Architecture studios: Balearic Institute of Housing - Institut Balear de l’Habitatge (IBAVI)

Main sponsor: IBAVI

Year completed: 2023

Materials: marès sandstone, wood (partially from reuse), reused roof tiles, handmade kitchen tiles

Total area: 502 m2 

Prizes: IBAVI received the 2022 AR Emerging Award as recognition for the evolution of its approach from Life Reusing Posidonia to Santa Eugènia.

Regional background

In Spain, the construction industries account for 17% of CO2 emissions and despite this, there is no widespread debate about the importance of reducing materials emissions during building work (grey energy). It is therefore essential to reconsider the industrial processes during construction works in addition to the energy efficiency of the final building.

Social housing projects in Spain are usually awarded through architectural competitions organised by municipal or regional authorities, but in-house architects may also design projects.

Since 2010, the Balearic Institute of Housing (IBAVI) - the public agency of the Ministry of Agriculture, Environment and Territory of the Balearic Government responsible for providing and maintaining social housing - has been developing internal housing projects to demonstrate the environmental benefit as well as the economic and constructive feasibility of using local materials. These one-off initiatives seek to provide reference values for energy-efficiency requirements for future architectural competitions.

Solution

The building of six housing units in Santa Eugènia, a small town in the centre of Mallorca, marks the culmination of research carried out by IBAVI on the potential of massive stone construction to produce social housing.

The project takes stock and updates the IBAVI’s experience of “Life Reusing Posidonia”, a prototype of affordable, sustainable, energy-efficient housing in Formentera. Following a mapping of resources in Mallorca, it aims to develop a sandstone construction system that is faster, cheaper, easier and more refined than previous IBAVI buildings.

The 6 dwellings in Santa Eugènia are built on the site of an old garage whose materials (sandstone walls, window blinds, roof tiles) have been reused to create a two-level building. The double-oriented pass-through apartments make the most of the conditions of sunshine and ventilation. All dwellings have access to an outdoor community patio. The building is based on a structural system of parallel vaults between upper and lower floor. A colonnade of stone piers supports stone lintels. On the first floor, the vertical structure repeats the 80 x 40 cm marès pilasters on the ground floor. Wooden trusses support the ventilated roof. All the spans between pillars are the same to make the construction easier and compensate the extra cost of using natural materials. Windows are arranged on vertical axes to make the walls and lintels simpler to construct.

The use of local marès stone not only lowers local carbon emissions compared with conventional materials produced with fossil fuels, but greatly improves thermal inertia, and therefore comfort.

Criteria for high-quality (context, sense of place, diversity, beauty)

• The project is the result of a comprehensive study of site conditions: winds, solar orientation, rainfall, geotechnical, morphology and urban context, local regulations, reusable waste and local materials, available industries, building tradition and crafts, available clean energy, full-cycle water management, ecological footprint reduction, and dwelling typologies adapted to the needs of potential residents.
• The project links heritage, architecture and climate change. Traditional architecture has been a constant reference as a way of working from economy of means and what is available locally. The materials used mainly come from the island and are sustainably sourced, for instance, marès sandstone and re-used wooden formwork boards that support the 25 cm of Posidonia oceanica sea grass used for insulation.
• This is the most energy efficient building achieved by the IBAVI personnel to date: energy class A with an annual demand for combined cooling and heating consumption of 4.8 kWh/m² for the year 2020 and 6.4 kWh/m² for the year 2050, with a theoretical scenario of +2 ⁰C.
• Building houses with eco-friendly materials and processes is environmentally beneficial and improves quality of life at almost the same cost of conventional construction. The project demonstrates that sourcing local materials enhances the connection to the place and the efficiency of bioclimatic strategies.
• Elements salvaged from older buildings – e.g. window blinds, traditional Arabic tiles – provide the dwellings with delightful uniqueness, a highly unusual touch for publicly built housing that is all-too-often soullessly standardised.

Governance and management

11 IBAVI staff members and 7 external technicians.

Budget and financing

Total budget: €889,120.41

65% funded by the IBAVI, 26% by NextGeneration EU and 9% funded by the national government through the National Recovery and Resilience Plan (Plan de Recuperación, Transformación y Resiliencia, PRTR).

Transferable ideas

• Look for the local low-carbon resources to face the climate conditions through passive solutions, using vernacular architecture as guide map.
• Learn or recover the techniques and knowledge to build with at least one of these resources and update the technique to make it affordable.
• Promote technical skills and knowledge update and development for any stakeholder involved in the construction process: designers, technicians, workers, builders, industries, etc.