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Building study

Sustainable building, sustainable living: La Borda, Barcelona by Lacol

Le Border by Lacol   pix
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Working with the future residents of the La Borda social housing complex in Barcelona, Lacol arquitectura cooperativa designed a tall CLT building that promotes a low-impact way of life. Photography Lacol, Lluc Miralles, Anna Bosch Miralpeix, and Chopo

Peering over the steel balustrade from the sixth floor of La Borda, the co-operative housing project close to Barcelona’s Sants district, I see and hear kids playing. My visit coincides with the ongoing coronavirus lockdown in Spain, so its young residents are still home from school. Indeed, my visit isn’t actually a visit at all: I glimpse inside the structure via video call in the same way we have all ‘visited’ friends, family or colleagues for much of this year. Inside La Borda however, it seems that social distancing works a little differently. 

 

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Le Border by Lacol pix2

‘In a way, we are managing as one household, at least for the kids,’ explains Cristina Gamboa, member of Lacol arquitectura cooperativa – the co-operative of architects who designed La Borda – and a resident of the building. ‘Some of the parents have set up a school so they can be together for some hours a day.’

This collectively managed response to social care during the coronavirus lockdown is indicative of the broader workings of the community at La Borda, whose 28 residential units were completed in October 2018 after a lengthy participatory design and construction process. Located on the edge of Can Batlló, a former industrial zone and site of grassroots social and cultural organising in recent years, La Borda dates back to 2012, when neighbours and activists – members of the nascent Lacol among them – began discussing Barcelona’s housing crisis with more urgency. ‘We developed our understanding of architecture and the role of the architect in relation to society in parallel with the processes of Can Batlló,’ says Gamboa. 

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Out of these discussions, a co-operative was formed, which negotiated with the municipal government for a 75-year lease on public land and received financial support through loans, grants and membership contributions to begin work on the design and construction process. Crucial to this was the active participation of the building’s future residents. They organised into thematic working groups, one of them an architecture group, that fed into a general assembly. These groups and assemblies would come to define the priorities for La Borda in its design, construction and lifetime: active participation, collective ownership, affordability, and sustainability. 

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The outcome of the discussions is a 3,000m2 complex built from a structure of Spanish cross-laminated timber (CLT) and concrete. All the residential units are organised around a central courtyard and beneath a polycarbonate roof that acts as a greenhouse, capturing solar heat energy during the winter and drawing in additional ventilation through the summer. The complex’s four-storey north-facing façade is relatively closed to the street, while its six-storey southern façade, where most of the apartments are located, is characterised by French doors and lightweight steel balconies to make the most of the sunny Catalan climate. In an unprecedented move (by Barcelona’s previous housing standards), and after a lengthy process of persuading the local authorities, the development has no car park. Not only does this save an estimated 500-800 tonnes of CO2 over the course of the project’s next 75 years, but it also saved a significant chunk of the construction budget that could then be put towards funding the timber structure. 

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Apart from the well-known carbon sequestration benefits of CLT, building with it requires a shorter construction period. A regular, rather than low-cement, concrete was used at La Borda for budgetary reasons, but the lighter mass of the CLT reduced the volume of concrete required for the foundations. In addition, the use of such timber removes the need for internal cladding or suspended ceilings, further reducing construction waste. ‘The wood was much more expensive, but we tried to have a more global understanding of the implications of this material decision,’ explains Gamboa. 

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Crucially, notions of sustainability play out at La Borda in multiple ways. Alongside design and programme decisions that allow for passive heating and cooling, or material choices that produced minimal waste during construction, communal and political decisions have been incorporated into the building’s social DNA, which will allow for a long-term reduction in emissions over the lifetime of the complex. One straightforward example is the provision of communal facilities: a shared laundry room with five washing machines requires less energy to run than one machine per household. Similarly, a kitchen-cum-dining room and other multipurpose spaces have been designed to draw residents out of individually or separately heated spaces as often as possible. These communal spaces also augment the relatively small apartments, which were designed with personalised but straightforward variations to floor plans measuring 40m2, 60m2 or 75m2

More subtly, Lacol worked with residents so they would become what Gamboa describes as ‘empowered’ and ‘active users’ of the building. In the early stages of the project, Lacol interviewed the future residents to gain a detailed understanding of their individual energy usage and needs, while increasing their collective awareness of energy poverty and the climatic performance of different buildings and materials. 

‘Empowerment is a word that has been overused but we understand that, if people are to make technical decisions, they need to have all the information beforehand,’ says Gamboa. With this increased awareness, the building’s responses to changes in the weather can be managed by the residents through simple processes such as manual ventilation or shading, rather than policing personal data, or digital and/or mechanical solutions. 

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Not that the community at La Borda is tech-shy. A small number of the apartments’ CO2 levels, as well as the building’s overall energy and thermal performance, are monitored by a co-operatively-run clean energy company. This allows for ongoing adjustments in the running of the building. For example, monitoring of the data revealed that, despite its communal usage, a disproportionate amount of energy was being expended by the laundry facilities; now only one of the machines runs with hot water and energy consumption has gone down. 

There is, it seems, a broader lesson in this approach to building and designing for the climate crisis – one that goes far beyond the mere technical details of materials or energy systems. The ‘active users’ at La Borda, be they the residents or the resident–architects, treat the project as an ongoing and incomplete process rather than a finished product, a point neatly illustrated by the renaming of the architecture working group to the ‘self-build and maintenance group’. 

Lacol’s sensitive design allows for adjustments and alterations to take place to address existing needs (solar panels are currently being added to the roof, for example) – and to unknown future contingencies: the apartments are future-proofed by virtue of their basic and flexible floor plans. 

What’s more, La Borda lays out a model for sustainable building and living that doesn’t rely on luxurious, tech-oriented solutions. On the contrary and, as with Mikhail Riches’ and Catherine Hawley’s celebrated Passivhaus social housing at Goldsmith Street in Norwich, the low-tech solutions and material decisions at La Borda actually make for greater affordability through energy efficiency and shared resources. The monthly rent for residents is about 20 per cent less than the local private-sector average. This gives the model a certain replicability and Lacol is at work on another co-operative housing project nearby which, Gamboa says, will benefit from lessons learned at La Borda – by aiming to further reduce heat retention during the summer months, for example. 

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At the heart of this project and the broader work of Lacol is an understanding of the link between social and environmental justice. The right to housing has been fiercely contested in recent years in Barcelona, but has had high-profile support from Ada Colau, the current mayor and a former housing activist who has expropriated and municipalised empty private flats and introduced new social housing quotas. A radical trailblazer by current European standards, Colau’s administration has championed La Borda’s social and political model. The municipality is also promising bold moves in environmental policy, although these tend to focus on issues relating to the public realm, rather than domestic spaces, such as disincentivising the use of private cars and increasing the number of pedestrianised and green areas. 

‘All the public agencies, the public agency of housing in Barcelona, all the semi-private institutions that are developing housing, came to La Borda,’ says Gamboa. ‘From the public sector they are really interested in what we have applied here in terms of energy, because collective systems are not well understood.

‘Also, people were really worried about the use of wood in the structure but, since this project was completed, many, many others have started with these strategies.’ 

At La Borda there are clear lessons for policy makers and architects, in Barcelona and further afield, on the alignment of housing and environmental strategies and – by a crucial extension for these times – the alignment of housing and environmental rights.

George Kafka is a writer, researcher and editor of works on architecture and urbanism

Lluc miralles (14)

Architect’s view 

One of the singularities of the project is the participation of the user in all its phases, from the design to the construction and further management. Their involvement has been crucial for defining the environmental strategies, and for challenging standards and current regulations.

The first action to reduce the environmental impact during construction was to redefine the programme. The co-operative decided to not build underground parking for cars and estimated a saving, after 75 years, (construction and use) of 500-800 tonnes of carbon dioxide. This strategy also gives a direct benefit in sustainable mobility and reducing the inhabitants’ ecological footprint. A change in the regulations was needed; this was made at city level and now applies to all new buildings. The second action was the use of wood for most of the structure; this became the highest building constructed from cross-laminated timber in Spain. 

Once the programme was defined, passive bioclimatic strategies were developed, as much as possible with solutions that involve the users’ active role in climate management. The patio covered with a greenhouse allows solar radiation to be captured in winter, while the chimney has been designed to assist ventilation in the summer. A high level of air-tightness was specified in doors and windows. La Borda has a centralised system to generate hot water and heating using a biomass boiler, and solar panels will be installed in the upper terrace. It is possible to create energy from totally renewable materials without the need for fossil fuels. The result is a net energy consumption rate of almost zero while maintaining a level of comfort in the domestic spaces that comes with the least associated cost.

Cristina Gamboa, architect, Lacol

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Client’s view

La Borda wants to promote more communal forms of co-existence that enhance the relationships between the people living there and establish co-operative links in domestic work and care by making visible the private spheres of everyday life. It has become a pioneer in demonstrating that affordable, sustainable housing is possible. 

The co-operative prioritised creating a building with minimal environmental impact in its construction and lifetime. Simultaneously, a basic objective was to eliminate the chance of energy poverty among its users, which some of them suffered due to the high cost of energy and lack of economic resources.

During the design process, it was essential to understand the relationship between an active role and a passive building, and the power of daily practices in reducing energy consumption and environmental impact. The initial strategy to reduce energy demand optimised the scheme: the underground car park was eliminated, services were grouped, the surface area of the houses was reduced, and risks – including specifying that the the highest building be constructed with wood – were taken on. In total, 25 per cent of the total internal area was earmarked for communal spaces. It has a communal kitchen, which can be used for large meals or as a meeting point. There is also a 100m² multipurpose space, two rooms for guests, a laundry room, a large central circulation space, bicycle parking and outdoor terraces. 

These spaces and shared habits increase the collective awareness and sense of empowerment, and facilitate the development of communal activities.

Elba Mansilla, La Borda resident

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Structural designer’s view

The assembly of the structure lasted just over a month, providing a further example of how using CLT is a game-changer in terms of speed of construction. 

The timber used in the structural CLT was pinus insignis, from the Basque Country. Tests conducted by the manufacturer during construction confirmed the huge reduction in variability of mechanical performance offered by CLT when using this local species.

The slenderness of the concrete and timber columns in the ground-floor spaces shows the extent to which the favourable resistance -to-weight ratio of timber can be exploited in the structure. Each ground-floor column – totally exposed and without any covering – has 90-minute resistance to fire, which is similar to the timber slabs. 

This slenderness has the effect of a ‘fuse’ mechanism: in the event of a fire and if any column failed, the main building’s structure would still act together as a structural box, cantilevered out in the façade area. 

As a result, a huge reduction in the overall volume of structural material is achieved.

The vertical core of the building was initially planned to be constructed in precast concrete, based on the original projected cost benefits. However, when the cost of achieving the required multiple joints was factored in, CLT proved competitive and was used instead. 

It was formed of large sheets, 30cm thick. This thickness, necessary to limit lateral wind oscillation, allowed the walls to remain exposed, without the need for a coating, and is able to resist a 120-minute external fire.

For the construction, all that was needed were six lorryloads, carrying a total of 500 CLT panels with a volume of 720m³ – approximately 350 tonnes of timber – and 150,000 screws.

Miguel Nevado

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Working detail 

To understand the working detail and choice of materials, it is essential to understand how severe the budget restrictions were. Each detail was evaluated in relation to the economy, energy, fire or acoustics criteria, taking into account the overall process of construction. 

As an example, the structure of six floors has been fabricated using cross-laminated timber. This is a lightweight, high-quality, renewable material – unlike conventional construction materials such as steel or concrete, which have a very high energy cost and are not renewable. Despite being an expensive material, the timber structure reduces the volume of the foundations, the insulation on façades, the number of internal walls, and the build time – all of which, together, make it affordable. 

Another example is the greenhouse: a device to reduce the energy consumption, it was an additional cost. We looked for cheap agriculture technology and evaluated how it might reduce the insulation or waterproofing requirements for the courtyard’s internal façades. This is the only element of La Borda that is remote-controlled; to ensure optimal performance it has sensors for carbon dioxide, temperature, wind and smoke.

Pol Massoni, architect, Lacol

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Project data 

Start on site February 2017
Completion September 2018
Gross internal floor area 3,071m² 
Construction cost Total cost of development: €3,275,000 (£2,944,000); total construction cost: €2,460,000 (£2.2 million). €120,000 (£108,000) is included for the materials for the second phase – this is for the communal areas and will be self-built over time by La Borda’s inhabitants
Construction cost per m²€840 (£755)
Architect Lacol arquitectura cooperativa
Client Cooperativa d’habitatge La Borda
Structural designer Miguel Nevado
M&E consultant Societat Orgànica
Project manager José Juan Martínez Larriba
Main contractor MCM
CAD software used AutoCAD
Environmental consulting Societat Orgànica
Acoustics Grisel.la Iglesias, Àurea Acústica
Cost control and work supervision Xavier Aumedes and Gemma Rius, Aumedesdap
Project consultants Coque Claret and Dani Calatayud, PAuS (Architecture and Sustainability Project)
Promotion co-ordination La Ciutat Invisible
Service design Holon 

Performance data 

Percentage of floor area with daylight factor >2% 35%
Percentage of floor area with daylight factor >5% 23%
On-site energy generation 30% of electrical consumption with solar panels, 100% of heating and hot water with pellet boilers
Heating and hot water load 39.81 kWh/m²/yr
Total energy load 56.08 kWh/m²/yr
Annual CO2 emissions 6.1 kgCO2/m²
Annual mains water consumption 25.25m³/occupant
Overall thermal bridging heat transfer co-efficient (Y-value) 0.07 W/m²K
Overall area-weighted U-value  0.82 W/m²K

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