Winning solution of the urban challenge promoted by the municipality of Barcelona "Regeneration of existing residential buildings with innovative sustainable systems"

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Aligra is an innovative and sustainable system that was born as a response to the Urban Regeneration Program of the Barcelona City Council (of the BIT Habitat foundation), which develops a global, unitary and multidisciplinary strategy of actions on vulnerable buildings and urban fabrics in situations of insufficiency or degradation. The result is an integrated prefabricated construction system based on two-dimensional (2D) elements, which learns from the most interesting solutions already offered by the market, and translates them into a generic, open-source system, adaptable to any tender or construction situation without the restrictions imposed by proprietary patents.

Aligra is designed to adapt to a wide range of situations, both at the architectural scale and at the urban landscape level. Different volume enlargement configurations have been analyzed from real buildings in the city of Barcelona, from residential blocks to properties in the Eixample, including some less common cases of buildings not aligned with the street. We have considered and analyzed cases of enlargement of the private space of dwellings, the introduction of galleries, the generation of private and collective open spaces, as well as the possibility of including new vertical communication cores.

The main features of the Aligra system are as follows:

  1. Economy of resources. The multilayer system, conceived in such a way that each layer fulfills several functions at the same time, offers maximum performance of the materials. This philosophy has led to the design of multipurpose construction elements that can be combined in a variety of ways to achieve different purposes.

  2. Modularity. Dimensionally, the physical part of the system is based on a 60 cm module, a size very compatible with current industrial and transport standards. The same modular composition criterion has been followed in terms of installations, including the proposed sensorization and software.

  3. Lightweight. The careful selection of materials and the optimal use of their performance allows the system to achieve considerably higher degrees of lightness than similar alternatives offered on the market. This improves assembly and disassembly processes in terms of safety, inclusiveness and energy savings.

  4. Ease of assembly. The combination of lightness and modularity, together with the use of reversible and accessible joints, greatly facilitates the assembly and disassembly of the construction elements.

  5. Ecological materials. The system prioritizes the use of healthy, renewable, recyclable and reusable materials, mainly CO₂ negative materials, non-emitting VOCs, hygroscopic, and materials that do not retain or propagate electromagnetic radiation.

  6. Flexibility to the project. By offering a wide range of materials and thicknesses, the system adapts to very diverse situations, so that it greatly facilitates the conception of the architectural project, as well as its adaptation to eventual changes or, even, to the participation of future users.


In coherence with the requirements of the call, the proposal is structured from 5 kits, in a synergic system that seeks the best performance of their interconnections and interactions.


1. Volume extension kit

It is a two-dimensional, light and dry modular system, removable and reusable, mainly based on micro-laminated wood. The proposed modulation allows to easily solve several extension measures. The system differs from other wood-based solutions by reducing the use of material, in an exercise of radical optimization of resources by taking advantage of the most advanced techniques of the wood industry. The combination of a lightweight timber framing with a reinforced concrete compression layer allows the structural and acoustic performance of the slab module to be improved at the same time.


2. Bioclimatic envelope kit

The result is a modular system with different possible combinations, adaptable, depending on the addition or substitution of materials, for new construction, renovation, living spaces and bioclimatic spaces. It differs from the existing alternatives in the market for its dry, reversible and recoverable materials. Industrialized off-site system, manufactured in the workshop, designed in BIM technology and manufactured using CAD-CAM and dry-assembled with reversible joints.

It is also combinable, based on the same modulation and anchoring systems, closing and cladding panels with different functions: thermal insulation (TI), TI plus thermal cushion space or bioclimatic gallery with hot air generation, TI plus natural ventilation with and without energy recovery, TI plus parietodynamic wall for hot air generation and TI plus photovoltaic cladding for the production of renewable electric energy. Integrator, from a common structural frame and geometric definition, different materials and building components available on the market that can be accommodated in the construction system. It is, therefore, an open system that can, by changing its configuration, respond to the characteristics of the building stock, climate, regulations and construction processes common in the city of Barcelona but potentially also other environments.


3. Retention roof kit

This kit consists of a two-layer composite system, which integrates a structural cistern tray that can support two types of top finish layer: a vegetation layer and a walkable layer, without prejudice to the possibility of developing other types in the future. The water recovered by the cistern is used for drip irrigation of the vegetation cover and the vegetation envelope on the façade. In the event of torrential rains, the system drains into the downspouts when it reaches its maximum capacity. Drip irrigation works with both rainwater and, in emergencies, with mains water. This mode is activated at low levels of water stored in the cistern or when the water quality sensor gives a signal for renewal. The emergency system refills the cistern until the water level required for daily irrigation is reached. It is monitorable and adjustable in quantity and frequency of irrigation by the user through the smart building kit app.


4. Photovoltaic kit

It is a modular system that will allow the creation of an energy community that will be able to supply energy for the entire building. Fully integrated solution that reduces the problems associated with the installation of this type of system in residential buildings (space, ease of installation, constitution of the community). It has a photovoltaic pergola that will make it possible to create new shaded areas on the roof, without losing available surface area.


5. Smart building kit

The Smart building kit constantly monitors the indicators provided by multiple sensors on the environmental, water and energy performance of the bioclimatic skin, the photovoltaic panels and the retention roof. When necessary, it also executes automatic control commands of the installations to improve these performances. The kit includes all the necessary infrastructure to perform these functions.

The monitoring and control system uses open source hardware and software components. These components are inexpensive, easily replicable and even do it yourself. The control functions are open to gamification, so that the user community can adopt responsible water and energy consumption patterns.

October 2022 December 2023
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