Sun-dried earth blocks was used in construction approximately 8000 B.C and it is estimated that earth-based shelters house about 50% of the world’s population [22]. Earth has been most widely used construction material in many developing countries and continues to be the major means of construction [18]. According to Schroeder & Lemke [25], earth building materials has less negative impact on the environment, they are inherently energy efficient compared to other building materials, and less risky on people health. Earth construction, for example, consumes less non-renewable energy than fired masonry, concrete blockwork and heat/humidity buffering [4]. According to Reddy et al [23], in modern interpretations, earth as a construction material has negligible life-cycle impact, is completely recyclable, and it contributes almost zero-carbon footprint.
Earth is not only environmentally viable; it is also cheaper, available in large quantities and easy to work with especially forming into building components [1]. In other words, earth construction carries many economic benefits and a primary reason for adopting contemporary earth construction is that it can address urban housing crises, especially in developing countries where it is readily embraced [29]. Interest in earth construction in developed countries, by contrast, is more often driven by potential environmental gains as opposed to its economic value. In order to achieve overarching purpose of this study of informing the diverse benefits of earth material to construction practitioners, this study aims to identify and explore the wide range of benefits associated with earth construction in UK urban housing. Considering the exploratory nature of these aims, the study begins with a critical review of relevant literature on the advantages of earth material as a primary construction material. Furthermore, the paper analyses and validates these benefits through empirical research methodology including the Delphi technique and in-depth interviews - a process in which findings in literature are compared and contrasted against the perspectives of professionals in the field (i.e. construction professionals) through questionnaires and interviews.
According to Houben & Guillaud [11], through modern construction methods, earth is typically stabilised through three major processes:
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Physically by modifying the percentage of mixed soil particles and texture of the earth by varying soil ingredients.
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Chemically by mixing chemicals (stabilisers, such as, cement, lime, gypsum, fly ash, etc.) or other materials to modify the properties of the soil.
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Mechanically by applying force directly onto the soil compressing or ramming. It alters the permeability, density, durability, strength, compressibility, and porosity of the earth.
Therefore, earth stabilisation must not be understood as only mixing cement with it. However, the benefits of using earth as building material are many, as summarised in Table 1, which presents an in-depth summary of the generic benefits of earth material as identified in literature.
Table 1
Advantages of earth as building material [30, 31].
Benefits/Advantages of earth as building material
(summarised review of the literature)
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Authors
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1. Use of earth is economically advantageous.
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[8, 28, 20, 13, 5, 27, 10, 18, 1, 17, 19, 14, 11, 12, 3, 21, 9]
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2. Earth construction use simple tools and unskilled labour.
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3. It promotes housing construction in the form of ‘self-help’.
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4. Earth can build extra secured and strong structures.
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5. Earth material has low embodied energy; therefore, considered as energy saver.
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6. Naturally balance interior temperature and humidity in an earth building.
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7. It is fire resistant.
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8. It creates employment opportunity.
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9. Earth is considered as sustainable building material.
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10. Earth walls preserve organic materials, such as timber.
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11. Pollutants are absorbed by earth wall.
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12. Designing with earth is easy and can produce building with high aesthetic value.
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13. Earth wall possess high insulation property, therefore, excellent in controlling noise.
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14. Earth is local building material; therefore, it promotes heritage, tradition and cultural practice.
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15. It is available worldwide in abundance.
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As shown in Table 1, a major focus of research to date has been on economic benefits associated with contemporary earth construction. However, researcher Sanya [24] stated that economic advantage of earth is not always be achieved. Given conflicting views on the economic viability of earth construction, it is pertinent to investigate this benefit in more detail. Environmental benefits also dominate current literature sources, particularly with regard to certain contexts. In India, for example, studies have shown that one m2 CSEB construction of masonry consumes five times less energy than one m2 of wire cut fired brick masonry and fifteen times less than country fired bricks [17]. Maini [17] also states that CSEBs are eco-friendlier than fired bricks and consume less energy and pollutes less air during manufacturing than fired bricks. Further to this, Adam and Agib [1] emphasize how processing and handling soil requires low energy input; the author referred to a study (Desert Architecture Unit) and stated that 36 MJ (10 kwh) energy is consumed in the production of one m3 of earth, whereas 3000 MJ (833 kwh) energy is consumed in the production one m3 of concrete.
Schroeder and Lemke [25] systematically explain and illustrates how earth construction can become self-sustaining. The soil is collected/extracted from the ground with its natural state; preparation such as classification, pulverisation, drying is done with its aim to be used in the construction. Thereafter, the soil is used to complete the building. The earth building last long time, however, in the case of demolition the earth building goes back to the ground, thereafter can be reused and recycled as earthen materials. This is how the life cycle of earth becomes self-sustaining. In this way, earth material is ecologically advantageous. As research emphasizes, contemporary earth construction is often more economically and environmentally sustainable than conventional building materials (i.e. fired brick and concrete) and may play a fundamental role in cutting excessive CO2 emissions in the urban housing projects. A critical review of existing literature, however, reveals that sparse research so far carried out that identifies, explores and analyses the advantage of earth material specifically in the case of UK urban housing. Benefits mentioned by various construction professionals and authors in literature are also, more often than not, anecdotal and based on individual perceptions; thus, empirical data is lacking and refining of data via rigorous scientific processes. Responding to the need for informing the benefits of contemporary earth construction to UK professionals, therefore, this study aims to identify the benefits in UK context.