The design depends on a concrete ceiling that stores the night’s coolness, a window that someone opens by hand, and a dynamic thermal simulation that shows the two together can keep summer within SIA 180. This is building physics that Transsolar’s climate engineers modelled floor by floor. Last weekend it was also a door that anyone in Zurich could walk through.

By the organisers’ own list, about 145 places in and around Zurich opened for free on 26 and 27 September. It was the 11th edition of Open House Zürich, under the motto “Architektur für alle”. Open House began in London in 1992 and came to Zurich in 2016. It is run by the non-profit Verein Open House Zürich and the volunteers who staff the doors: students, pensioners, employees and job seekers. Their names never appear on a programme, but the weekend would not happen without them. Most visitors go for the houses. We went through the list looking for the offices.

An office inside its own bet

The office story that matters is at Binzstrasse 29. EM2N, founded in 1997 by Mathias Müller and Daniel Niggli, designed the Büro- und Gewerbehaus there for Swiss Life. Transsolar describes the brief as a “future-oriented, largely decarbonized ‘low-tech’ building”. It was completed in 2023, with about 7,000 m² over six storeys and a basement. According to Architekturpreis.ch, office floors 3 to 6 have no mechanical ventilation and breathe through the façade. The ground floor, the commercial floors and the meeting rooms do have ventilation, and shafts are reserved so services can be added later. The concrete ceilings are thermally activated. WaltGalmarini’s engineers designed prefabricated ribbed slabs that span 8.4 m. Reversible heat pumps on geothermal probes and 200 m² of photovoltaics replace fossil fuels entirely.

Then, in September 2023, EM2N moved its own office into the building. Its staff now test the bet every working day. On Saturday, the Open House entry listed partner Gerry Schwyter for four one-hour tours. When we checked, the 14:00 slot was fully booked. We were not there and won’t pretend to know what was said.

We don’t need to. In our profession, this almost never happens: a post-occupancy evaluation done on yourself, in public. Most offices hand over the keys and never come back. An office that works inside its own bet, and then explains it at the door to strangers, has to be able to say in one sentence why the windows open and why the ceiling is bare. If a partner can’t explain a decision at the door, the office never wrote it down.

←TODAY: In 2026 an architecture office works inside a window-ventilated building it designed itself, and opens it to the public. →3012: The buildings that last are the ones whose reasons were written down where the next generation could find them. Fulcrum: You can only explain a decision to a stranger if you can still explain it to yourself years later.

What it asks of the rest of us

A quick honest note about ourselves: we are 14 people in a half-renovated Werkhalle on the Sihlquai. This year the “Urbane Produktion” series had a stop on our street, at Sihlquai 340. We have never opened our own door. If a visitor asked why our last competition entry had its particular section, the answer would sit in three email threads, one Archicad view and one colleague’s memory.

The trade-off is real. A window-ventilated floor gives up the precision of a machine for the habits of the people inside it, so comfort depends partly on who opens which window, and when. You can’t fix that trade-off in the drawings. You can only measure it and explain it, over and over, and EM2N chose to do both.

Atelier: A walkthrough is the cheapest way for an office to check its own decisions. Teams using AI to draft project texts will notice first that the model can only repeat reasons someone actually wrote down. Monday move: pick one finished project and write its tour script, with five decisions, one sentence each and one number each.

Hack: Put that tour script under version control next to the project, so the reasons change along with the model. Five lines of shell are enough:

mkdir -p docs && cat > docs/TOUR.md <<'EOF'
# Five decisions: one sentence, one number each
1. Why the windows open: ...  (proof: SIA 180 check, ...)
EOF
git add docs/TOUR.md && git commit -m "Tour script: five decisions, five numbers"

The same file works as the first draft of a competition reference, a project page and a new colleague’s first reading.

PAZ Takeaway: PAZ can set up PAZ-GPT on an office’s own decision logs and tour scripts. A new Praktikant could then ask “why is the ceiling bare?” and get the office’s own sentence, with the project file it came from. The knowledge stays in the practice when people leave.

Pick the project you are proudest of and write down, in one sentence, why its windows open.

Sources & Further Reading

• Primary: Open House Zürich 2026 — Architektur für alle