The Poseidon Adventure

Photo: José Hevia

[Originally published in The Architectural Review July-August 2019]

The small, idyllic Mediterranean island of Formentera, Spain, isn’t the first place that comes to mind as a hotbed of architectural experimentation. Yet it is home to a pair of discreet terraces that constitute an ambitious experiment in low-carbon housing construction. This is a research project that has the full support of the European Union, government agencies and universities in which research into extinct vernacular building traditions was undertaken, carbon footprints of a wide range of building materials were calculated, and energy consumption in the post-occupancy stage is currently being monitored. These rather quaint terraces belie experimentation that aims to change nothing less than the way we build.

True, we normally associate ‘experimentation’ with a deeply personal artistic search for novel architectural form rather than with an effort to improve building performance. But if carbon emissions from the construction sector are to be significantly lowered, then what we need are verifiable, conclusive scientific studies confirming what is truly ‘green’ as opposed to merely ‘green washing’.

Completed in 2017, Life Reusing Posidonia is a publicly built, affordable rental housing project designed by civil-servant architects of the Instituto Balear de la Vivienda (Balearic Institute of Housing), or IBAVI for short: a public agency of the Ministry of Agriculture, Environment and Territory of the Balearic Government responsible for providing and maintaining social housing in this Mediterranean archipelago. Normally, social housing projects in Spain are awarded through architectural competitions organised by municipal or regional authorities but, in the case of small projects, they may be done by in-house architects. In this case, IBAVI wanted a pilot project with which to test and establish new, more-stringent energy-efficiency requirements for future architectural competitions.

To this end, in 2012, it applied to the European Union LIFE+ 12 programme for a Climate Change Adaptation project grant with the support of the Balearic General Directorate of Energy and Climate Change, receiving €754,012 – or almost half the building’s construction budget – to ‘demonstrate the feasibility of developing a multi-family residential building with a significantly reduced ecological footprint’. IBAVI architects remark that the EU grant programme is intended for ‘nature conservation’ and ‘climate change adaptation’ projects and that this is only the second ‘architectural’ project to be awarded such a grant in Spain.

For this experiment, IBAVI set out to achieve a 50 per cent reduction in CO2 emissions during construction, a 50 per cent reduction in construction waste, an Energy Class A rating, a 75 per cent reduction in post-occupancy energy consumption and a 60 per cent reduction in water consumption – and all without increasing construction costs by more than 5 per cent. The relative isolation of this 83km2 island, only 4 nautical miles from the island of Ibiza but over 54 miles from the Spanish mainland, added a further challenge.

To lower the construction carbon footprint as much as possible, materials were analysed with respect to both their embodied production energy and all transport energies involved, from extraction through processing, to on-site delivery. Even the type of fuel used by different brickyards was taken into consideration, as was the regional availability of salvaged building elements that could be reused. Research into historical precedent was also conducted: material samples from vernacular centuries-old buildings in the area were analysed in university laboratories for their composition and performance over time. It was discovered here, for example, that Posidonia seagrass (or Neptune grass) – a plant that washes up on beaches throughout the Mediterranean and was long ago harvested and dried for use as thermal insulation in houses – acts as a natural preservative of timbers, as well as of itself, due to its salt content. Today, this ‘nuisance’ is cleaned up from beaches in summer to appease tourists.

The data collected in the research phase was then charted in the form of a ‘resource map’ that compares the carbon footprint of different materials at the project’s location, permitting the least carbon-emitting materials and methods to be selected. The map produced some surprising results: while local Posidonia seagrass turned out to be the most advantageous thermal insulation material in terms of carbon emissions, engineered wood imported from Austria was a structural material that emitted much less carbon than concrete from neighbouring Ibiza, only a quick ferry trip away. As architect Carles Oliver likes to say: ‘restrictions stimulate creativity’.

With all the research, it took nine years before Life Reusing Posidonia was completed in the small, charming rural village of Sant Ferran de ses Roques in the middle of Formentera island. Situated at a quiet street intersection, the two terraces – each facing a different street – occupy a corner of a trapezoidal block near the local school and small businesses, including the atelier of a guitar-maker. Dwellings are at both ground and first-floor levels of the terraces, each with their own direct street access as well as private outdoor space:  ground-floor dwellings each have a small entrance patio and a rear courtyard, while upper-floor dwellings each have a private roof terrace with spectacular views of the town, landscape and sea.

To reduce lifetime energy consumption, dwellings were designed to exploit to the full summer breezes and winter sun, but also to protect against their counterparts – winter breezes and summer sun. The compact, efficient units – this is social housing, after all – are laid out in a chequered pattern with two bedrooms in one pair of diagonally opposite corners, and both front and rear exterior openings of a central living room in another pair of diagonally opposite corners, an organisation that enlarges the living room perceptually while facilitating summer cross ventilation. The upper-floor dwellings, which are more exposed to the elements, feature a thermal chimney in the middle of each living room in the form of a small 1-metre outcrop in the ceiling with two openings: a south-facing clerestory window for passive solar heating in winter (shuttered in summer) and a north-facing operable one for extra ventilation in summer. Ceilings throughout expose Austrian glulam rafters, lending the spaces an air of nobility, while elements salvaged from older buildings – mainly old, solid-wood doors – provide each dwelling with delightful uniqueness, a highly unusual touch for publicly built social housing that is all-too-often soullessly standardised. The reason these architects could get away with this bit of subversion was that reusing old doors was the least carbon-emitting option.

The fact that civil-servant architects have created such soulful, beautiful housing is truly remarkable in this neoliberal day and age in which things ‘governmental’ are all too often dismissed as ‘inefficient’ or ‘inhumane’. The buildings do not feel the least bit institutional. On the contrary, they possess a sense of local character that makes them fit right in with their small-scale, finely grained setting. Formentera is one of the few remaining Mediterranean paradises that has not been spoiled by mass tourism; spoiling it with mass housing, no matter how ‘architectural’, is not an option.

The architects visit the project regularly, conducting ‘house calls’ to see how residents are adapting. The dwellings are inhabited with utmost normality. There is no feeling whatsoever of living in an experiment. In one of the upper-floor units, a cyclist was busy hanging his road bike inside his living room’s thermal chimney, while another dwelling’s living room was strewn with toys. Residents seem comfortable and well settled, proudly displaying their new homes.

In many efforts to design ecological buildings, a single material or method often becomes an architectural leitmotif – or a one-liner – that permeates the entire work, exhausting every possibility of that material, sometimes to death. That is not the case here, despite the name of the project title. Life Reusing Posidonia is holistic, synthesising research with ideas to arrive at an outcome that doesn’t appear the least bit ‘eco’ or ‘experimental’. From a distance, it could almost be mistaken for a local vernacular building, rather than a work of award-winning architecture (it won the 2018 FAD prize for architecture and was shortlisted for the 2019 EU Mies van der Rohe Award), and this is precisely its virtue, given the climate emergency we face. Vernacular ‘normality’ is a useful strategy for low-carbon architecture to gain the wider acceptance that is urgently needed.

Clearly, no single, universal, one-size-fits-all approach exists for achieving low-carbon architecture: the diversity of planet Earth’s terrain, climate and locally available materials – precisely the factors that shaped vernacular building traditions before the onslaught of globalisation – will always condition architecture. But, at the same time, a strict return to vernacular tradition is not an option either, given that the world’s population is now much more urbanised, not to mention exploding.

The research behind Life Reusing Posidonia shows that there are certain new materials with advantageous carbon footprints that merit import from afar. At the same time, it encourages us to research our vernacular heritage for forgotten possibilities. Of course, exporting Neptune grass all over the world makes no sense at all – aside from the fact that, in Spain at least, it is protected by strict harvest quotas. However, in this particular place, it proves to be the best insulation material when taking carbon emissions into account. Each place is the centre of its own resource map with its own place-specific material combinations that draw on the best of two worlds, the local and the global. There may not be a Planet B, but there is an entire other world of material discoveries to be made.

Photo: Marià Castelló

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