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«CSAAR (7: 2010: Amman) Sustainable Architecture and Urban Development \ Edited by Steffen Lehmann, Husam Al Waer, Jamal AI-Qawasmi. Amman: The Center ...»

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The formwork may have varying dimensions, in the Draa Valley has an average size of200 cm in length, 80 cm in height and a width varying from 60 to 100 cm depending on the height of the building; the height of the plans depends on a finite number of rammed earth blocks. The rammed earth walls behave monolithically, the mass gives stability and strength but low ductility for the response to the earthquake. Thermal inertia is directly proportional to the thickness, these walls are therefore particularly suitable for very hot climates or characterized by extreme temperature changes, as in the pre-desert c\imate. For the rammed earth, the material preparation and its implementation coincide. The material transformation is totally in the yard and requires technical knowledge that is acquired through experience, since the wall performance will depend entirely on the choice of earth, by mixing and its implementation (Baglioni, 2009, pp. 61-67 & 96-105). The earth required for the rammed earth must be weH graded, with gravel, sand, silt and an optimum clay percentage of 20%. The earth is mixed with water in varying percentages, between 4 and 18%, according to the type of earth used, and let repose for at least 2 days before being placed in work. The cohesive effect isn 't entrusted only to the clay but also to compaction during implementation. The rammed earth geographical diffusion and the luck along the time are due at least three factors: the ease of finding a suitable soil type, the low amount of water compared to other earth construction techniques or concrete; the reducing use of other natural materials Iike wood. By contrast this technique requires a large amount of earth and long lead times due to drying.

Sustainable Architecture and Urban Oevelopment The mud bricks are sun-dried blocks of earth, shaped in wooden molds. The block sizes vary widely according to local building traditions, though usually resort to a width equal to half length and height equal to a half width. The earth must be carefully selected, rich in c\ay (at least 40%) and without gravel. It adds a lot of water until obtain a malleable and plastic dough that is left to rest for at least 2 days. Oue to the large amount of c\ay and water, the mixture is subjected to a strong withdrawal during drying, to limit the effect is generally added straw or other fibers (vegetab1e or animals). The mud bricks are formed by hand into the molds and allowed to dry in a large sunny area, turning on all sides; once dried can be stored and used later. The drying phase is critical for the mud brick success, it must be smooth and would be better not expose them to direct radiation at least in the early days; the drying times vary according to c\imate and seasons, from 2-3 days in summer and 10-15 days in winter.

238 Eliana Baglioni The mud brick wall realization follows the same construction rules of a traditional masonry: the adobes are put in place, at 2-3 or 4 heads, with a earth mortar generally achieved with the same dough; you can build relatively thick walls (min. 30 cm) with a strong inertia, but from a low response to the earthquake, behaving so fragile. The vegetable fiber addition to the mixture improves the material tensile strength, but doesn't make it structurally resistant to this etfort. The mud bricks walls are characterized by high thermal inertia due to the high specific gravity and therefore turn out particularly suitable in the areas with high climatic temperature range. In the Draa Valley the mud bricks are used where the rammed earth masonry is difficult or inappropriate: in the upper floors, where carry the dough is difficult and tiring; as astring course to complete the thickness of the wooden floor; above the doors and windows Iintels where press the earth isn 't recommended, but is in the pillars and walls of the patio that the mud bricks plays its prince role, pushing up its bearing and decorative capacity (Baglioni, 2009, pp. 68-71 & 106-119).

In the earth masonries, whatever they are, a key role is played by basements, preferably on stone or brick, which have the principal function to limit the capillary rise ofmoisture from the soil (Baglioni, 2009, pp. 88-95).

In the Draa Valley, the earth is an essential element of almost every technological solution, pIasters and mortars are made with earth, floor and roofs are made of palm wood structure, which is superimposed a reed and various Sustainable Architecture and Urban Developmcnt layers of pressed earth. Regarding the floor plan we have two layers of clay earth, both ofthickness of about 5 cm, the first is dry and the second is wet. The roof, having to perform the protecting function of the entire building from the weather, differs in quantity and quality of the earth layers and, thus, in the thickness. The package consists of three layers of clay, each of thickness of 5 cm, with different functions and made with different mixtures. The first layer is made with a mixture similar to the rammed earth mixture, so humid, but prepared with a finer earth; the second layer is dry and its function is to absorb water infiltration when the top layer doesn't had a perfect seal. The last layer, in addition to finishing function, must be waterproof, it's therefore done with a moist mixturc of earth and Iime or earth and straw. Lime is a natural stabilizer which makes the clay waterproof and, on ce dry, makes the dough more resistant.

The roof needs frequent maintenance because it's subject to degradation caused by rain, wind and sandstorms. Maintenance is performed every 4 or 5 years, creating a new layer above the existing finish. (Baglioni, 2009, pp. 141-151).

The date palm is the backbone of the pre-Saharan oases ecosystem and marks the border between the Sahara and the Mediterranean culture. As the only wooden materials usable in eonstruction field, is used to achieve the doors and windows lintels and the horizontal structures of the floors. Its meehanical performance are low, because its trunk consists of bundles of parallel fibers that.

subjected to loads, doesn 't ensure effective mutual cooperation and suffer intense inflections. The problem is then content and controlled maintaining the lights relatively smalI, generally 2 to 2.5 m (up to 4 m); dimension that becomes areal module for any building construction (Baglioni, 2009, pp. 84-85).

Let's see how all the materials used are natural, readily available on site and present in large quantities.

The raw earth housing yard are traditional and managed by small artisan "company" consist of a master chief, called maälem, and a variable number of workers or laborers, but no more than a few units. The working tools are proportional to the type of yard, traditional and craftsmanship (Baglioni, 2009, pp. 73-79).

Sustainability of these techniques is also in the use of local workers and often in the family participation at the construction process.

Unfortunately, in the Valley, we are seeing a gradual abandonment of row earth patio hornes in favour of houses increasingly built with concrete blocks, which retain, however, the patio type. The use of cement is spreading because it's considered index of development and progress, although, in this context, is often the bearer of eompletely inadequate results to the local environmental conditions. The conerete, in fact, unlike the earth, doesn't guarantees the maintenance of a climatie eomfort inside the horne, creating rooms hot in summer and cold in winter. These data are demonstrated by the fact that the 240 Eliana Baglioni inhabitants of the concrete houses suffering from rheumatism in the winter and move into the earthen houses in summer, because are more fresh.

The Benefits and Potentiality of The Earth Construction Material At the point of views of sustainable building, of energy saving and safeguarding of the planet, the earth, too often underestimated because it's considered a poor material and bound only to the rural environment, presents, on the contrary, many advantages that should help his re-entry among contemporary building materials. Firstly, it's a readily available material on almost all the Planet, as witnessed by its wide use in the vemacular architecture of the most different regions. Although there has been made, in relatively recent times, studies on optimum earth used for construction, the large existing built heritage, often centuries old, shows the great adaptability of earth to be used for constructive purposes. The man, moreover, has always been "engineer" to improve the performance of the available material, making mixtures between different types of earth or additive the mixtures with other "ingredients" mainly from natural sources (straw, vegetables and animal fibers, rice hulls, sawdust, dung, succulent plants extracts, casein, lime, graphite, bitumen, cement, etc.). The earth is an ecological and completely recyc1able material, is reusable both in construction that maybe in the agricultural field, in fact, the earthen buildings, if left to themselves, co me back to be earth. The earth allows a great variety of different technologies (rammed earth, mud brick, wattle and daub, cob, straw-earth, wood­ earth, etc.) all providing low water-consuming for the dough production. The production and installation of earthen techniques, don't require special skills and can therefore be made on site and using local human resources.

This has many advantages: a low product cost and a low energy consumption for its production, a minimum consumption of non-renewable resources, but especially the opportunity to train local workers and so create new skills or new jobs. Another advantage is the possibility to have a economic constructive process and to ensure the maximum respect of the local building techniques, achieving a better integration of new structures in urban and social context, avoiding the imposition of new forms and new systems. The earth also provides very good c1imatic performance, acting as a natural temperature and humidity regulator. The material inertia makes the heat absorbed from the wall are distributed in the interior within a considerable displacement time: at a constant temperature the effect isn't evident, but in c1imates with high day-night temperature excursion the heat accumulated during the day is dispersed at night and the moming the wall is cool again, the phenomenon is also reflected in the season. The earth is also a humidity regulator, able to absorb the air humidity and dropping it when the environment becomes drier. These properties mean that the rooms inside earthen walls, are healthy and have comfortable and constant c1imatic conditions in all seasons. Finally the earth has a good resistance to the fire and can easily be "restore" because it's enough to produce a earth mixtures similar to the originals for compensate any cracks.

Sustainable Architecture and Urban Development Unfortunately, the prejudices on this material are still very rooted because it's considered a vulnerable materials. In fact the only earth vulnerability is water, wh ich can be easily solved with the implementation of appropriate bases and covers, with the use of efficient rainwater removal (guttering and downpipes), and with the possible addition of "stabilizers" materials to improve the performance. A key role, in the protection to the water, is played by the piaster, also made with clay, which must be frequently maintained and renewed.

4 Conclusions: The Actualization Of Traditional Building Techniques [s undeniable that the traditional hornes, alone, they can't cover some new social and housing demands, but the solution isn 't necessarily in abandoning or on imposing different lifestyles related to the modemity stereotypes. A clever solution would be respect local diversity, recognized as adequate and sustainable, continuing the "natural" process improvement to adapt to new needs (social, environmental, economic, regulatory, etc.).

As regards new buildings, in this quest for sustainability, during the design and planning phase should be used functional principles and technological building systems that can reduce substantially the energy consumption and the waste generated from the production, construction and life of the building, should also plan the disposal step and the recycling and reuse of materials. It's important that each house is worthy and healthy, that are used healthy materials and not harmful to human health, which takes into account the comfort conditions (lighting, ventilation, humidity, sunshine, clean water, sewer, disposal waste, etc.). and that you respect the cultural, economic and social diversity.

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