Embodied energy demystified
Air-conditioners and water heaters were the biggest energy guzzlers in his house, believed Atul Prakash until he was told about the energy footprint of his recently purchased house. The senior analyst at a Hyderabad-based multinational company was shocked to know that when he took possession of the house, it had already consumed the energy a house usually consumes during its life cycle of about 80 years.
Appliances consume energy to operate, but materials used in the construction of buildings consume energy, too. Embodied energy, or EE, is the sum of all energy used in the construction process—right from extraction of raw materials, manufacture of products to their transportation and incorporation in buildings.
Lesser the extraction, processing and refining, lower is the EE, and greener the product. People hassle more over reducing operational energy, or energy used to operate equipment, because it affects their day-to-day lives. EE is intangible and, therefore, largely neglected. EE of any building can be less than or greater than its operational energy. If a building is highly conditioned through artificial means, its operational energy can be more than EE.
But assessing EE accurately is difficult, says B V V Reddy, professor at the Indian Institute of Science, Bengaluru. This is because energy consumed in the making of a building material is documented only till the factory gate. From there, the material can traverse several areas and keeping track is not easy.
Researcher G Ding of University of Technology, Sydney, found that EE of a residential building is in 3,600-8,760 megajoules per square metre (MJ/m2) range and that of a commercial building is 3,400-19,000 MJ/m2.
Major EE contributors
Cement, steel and bricks, the basic construction materials, are the major EE contributors. Their use can be reduced only to an extent. Materials like ceramic and vitrified tiles, which are highly energy intensive, can be easily replaced with energy-benign materials like stone.
Transportation also has a sizable contribution to EE. Delhi-based architect Deepandra Prashad says fly ash brick has less EE compared to stabilised earth block. But it loses its green edge if it travels more than 50 km. It’s the same with green building materials like bamboo and mud.
About 25 per cent of India’s total primary energy demand is attributed to manufacture of building materials, says Reddy. Another 15 per cent is to operate them. Buildings account for the largest energy and ecological footprint. Globally, buildings consume one-third of the world’s resources. In India, the construction sector adds 30 per cent of the greenhouse gas emissions, states a 2007 report by the Indian Network for Climate Change Assessment. Companies claim they offset carbon emissions by taking steps such as planting trees and installing energy-saving bulbs in villages. While such steps are commendable, most companies do this to claim green credentials for products that are harmful to people and environment.
To make our surroundings environment-friendly, Indian regulators are pushing for energy-efficient buildings with tools like energy conservation building code (ECBC). But it does not take into account EE of the building materials, says Anurag Bajpai, director of Green Tree Building Energy Consultant, Delhi.
In the UK and Australia, building regulations include grading of materials based on their environment impact. In India, there is acute shortage of research on EE of building materials, says Reddy. The unstructured nature of the little research complicates the issue of incorporating EE in ECBC.
“It is important to consider the durability and recyclability of a product as well,” says Prashad. Using recycled or reclaimed material lowers EE. It is also good to invest in products that can be recycled or reused. At times, it makes sense to invest in high EE products that will last the duration of the building than in low EE products that will need to be replaced frequently, or require considerable maintenance.
While India is taking time to wake up to the importance of reducing EE, the West is a step ahead trying to lower embodied carbon of materials. Embodied carbon takes into account the source of energy and then evaluates its impact on environment. So while the same product made in different factories—such as one using coal energy and the other hydro power—may have the same EE, they will have vastly different embodied carbon values.
Government bans on mining of stone, sand and earth, among others, indicate a deepening crisis of resource overexploitation. Low market prices of products made of these materials, which have high EE value, complicate the problem. High EE products should be more expensive to dissuade its use,” says Prashad.