Embodied energy, the energy “baked in” to materials, is a controversial subject. Some experts do not think it very important, since adding a little embodied energy in the form of insulation will save many times as much energy over the life of the building. Others believe that a long life cycle is far more important, so if more durable materials have a little more embodied energy, so be it. Most don't even bother thinking about it at all. (More explaining on TreeHugger here)
Prashant Kapoor of George Washington University, and the Principal Industry Specialist -Green Buildings at the World Bank Group, points out in certain circumstances, it can be very important indeed. He notes on his website, Sustainable Views, how in the 90s, he was working on a building near Bangalore considering whether to roof the building with terracotta tiles or plastic sheets.
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.
In Dhaka, the capital city of Bangladesh, the embodied energy and carbon from making bricks and tile is “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.
He also explains why the more efficient the building is, the bigger the problem becomes. “The reality is that as energy consumption is driven down, the relative importance of embodied energy increases.”
Kapoor helped develop software for the World bank, the Edge app, that helps the industry determine which materials and building elements have the highest embodied energy. Looking at a typical office block, he notes that the structural concrete slabs contain 55 percent of the building’s embodied energy. But there are many ways to build a structure with lower impact. He shows various floor slab configurations:
It is obvious that the default, the standard reinforced concrete slab, is pretty much the worst of any form of construction. Kapoor concludes:
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.
Of course, Dr. Feist is right; embodied energy is not the most important thing we have to worry about. But we are building so much, and so much of it is made from concrete and fossil fuels without consideration of the carbon load we are adding to the atmosphere right now, not to mention the other pollutants and particulates put out directly or through power generation. We cannot ignore it.
Read more at the really interesting Sustainable Views.