The lowest-carbon concrete in Switzerland is the concrete already poured. Circular-economy research keeps arriving at the same point. The first material bank is the standing building, and the most valuable design move is often subtraction. In Renens (VD), beside the CFF tracks of the Ouest lausannois, that idea now has a body you can walk through.

Creative Factory is a former Coop logistics ensemble, built in stages from the 1950s. Between 2022 and 2025, Bauart Architekten und Planer turned it into 51 homes, craft workshops and a training centre for ORIF, for the owner Patrimonium, with Implenia Schweiz as general contractor. In June it won the Jury Prize for Residential Adaptive Reuse at the 14th Architizer A+ Awards, against entries from more than 80 countries, as EPFL news reported. On 12 October espazium published Marc Frochaux’s critique in German, “Die Hand und der Handschuh”. The French original appeared in July.

The cut

I know what it means to be deep. The main building here is more than 20 m deep. That floor plate was made for pallets, not for people who want morning light. Bauart’s answer was a saw, not a new skin. The slabs were cut open to form a central atrium, lit from above by two roof light wells. That new interior street became the spine for the 51 flats, which range from 1.5 to 7.5 rooms and 40 to 240 m².

The frame stayed. The reinforced-concrete skeleton and its mushroom columns are kept and put on show. Frochaux compares their capitals to chanterelles. A structure that carried crates for decades now carries kitchens, and its most elegant part finally has an audience.

←TODAY: In 2026 a 1950s Coop warehouse in Renens houses 51 homes, workshops and ORIF on its original mushroom columns.
→3012: In Zurich-3012 every slab carries its next address before the saw touches it.
Fulcrum: The cheapest light is the hole you cut, and the cheapest paving is what came out of it.

Where the concrete went

The pieces sawn out of the atrium did not leave in a skip. They came back to the park as paving, cobbles and benches. Emmanuel Rey, Bauart partner and EPFL professor at LAST, is plain about the cost. On-site re-use, Rey says, is a “verlockende Idee”, a tempting idea, but carrying it out is harder than it looks. That is the trade-off, stated by the architect who did it. Reuse moves the work from the supplier’s catalogue to the site. There, every slab has to be cut, lifted, checked and placed by people whose names rarely reach an award jury.

On the south face, a light steel layer stands off the old concrete. It carries balconies, sun shades and climbing plants, a second and softer skin that the heavy body could never have grown alone.

Lungs and blood

The energy jump is the kind I envy: from GEAK class G to B. A 100,000-litre oil tank came out, a connection to the Lausanne Ouest district-heating network went in, and a PV canopy now covers the parking. The project cost about CHF 50 million, including a CHF 1.2 million subsidy. Agnès Haulbert, Senior Director Real Estate at Patrimonium, calls it “wichtig”, important. The owner plans about CHF 113 million of portfolio renovation for 2025–2050. The site was never zoned for transformation. The owner started the conversion, and keeping the structure kept a volume that demolition would have cut back.

From where I stand in the late 2070s, the buildings that aged well were the ones plugged into shared, local systems: a district network that a technician in the canton can still read, not a private tank or a private cloud.

Building-sense: A building living through this would feel the cut first as a change in pressure, with air and light suddenly reaching a core that had been dark for decades. Then it would feel relief: no tank in the basement, and heat arriving from the neighbours through a shared network.

Atelier: An office with a deep-plan conversion on the desk is tempted to model the new building and leave the old one as grey background. Renens argues the reverse: the existing structure is the first client. Monday move: add a “reuse destination” column to your office’s demolition schedule template, and refuse to issue it with that column empty.

Hack: Tag the concrete you are about to saw out with its next life, inside the Rhino model, before it vanishes from the drawing. Select the slab pieces you plan to remove, measure each one, and write the destination into its user text so the schedule can read it later:

import rhinoscriptsyntax as rs
for obj in rs.GetObjects("Pick slab pieces to cut out", 8):
    area = rs.SurfaceArea(obj)[0]
    rs.SetUserText(obj, "area_m2", str(round(area, 2)))
    rs.SetUserText(obj, "reuse_to", "park paving")

Run it in Rhino’s Python editor, then read the keys back in Grasshopper to total the reusable area per destination. A PAZ BSS student took this thinking further in RE-MIXER, a final project that catalogues concrete elements by material, size and structural capability, much like Lego assembly instructions.

André Corboz, the urban historian Frochaux cites, said that bringing old structures back to life means finding the hand that fits the glove. In Renens the glove was a Coop warehouse, and Bauart and Patrimonium found the hand. There was no Death Star clean slate here. It was the Rebel way: rebuild with what the old Republic left standing. Before you draw a new line on an existing building, walk its columns and decide which of them deserve an audience.

Sources & Further Reading

• Primary: espazium — Marc Frochaux, “Die Hand und der Handschuh”
• Reinforcing: EPFL news — Architizer A+ Awards