What is Embodied Energy?
Embodied energy is the total energy inherent in any man-made item. The embodied energy is the total energy consumed in the materials acquisition, production, assembly and transportation. In today’s world, embodied energy is often thought of in terms of barrels of oil.
At times, embodied energy can create a bit of a paradox. Say you don’t already own an automobile, and are in the position of purchasing one. Fuel consumption, for environmental reasons, is an important issue to you. Therefore you, and the environment, will be better served by purchasing an automobile that gets high gas mileage – so go ahead, buy the hybrid instead of the SUV.
However, lets say you already own the gas-guzzler. Does it make sense to sell it and buy a new vehicle that gets better gas mileage?
Consider that the manufacture of a new automobile, in materials and energy, represents between twenty-five and forty barrels of petroleum. How many miles will you have to drive the new car, taking advantage of its higher efficiency, before you have saved twenty-five to forty barrels of oil? That will depend on what kind of fuel economy you were experiencing with your previous vehicle. Then, once you’ve saved those twenty-five to forty barrels of oil, you’ve simply broken even; there has been no net benefit for the environment yet.
Embodied Energy and Buildings
When retrofitting any existing structure with energy saving materials, a simple question exists for most homeowners. What is the return on investment? That is, how long will it take for the modification, such as weather stripping or a new heat pump, to pay for itself in terms of the energy it saves? From a global environmental point there is a similar issue. One must also consider the energy embodied in the modification itself, as no net positive benefit for the environment has occurred until the energy saved exceeds the energy embodied in the modification itself.
Similarly, some energy saving modifications can have long payback periods as well. The unfortunate reality is, substantial passive solar design elements can be very difficult and costly to apply as retrofits. A structure should be designed for passive solar heating and cooling from the beginning.
The materials used in any building represent embodied energy. Those materials can be arranged into a conventional building that will have predictably higher future energy requirements for heating and cooling. Alternatively, those very same materials can be arranged as a passive solar structure, which will have significantly lower future energy requirements, reducing the buildings impact on the environment and the owner's pocket book. At Design Northwest we believe it makes the most sense to arrange those elements into a highly efficient structure from the onset.
|
