the IndiTherm EPD, one declared unit contains 4.05 kg hemp, 0.405 kg polymer binder and 0.045 kg fire retardant.[1] According to ETA-05/0037, Thermo Hanf contains polymeric or biopolymeric binding fibres and a fire retardant added during manufacture.[3] STEICOflex 038 lists wood fibre, polyolefin fibre and ammonium sulfate.[5] According to the STEICOtop EPD, the board is 80–100 % wood, 2–10 % adhesives and 2–10 % polymers.[8] All four products therefore contain non-fibre components, in amounts that depend on the product.
What we could not check
- We did not read the test reports behind any datasheet value, nor the full text of EN 13171 or EN 13501-1.
- IndiNature told us on 14 October 2026 that IndiTherm's renewed EPD is in verification, so we could not read it; we read the earlier version, whose printed validity ended on 13 April 2026. We also did not check IndiTherm's BBA certificate on the BBA website, and we did not confirm Pavatherm-Combi's Keymark registration in a register.
- We did not read a hemp-fibre EPD other than IndiTherm's, and no EPD for Thermo Hanf, Pavaflex or Pavatherm-Combi.
Frequently asked questions about hemp and wood fibre insulation
What is the declared thermal conductivity of hemp and wood fibre insulation?
In the documents we read, hemp-fibre batts declare 0.038 to 0.043 W/(m·K) (IndiTherm 0.039 in both its EPD and its BBA certificate; Thermo Hanf 0.038 to 0.043 in ETA-05/0037), and wood fibre batts and boards declare 0.038 to 0.041 on their datasheets (STEICOflex 038, Pavaflex, Pavatherm-Combi; the STEICOflex EPD prints 0.036). The test conditions and declaration routes differ between the documents.
Do hemp and wood fibre insulation declare the same fire class?
In the documents we read, both are Euroclass E under EN 13501-1: IndiTherm and Thermo Hanf for hemp, STEICOflex 038, Pavaflex and Pavatherm-Combi for wood fibre. The class applies to the product as tested, not to a wall assembly.
Can the EPD carbon figures of the two materials be compared directly?
No. The IndiTherm EPD declares 1 m² at 100 mm thickness, while the STEICO EPDs declare 1 m³ of product. The reference service lives (100 years, 50 years, not defined) and the end-of-life modules also differ, so each figure only describes its own product.
Do the hemp and wood fibre products have valid certificates?
ETA-05/0037 for Thermo Hanf is dated 27 March 2026, and the DIBt listing shows no expiry for it. IndiTherm's EPD document states validity to 13 April 2026, and we found no entry for it in the EPD International library on 8 October 2026. The STEICO EPDs are valid to 26 March 2031.
Are hemp and wood fibre insulation fully natural?
No. IndiTherm contains 4.05 kg hemp, 0.405 kg polymer binder and 0.045 kg fire retardant per declared unit. Thermo Hanf contains polymeric or biopolymeric binding fibres and a fire retardant, and STEICOflex 038 lists wood fibre, polyolefin fibre and ammonium sulfate.
Related reading
For the materials themselves, including hempcrete, see our hemp profile and wood fibre insulation profile. Other fibre insulations: flax, sheep wool and cellulose.
Sources
- Industrial Nature UK Ltd (IndiNature), Environmental Product Declaration "IndiTherm", EPD-IES-0020226, version 2025-04-14, printed validity to 2026-04-13; The International EPD System, EN 15804+A2; LCA by Dr Callum Hill (Renuables), individual verifier Dr Hudai Kara (Metsims). Used for IndiTherm values, declared unit, modules and content. Manufacturer-commissioned, third-party verified; full text read, ASBP-hosted copy. PDF
- British Board of Agrément, Agrément Certificate 23/7060, Product Sheets 1 (timber frame walls), 2 (pitched roofs) and 3 (suspended timber floors), Issue 2 of 8 May 2024, originally certified 21 December 2023, Industrial Nature UK Ltd. Used for the declared conductivity 0.039, fire classification, vapour resistivity and use limits (wall sheet). Independent certifier; full text read from copies supplied by IndiNature on 14 October 2026; current issue not checked on the BBA website. bbacerts.co.uk
- 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 conductivity, density, vapour resistance, fire class, composition and intended use. Independent assessment body; full text read. PDF
- Deutsches Institut für Bautechnik, approval listing for ETA-05/0037, read 8 October 2026. Used for the issue dates and the absence of an expiry date for the current version. Independent register. dibt.de
- STEICO SE, "Technisches Merkblatt STEICOflex 038," version 8, 21 September 2026 (German; regional validity DEU, AUT, CHE). Used for conductivity, density, vapour resistance, specific heat, fire class, composition, claims and use. Manufacturer datasheet; full text read. PDF
- SOPREMA, technical data sheet BETF-INSEU0029.a/EN "PAVAFLEX Flexible insulation board" (undated). Used for conductivity, density, specific heat, fire class and use. Manufacturer datasheet, hosted by a distributor; full text read. PDF
- SOPREMA, technical data sheet BETF-PAVAT0028.a/EN "PAVATHERM-COMBI" (undated). Used for conductivity, density, vapour resistance, specific heat, fire class, Keymark as printed and use limits. Manufacturer datasheet; full text read. PDF
- STEICO SE, Environmental Product Declaration "STEICOtop," NEPD-11326-11326-2, EPD Global, issued 27.03.2026, valid to 26.03.2031; declared unit 1 m³; LCA author STEICO SE; verification through EPD Global's tool route. Used for the board's carbon figures, content and technical data. Manufacturer-authored; full text read. PDF
- STEICO SE, Environmental Product Declaration "STEICOflex," NEPD-11346-11346-2, EPD Global, issued 27.03.2026, valid to 26.03.2031; declared unit 1 m³ (50 kg); reference service life not defined. Used for the batt's carbon figures. Manufacturer-authored; full text read. PDF
- The International EPD System, EPD library searches for "inditherm", "Industrial Nature" and "EPD-IES-0020226", run 8 October 2026: no results for any. Independent register; search interface only. environdec.com
