The major challenge of rehabilitating existing housing

Rehabilitating existing housing is an urgent necessity across Europe today. The lack of thermal insulation increases energy consumption and contributes significantly to greenhouse gas emissions. At the same time, outdated water installations lead to unacceptable waste of an increasingly scarce resource, while deficiencies in accessibility and habitability negatively impact the quality of life for thousands of people. In Barcelona, for example, 85% of rental housing presents at least one of these issues.

Residential rehabilitation is not only a challenge but also an opportunity to transform cities toward sustainability and comfort.

Prefabricated timber as an innovative solution

The amendment of the Catalan Urban Planning Law (2022) allows volumetric extensions of buildings in exchange for improvements in habitability, accessibility, and energy and water efficiency. This is where timber prefabrication comes into play: a system that combines speed, efficiency, and sustainability.
The advantages are multiple:

• Reduced construction time and costs.
• Lower environmental impact through the use of renewable materials.
• Creation of quality jobs and strengthening of the local productive fabric.

Aligra: a versatile modular system

Aiguasol, in collaboration with Straddle3, Societat Orgànica, Tallfusta, and Tejido, we have developed Aligra. This solution, winner of the Barcelona Innova Urban Challenge “Regeneration of Residential Buildings with Innovative Sustainable Systems,” leverages these opportunities through an integrated system of prefabricated timber modules designed to adapt to any existing building, climatic conditions, or current regulations.
The modules are two-dimensional, lightweight, and easy to handle, store, and transport. They connect via reversible joints that facilitate assembly, repair, reuse, and recycling.

Based on these modules, Aligra offers five three-dimensional kits that address the most common needs:

• Kit 1: Façade Cladding
  Ventilated façade panels that improve both the thermal performance and aesthetics of buildings. Finishes are available in various colors and textures, with the option to add or replace layers according to requirements.
• Kit 2: Extension Gallery
  Laminated veneer lumber (LVL) structural frames that allow housing extensions with terraces, glazed galleries, or interior rooms. Quick assembly and minimal disruption to residents.
• Kit 3: Photovoltaic Pergola
  Roof structures equipped with slightly translucent bifacial solar panels that generate renewable energy and provide visual comfort. Facilitates self-consumption and the development of energy communities.
• Kit 4: Rainwater Harvesting Tank
  Reused HDPE tanks that collect rainwater for irrigation and sanitary use. Equipped with filtration and water quality monitoring systems, they can be transformed into accessible or green roof surfaces.
• Kit 5: Monitoring Sensors
  Affordable smart building system that monitors temperature, humidity, CO₂, and water levels. Can automate blinds and windows and provides alerts and recommendations to promote responsible water and energy consumption.

Environmental impact, circularity, and energy efficiency of Aligra

Aligra combines energy efficiency, sustainability, circularity, and urban resilience, turning residential rehabilitation into an opportunity for a sustainable and comfortable future.

Urban Resilience and Heat Island Mitigation

• Roofs with rainwater tanks and vegetation, as well as the use of lightweight materials such as timber, reduce exterior heat accumulation.
• Setback designs create more shaded areas and minimize façade heat absorption.
• Reduced thermal inertia contributes to a cooler and more comfortable urban environment. 

Rainwater Management

• Roof-tank systems provide a high degree of irrigation self-sufficiency, adapted to Mediterranean climate and low-water vegetation. 
• The system can integrate into overall non-potable water management in the building, combining rainwater and greywater for landscaping and other uses. 

Thermal Comfort and Energy Efficiency

• Façades rehabilitated with Aligra improve thermal transmittance (U-value) in accordance with CTE standards.
• Fixed and movable solar protections, airtight windows with Class 4 performance, and reduced thermal bridging help decrease energy consumption and improve occupant comfort and health.
• The bioclimatic gallery increases usable floor area while maintaining comfortable conditions throughout most of the day.
• Combining passive strategies with integrated renewable energy can reduce operational energy use by up to 60% and embodied energy in material production by up to 40%, with an 85% reduction in CO₂ emissions compared to conventional construction. 

Circularity and Material Reuse

• Modular and reversible system with demountable mechanical connections facilitating component and kit reuse.
• 30% of materials can be reused in new constructions, 65% recycled, and only 5% cannot be reused or recycled.
• Repurposes materials from other uses, such as cladding panels and hardware, promoting a circular economy.
• Local production of components in Catalonia minimizes transport and associated impacts. 

Embodied Energy and CO₂ Reduction

• Analysis of the total module materials shows 81.6 kgCO₂eq/m² and 1,437 MJ/m², compared to 550 kgCO₂eq/m² and 2,400 MJ/m² for conventional buildings.
• This represents an 85% reduction in CO₂ emissions and a 40% reduction in embodied energy, contributing to the sustainability of the building’s full life cycle. 

Alignment with European Norms and Policies

• Aligra aligns with sustainability frameworks such as Level(s) and the EU Taxonomy, promoting circular material management and global warming potential calculation.
• Modular design and the use of local, recoverable materials reinforce urban resilience and energy autonomy of buildings. 

The Aligra revolution

With Aligra, residential rehabilitation shifts from being a challenge to an opportunity for modernization, sustainability, and improved quality of life. Buildings are transformed into more comfortable, efficient, and connected spaces, while reducing costs, timelines, and environmental impact.

Aligra does not merely repair buildings; it prepares them for the future.