The use of traditional building materials and design is often found itself in a difficult situation, that is either being under the threat of perished under the force of modernisation or being innovatively implemented to meet modern building standards and living conditions. Traditional building materials and design have gained renewed attention in the green building movement, thanks to the use of locally accessible resources that address local conditions in a cost effective way.
Many traditional building materials have benefited from innovative technologies in both manufacture and application. These developments have made several traditional building materials more financially feasible, environmental friendly and technically sound. The following examples highlight practices and technologies that contribute toward mitigating climate change.
Earth-related building materials. In many non-urbanised areas in India, East Africa and South America, raw earth is abundant resource, which has popularly been used as building material. Over times, modern technologies have renovated the use of raw earth materials to improve their performance. For example, raw earth materials are converted into compressed earth blocks, made of a semi-dry mix of clay and sand and produced using a mechanised hydraulically compressed block machine. These blocks are reported to have a load-bearing strength two-thirds that of concrete masonry blocks (Mehta and Bridwell, 2004). A further improvement is achieved by mixing earth with a small percentage of cement during the production process to create compressed stabilised earth blocks. These blocks have better compressive strength and water resistance, and allow for thinner, higher walls to be built. Stabilised compressed blocks also take 3-5 times less energy to produce compared to conventional fired bricks (Auroville Earth Institute, 2009).
Stabilised rammed earth foundation is an innovative application of earth-related building materials. The soil, which is excavated from the trench foundation, is sieved and mixed with cement and sand to become construction materials for the building foundation. Stabilised rammed earth foundation has been reported to be used for buildings up to four storeys in height (Auroville Earth Institute, 2009).
Traditional Chinese practices of building orientation and interior space organisation were based on the belief of enhancing occupants’ health and wealth by tapping into the characteristics of natural materials and directional coordinates e.g., placement and orientation of windows, doorways, passages, interior and exterior layouts according to certain principles to promote positive ‘air and energy flow’ within a space. Such arrangements are believed to promote the positive health (mind and body) of occupants. The belief used to be criticised as having no scientific proof. However, recent research shows that many principles in these traditional practices of building orientation and interior space organisation are in line with certain sustainable building principles (Zhong and Ceranic, 2007). Furthermore, modern interpretations of certain traditional practices show that they are in line with the principles of sustainable building design. Some examples are highlighted in the next session – Feasibility of the technology and operational necessities.
Traditional building design strategies in the Mediterranean demonstrate that local wisdom involves designing with the local climatic conditions in mind. Traditional Mediterranean buildings are generally oriented to the south with a long east-west axis, to respond to solar direction and summer breeze. A courtyard and a solarium (an internal space adjoining the courtyard) act as climate moderator for the whole building, and are almost always found in Mediterranean traditional building. Some key functions of the courtyard include creating a microclimate, e.g., providing shade and evaporative cooling during summer, and allowing sunshine during winter through planting deciduous vegetation, high external wall, water features, etc.
Traditional Mediterranean buildings have thick walls which are built from stone and sun-dried mud-brick and rendered with mud plaster. These materials allow the thick wall to smooth out the large diurnal temperature variations in summer, and to act as thermal mass to warm up the internal space at night during winter. The walls are also painted in white (which can still be seen on buildings on Greek islands) to reflect the harsh solar radiation of the arid climate. Small windows are strategically located high on walls to foster cross ventilation during the summer, and are closed with small dense bushes (acting as thermal insulation) during winter. Deep recessed windows on walls and overhang from elements such as balconies act as sun shading devices (Lapithis, 2004).
Water-cooling envelope works based on evaporative cooling principle, in which the air temperature drops when the air volume takes up water by transforming it from liquid to vapour. The principle is applied through providing water film over the surface of building envelope, especially the roof, to bring down its temperature below the ambient air’s temperature. The roof surface will then act as a means for heat to be transmitted from inside the building to the ambient air. The process cools the air without increasing the humidity inside the room, and thus improves the room’s thermal comfort level.
Innovative implementations of this principle include the installation of water sprayers on the roof, or roofpond systems. The roof-pond system includes a water pond on the roof with operable reflective insulation. During hot summer days, the reflective insulation covers the whole pond and protects it from solar heat gain. The water body keeps receiving heat from the space below through the roof, and as such, cools the space below. During the summer night, the insulation is removed and the heat stored in the water body is released to the outdoor ambient air through evaporation, convection and radiation. During winter days, the insulation is removed so that the water and black surface of the roof absorbs solar radiation, and warms up the space below. During winter nights, the insulation covers the whole pond, so that the water body becomes thermal mass to keep the space below warm.
Another form of water-cooling envelope is found in some heritage Indian buildings, in which water pipes are installed inside the walls to cool the building. The application of water-cooling walls in the Lotus Mahalis an example. When the ambient temperature is higher, water in a storage tank is circulated in the hollow place inside the wall, and cools the building (Panasia Engineers, 2010).
Wind towers: also known as wind catchers, apply evaporative cooling principles inside a building to supply cool air to ventilate the internal space. Wind towers are traditionally used in the Middle East, where daytime air temperature is high and humidity is low. A typical traditional wind tower comprises an air inlet facing the prevailing wind direction to scoop the wind into a vertical shaft. Immediately behind and below the air inlet is an earthenware jar of water, which is taken up and transformed into vapour by the dry air wind. During this evaporative process, the air becomes cooler and sinks. This reinforces the air movement downward, providing a draft of cool air to the interior. After the whole day exchanging heat, the wind tower gets warm in the evening. Therefore, a reverse airflow pattern occurs during the night, when cooler room ambient air comes in contact with the bottom of the warm shaft, becomes warm and rises. Such air movement, while providing ventilation to the interior space, cools the surface of the tower to be ready for the next daytime operation. Renovations to the application of the traditional wind towers include the design of moveable air inlet, which can automatically track the wind direction for more constant cool air supply to the room (s), and the use of mechanical mist spray instead of water jars to reduce maintenance needs.
As most of the traditional building materials and technologies originate from rural settings, they are suitable for low-rise and low density settings. Renovation and the innovative use of such materials and design techniques keep them relevant to the modern building standards, to meet occupants’ aspiration for better lifestyles, and to overcome the engineering pitfalls, so that they can be applied in larger scale buildings to meet the global trend of urbanisation. To be main streamed, the renovation and innovative use of traditional building materials and design must meet more stringent building standards, especially requirements related to safety and environmental health.
Earth-related building materials. Soil types from different local contexts have different characteristics, which result in different load bearing strength, and require different ratio of mixture with cement and sand to reach certain strength performance. Prior to application in a building structure, it is crucial to research and test the performance of such materials to safeguard construction safety issues.
On the other hand, an important application requirement for a stabilised rammed earth foundation is that the width of the foundation is recommended to not be smaller than its depth. This is because earth has high compressed load bearing but is weak in terms of withstanding shearing forces. The force of the building’s walls, more so in columns, will create pointed loads on the foundation. These pointed loadscreate shearing loads at the bottom of the foundation. Therefore, a foundation section with a depth smaller than its width is weaker and can easily fail to sustain such shearing forces compared to a deeper foundation. A way to mitigate such loading issues is to reinforce the foundation with a sub-frame, such as metal, wood and bamboo.
Traditional building design strategies in the Mediterranean demonstrate a range of passive solar design strategies and techniques to bring environmental comfort to occupants. In a traditional Cyprus house, for example, the solarium and courtyard function as climate modifiers (Serghides, 2010). The solarium is an internal space, adjoining the courtyard. Its south elevation opens to facilitate the seasonal indooroutdoor flows of daily activities (e.g., cooking, washing, eating and so on). The south-facing overhang of the solarium is designed to allow winter sunlight to penetrate deep into the space. The south-facing courtyard acts as a sun space. Both the solarium and courtyard are made of high thermal mass materials, such as stone paving, adobe walls, stone staircase and pools, to create a more pleasant microclimate along the long front facade of the house. The front wall of the courtyard also acts as buffer to cold winds. During summer, planting and soft-scape in the courtyard provide shade and a cool microclimate in front of the house. The pool and fountain in the courtyard provide evaporative cooling. The designs of arches, overhangs and openings on the wall facing the courtyard help channel summer breezes into the house. Openings are small on the east- and west- facing walls to avoid hot summer sun. Thermal mass materials in the courtyard and solarium absorb the heat during the day and release back to the ambient air at night effectively due to the large diurnal fluctuations of temperature in the hot arid Mediterranean region.
Traditional Chinese practices of building orientation and internal spatial arrangement require a good understanding of the logic behind each principle in order to maximise the environmental performance benefits scientifically. For example, one of the traditional practices describes that it is ideal for a house to have its front orientated toward a water body to the south, and the rear of the house backed by a hill slope on the north. Mapping this approach to the climatic conditions in many regions in China shows that:
- The prevailing winter wind direction in general comes from the north. Therefore, the hill slope on the north protects the house from cold winter wind
- Due to the northern latitude location, sunlight accessibility comes from the south. Therefore, by orientating the front of the house with windows facing south, low-angle winter sunlight can penetrate deep into the interior, providing natural warming effect, and enhancing thermal comfort for the occupants
- The prevailing summer wind direction generally comes from the south. Together with a water body, the wind creates a more comfortable microclimate, enhanced by evaporative cooling in front of and surrounding the house.
Water-cooling envelope is ideal for hot and arid regions, such as north-western India, However, it is less effective when applied in the hot and humid regions within the tropical belt. The reason is that the high humidity in the air reduces the effect of evaporation, and that the variation of outdoor air temperatures between the day and the night is minimal. As the water-cooling envelope in the roof surface is constantly in direct contact with water, a good roof water-proofing system is required. In the case of roof-pond system, it is important for users to understand the system’s operational logic, so that the system can function as intended.
Wind towers do not function in hot and humid regions, due to the high humidity of the outdoor ambient air. They are highly applicable in hot and arid climatic regions such as the Middle East, Sub-Saharan Africa, and north-western India. The dry air and the wide range of day and night temperature are key to the function of wind towers. Wind towers require frequent maintenance to keep the water jar clean, to refill water, and prevent birds nesting in the tower.
Feasibility for implementation
The implementation of traditional building materials and design has already taken place at a local level at many regions in the world. However, the pressure of urbanisation and the aspiration of living in modern houses with modern materials, finishes and technologies have led to the gradually phasing out of such materials and design. Innovative use of such materials and design help keep them upgraded to meet the new demands and expectations. In such context, the main challenge for large-scale implementation is to overcome the negative perception of such innovative use of traditional building materials. For example, earth-related materials are often perceived as building materials for the poor.
Capacity building and re-education is required for local architects, engineers and constructors in order to broaden the adoption of these practices. To do so, good pilot projects to demonstrate the quality and performance of such materials and design are useful. Such demonstration projects can be initiated by local governments or NGOs in collaboration with the private sector and supported by local government. The second model has been reported to be popular and effective in Africa, where NGOs take on the liaison role between government agencies and the local communities. NGO involvement helps reduce bureaucracy and free the government agencies from the day-to-day running of the project (Mehta and Bridwell, 2004). Capacity building and training workshops are useful and can be held by NGOs to upskill local work forces on new techniques and innovative applications of traditional building materials and design. The operations of NGOs will be more fruitful with supportive government policies.
The implementation status of renovation and the innovative use of traditional building materials and design, varies depending on the individual techniques and practices in a particular local context. Some are thriving and others are under threat of being lost. As most of the traditional building materials and design originate from rural settlements and are suitable for low-rise and low density settings, they are becoming obsolete under the pressure of urbanisation, particularly in developing countries. Although their renovation and innovative use can help modernise their quality and application, the results have certain limits. Below are some observations regarding the implementation status and market penetration of renovation and the innovative use of traditional building materials and designs:
- If a rural area is earmarked to be urbanised to become a small town (e.g., those with building height of about 3-4 storeys), earth-related building materials can thrive if their quality, performance and aesthetic quality stay close to those of masonry products. The lower cost and availability of local resources help them stay competitive. Water-cooling envelope, Mediterranean design principles, wind towers and the traditional Chinese practice of building orientation and interior space organisation may stay relevant.
- If a local area is earmarked to be urbanised to a medium to high density town/city, it is difficult to implement earth-related materials. Furthermore, raw materials such as soil and vegetation may be less abundant or no longer available locally. The traditional Chinese practice of building orientation and interior space organisation (thanks to its indoor application component), is largely unaffected by higher density urbanisation and is still applicable in such context. Likewise, the traditional Mediterranean design principles, i.e., thicker walls (especially on the east and west facing walls), solarium and courtyard, overhang, balcony, etc. – also remain relevant in a higher density urban context.
- From a lateral inter-regional relationship perspective, there is a huge potential for South-South transfer, especially between regions with similar climatic conditions, for most renovation and innovative use of traditional building materials and design. This is largely due to similarity in local materials i.e., soil, sand, wood and bamboo – available in most regions. What needs to be transferred are the principles, technical skills and equipment.
Innovative use of traditional building materials and design are relevant and beneficial to developing countries, especially least developed countries, because of the following characteristics:
- Well-established and proven technologies and practices, which are updated for better performance and innovatively used for wider application in the local context, where they are implemented
- Appropriate to local climatic conditions, and as such being energy efficient with little effort
- Using locally available and accessible resources, to reduce the need for transporting materials from afar
- Nurturing local building material manufacturers
- Alleviating shortages of construction materials for certain regions and nations during construction boom periods
- Providing job opportunities for local work forces, whose skills and experience are readily relevant, due to the familiarity to the materials and techniques involved.
- Low-cost to no-additional cost for implementation
- Resulting buildings that are socially and culturally familiar to the users.
Appropriate renovation and innovative use of traditional building materials and design usually require no additional to very little additional financial investment, due to the readiness of local work forces and availability of local resources. For example, compressed earth blocks or stabilised rammed earth foundations are the main material sources for many low-cost but good quality houses in rural India and Africa. The implementation of wind towers and water-cooling envelopes require financial arrangements for additional construction costs and maintenance. The traditional Chinese practices of building orientation and internal spatial arrangement are cost-free to implement, as these practices and techniques do not require additional technologies or materials to be implemented.
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