Terracotta tiles or plastic sheets? This was the decision to be made when considering roof materials for Nrityagram, a dance training center on the outskirts of Bangalore that was designed and constructed back in the early 1990s. The project marked the beginning of my interest in lifecycle environmental impacts and in understanding how to best determine the “lesser evil” among building materials.
It was clear there was something wrong with the general consensus at the time that “earthy” clay tiles and bricks were natural materials and therefore “environmentally friendly.” The tiles used up precious top soil in the surrounding villages and took excessive energy to bake them, emitting deadly polluting particles into the atmosphere.
We didn’t have the tools then to determine the best choice for materials. I was fortunate to have had a chance to work under Nigel Howard at BRE to develop ENVEST, the first software tool of its kind for estimating the lifecycle environmental impact of buildings.
Embodied energy is about the way a building is built rather than how it is used. It concerns the “upstream” value of the energy consumed by all of the processes associated with building production, from mining and the processing of natural resources straight through to manufacturing and transport. Embodied energy is the “front-end” component of the lifecycle impact of a building — and it is the part that can never be changed.
The worst culprits in building materials manufacturing are easy to determine. Five to seven percent of global CO2 emissions are caused by cement plants. The iron and steel sector account for 11% of global CO2 emissions. And more than 5% of the world’s entire electrical generation is spent on the production of aluminum.
A lot of these manufactured materials are going towards the construction of new homes and commercial buildings due to the construction boom that is happening in the developing world, where population growth and migration to cities will contribute to doubling building stock by 2050.
The environmental impact from manufacturing can be a lot more direct for some building materials. For example, the brick sector emits large volumes of black carbon and other suspended particulate matter. According to the Norwegian Institute for Air Research, brick manufacturing kilns in and around Dhaka city are responsible for 58% of the capital city’s air pollution — much more than cars, power generation and other industries combined. Brick kilns are a major source of air pollution not just in Bangladesh but across South Asia and China, together accounting for 75% of the global consumption of clay bricks. More than one trillion bricks are produced annually in these countries, resulting in 1.4% of global GHG emissions. To avoid the continued compulsive use of such resource-intensive building materials, actionable change must occur.
For those who still need convincing, consider the role that iron/steel, cement and industrial electricity play in India’s carbon footprint.
Most of the focus in the building industry has been on immediate impacts. For example, how can money be saved by reducing operational energy? The reality is that as energy consumption is driven down, the relative importance of embodied energy increases. For example, while adding roof and wall insulation to an un-insulated building reduces the building’s operational energy, it also increases its embodied energy. The proportion of embodied energy compared to operational energy can jump from 10% to 15%. If more and more insulation is added, the embodied energy of the insulation increases but the “return on energy” in terms of operational savings decreases. As the global trend is towards tighter regulations for operational energy consumption (especially in climate zones with high heating and cooling requirements), we must consider the impact of the choices that we make when selecting building materials.
At the International Finance Corporation, we created the free EDGE software to help the industry determine which building elements have the highest embodied energy — and where there are alternatives to reduce embodied energy. For instance, in a 6000m2, five-story office block, about 55% of the building’s embodied energy is from the structural concrete slabs (roof and floor), 20% from windows, 15% from walls and the remaining 10% from flooring.
Given its high embodied energy, finding realistic ways to reduce the embodied energy of the roof and floor structure is critical if one is serious about designing a green building. Generally, these alternatives fall under four main categories:
• Reduce the quantity of materials used (i.e., steel and concrete) by adding “filler” in slabs and/or reducing column spacing.
• Substitute high-embodied energy materials with lower embodied energy for example, adding Pulverized Fly Ash (PFA) or Ground Granulated Blast Furnace Slag (GGBFS) instead of cement to concrete.
• Selecting a more efficient construction technology such as post-tension concrete slab or planks and joists.
• Finding a completely different material such as timber floor construction.
Options that are practical and realistic depend to a large degree on the city or country where the project is located and the materials that are available, as well as the size and scale of the building. In most cases, paying attention at the early design stage and making sensible design and specification choices can reduce the embodied energy of a five-story office building by more than one third.
There are positive signs that mainstream building material manufacturers are attempting to tackle climate change impact. With companies such as Lafarge Holcim pledging to cut CO2emissions by 40% per ton of cement by 2030 we are likely to see more such commitments. The Paris Accord is driving over 200 companies to commit to Science Based Targets, surpassing expectations for corporate climate action.
Given the important role that building materials play in global resource consumption, air pollution and GHG emissions, it is essential that the measurement of embodied energy become a crucial part of the decision-making process for responsible designers and clients. Recognition must also be given to those that are responsible in their choices. Through greater awareness we will create a larger market for low-embodied-energy products and put pressure on all manufacturers to develop alternatives for their respective markets.
Prashant Kapoor is principal industry specialist for green buildings of the International Finance Corporation’s Climate Business Group. IFC is the private sector development arm of the World Bank Group.
Republished from Green Breakthroughs by Prashant Kapoor | Business World – Property Section, March 21, 2017