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A second life for used clothes: From the wardrobe to a building’s façade

MÒNICA ARDANUY. Professor of Textile Engineering, Department of Materials Science and Engineering, Universitat Politècnica de Catalunya · BarcelonaTech

HEURA VENTURA. Professor of Textile Engineering, Department of Materials Science and Engineering, Universitat Politècnica de Catalunya · BarcelonaTech

JOSEP CLARAMUNT BLANES. Associate professor, Universitat Politècnica de Catalunya · BarcelonaTech

The amount of clothes waste generated worldwide is between 35 and 95 tonnes annually. This is an enormous amount, complicated by the added difficulty of separating the elements that have been sewn on (such as buttons and zips) and the types of fibres by their composition. Consequently, most textile waste ends up in dumps or incinerators.

The TECTEX research group of the Universitat Politècnica de Catalunya has designed a process to use this waste as a new construction material.

Our common future

This year marks thirty-five years since the publication of the report Our Common Future, better known as the  Bruntland Report. This report, backed by the United Nations, defines sustainable development as that which meets the needs of the present without compromising the needs of future generations.

However, under this simple definition is a concept that is hard to quantify. Although the sustainability of a product or service can be compared with that of another, it is hard to determine the absolute value of its sustainability.

In any case, 35 years of reflection on this topic have served to raise social awareness of the importance of preserving the environment.

Construction: a key sector in sustainability

All sectors are now developing environmental awareness. Among them, the construction sector is key for improving sustainability overall.

Construction is responsible for approximately 35% of carbon dioxide emissions, 40% of energy consumption and 45% of solid waste in the European Union.

This calculation includes the entire life cycle of buildings, from their construction to their demolition, as well as their use. In fact, the use phase has the greatest environmental impact.

Much of the energy consumption and carbon dioxide emissions are produced during this phase. Therefore, in recent years, the strategy to improve sustainability in the sector has focused on taking measures relating to the use phase of constructions.

Current regulations on air conditioning and energy consumption of buildings are stricter. This has led to an improvement in thermal insulation, greater use of renewable energies and a reduction in electricity consumption. Due to this effort, environmental impacts have been considerably reduced in the use phase. However, they must continue to be reduced in all phases of construction.

How can we continue to improve sustainability in the construction sector?

One way to continue to improve the sustainability of buildings is to reduce the impact of construction materials.

The current strategy is focused on reducing the energy of production processes and the use of more sustainable materials. These materials include renewable and recyclable materials and those from waste recovery.

This last option allows waste to be reincorporated that would otherwise accumulate in dumps or be dispersed in the environment. This multiplies the environmental benefits.

More sectors adhere to sustainability

Another key sector for improving sustainability in general is that of textiles. In fact, the fashion sector is developing awareness of the problem and moving towards sustainability. One of the challenges faced by this sector is how to manage the large amount of waste that is generated.

Worldwide, waste from clothes stands at between 35 and 95 million tonnes annually. In addition to representing an enormous quantity, there is the added difficulty of separating elements that have been sewn on (such as buttons and zips) and types of fibres depending on their composition. Consequently, most textile waste ends up in dumps or incinerators.

From textile waste to material for the façades of our buildings

In this situation, the TECTEX research group of the Universitat Politècnica de Catalunya has proposed a new construction material that uses textiles. The material (developed at laboratory scale) includes in its composition binders and mineral loads as well as textile waste. Its characteristics and properties are optimal for its use as rendering of ventilated façades. It could also be used as floating flooring, acoustic false ceilings, drywall and in other similar applications.

Laminado de cemento con refuerzo textil

The ventilated façade is a modern construction solution that is derived from the old mode of English construction called a cavity wall. To meet comfort needs, British buildings evolved towards solutions that have been adapted and consolidated worldwide.

Their façades are formed by several continuous layers, as if they were onions. Normally, they have an inner layer, an insulation system to protect against humidity and temperature, a ventilated air chamber and an exterior layer of protection.

This last layer mitigates thermal changes and avoids solar radiation. Consequently, it should be constructed of a light, resistant material that can reduce to a minimum the required support structure.

In this context, the material developed by TECTEX has great potential. The solution meets these characteristics as it combines lightness and the resistance provided by the textile reinforcement. This reinforcement also improves the thermal insulation capacity and acoustic absorption. In addition, this material can incorporate other functions such as self-cleaning or thermal absorption, which can be obtained by including special additives.

Manufacturing process and properties of the material

The material developed is based on waste of triturated textiles that, after a mechanical, low energy process without the addition of chemical products, ends up forming a thin felt. In addition, a paste is created based on cement and mineral loads. Afterwards, the fibre mats are mixed with paste and piled up in layers formed of laminates with thicknesses between one and two centimetres, depending on the final application.

Immediately afterwards, the laminate is compacted to reduce the porosity and improve the adherence between the paste and the textile reinforcement. Finally, the material is put into a curing chamber so that the paste hardens.

For the ventilated façade plates, the ideal binder is cement, as it withstands the elements better. However, other types of more sustainable binders are studied such as limescale or mineral polymers.

The result of this process is a very light material with good resistance to flexion and impact. By way of comparison, it withstands flexion to the same extent as compact stone or better quality brick. In terms of impact, its resistance is a hundred times higher than either of them. In addition, a façade built with natural stone weighs five times more and one made of cement weighs twice as much.

However, the most important factor is that a building such as Casa Milà (La Pedrera), the last civil work by Antoni Gaudí, could be clothed in waste equivalent to over eight thousand shirts.

This article was originally published in The Conversation.