The Initiative for Green Habitats represents a long term commitment towards providing solutions for the creation of Sustainable Built Environments. This blog attempts to provide an insight to our views, commentaries on our work, ideas that we are working on, and provoke thought where there are more questions than answers.

Tuesday, April 5, 2011

The value of embodied energy in this world of energy efficiency

The world of today seems to be caught in this frenzy of energy efficiency... ok maybe only that part of the world that is focussing on reducing our impacts on the environment. Rightly so. The dots have been connected from the spending of units of electricity or fuel from petroleum products and coal to the emission of Carbon Dioxide into the environment. Various figures are thrown around ranging from around 1 kwh of electricity leading to between 0.8 to 1.2 kg of CO2. Similarly, 1 litre of diesel or 1 kg of coal burnt leads to about 3.2 and 2.3 kg of CO2 emissions.
The significance of energy efficiency by reducing energy consumption in any form is significant. A residential building for example stands to reduce about 1 ton of CO2 emissions every year, by adopting specific energy efficiency measures. This example however, is for a home in Bangalore that uses air-conditioning moderately. The emission reduction by taking such steps can vary hugely in different categories of residences and is more significant in higher energy consuming built environments- commercial buildings, 24x7 office buildings, air conditioned complexes, hospitals and industry. But any savings is significant, specially if you extrapolate it across an entire city, or, nation.
But what about the making of the building itself? Any building activity today is supported by huge energy guzzling building materials and services industry, not to mention the transportation of materials. More products are today industrialised than ever before... Demand for more buildings fuels more such industry and therefore a greater consumption of natural resources with expenditure of huge amounts of energy in doing so. It is only fair to take into consideration all this energy, or, the proportionate share of that per square metre of building built as the energy of making that building. The embodied energy of a building therefore, is the sum of the total embodied energy of all parts of the building. This embodied energy calculated in Mega or Giga Joules or in kwh is converted to achieve the sum CO2 emissions in kg or tonnes.
There are a slew of embodied energy figures for various materials, and the list is not exhaustive... from an Indian perspective, but Institutes like IISc and IIT Roorkee are taking their shot at providing some baseline figures.
The savings calculations however are an entirely different deal. The current method is to compare the sum embodied energy of your building to that of a baseline.... which, in simple terms means a building that can be considered similar in size, scale, purpose and group that it caters to, but built using conventional, current and commonly used building materials and systems. However, the more efficient way, is to compare your savings (in terms of your design and layout) to the alternative materials and systems that you could have used in the very same building that is being assessed.
So how much can we save by reducing the embodied energy of a building? A substantial sum depending on the choice of building material, system and the management of construction. In one building that we built, we estimated about 20,000 tonnes of CO2 emissions saving for about 25,000 sq metres of construction....while in an another building the figure same figure fell to about 5,000 tonnes for a building of about 8000 square metres. Why the difference? Simple. One building adopted achieved greater reductions due to the kind of technologies adopted....building blocks, avoiding a basement, flooring choices, etc. The savings could have been more in the first building.... if we had adopted a more energy efficient alternative to the RCC slab... or, by finding better alternatives to the internal roads built.
A building takes anywhere from 8 months to about 36 months to build, depending mainly on size and scale, and therefore the time frame for these substantial emissions for the building process is also limited to that. Energy savings in operations on the other hand adds up over the lifetime of the usage of the building. Savings in embodied energy could range from about 0.5 to 1.0 tonne per square metre. In a residential building, the energy spent ranges from about 5 to upwards of 20 kwh per square metre per year depending on the income group and the level of air-conditioning. In 20 years, this translates to about 100 kg to 400 kg of CO2 emissions. In a commercial building, a savings of about 50kwh per annum per square metre would mean a CO2 emissions savings of about 80-100 kg. In about 20 years, that would mean about 2 tonnes of CO2 emissions saved.
Just by these above cases, it is clear that the impact of how we build is significant and that one cannot neglect the CO2 emissions savings due to choices made in the building process.

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