Embodied energy in existing buildings

18 Apr

A culture of reuse

We know that the way we use our buildings causes big problems but incredibly, we keep trying to solve the problem by constructing more and more new buildings while largely ignoring the ones we already have. That makes no sense. In addition to building green, we have to make wiser use of what we’ve already built.

One of the basic truths we acknowledge about climate change is that it is fundamentally the result of overconsumption of natural resources namely carbon-intense resources such as oil and coal. We often think of this in terms of the oil needed to power our cars, and the coal that powers many of our buildings but constructing buildings is also an energy- and carbon-intense activity.

The retention and reuse of older buildings is an effective tool for the responsible, sustainable stewardship of our environmental resources including those that have already been expended. This is “embodied energy.”

Buildings are vast repositories of energy. It takes energy to manufacture or extract building materials, more energy to transport them to a construction site, still more energy to assemble them into a building. All of that energy is embodied in the finished structure and if the structure is demolished and landfilled, the energy locked up in it is completely wasted. What’s more, the process of demolition itself uses more energy and, of course, the construction of a new building in place of the demolished one uses more yet.

Let me offer an example:
Boston City Hall has about 500,000 square feet of space. The amount of energy embodied in that building is about 800 billion BTUs. That’s the equivalent of about 6.5 million gallons of oil and if the building were to be demolished, all of that embodied energy would be wasted. What’s more, demolishing City Hall would create about 40,000 tons of debris. That’s enough to fill more than 250 railroad boxcars a train nearly 2 ½ miles long, headed for a landfill that’s probably almost full already. Finally, constructing a new 500,000-square-foot building on the City Hall site would release about as much carbon into the atmosphere as driving a car 30 million miles or 1,200 times around the world.

One final point: Don’t assume that the energy expended in manufacturing a building is offset by the efficient operation of new green buildings. In fact, a recent study from the United Kingdom found that it takes 35 to 50 years for an energy-efficient new home to recover the carbon expended in constructing it.

According to the Building and Social Housing Foundation and Empty Homes Agency in England, it takes about 50 to 65 years for a new, energy efficient building to save the amount of embodied energy lost in demolishing an existing building.

It all comes down to this: We can’t build our way out of the climate-change crisis. We have to conserve our way out. No matter how much green technology is employed in its design and construction, any new building represents a new impact on the environment. The greenest building is one that already exists.

One Response to Embodied energy in existing buildings

  1. Lissi says:

    lol!! this is a cool idea! 😀

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