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Construction, technologically speaking, is marked by a big delay in terms of industrialization. The building site is dominated by outdated habits and thus efficiency is very low and risks are high. Labour is low skilled, delivery times are long and the quality of the product is unreliable. Prefabrication of construction elements, such as parts of the facade and concrete floors, not only reduces execution periods (with all that this implies in terms of the costs for qualified staff, infrastructure and machinery) but also the margins of error in the execution, as one is working in the factory and not on site. Production in the factory and dry-construction improve working conditions and thus the technical quality of the building. Industrialization has ignored construction and vice versa. A sincere commitment to innovation in building technologies, with a realistic attitude regarding the conditions of today, can for that same reason cause great improvement.
As a result of the above the costs of building have soared. Construction suffers the serious delays in delivery, the cranes that don’t pay off, the qualified labour that can not work efficiently if the progress is insufficient, and so on. All this has its effect on the Price of the final product. Henry Ford showed the world between 1908 and 1925 how much industrialization can help to advance. During these years Ford was able to bring back the price of the T-Ford from 850$ to 290$. Construction should also be able to improve its economic performance, using the same techniques that Ford applied: reducing delivery times, the use of raw material and of labour, optimizing transport and securing a better quality. Consequently the financial management of construction can also change radically.
The desire to address our work in a sustainable way has been the main motivation to apply industrial technologies to design and construction. The R&D&I project of the DOM system seeks a simultaneous improvement in technological and environmental performance. The smaller energy consumption during construction and during the exploitation of our buildings, and also the reduction of the use of raw materials are both manners to achieve less CO2 emissions. In addition we consider the shorter construction works and its smaller inconveniences for the neighbourhood, the long lasting durability on account of the improved quality and the greater affordability due to lower prices as aspects that increase the social sustainability of construction.
The exaggerated extravagance of the architecture from the turn of the millennium has found its clear delegitimization in the 2008 economic crisis. B01 arquitectes believes that at this moment the ambition of architects should be to aim at coherence between architectural expression and construction technologies, which again invokes the words of Mies van der Rohe of almost a century ago. Rationalizing already during the design the construction of a building should be an important goal for architects today. The idea that industrialised building systems should lead to an emphasis on the architectural phenomenon of repetition, and thus reduce the diversity in expressiveness, is a paradigm that we accept without any problem. We consider it one of the many conditions that an architect has to deal with, and not as a hindrance to realise a sophisticated, beautiful and even impressive architecture.
The basic elements of prefabrication
The catalogue of the Pujol group and the models of their prefabricated fee standing houses were the starting point for the DOM system and these marked the areas of research. We did not want to deviate from the already tested products, and we renounced the invention of completely new elements, needing new production chains. Instead we adapted and upgraded those products that are already being commercialised successfully by Pujol, thus improving the performance of the building, composed of these elements. Working with these basic elements implies an assemblage on the building site and arriving there with only flat elements, which are easy to transport. Reducing to the maximum the volume of the ‘package’ (speaking in IKEA terms) is an important condition in order to be able to apply the system in multiple occasions. While designing the different parts of the building we respect maximum sizes, so that the truck can reach the site over conventional routes.
Hollow core slabs
The hollow core slabs that Treanor Pujol produces in Leeds are made using prestressing technology to lighten the slab and save concrete. Their width is 1.20m, they weigh 320kg/m2 and a 300mm deep slab can span 12 meters. The DOM system has incorporated in the production of these slabs an underfloor heating circuit. Introducing these installations in the factory only leaves the final finish to be placed on site. The main arguments to resort to underfloor heating are the creation of a healthier interior climate since it doesn’t move air and dust, a more comfortable thermal sensation using radiation and not convection, and the fact that heating through water can work at more moderate temperatures than air-conditioning, which implies a reduction of the energy consumption of the climate control. The design, development and application of this hollow core slab complies with building regulations concerning acoustic insulation (air-borne sound insulation: 50 dBA / structure-borne sound: 65dBA) and thermal insulation between dwellings (0.4 W/m2K). The design of the slabs and the whole of the system make in unnecessary to apply a structural concrete topping on the site in order to consolidate the stability of the overall structure. This development makes the use of the prefabricated underfloor heating highly effective, it simplifies and shortens the building process and it enhances the concept of dry construction.
Structural wall panels
Treanor Pujol produces structural wall panels with a width of 2.40m and a length according to transport permits. The panel has corbels supporting the hollow core slabs. Working with these panels leads to a direct synergy between architecture and structure. On the one hand it makes the use of pillars and beams unnecessary, liberating the whole surface between facades from structural obstacles and thus creating unrestricted possibilities for subsequent reforms. Furthermore the panels allow the incorporation of carpentry the factory, as Treanor Pujol already does. The DOM system reduces in this aspect even more the tasks that normally are being executed on the site. The wall panel contains all necessary layers to comply with facade insulation regulations and the inner and outer finishing. The plain pre-cast concrete is an excellent and durable finish and can adopt different colours and textures like brick, wood or natural motifs, using various moulds. There is also the option to apply on top of the insulation a reinforced plaster finish. In the interior the plain concrete, finished with painting or wall paper, has the great virtue of the thermal accumulation that takes place in the 16cm thick structural mass. The storage capacity that is generated in this layer is very convenient for buildings with continuous occupation such as dwellings, offices, schools and hospitals. It also reduces the energy consumption for climate control and it improves the thermal comfort quality of the interior. The DOM system eliminates every thermal bridge and places all structural elements on the protected side of the thermal insulation. The exterior layer of 6cm concrete is attached to the interior wall in such a way that no thermal transmission takes place between both sides of the insulation. The U value is adaptable, rounding about 0.20 W/m2K, counting to obtain a code level 4 qualification for the whole of the building. There is compatibility between the structural role that the facade obtains and the desire to have large windows, opening up to the outside. To exceed the standard 1.40m wide openings within one 2.40m wide panel, two symmetrical panels width the opening on the side can be combined, one next to the other. The total width of these two can then create 3.40m wide windows.
The DOM system introduces the incorporation of different types of installations and their control in the phase of factory / production. The underfloor heating, placed on top of the hollow core slabs, is being tested in the factory and the confirmation of the pressure resistance of the circuit guarantees the quality of the product. This gives a security control far beyond what can be achieved on the building site. As far as the interior distributions are concerned, we aim to rationalize all ventilation, water, sanitation, climate control and electricity connections. A clear functional order is established in the floor plan to enhance easy execution and future maintenance of all installations. With the same methodology that the Treanor Pujol factory already has, also the installation modules for bathrooms and kitchen could be prefabricated, leaving only their connections to be done on the building site. Through these modules the whole horizontal interior installation conduction within each property is being stream-lined and the hollow core slabs are freed from perforations that would diminish their load-bearing capacity. The collective part of all networks runs through vertical connections chambers / shafts, defined by the structural precast concrete elements.