A former brewery in Berlin-Neukölln, converted by LXSY Architektur into 4,690 m² of coworking and community space for Impact Hub Berlin, is presented as having “around 70 % of the materials recycled or sustainably sourced”: reclaimed windows and steel gratings, wood residues, hemp-lime walls, straw and felt panels, and a new timber gallery inside the retained industrial volume. It is a good project. The claim, as published, cannot be checked, because it states no denominator, no element list, no pathway per element, and no data source. This article takes the project as described in Revalu’s journal, which lists it as a finalist in Revalu’s 2026 Open Call, and shows what the same story looks like with the disclosure block a checkable claim needs.
Nothing here is a criticism of the architecture or the people who built it. It is a demonstration, on a real and well-chosen example, of the difference between a circular description and a circular result.
The short version
- The published claim: “around 70 % of the materials are recycled or sustainably sourced” (Revalu journal, 22 September 2026). Another write-up of the same building says it sourced “about 80 %” of its construction materials sustainably (housingcoop.eu, CRCLR House). Neither states a basis.
- Checkable would be: denominator (mass, cost or count), scope (which systems), an element list with quantities, a pathway per element (retained / reused / recycled content / new bio-based / new), a data source per element, and a range.
- On an illustrative reconstruction with plausible round quantities, the same conversion scores about 90 % circular by mass and about 15 % by cost, because the retained brewery shell is nearly all the mass and the new fit-out is most of the money.
- “Recycled or sustainably sourced” merges reuse (indicative carbon factor 0.05–0.15 × new) with new bio-based products (1.00 × new, with stored biogenic carbon). The carbon consequences differ by an order of magnitude.
- Elementa’s pre-assessment produces most of this block: element list, pathway, source and indicative carbon, plus indicative assembly costs where its Austrian cost reference applies. It is decision support, not a certified LCA.
- All figures here are indicative or illustrative, for early comparison, not for certification or compliance.
What was actually claimed?
Revalu’s journal post describes the project and makes one quantitative statement: “Around 70 % of the materials are recycled or sustainably sourced.” The materials named are reclaimed windows, reclaimed gratings, wood residues, hemp-lime walls, felt and straw panels, and a timber gallery, sourced “from demolition sites, exhibitions, museums, surplus stock and local sources”. The building is 4,690 m². No LCA, EPD, GWP figure, mass, cost or element count is given (Revalu, ibid.).
That is not unusual. It is how most circular case studies are written. What makes this one a useful example is that the material palette is specific enough to reconstruct what a checkable version would contain.
Three things are missing, and what “70% circular” means explains each in detail:
- The basis. 70 % of mass, of cost, or of the number of components? Each gives a different figure on the same building.
- The split. “Recycled” and “sustainably sourced” are different pathways. One avoids manufacturing emissions; the other is new manufacture with a better supply chain.
- The list. Which elements were counted, at what quantity, from which source.
Citation capsule: The Impact Hub Berlin conversion (LXSY Architektur, 4,690 m², former brewery, Berlin-Neukölln) is published with the claim that around 70 % of materials are recycled or sustainably sourced, naming reclaimed windows, gratings, wood residues, hemp-lime, straw and felt panels and a timber gallery, but without a denominator, element list, pathway per element or data source (Revalu journal, 2026).
What would the checkable version look like?
Below is an illustrative reconstruction. The element types come from the published description; the quantities are plausible round numbers for a conversion of this size, chosen to show the mechanism. They are not survey data from the project and should not be quoted as such.
| # | Element (system) | Pathway | Mass (t) | Cost (k€) | Data source | Indicative carbon factor |
|---|---|---|---|---|---|---|
| 1 | Existing masonry shell, slabs, foundations (structure, envelope) | Retained | 1,800 | 150 (repairs) | Survey | 0.05 × new |
| 2 | Reclaimed windows (envelope) | Reused | 6 | 60 | Salvage record; no EPD | 0.15 × new |
| 3 | Reclaimed steel gratings (fit-out) | Reused | 4 | 20 | Salvage record; no EPD | 0.15 × new |
| 4 | Wood residues as fit-out timber (fit-out) | Reused | 5 | 15 | Salvage record; no EPD | 0.15 × new |
| 5 | New hemp-lime internal walls (fit-out) | New, bio-based | 90 | 220 | Manufacturer EPD | 1.00 × new (stored biogenic C) |
| 6 | New straw panels (fit-out) | New, bio-based | 8 | 40 | Manufacturer EPD | 1.00 × new (stored biogenic C) |
| 7 | New felt acoustic panels (fit-out) | New | 3 | 90 | Manufacturer EPD | 1.00 × new |
| 8 | New timber gallery (structure) | New, bio-based | 60 | 380 | Generic dataset | 1.00 × new (stored biogenic C) |
| 9 | New services, finishes, fixtures (services, fit-out) | New | 40 | 700 | Generic dataset | 1.00 × new |
| Total | 2,016 | 1,675 |
Now the percentages, each with its basis stated:
| Basis | Retained + reused (rows 1–4) | Retained + reused + new bio-based (rows 1–6, 8) | All “circular-sounding” (1–8) |
|---|---|---|---|
| By mass | 1,815 / 2,016 ≈ 90 % | 1,973 / 2,016 ≈ 98 % | 1,976 / 2,016 ≈ 98 % |
| By cost | 245 / 1,675 ≈ 15 % | 885 / 1,675 ≈ 53 % | 975 / 1,675 ≈ 58 % |
| By element count | 4 / 9 ≈ 44 % | 7 / 9 ≈ 78 % | 8 / 9 ≈ 89 % |
| Excluding the retained shell, by mass | 15 / 216 ≈ 7 % | 173 / 216 ≈ 80 % | 176 / 216 ≈ 81 % |
Every cell is a defensible “circular percentage” for the same building. “Around 70 %” sits comfortably inside the range; so does 7 % and so does 98 %. That is the point: without the basis, the number is not wrong, it is unfalsifiable.
The last row is worth pausing on. If a case study is about the fit-out strategy, which this one is, the honest denominator excludes the retained shell, because the shell was not a material decision. On that basis, genuinely reused material is around 7 % by mass and the rest of the “circular” share is new bio-based product. That is a perfectly respectable result. It is a different result from “70 % recycled”.
Citation capsule: On an illustrative reconstruction of the Impact Hub Berlin conversion with round quantities, the retained-plus-reused share is about 90 % by mass and 15 % by cost; including new bio-based products it is 98 % by mass and 53 % by cost; excluding the retained shell it is 7 % by mass reused and about 80 % including new bio-based. A circularity percentage without its basis and scope can take any of these values.
What does the split change for carbon?
The reconstruction also shows why the “recycled or sustainably sourced” merger matters. Take Elementa’s indicative pathway factors and the EPD figures from the material posts in this series:
- Retained shell (row 1). At 0.05 × new, retaining 1,800 t of masonry and concrete is the single largest carbon decision in the project by a wide margin. It is also the one decision that had nothing to do with the material palette.
- Reclaimed windows and gratings (rows 2–3). Reuse at 0.15 × new. The only published study of window reuse puts the saving at 58–63 % of a new window’s embodied carbon, with the reused unit’s U-value as the operational caveat (see reclaimed windows).
- Hemp-lime and straw (rows 5–6). New manufacture. Cradle-to-gate totals are negative because of stored biogenic carbon, and comparable on GWP-fossil only: a straw wall panel at about +17 kg CO₂e/m² fossil, a straw board at about +4 (see straw panel EPDs and biogenic carbon in EPDs). Good choices, but not “recycled”.
- Felt panels (row 7). New, typically 60 % recycled PET; about +2.5 kg CO₂e/m² fossil, lower than a wood-wool alternative on that basis (see acoustic panels). Here “recycled content” is real and quantified in the EPD.
- Timber gallery (row 8). New structural timber. Stores biogenic carbon; fossil emissions are what to compare against a steel mezzanine, for which no element-level public figure exists.
Reading down that list, the carbon story of this conversion is: the shell, then everything else. The fit-out choices are thoughtful and mostly low-fossil, and they are a second-order effect next to keeping the brewery. A claim that presents the fit-out palette as the headline and the retention as backdrop has the emphasis reversed, which is why “70 % circular materials” and “70 % less carbon” are unrelated statements.
Citation capsule: In an industrial-to-coworking conversion, retaining the existing shell (indicative factor 0.05 × new) dominates the embodied-carbon outcome; reclaimed windows and gratings (0.15 × new) are the only genuinely reused fit-out elements; hemp-lime, straw and timber are new bio-based manufacture comparable on GWP-fossil with stored biogenic carbon reported separately; felt panels carry quantified recycled content. “70 % circular materials” does not translate to a carbon saving.
What would we publish instead?
The same story, with a disclosure block. Six lines, one table:
- Basis: by mass, with cost as a second column.
- Scope: structure, envelope, fit-out, services; retained shell shown but reported separately from fit-out decisions.
- Element list: as above, with real quantities from the survey and bill of quantities.
- Pathway per element: retained / reused / recycled content (with %) / new bio-based / new.
- Data source per element: survey, salvage record, EPD (with registration number and verification type), generic dataset.
- Range: concept-stage quantities ±, and which numbers are EPD-declared versus estimated.
With that block, “around 70 %” becomes “90 % by mass including the shell, 7 % by mass reused in the fit-out, 53 % by cost including new bio-based” — three numbers, each checkable, each saying something different and true. That is a stronger case study than one round number, because a reader can see what was decided and what was inherited.
This is what Elementa’s pre-assessment produces. You describe the existing building and the proposed one system by system, assign each element a pathway and a data source, and the tool reports indicative carbon per element and in total, with the basis visible and the verification level of each source labelled. For Austrian projects it adds indicative costs per assembly, from a versioned 2026 reference of expert estimates (mostly ±15–25 %), where you choose an intervention for each assembly; roofs and doors have no reference rate and stay uncosted, and a reused component needs a quote you enter, since the reference has no salvage intervention. It is built for the moment before formal assessment, when the retain-or-replace decisions are still open; it is not a certified LCA and does not claim to be.
Citation capsule: A checkable circular case study states its basis (mass and cost), scope, element list with quantities, pathway per element, data source per element with verification level, and a range. Applied to the Impact Hub Berlin conversion it would replace “around 70 %” with separate, verifiable figures for the retained shell, reused fit-out elements and new bio-based products.
Frequently asked questions
Is the Impact Hub Berlin conversion a good circular project?
By the published description, yes: a retained industrial shell, reclaimed windows and gratings, wood residues, and bio-based fit-out materials. The reservation in this article is about the claim, not the building. “Around 70 % recycled or sustainably sourced” cannot be verified because no basis, element list or source is given.
How much of the Impact Hub conversion is verifiably circular?
No share can be verified as published. On an illustrative reconstruction, the retained-plus-reused share is about 90 % by mass and 15 % by cost; excluding the shell, reused fit-out material is about 7 % by mass. All of these are consistent with “around 70 %” under some choice of basis and scope, which is why the basis has to be stated.
Are the quantities in this article the real project figures?
No. The element types are from Revalu’s description; the masses and costs are illustrative round numbers for a conversion of this size, chosen to show how the percentage moves with the basis. They must not be cited as project data.
Where does the carbon saving in a conversion like this come from?
Almost entirely from retaining the existing structure and envelope. Published adaptive-reuse projects report 68–82 % less embodied carbon than an equivalent new build when the structure is kept (see refurbishment vs demolition). Fit-out reuse and bio-based products are worthwhile but second-order by comparison.
Can Elementa certify a circularity percentage or carbon saving?
No. Elementa produces indicative element-level pathways and impact classes, and expert-estimate assembly cost ranges for Austrian projects, for early comparison, with data sources labelled. Certified figures need a formal LCA by a qualified assessor.
The takeaway
A brewery kept, windows and gratings reclaimed, walls in hemp-lime, a timber gallery: this is the kind of project the industry needs more of. It deserves a claim that can be checked. “Around 70 % recycled or sustainably sourced” is not that claim; a table with a basis, an element list and a pathway per element is. The number that comes out of the table will be less tidy and more useful, and it will show the truth that the round figure hides: the shell is the saving, the palette is the craft.
If you want your own conversion assessed that way, element by element, with the basis and sources visible, before formal assessment, start a project.