There is a general consensus on the need to reduce carbon dioxide (CO2) emissions. A key means of reducing equivalent CO2 emissions is by reducing energy consumption. Strategies including the implementation of energy performance certificates (Directive 2002/91/EC) can help work towards this objective. For the building sector reducing energy consumption means taking a lifecycle approach and addressing consumption at each stage, including the sourcing of materials, construction, use and end-of-life. There has been much awareness developed in recent years on the importance of energy-efficient buildings, including the use of insulation, solar panels and efficient lighting systems. However, more attention is needed to address emissions generated during the construction phase. The manufacture of concrete is currently responsible for 75% of the emissions from the construction sector. There is a need to consider alternative building systems that can reduce CO2 equivalent emissions. An interesting option is using local resources with low embodied energy, and a return to traditional methods of architecture. Posidonia oceanica (Neptune grass) is a seagrass species endemic to the Mediterranean. On the Balearic island of Formentera, it has been traditionally used in multiple applications, including the thermal insulation of buildings.
The objective of LIFE REUSING POSIDONIA was to demonstrate the feasibility of developing a multi-family residential building with a significantly reduced ecological footprint. The project aimed to reduce energy and water consumption and the production of waste during the construction phase and service life of the buildings. It aimed to implement and evaluate alternative construction techniques for a building complex with a total floor area of 1.083 m2. Specifically, Neptune grass packed in re-used pallets as insulation material, and non-reinforced lime concrete in the foundations.
LIFE REUSING POSIDONIA developed an innovative multi-family residential building model with a significantly reduced ecological footprint on the Balearic island of Formentera (Spain). The project partners constructed 14 prototype public protection dwellings to demonstrate the feasibility of this alternative building model, which links heritage, traditional architectural methods, and climate change.
A starting point was prioritising the most ecological locally-sourced products and demonstrating their economic viability: i) reusable local waste (e.g. dried Posidonia, straw, reused wood); ii) local eco-friendly products (e.g. marès sandstone, clay, slabs and bricks fired in a biomass kiln); iii) non-local eco-friendly products (e.g. laminated wood, hydraulic lime, silicate paint); and iv) recycled or optimised products (e.g. Ytong concrete blocks, or 85% recycling rate metals). For instance, the prototype building had roof insulation made of 16 cm of compacted dry Posidonia in reused pallets and walls incorporating a 25 cm thickness of Ytong, floors and foundations were made using natural hydraulic lime, acoustic insulation on floors and walls was provided by natural cork and recycled cotton boards, and windows that were all low emissive and made of wood. This ensured a high level of comfort inside (average 21ºC in winter and 26ºC in summer) with a very low energy use.
The project team demonstrated significant environmental benefits for the building. Its construction, avoiding 746 246 kg/CO2 (60.7% reduction) compared to conventional buildings, is rated Energy Class A. There was a 75% reduction of useful energy during the lifetime of the building, a 60% reduction in water consumption, and a 50% reduction in waste production during the construction phase. Healthy indoor air quality was obtained by selecting products that do not emit volatile organic compounds (VOCs) or formaldehyde.
The project contributed to EU policy relating to energy efficiency, climate change mitigation, and the circular economy. It informed three regional regulations promoting ecological construction materials; while its outputs were incorporated in the "Catalogue of sustainable materials available in the Balearic Islands”.
The project team actively communicated and disseminated their approach, for example, reaching almost 300 000 visitors on their website. The project has been presented in several universities as an example of sustainable construction and alternative architecture, in line with the needs of local people and local resources. In addition, 40 conferences were held to validate the status of the prototype as a reference model, involving universities, architecture schools, professional colleges and other relevant institutions.
The project had a significant social component from the very beginning. The 14 dwellings were constructed at the Social Housing Development in Formentera, and awarded to local people in vulnerable situations, either socially disadvantaged or on low incomes. As a direct result of the project, 41 jobs were created to carry out work on the prototype (all workers living in Ibiza or Formentera). The beneficiaries have demonstrated their commitment to implementing the new building model demonstrated, for example, IBAVI is planning new Public Protection Housing projects that meet objectives established in LIFE REUSING POSIDONIA.
Though the main aim was not to obtain economic benefits, the prototype building was constructed with only an additional cost of 5% over the usual price. This means that the new building model is perfectly marketable, as well as being technologically feasible and easily replicable. It is also designed to be non-dependent on conventional heating-cooling systems, providing benefits to tenants due to savings on energy consumption. The local traditional architecture enables the building to be more self-sufficient in terms of energy and the use of local materials.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).