PRIMARY ENERGY ESTIMATION FOR CONTEMPORARY HOUSING IN NORTHERN INDIA

Abstract

The construction sector is an important part of the Indian economy and makes a significant contribution to its development. But it is also a major consumer of energy, mainly required for the production of building materials, alongwith their transportation to and use at the site of construction. There is also a rising demand for building materials, primarily due to housing, since it accounts for nearly 60% ofthe materials consumed by the construction sector in India. Moreover, the pressing need for housing in India cannot be met by the existing supply ofbuilding materials. Therefore, it is imperative to: L Check the energy consumption of the construction sector by reducing the energy needed for construction 2. Provide larger quantities of building materials to meet their increasing demand Both these objectives can be achieved by providing energy efficient substitutes for the conventional building materials. These alternatives will help to reduce the energy required in construction. Moreover, it will be possible to manufacture larger quantities of such materials within the existing levels of energy consumption of the construction sector. Since housing is the single largest segment ofthis sector, therefore it shall be the focus ofthis study. Energy consumption can only be reduced by first estimating the energy required for construction, termed as the Construction Energy Cost (CEC). The CEC comprises of: !• Primary Energy Cost fPECY i.e., the energy cost of civil work, which has the following components: A. Total Embodied Energy Cost of civil work (EECr) includes the total energy embodied in the building materials, i.e., the sum of the energy needed to quarry the raw materials, transport them to the manufacturing units, manufacture the building materials and transport the materials to the distribution outlets. B. Total Transport Energy Cost of civil work (TECj) includes the total energy required for transporting the building materials from the distribution outlet to the site of construction. 2. Secondary Energy Cost (SEC), which consists of the energy consumed in the construction work on site, the energy needed for the installation of electrical and sanitary fixtures, the energy needed for providing the infrastructure for the project and the energy consumed by the workers engaged in the construction work Therefore, CEC - PEC+ SEC Where, PEC - EECT + TECT Studies have shown that PEC is the larger component, generally accounting for nearly 80% of the CEC. Therefore, any reduction in the PEC will result in substantial savings in the CEC. The aim of this research is, therefore, to estimate the PEC in housing construction and to study alternatives for its reduction. The scope of the work is restricted to the contemporary housing in the plains of Northern India. The literature survey reveals that limited research has been done to determine the PEC. In India, researchers have obtained the energy values of building materials and carried out energy analysis of building components and some items of civil work, but no method has been developed so far to estimate the PEC of complete dwellings. Therefore, a methodology has been developed in the present study for estimating the PEC, which can be directly applied to any housing. The approach that has been evolved is to estimate the energy components of the PEC, viz., the EECT and the TECT, by adopting the same format that is used for estimating the construction cost of civil work, i.e., the detailed cost estimate. Both EECT and TECT estimates have been prepared and totalled to give the PEC of any given dwelling or project. The Embodied Energy Rates (EER) to estimate the EECT and the Transport Energy Rates (TER) for estimating the TECT have been computed. A 'Schedule of Energy Rates' has been compiled, listing the EER and TER. This methodology for estimating the PEC has been applied to sixteen case studies ranging from single and double storeyed dwelling units to four storeyed housing projects. The single and double storeyed units are all in load bearing construction, whereas the four storeyed housing projects are both in load bearing and RCC structural frames. Detailed PEC estimates have been prepared for all the projects, which reveal that masonry and RCC work are the major determiners ofPEC for all the projects. Bricks and reinforcing steel, which are the main constituents of the masonry and RCC work, have an average combined share of 60% in the PEC. Masonry work is found to be the single largest contributor to the PEC for nearly all the projects. The reason for its high energy and cost share is the use of traditional burnt clay bricks. They alone account for upto 80-85% in the energy share of the masonry work in the PEC. The energy rates of all the projects have also been obtained. These reveal that the double storeyed load bearing housing construction has the lowest range of energy rates ofthe types that have been studied for the North Indian plains, whereas this range is the highest for single storeyed load bearing units. The energy rates of the typical Indian projects studied are found to be comparable to those obtained by other authors internationally. Both linear and quadratic Equations have been derived for providing a preliminary PEC estimate of any dwelling or project for a given plinth or floor area in the studied categories. The suitability of these Equations has been examined by computing the percentage deviations of the PEC obtained from them vis-a-vis the actual values from the detailed estimates. Since masonry work is the single largest contributor to the PEC, it has been selected to study the energy savings that can be achieved by using alternatives. The results show that there is a fall of upto 35% in the PEC by using alternatives to the traditional bricks. Aerated or hollow concrete blocks (40 cm x 20 cm x 20 cm) with 1:6 cement mortar (1 cement: 6 fine sand) give energy savings in the range of 25-35% over traditional brick masonry, whereas masonry work in 1:6 cement mortar and clay flyash bricks or Fal-G blocks give energy savings of 15- 25%. Other masonry units also provide energy savings, which range from as low as about 1.5% (using modular bricks) to as high as 23% (using solid concrete blocks). 1:6 cement mortar (1 cement: 6 fine sand) has the least energy value of all the mortar mixes considered. Equations have also been derived for estimating the PEC of housing construction using the most suitable alternatives. The reduction in energy cost means that, PEC remaining constant, more volume of masonry work can be achieved by replacing traditional bricks with these energy efficient alternatives. The added advantage is that materials like clay flyash bricks utilise flyash, thus reducing its ecological hazard. Moreover, replacement of clay with flyash saves topsoil and hence, prime agricultural land. Further secondary energy savings occur in the plastering work because the mechanically produced alternate masonry units give fairly smooth external and internal wall surfaces due to their uniform shape and size, thus reducing the quantity of plastering needed for satisfactory coverage. New light weight materials donot cause a major change in the PEC of housing construction in traditional brick masonry. But, since they show little change in the PEC of the projects (except for PVC), they can be suitable in a future scenario when bricks may not be sufficient to meet the growing demand. It is evident from the foregoing discussion that the construction work using substitutes will compare favourably with traditional brick construction, particularly if the alternate masonry units are manufactured and used on a mass scale. Moreover, masonry work utilising bigger units like hollow concrete blocks (40cm x 20cm x 20cm) and aerated concrete blocks have the added advantage of having fewer joints, resulting in considerable savings in the mortar requirement. Thus, the energy required by the construction sector will be checked, particularly with regard to housing, which is its single largest segment. The demand for more building materials for housing construction will also be met within the existing levels of its energy consumption and within the contemporary methods of construction.