Fabricating Residues: Using Agricultural Residues in Housing Construction Kareem Elsayed

Ateneo
Sapienza Università di Roma

This work is part of an ongoing doctoral research studying the use of digital fabrication in the field of low-cost housing. The study was motivated by the rising demand of world population especially in poor and developing countries and the extreme refugee displacement challenge around the world. The informal response to the problem relies mainly on handcrafted processes, resulting in an increase of urban slums in big cities. Sanitary and spatial qualities are often overlooked. On the other hand, most of the formal sector produces monotonous environments based on the idea of mass production; “one size fits all”. This response fails to meet the individuality and cultural differences of the population, even if it provides desirable/acceptable sanitary conditions.

The author previously performed an investigation examining built prototypes of digitally fabricated houses within the last two decades in an attempt to understand the limitations and potentials of applying these technologies to the affordable housing sector.

Among the limitations of the wide application of digitally fabricated housing is the lack of a bench mark defining what is regarded as a “low-cost” affordable house. Price indicators showed a wide gap between prices in the US and Europe compared to Africa and South America. Almost all analysed prototypes utilized timber/plywood panels with very few exceptions. This becomes a limitation when working in countries that have no tradition of timber building construction. The investigation therefore was oriented towards finding alternative materials that better fit the economics of developing countries and the processes of digital manufacturing.

On the potentials side though, digital fabrication promises to provide a process that is efficient and quick while maintaining the possibility of customization. Conceptually, mass customization combines the economy of scale of mass production and the freedom and functional qualities of customization.

Besides having a growing population and lack of adequate mass housing solutions, a large number of African countries have a long traditional agricultural history. They face a yearly challenge to dispose agricultural residues. Unfortunately, the current practice is burning them forming huge clouds of smoke above the countryside. The environmental impacts are utterly harmful causing lung diseases among many other effects.

There has been on-going research exploring the use of condensed, treated rice straw as a cementitious building block. Researchers also explored straw bale construction as an alternative economic environmental construction method for low cost housing. It proves to be a promising solution yet few researchers have started exploring prospective use of rice straw in flat sheets in a structural manner. This particular application is of great potential and interest to the field of sustainable digital fabrication in which the authors are currently involved.

The selection of ECOboard resin bonded rice straw panels as the base material promises to address more than one issue concurrently; first, minimizing the environmental impact of abundant un-used agricultural residues. Second, adding economic value to materials that previously had no/little value. Third, lower the initial cost for the construction of the house if used in a structural manner. Fourth, fits the available relatively cheap digital fabrication technologies available through Fablabs and hacker spaces. The standard equipment provided by these labs are considered to be a defining factor to the development of the housing prototype as the intention is to democratize the means of production and make it available for low-income, low-cost construction.

The doctoral research proposes a housing design system that mainly consists of: an off-site prefabricated core that includes wet spaces; a set of modular parametric wall and floor/ceiling assemblies to account for the required design flexibility. The modular parametric design vocabulary is based on the concepts of “platform framing” which is the most prevalent method of light wood framing. In this kind of framing, the studs are interrupted at each floor level by the floor slab (platform).

In order to validate the viability of this design system, the research currently focuses on testing the structural performance of agricultural residue based sheets in the construction of integral joints and more specifically snap-fit joints. From an economic point of view, integral joining promotes cost savings due to the fact that the joint behaviour is attributed to its geometrical characteristics. No use of mechanical attachments and glue is protected.

The structural testing is in the planning phase. Single panels, wall, ceiling and floor assemblies shall be subject to compressive, tensile, concentrated and shear loads. The major part of the research will focus on the performance of these assemblies. This paper will attempt to answer the question of whether snap-fit joints can be used in a structural manner. If yes, what are the design criteria that can inform the design of the housing system?

This paper adds a semantic layer of knowledge to the design system for a housing unit through better understanding of assembly behaviour using agricultural residue panels. The designed snap fit joints will be revisited in the light of the Computer Numerical Control (CNC) fabrication technology and the building material used which is expected to behave differently compared to plywood or timber construction. With this understanding, an informed selection can be made of best performing joints and thus a more resilient construction based on local materials. This will eventually imply rethinking issues of tolerance, friction and assembly planning. The ultimate goal is to test the viability of the material and the construction system and whether it minimizes the cost and environmental impact of construction in developing countries.

Lascia un commento