Additions to a cooperative housing block in Zrich by Ltjens Padmanabhan aim to extend the inhabitants existence, both in the building and on the planetIn 2007, French practice Lacaton & Vassal with Frdric Druot published Plus, a manifesto for never demolishing, never removing or replacing, but always adding, transforming and reusing. A cornerstone of their proposal was extending and adding balconies and winter gardens to postwar housing blocks a theory the architects went on to realise in three renovation projects, most famously at Grand Parc in Bordeaux in 2016. Balcony extensions were not invented by Lacaton & Vassal the augmentation of limited outdoor spaces, either formally or through more precarious or extralegal means, is nothing new but this work brought the potentially transformative impact of extending balconies on existing apartment buildings to international attention.If these vast, statefunded rehabilitation programmes have a distinctly French flavour, then the latest example by Ltjens Padmanabhan, in a peripheral district of Zrich, is decidedly Swiss. The modest ninestorey block is a far cry from the behemoths of Lacaton & Vassals Grand Parc, and the building is owned and managed by a nonprofit housing cooperative, rather than a state housing provider. In Zrich, nearly one in four dwellings is managed by a cooperative or public foundation; social housing owned by the state is rare. Inhabitants are active participants in the running of the building, rather than intermittently consulted and frequently dictated to, as is often the case for state social housing tenants.The apartment building is located in Hirzenbach, a garden suburb designed by the city architect Adolf Wasserfallen and built between 1955 and 1967, with gardens by landscape architect Willi Neukom. The neighbourhood was conceived as a mix of fourstorey collective villas, ninestorey blocks and a handful of 18 or 19storey towers, distributed like Lego blocks across a green blanket of parkland. Like the surrounding Schwamendingen district, the area was inhabited largely by Swiss workers employed in the local engineering industry.However, following the deindustrialisation of the city in the 1980s, many original residents moved away. Hirzenbach is not a wealthy neighbourhood; eight per cent of residents received welfare payments in 2023, double the citys average. The city has made attempts to rejuvenate the neighbourhood: Stettbach station was opened in 1990, connecting to Zrichs central station in 10 minutes, and a 2005 city directive advocated and offered guidance for the development of the Schwamendingen district. Today, the area is undergoing intense densification, with the population predicted to soar in the coming years. Rents are beginning to rise and many of the current residents are having to move further out of the city.In contrast, the co-operative on Hirzenbachstrae is committed to maintaining low rents but this has not manifested in a lack of investment. The building was extended in 2007; stacks of large kitchendiners were added to the two and threebedroom apartments facing the street, and the former kitchens were converted into large family bathrooms, to designs by KLP Architekten and at a cost of CHF10 million (around 9 million).Just over a decade later, in 2020, residents decided to extend again, launching an architectural competition which was won by Ltjens Padmanabhan. Their proposal extended the existing balconies by more than a metre to a generous depth of 2.2m. The added concrete slabs are supported by a galvanisedsteel armature of Isection columns, besides which silvery rainwater pipes snake to the ground. Balconies are efficiently separated by white metal dividers and the existing acidgreen awnings were preserved and moved outwards to the new balcony edge. Throughout the yearlong construction period, residents were able to remain in their homes.The new balustrades are formed from angled metal grilles, jutting out like the serrated edge of a grater. The decision was made by the members of cooperative a few months into the project, just before work had begun onsite, to add photovoltaic (PV) modules to the grilles an ambition which the design could gracefully adopt with few changes. The solar cells are set in a pattern that allows light through the glass around them, throwing op artesque shadows through the gridded balustrades. From across the garden that unfurls at the buildings base, the solar cells add a granular texture and rhythm to what otherwise appear as monumental bands stretching 65m across the building, like the slats of a monumental Venetian blind.The grilles could easily incorporate the solar panels, the inflection benefiting the PV systems efficiency though the 77 angle is far from the optimal angle of 39 at this latitude. The balconies also face west, rather than south. The array, in addition to a small existing PV installation on the roof, is estimated to generate 53,200kWh annually; a rough calculation indicates this could supply around 30 per cent of the electricity for the buildings 81 apartments.Coined Balkonkraftwerk (balcony power station), the addition of solar panels to existing balconies is enjoying a rise in popularity; to date, PVs have been installed on 1.5 million homes in Germany and are increasingly common in Spain, France, Italy and Poland though this phenomenon refers to plugin panels installed in individual properties, rather than the communal array in Hirzenbach. Solar power at any scale remains something of a novelty in Switzerland: of the electricity Switzerland produces, only six per cent is solar according to the International Energy Agencys latest figures; the majority is hydro or nuclear.As Daniel Knott has written in The Architectural Review, at a building scale, PV technology is not a silver bullet. PVs can contribute to an increased urban heat island (UHI) effect and can often be a missed opportunity for urban greening; in this case, the original plan to trail vegetation on the balustrades was shelved with the introduction of PVs, as it would interfere with the panels efficiency. In the leafy, periurban fringe of Zrich, this seems a compromise worth making for lower energy bills, and the carbon cost of producing the PVs (significantly, the processing of silicon) and constructing the concrete and steel armature on which to hang them, will be offset by the renewable energy they will produce within a few years. The carbon cost is dwarfed when compared with the emissions of demolishing the building and building a new one as the architects argue, the projects sustainability is contingent on extending the buildings functionality and usability.It is important, however, not to overlook the ecological damage caused by both PV manufacture and concrete and steel production, which cannot be offset. The possibility of constructing the balcony extensions out of timber was not entertained by the architects, opting for steel due to structural demands (the structure is 26m tall) and fire regulations, and concrete slabs as this was the simplest and structurally easiest. These materials withstand weather pressure the best, leading to a longer lifespan in Zrichs climate. Whether these reasons justify the use of highcarbon materials at this critical stage of the climate emergency remains contentious, and the fact that renewable materials are still not more forcibly encouraged in a city like Zrich is increasingly urgent and disappointing.The communal garden room was conceived as a hut in a clearing. The rippling fibre-cement board imitates the fabric of a marquee tent, while the acid-green door frames reference the green awnings on the buildingCredit:Philip HeckhausenIn contrast, the small garden room that also formed part of the project is largely built from timber. Conceived as a hut in a clearing, the structure borrows the language of modest, provisional periurban buildings part prefab Scout hut, part garden marquee, part woodcutters fairytale cottage. The tentlike illusion is aided by the corrugated fibrecement board walls which undulate like pleated curtains. The building nods knowingly to the 18thcentury socalled Guards Tent at Drottningholm Palace in Sweden, made of copper rather than the textile it imitates. At close quarters, the panels of fibre cement pull away at the corners, revealing the timber battens holding it together, like a house of cards that could be blown away in a strong gust.Inside, silver stripes and strings of lights drape down from the pitched timber ceiling like the inside of a circus tent. The corner of the enclosure holding a toilet and storage is fashioned into a green column that appears to hold up the tent like a maypole (it is in fact not loadbearing). The acidgreen column and door frames reference both the green awnings of its backdrop and, architect Oliver Ltjens suggests conspiratorially, James Stirlings Neue Staatsgalerie. The various whispered references are there for those in the know but perfectly enjoyable for those who are not. Some are accidental a neighbouring bike shed in the same corrugated fibrecement board is also inadvertently implicated in the joke.Inside, the festive atmosphere intensifies, with string lights and silver stripes emulating a circus tentCredit:Philip HeckhausenA paved area balloons out from the hut to accommodate overspilling festivities, and a playground has been installed on the southern edge of the grounds. The perimeter fence dividing the plot from its neighbours was removed during construction; there is currently no plan to reinstate it, and Ltjens hopes it stays that way, so that the new playground can be shared with children from the surrounding blocks.As we enter the second half of the 2020s, we must not be satisfied with carbon compromisesThe projects cost was subsidised by Zrichs city council on account of the PVs, and footed by the cooperative, supplemented by a small increase in residents rent no more than 10 per cent which was previously agreed with residents. Compared with Lacaton & Vassals Grand Parc, which cost roughly 50,000 per unit, this project cost around 50 per cent more. While the balconies in Zrich were extended by just over a metre, in Bordeaux the envelope was expanded by 3.8m, with some floor plans doubling though the Swiss residents did also gain a communal garden room and some energy sovereignty. In both cases, the considerable carbon saving of preserving the existing building and not building anew was compromised by extending using highcarbon materials.As we enter the second half of the 2020s, nine years on from the completion of Grand Parc, we must not be satisfied with carbon compromises. While Ltjens Padmanabhans project and others like it are to be commended it is almost utopian from the perspective of many of us living in cities like London adulation must be cautious.2025-02-05Eleanor BeaumontShare AR February 2025ExtensionsBuy Now