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Sustainable Building Technologies for Mass Application H ousing is more than a basic need. It is both a cause and a consequence of many socio-economic changes. It represents a powerful intervening tool to foster Sustainable Development at household, community, regional and national levels. Housing activities not only improve living conditions, but stimulate livelihood opportunities also. Housing has been the largest employment sector and a truly decentralised industry, functioning at all possible scales: large, medium and small.The rate of growth of housing activities has increased considerably in the past decade (as compared to earlier decades). A growth rate of 25.08% in rural areas and 42.33% in urban areas was computed in 1981-91. This translates to 2.34% and 3.89% annual growth rate in rural and urban areas, respectively. In rural India, there is also a market shift in construction practices. The major change has been the increase in the use of pucca (instead of kutcha) materials in buildings. Census records of 1971 to 1991 highlight the transition in the quality of buildings and indicate an accelerating trend. Recent surveys confirm the growing use of permanent materials. By the next Census in 2001, it is expected that over 50% of the construction that has taken place in India would be with "pucca" materials, many of which are cement based. The market for such materials and technologies should comfortably grow by at least 10% per decade. This accelerated growth in buildings can be attributed to growing aspiration levels of people, increased earnings and the change in attitude to housing and other building construction practices. Trends in the rural sector also indicate a steady move towards more pucca construction, using industrially processed, energy intensive and therefore more expensive building materials and technologies. This, in itself, is a positive phenomena as it results in more durable shelter, leading to a positive improvement in the quality of life. However, it is unlikely that through this process, the aspirations of an increasing population will be met largely due to resource constraints. The demand for building materials can be evaluated on the basis that the housing gap will be closed by the year 2010 and by the year 2020, housing will finally be available for the estimated population of 1308 million. The present mix of building technologies will result in a three-fold increase in the energy consumption and resulting emissions in the three decades, 1990-2020. Contributions to these emissions are projected to increase from 81 million tonnes of Carbon dioxide to 285 million tonnes. For the construction sector, this scenario is equivalent to a 4.3% increase per annum and a doubling of emissions in terms of the per capita contribution. Clearly, such a trend is not sustainable within the national economy or in the global context.In a situation where the demand is expected to grow exponentially, the cumulative energy requirement for the four materials is expected to increase from 742 in 1989-1990 to 2363 PJ by 2020, under the technology-as-usual scenario. The introduction of Best Practices will have a net positive impact, reducing the energy consumption by 17 per cent to 2000 PJ, in the year 2020. The energy savings possible through technology improvement alone will not be able to sustain supply nor satisfy demand. Augmentation of Supply The reduction of emissions and a positive impact on resource efficiency can become significantly greater through the promotion of low energy building material alternatives and options which rely on the highly efficient use of energy intensive materials like cement and steel. There is evidence from various parts of India that new walling materials, timber substitutes and roofing alternatives can be adopted within a reasonable time frame and on a wide scale. For walling, stone cement blocks have been widely accepted in areas where burnt brick production is either no longer economically feasible or the cost of transportation has become excessive. Ferro-cement and micro-concrete roofing tiles have achieved wide acceptance in recent years, especially in areas where the stone crusher waste is locally available. The directives of the Supreme Court of India have also given an impetus to the acceptance of flyash brick, sand-lime bricks and Fal-G blocks. The choice of technology for further augmentation of supply will need to be region-specific, taking into account the building practices, raw materials and environmental imperatives.
Sustainable Building Technologies are needed regionally to respond to increased aspirations of people and ecosystem limits. Within the context of the national economy, present trends show a growth in the use of energy intensive building materials but with limited options. Sustainable Building Technologies can be defined within a context in relation to necessary and sufficient conditions that they must satisfy. These are: Diversity : The diversity of material use is crucial to ensure that no particular resource is stressed. It also ensures enlarged options leading to the choice of building materials and combinations of use. Efficiency : The productivity of land, material, capital and energy resources is crucial to define sustainbility. The productivity of critical resources needs to be prioritised regionally.
Quality : The quality parameter is used to determine the quality of services provided through the technology and also denotes the net value addition in the local economy.
At the national level, the distribution of households according to the roofing system and affordability is available in Census records. Trends indicate that very limited diversity exists due to the limited number of walling and roofing options in use. The growth is noticeable in the use of building options, which are resource intensive and high energy consuming. As an example, increase in walling is largely due to the usage of burnt bricks. In roofing, Asbestos Cement (ACC), Galvanised Iron (CGI) and Reinforced Cement Concrete show a runaway growth. These options exert a tremendous pressure on material and energy resources, particularly during the period of high economic growth. Specifically in the case of Bundelkhand, the available limited options demonstrate "supply gaps" in terms of affordability. Roofing options at par with stone slabs (and cheaper than RCC) can have a large pie of the growing market. The alternatives which are positioned in this segment include microconcrete roofing tiles and ferrocement roofing channels. Quality of Shelter and Efficiency of Resource Use It is clear from the previous section that multiplicity of material use for walling and roofing and the emerging trends in new material usage can extend the diversity. The existing wall-roof combinations on Bundelkhand which determine the quality of shelter, are cross tabulated with the total embodied energy used in material production. As an example, burnt brick walling is frequently used in combination with burnt country tiles (BTK-BCT) or clamp bricks in combination with stone slabs (Clamp-SS). These combinations are associated with high energy usage, yet they only provide a moderate quality of shelter. The combinations which exemplify change are clamp bricks and BTK bricks in conjunction with RCC roofing, Clamp-RCC and BTK-RCC, whose use is widespread in the region and growing nationally. These combinations are also responsible for enhancing the diversity. The analysis of existing shelter trends in the Bundelkhand region also illustrates the emergence of a very disturbing trend. Any perceptible change or improvement in the quality of shelter is presently realised by enhancing the resource utilisation and increasing the energy intensity of building materials. The examples of BTK-RCC combination illustrates that these trends of improving the quality of shelter with an increased energy intensity are widespread in the region. The energy intensive options are appropriated inspite of these techniques affecting livelihoods adversely. As an example, RCC uses steel and cement which barely contribute to the local economy. These trends are obviously promoted by interest groups, who have no interest in the improvement of local factor conditions. Building solutions which offer a better quality shelter, without impinging further on the resource base, are possible. A cross tabulation of all combinations that are based on local natural resources and those which can be derived from waste materials, has been done on the basis of quality and energy/resource usage. A factor of four lowering in energy is possible with Ferrocement roofing in combination with burnt bricks produced with Vertical Shaft Brick Kiln technology or indeed with Concrete Blocks. These combinations provide a high quality of shelter with equivalence in performance and cost to existing high energy options. These have been classified as Desirable Options in Table 1 given below. The new alternatives which can have great relevance in the region are based on Sustainable Production Systems. These systems make it possible to achieve a reduction in energy intensity. Simultaneous reduction in material resource intensities for wall-roof combinations can also be achieved to derive major savings in the resource usage. Equivalence in performance is possible through alternatives that have intrinsically lower material dependencies. The high and negative environmental impact of material combination is designated by the category Undesirable in the given tables. The situation, while improving the quality of shelter, can be easily redeemed by combinations presented in the Desirable category. Referring to table 1, it is evident that the combinations in the Desirable category are the most preferred ones, while the Undesirable category should be avoided and phased out. From the two low energy options mentioned earlier, the Benchmark for the region has been determined. The benchmark combination of Ferrocement roofing and Concrete Blocks for walling gives a high quality of shelter with low energy intensity and low resource intensity. Other low resource combinations, which ensure a good quality of shelter and promote the diversity, are Concrete Block walling with Stone slabs and Micro concrete for roofing. These systems have achieved a widescale social and market acceptability in the Bundelkhand region. Cumulatively, the sustainable building material enterprises are able to generate goods and services worth Rupees Fifty Million. This figure is doubling every year, with the distinct possibility of achieving further growth through partnerships with the cement industry. q
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